OK.. Mini is back on the road, but not running well. For the record I haven't driven it... but the report is that it all seems lacking. Can't handle loads, lacks power etc... so... here's the spec.
998+60 (1050?)
12G295 head. Ported, opened comb chamber, skimmed, int/ext valves from big bore engine (not sure specifics there).
10:1 CR
VP7 cam (270/276)
Elect dist. with vacuum advance.
Twin HS2 carbs.
I was running HIF44, but it never ran perfectly... just too much carb... When it did go, it went like a scalded cat! 2500-6000rpm easy...
Question; What carb needle should I be starting with?? Not sure what needle was used (investigating now)...
My first guess is too much fuel getting in.
I'm out of country so wasn't involved in the set up.... but seems like the HS2's should work, but the set up might be wrong...
Thanks guys!
Rich
You really have to get a wideband hooked up to know.
... a what now? :(
You weld a bung into the exhaust right after the header collector, then insert an o2 sensor, then attach a wideband meter to it and you'll know at all times and under all conditions of load and RPM exactly what your mixture is doing.
Complete kits are in the range of $150-200.
Here's an example.....
https://www.summitracing.com/parts/inn-3918?seid=srese1&gclid=Cj0KCQjwgNXtBRC6ARIsAIPP7RuP79Jw8ZGqVNFQ3fZ2yrFsIVT62AhABX66kxj5X6eFQp_CeOFKlW8aApwCEALw_wcB (https://www.summitracing.com/parts/inn-3918?seid=srese1&gclid=Cj0KCQjwgNXtBRC6ARIsAIPP7RuP79Jw8ZGqVNFQ3fZ2yrFsIVT62AhABX66kxj5X6eFQp_CeOFKlW8aApwCEALw_wcB)
What is the timing set at initial and total advance?
Did you find out what needles in the carbs?
You could try gy needles as a starting point they'll probably be lean on the top end though.
Yeah I think I got mine off Ebay for $125. You're really just guessing till you either put the car on the dyno or hook up your own wideband. Dyno really only gives you a full throttle readout whereas in the car you can adjust carbs and needles for cruise. A lean 15:5:1 cruise air fuel feels perfectly normal, until you richen it down into the low 14s or high 13s air fuel ratios, then you realize how much seat of the pants pep you were giving up at the leaner mixture. Conversely a full throttle air fuel rich at 11:1 lacks power compared to high 12s to low 13s and is noticable if you have a built engine. Also lets you know if you're running dangerously lean at full throttle so you don't blow an engine.
Also lets say everything is perfect at full throttle but you have flat spots on throttle driving around town. We'll say you have blue carb springs and the wideband says on throttle you hit 18:1 briefly then settles in at 15:1. You now know to add red springs and add a higher viscosity dashpot oil. You can tune cruise A LOT by changing carb springs.
Thanks for the thoughts so far... gives me something to start thinking about.
Given the cam, what should I have expected them to set the advance at when they set it up? or does the cam profile matter for that?
I've got some investigating to do, but most of this will have to be sorted in the spring.
I have an adjustable curve electric dizzy. Baseline set to 10 at idle, comes on quick, tops out at 32 degrees. Number 8 on this chart. It responds well to the quick advance too I might add. This is on a built 1275/1310 with a 266 cam. On the dyno it didn't make any more power past 32 degrees either. Picked up a lot of power by getting air fuel in the 13:1 zone at full throttle. Cruise you want 14:7:1 in a perfect world, a smidge richer is better than leaner past that number.
Wideband gauge next to my tach (both must haves on a fast road build in my opinion) and 02 sensor location.
I set up the Inno we're building for an o2 sensor too, so we could get the carbs dialed in right.....it's an easy thing to do and you can move it from car to car or just leave it in like Dan does. The bung comes with a plug so once you're done you just cap it off.
Follow up question to this...
First I haven't done any work on the car... but those that did said that the timing of the dist arm looked like it was anywhere from 35-50 degrees off the number one point while it was at TDC. (static, not running)
Is there a chance that the timing was fine, but they had the wrong TDC?
Apparently they say that they fixed that, but now the car won't run... my math leads me to not having TDC set properly...
Thoughts?
Sounds very strange. It's easy enough to verify you are at TDC with the engine off by looking at your timing marks on the crank pulley (or through the clutch cover window on the flywheel). And of course then the rotor arm should then generally be pointing to the point on the distributor where the plug wire is connected to cylinder #1.
Quote from: BruceK on February 18, 2020, 01:15:39 PM
Sounds very strange. It's easy enough to verify you are at TDC with the engine off by looking at your timing marks on the crank pulley (or through the clutch cover window on the flywheel). And of course then the rotor arm should then generally be pointing to the point on the distributor where the plug wire is connected to cylinder #1.
Right... so... lets presume that they did that properly... any reason why the arm would be pointing so far off? is it physically possible?
There is one caveat to what Bruce said: cylinders #1 & #4 will both be a TDC at the same time, but only one at a time will be ready to fire. You need to make sure which it is by looking at the valve rockers. When #1 is ready to fire, #4's exhaust valve will still be partly open (closing as it is finishing the exhaust stroke), #4's intake will be starting to open, and both #1's valves will be fully closed.
Then you check the rotor is pointing to the correct lead for firing #1. Also, make sure the rest of the spark plug leads will be in the correct firing order going counter-clockwise (1-3-4-2).
As for your question about the arm pointing being far out of expectation, the distributor drive may have gotten pulled at some point in time and not put back in oriented correctly.
If you are referring to the timing marks (on either the flywheel or crank pulley), they should be as Bruce said: lined up with the pointers when #1 & #4 are at TDC.
Quote from: 94touring on October 27, 2019, 03:46:19 PM
Yeah I think I got mine off Ebay for $125. You're really just guessing till you either put the car on the dyno or hook up your own wideband. Dyno really only gives you a full throttle readout whereas in the car you can adjust carbs and needles for cruise. A lean 15:5:1 cruise air fuel feels perfectly normal, until you richen it down into the low 14s or high 13s air fuel ratios, then you realize how much seat of the pants pep you were giving up at the leaner mixture. Conversely a full throttle air fuel rich at 11:1 lacks power compared to high 12s to low 13s and is noticable if you have a built engine. Also lets you know if you're running dangerously lean at full throttle so you don't blow an engine.
Also lets say everything is perfect at full throttle but you have flat spots on throttle driving around town. We'll say you have blue carb springs and the wideband says on throttle you hit 18:1 briefly then settles in at 15:1. You now know to add red springs and add a higher viscosity dashpot oil. You can tune cruise A LOT by changing carb springs.
Wow, I'd love to get into the high 12s or low 13s on full throttle - I'm frequently seeing low-mid 10's, regardless of which oil or spring I try. I think I've got 10W synthetic in there now. Cruise and idle seem fine, and with good pick-up on part throttle acceleration - just can't 'floor it', though.
Quote from: BruceK on February 18, 2020, 01:15:39 PM
Sounds very strange. It's easy enough to verify you are at TDC with the engine off by looking at your timing marks on the crank pulley (or through the clutch cover window on the flywheel). And of course then the rotor arm should then generally be pointing to the point on the distributor where the plug wire is connected to cylinder #1.
And thought I'd add that each timing mark on the crank pulley or the flywheel is 4°.
Quote from: John Gervais on February 18, 2020, 10:27:22 PM
Quote from: 94touring on October 27, 2019, 03:46:19 PM
Yeah I think I got mine off Ebay for $125. You're really just guessing till you either put the car on the dyno or hook up your own wideband. Dyno really only gives you a full throttle readout whereas in the car you can adjust carbs and needles for cruise. A lean 15:5:1 cruise air fuel feels perfectly normal, until you richen it down into the low 14s or high 13s air fuel ratios, then you realize how much seat of the pants pep you were giving up at the leaner mixture. Conversely a full throttle air fuel rich at 11:1 lacks power compared to high 12s to low 13s and is noticable if you have a built engine. Also lets you know if you're running dangerously lean at full throttle so you don't blow an engine.
Also lets say everything is perfect at full throttle but you have flat spots on throttle driving around town. We'll say you have blue carb springs and the wideband says on throttle you hit 18:1 briefly then settles in at 15:1. You now know to add red springs and add a higher viscosity dashpot oil. You can tune cruise A LOT by changing carb springs.
Wow, I'd love to get into the high 12s or low 13s on full throttle - I'm frequently seeing low-mid 10's, regardless of which oil or spring I try. I think I've got 10W synthetic in there now. Cruise and idle seem fine, and with good pick-up on part throttle acceleration - just can't 'floor it', though.
Quote from: BruceK on February 18, 2020, 01:15:39 PM
Sounds very strange. It's easy enough to verify you are at TDC with the engine off by looking at your timing marks on the crank pulley (or through the clutch cover window on the flywheel). And of course then the rotor arm should then generally be pointing to the point on the distributor where the plug wire is connected to cylinder #1.
And thought I'd add that each timing mark on the crank pulley or the flywheel is 4°.
What needle are you using?
Hi - been a long time...
I'm using the AAA needle - KC originally used one on the engine before he sent it to me. Of course, he used it in a moderately-worn/average HS4 and I've got it in a brand new HIF38.
Have you any ideas that I may have missed? Oils, HS blue spring (too weak, sputtered like heck); I've even shortened the carb's brass damper (- 1½ mm) in order to get it to rise quicker upon initial acceleration.
Sooo, I've just gotten used to not stomping my foot down for now.
If your cruise is good then your cruise stations and spring and oil is good. You probably just need a leaner needle in the upper stations for WOT. You can try a much leaner needle over the entire profile and if your cruise becomes too lean, toss in a red or yellow spring to richen cruise back up.
Not a bad thought - why not, it's worth a shot. Just need it to stop raining and the wind to die down. We've had non-stop crappy weather for the past couple o'months - heck, I haven't even done any fishing and there are still those trees I've been wanting to cut down...
Update on my original post... would welcome thoughts.
I have had the car running, finally. I opened up the twins and found that the needles were AH2 and the springs were not marked any colour... I added Blue springs and M needles (leaner).
Granted that I need to strobe the timing in at some point, but its close... and I have not sorted a WB as suggested.
Anyway, it idles ok... revs ok parked, but runs like crap on the road. Its not pulling much power and misses and faulters under load. Had to nurse it up a hill in 2nd gear just to get home! Its also a bit difficult to start when its been warmed up. It doesn't jump to life like you might think, but lots of cranking and it just sort of sputters to life.
Thats the best I can describe it... any words of wisdom?
Note: I have 45D type dist, Accuspark Electronic.. new plugs, wires, coil... everything...
Quote from: 94touring on October 27, 2019, 11:21:21 AM
You really have to get a wideband hooked up to know.
I'm going to quote my original reply lol. My guess is you're lean. Try pulling the choke when it's barely running under load and see if it improves
Probably lean like you say. I have switched back to AH2 needles with the light springs... Last time I was putting along and pulled the choke it wanted to die...
Do you have red springs to toss in or double up the unknown springs you pulled out and see if cruise and partial throttle improves. That will effectively richen the mixture at cruise as well as idle. If it makes it worse then you're too rich.
Ok... so educate me on the springs... the blue (2.5 oz) spring will do what for me? I went with that as a starting point as the early 998 Coopers call for it. The spring that came out was much tighter, just not marked.
The 12G295 head I have has big valves, and was ported... larger combustion chamber with a skim to keep the CR at about 10:1. So, thinking I just need a richer mixture overall with all that air getting pulled in. I still have the HIF44 avail to go back on... it has a modified BDL needle for reference.
Rich
Blue are lean springs
Red are richer springs
Yellow is very rich springs
Green are turbo and extra rich springs
The leaner the spring the higher the carb piston rides, which alters bernoullis principle. You get less velocity/pressure differential over the needle port and pull less fuel at that particular needle station. If you hold the carb piston down using a stiffer spring, you get higher velocity of air and will pull more fuel.
These effect idle and cruise. WOT isn't effected as much.
I fine tune my piston cruise ride height by adding 0.7 oz washers to the tops of the pistons where the springs ride. Blue as a recall is 2.5oz and red 4oz. With a wideband you can dial it in pretty tight.
Interesting... thanks.
Just trying to get it drivable... gonna have to seek out someone to weld in the port for a WB at some point.
50.gif :-[ 8.gif
I am at a complete loss... Cold it will start with some choke, but not without a bit of cranking. I have richened it out (AH2 needles but still with blue spring), and at idle it misfires, and misfires under load on the road. Brief moments of smooth but not really. Warm (hot start), the only way to start the car is to have someone crank and I physically lift up the carb pistons until it lights up... then idles misfiring.
Everything is new.... everything is connected etc... no valves sticking... plug gaps by the book .032
Driving, I can tell that it just wants to fly.... but is misfiring all over the place...
WTF. 9.gif
Did you say you have an HIF44 too? Put that on and see if it runs OK?
That may be the next step... but I mean there has to be a way to get twins to work on what is essentially a warmed up 998 Cooper....
How far out does the timing have to be to cause the misfiring? It runs well enough to think that the timing is pretty close...
Misfiring may be more on the ignition side. Too retarded will pop out the carb and cause lousy driveability.
Advanced being further BTDC? and retarded being closer to TDC or ATDC?
To advance the timing, i'm rotating the dist clockwise?
Yes, clockwise.....to advance
I was only thinking that if it ran good with the HIF44 you could rule out everything else. Likewise, if it ran the same with the HIF44 your problem is probably not the twins.
Timing gun is ideal but you can get in the ballpark by rotating the dizzy clockwise to get the rpms to rise. Once the rpms begin to drop the further clockwise you go, turn it counter clockwise to drop the rpms approximately 250rpms.
Have you checked the distributor and coil?
A lot of problems that you may think are carb related are sometimes ignition problems.
Dist is brand new... Accuspark Electronic (45D), just replaced the cap as it was faulty. Coil looks great. Its an "Intermotor" sport coil from Moss. 3ohm 40Kvolt type. How would I test if to see if it is good or not?
Plug wires in the correct firing order?
Have the old coil to swap in to see how it runs?
Nah, the old coil was last used in 2006 when it was last on the road... I could buy a new one and see, but that seems expensive. I have no reason to suspect this coil is bad, but don't know how to check either.
By all accounts this should run...
I moved the ground strap to a better location... no change. Spark everywhere, but still misfiring at all times (idle, cruise and bad under load).... gonna borrow a timing light... ugh...
OK, back to basics, run compression.....check valve clearances.
Valve clearances were a bit tight, at .008 I brought them back to .012 per the book.
Carbs appear to be doing what they should.. I don't have a test gauge for compression... so more to follow. When running and I remove the plug leads in sequence, nothing really changes in the misfire... just RPM drops a bit as you'd expect. The Leads are in the right order... the timing is pretty close that it wouldn't be causing it... Coil tests fine (3.0oms and 98koms).
Back to the AH2 needles with stronger springs, it actually got worse.
I just don't get it...
Vacuum leaks along the manifold?
Just for comparison here's the difference between your needle choices. Nothing too crazy.
Yeah I did the same comparison... I don't think its the carbs.
It runs like its misfiring across all 4, but still running. Absolutely now power at all... under load put the throttle even down a bit, and it just sputters and farts. Nothing...
Is it possible for the coil to test fine... but still be bad?
I'm sure it's possible.
Verify this also. Only takes a second.
yup. checked that... firing order is fine.
Distributor advance not operating correctly?
Oil in the carb dashpots?
Just tossing out a couple ideas about things that have been known to have similar symptoms.
Dashpots have oil...
The distributor is new... (accuspark). Not sure how I would check that, but I suppose its possible.
Do you have the old distributor to try?
Nope. Well, yes I do, but its an old points type and was quite old anyway...
I've decided to bite the bullet and remove the twins and re-install the HIF44 that it was built with in the first place. Its a free effort, and if the condition persists then at least I will have learned something new.
I took my twin hs4s off and put a hif44 on. The twins were just too fussy to get perfect.
Quote from: Hercplt on July 28, 2020, 10:13:41 AM
Nope. Well, yes I do, but its an old points type and was quite old anyway...
I've decided to bite the bullet and remove the twins and re-install the HIF44 that it was built with in the first place. Its a free effort, and if the condition persists then at least I will have learned something new.
Sometimes when more than one item has been changed you just need to go back and change the old items back to the original ones one at a time to see where the problem is.
So HIF44 runs on choke... but barely... dies with any throttle... still misfires. Often won't fire at all, but the coil produces spark as well as plugs. Wondering if the coil just isn't doing enough.
Going to check compression next... maybe switch the coil with one that I know works on my dad MGB.
... the adventure continues... 8.gif
OK so you've ruled out the carbs as the problem.....if you don't have a massive air leak it has to be elsewhere.....I agree - check compression - if that's good swap the coil
If swapping out the coil does not work I guess you need to install the old points distrbutor.
I re-installed the twins, and for about an hour I had it running well. (not driving as I need a new throttle cable)... anyway, it ran and revved in the garage just fine. Some hesitation here and there, but nothing like before.
Now it won't start.
However, when cranking, if I use my fingers and lift the dashpot pistons it will fire and try to run... but not run on choke or throttle.
The coil tests fine (3ohm, 9800oms and 12V where it needs it)... It ran good so timing must be at least ok. Electronic dist looks good...
The fellow (Brit Ex-pat / mechanic) that put it together for me suggested that the carbs may be too small and not allowing enough fuel-air mixture through the carbs. What the hell am I missing?!!
I mean really... large bore 1275's with worked head can run twin 1.25s... why can't my 998?
He thinks the cam is too hot... but I'm not sure. Its a APT (Visard) VP7, which according to the spec sheet is suited to all A series, mild road cam (1500-7000 rpm). Engine is +60, head is 12G295 with opened chamber / ports and large valves.
I think this is a starting issue, rather than a running issue now...
What am I missing?
50.gif
These other folks are a lot more knowledgeable than I am on these things so I would only take this for what it's worth, which probably isn't much. I was having similar issues to what you are describing here, I have a 1275 with a 266 fast road cam and I could not get it to run consistently at all, one minute it runs fine, next it would not start, then it would back fire and carry on, always drove like crap.
New plugs, new wires, new cap & rotor, adjust valves......still the same. Changing out the coil, points, and condenser fixed it. Not sure which of the 3 it was since I changed them all at the same time but it starts flawlessly now and runs well for the most part. I think it was the coil but didn't want to push my luck by swapping it back to see.
I have dual HS4's which is way too much carb for my setup so getting that tuned properly is where my problems now reside. If you ever want to sell the HIF44 I am in the market for one LOL.
Quote from: Hercplt on August 11, 2020, 05:18:06 PM
I re-installed the twins, and for about an hour I had it running well. (not driving as I need a new throttle cable)... anyway, it ran and revved in the garage just fine. Some hesitation here and there, but nothing like before.
Now it won't start.
However, when cranking, if I use my fingers and lift the dashpot pistons it will fire and try to run... but not run on choke or throttle.
The coil tests fine (3ohm, 9800oms and 12V where it needs it)... It ran good so timing must be at least ok. Electronic dist looks good...
The fellow (Brit Ex-pat / mechanic) that put it together for me suggested that the carbs may be too small and not allowing enough fuel-air mixture through the carbs. What the hell am I missing?!!
I mean really... large bore 1275's with worked head can run twin 1.25s... why can't my 998?
He thinks the cam is too hot... but I'm not sure. Its a APT (Visard) VP7, which according to the spec sheet is suited to all A series, mild road cam (1500-7000 rpm). Engine is +60, head is 12G295 with opened chamber / ports and large valves.
I think this is a starting issue, rather than a running issue now...
What am I missing?
50.gif
Just a long shot here.
When you installed the twins did the manifold come with two locating rings that match up to the ports in the cylinder head?
If not just using the locating studs on a ported or normal head can be hit or miss, it is very easy to miss align the intake manifold to the head and you end up with air leaks.
Yes the intake has the locating rings...
Hazzaa!!! Success! 62.gif
Replaced the plugs with NGK non-resistor type... and reset the twins per the SU website... Back to M needles with blue springs... Revs, runs and drives with only a slight hint of hesitation. The plug leads were loose.. tightened them up. Reset the timing by feel for now. Totally psyched that I was able to run it 50km+ today all over town!! Popped and missed often enough to know that its not quite right, but cruised along at 60-70Mph. Part throttle in cruise or mild load and its doing well.
Long hills are a problem, as it bogs down and I end up plodding along up the hill in third. I seem to recall years ago with the HIF44 carb that this was not a problem... You think that the Twins are the problem? Its a VP7 cam (256??)
Anyway.. tonight is a success and having a beer in my Mini's honour... Cheers all for the advice these past few months!!!
Rich
71.gif
WooHoo. Congratulations
Good to hear you got it running better. It's always a good feeling when something just works like it should.
Thanks... I don't know that it "works like it should"... at least not completely. But I am happy for now.
Thinking I need a set of 1.3:1 rockers... re synch the twins, get the timing dialed in...
Long term... lose the VP7 and swap it with an SW5.
Questions... always more questions...
So, with the car running like a champ. I did a compression test. approx 90-95 psi across the board. My Brit mechanic guy says to give it some time, as we spent a lot of time cranking unburnt fuel through the engine... I mean lots... He expects that over time it should get better.
Car runs great, but taps out at 100kph (was doing 120+kph years ago). Up any hill, it just does not have enough power to even maintain speed let alone accelerate. With WOT it tends to mis and hesitate badly. So, yes I know I need a WB set up...
I presume that lack of power is compression related... and the wot hesitation is mixture? 75% throttle is great (except up a hill).
Thoughts?
That is pretty low compression, about half what I produce. Even still if you're air/fuel is off you're going to be running like crap.
I agree with Dan that the compression seems too low.
I am used to seeing around 150 in most of my basic Minis running mostly stock engines.
My Mini Marcos is a performance engine from Seven and it is around 200 on all cylinders.
So it used to do 120KPH with the same cam, carbs and rockers, and now it doesn't?
Or have you changed some of those things too?
I hope you haven't worn out the rings, but to test the theory you could pull the plugs, run a cold compression test, then squirt a bit of oil in the cylinders, crank it over a bit and run compression again. If you see a substantial gain - I would be somewhat concerned - if you don't I would be even more concerned!
Quote from: MiniDave on August 26, 2020, 04:44:07 PM
So it used to do 120KPH with the same cam, carbs and rockers, and now it doesn't?
Or have you changed some of those things too?
I hope you haven't worn out the rings, but to test the theory you could pull the plugs, run a cold compression test, then squirt a bit of oil in the cylinders, crank it over a bit and run compression again. If you see a substantial gain - I would be somewhat concerned - if you don't I would be even more concerned!
The twin carbs are the change... The engine wasn't very old (miles since rebuild). He opened it up to do the seals etc (it sat in storage since '06)... everything looked good inside.
Can you explain the oil in the cyl trick?? why and whats the difference with each result?
Edit: Its not blowing any kind of smoke (blue or grey)... at all... so its not burning oil past the rings as far as I am aware.
Rich
Squirting some oil down the bores and cranking it over (so the oil is distributed around the cylinder) will seal leaking rings up tighter, so the compression goes up. Which means the rings are worn. If the compression doesn't go up it either means the rings are so worn that it can't bridge the gap or there's something else wrong.
ok... Cold test;
1. 105
2. 80
3. 90
4. 100
With oil after cranking..
1. 115
2. 90
3. 100
4. 105
Not much improvement, maybe time to pull the head? I don't think given those results that there's anything that will improve with time and running.
I had similar problems with my 850. Hard to start no power etc. 0-60 mph was 37 sec about 10 sec over spec.
It ran great with no load but was not consistent. Couldn't figger out if carb or ignition was the problem.
Finally took compression as follows:
1.105
2.85
3.120
4. 80
Took the head off and found exhaust valve on #4 and #2 was not seating and showed gaps in the contact area and was obviously leaking. I hand ground the valve and seat of both 2 and 4 with valve grinding paste until full contact was achieved. I also honed #1 since it was slightly low compression.
Back together again the compression improved as follows:
1. 118
2. 112
3. 118
4. 130
Car ran great after this 0-60 mph improved to 21.6 sec better than spec. It ran great under load. And also started flawlessly. I also installed a Pertronix electronic ignition which improved performance.
As others have pointed out your compression seems to be too low.
Thanks for the info guys! Much appreciated.
I don't mind doing a valve job in the end... it seems less messy than redoing the rings.
will keep posted...
Pulled the head today, and this is what I found.
The similar low comp on all 4 makes sense now... Kinda surprised that the gasket did this, as its basically brand new.
Pics to follow...
Would welcome opinions on the cause of the leaks, and opinions on what gasket I should use. I have new copper type here that I can use.
Rich
:(
Yeah that's an issue. Was the head torqued properly? Though you probably didn't think to check before pulling it.
Also, check that head and block carefully to make sure it's good and straight - I might send it out to have it skimmed too....
Low compression completely explained now! Good that you found the problem, of course once you get the head sorted you'll have to go back into the carburetion again.
I always run the engine, then let it cool completely overnight, then retorque the head and readjust the valves and maybe do it again 1000 miles later.
Might be an ideal time to see what your compression ratio is and then skimming the head to raise it if it's low. Especially if the head isn't straight.
A good lesson here tho, any time you're trying to sort out an issue, start with the fundamentals - compression first, then valve adjustment, ignition, and carburetion last.
That head looks like it's been skimmed some already....check the block with a straight edge. If it's not flat it won't hold any headgasket. I like the composite ones better than the solid copper ones, but you do have to retorque them for sure.
What you are looking at is the bottom of the gasket... Looks aluminium? Yes the head has been skimmed... and looks pretty straight. Block is dead straight as well...
OK, not saying you didn't but are you certain that you have the gasket on right side up?
It's not unusual to have it fail between the middle two, but all 4 cylinders at once is not something I've seen unless the head or block weren't flat. As long as you've checked them I would clean everything up thoroughly and put your new gasket on and fire that mother up!
Can't seem to upload the other pic... but gasket was black side up to the head, and silver side was down toward the block. Not sure if that was right, but I didn't put the engine together this time, so it could be wrong I guess...
All 4 at once is odd. 2 and 3 are normal. That's why I wonder if it was under torqued, though you'd probably have been leaking fluids across the whole thing.
I'm with Da n and Dave. Looks kinda under torqued. Suggest you check stud thread height to make sure the nuts aren't bottoming out on threads giving a false torque. My engine has flat washers between head and nuts. not sure about the ones under the valve cover though.
I agree also - looks like it was under torqued and possibly not re-torqued after a couple of days.
I've had good success with the genuine Unipart copper small bore gaskets, carefully torquing to 45 lbs/ft, starting the engine and running until 'warm' without coolant, letting it cool overnight, re-torquing to 45 lbs/ft, adding coolant, then re-torquing again after a couple of days.
I haven't done a lot of head torquing so am not the expert however my brother used to build engine for a living. He always sprayed on a coat of aluminum paint (both sides) and swears by it. The one I took apart recently showed it made an excellent seal.
FWIW
Quote from: 94touring on September 01, 2020, 09:41:24 AM
All 4 at once is odd. 2 and 3 are normal. That's why I wonder if it was under torqued, though you'd probably have been leaking fluids across the whole thing.
Thats what I thought as well... but all the water ports are great... there was no coolant mixing with anything...
Quote from: tsumini on September 01, 2020, 01:15:52 PM
I'm with Da n and Dave. Looks kinda under torqued. Suggest you check stud thread height to make sure the nuts aren't bottoming out on threads giving a false torque. My engine has flat washers between head and nuts. not sure about the ones under the valve cover though.
Some of the head studs were loose it appeared when I un-did everything. I presume they should be snugged into the block by hand? followed by torquing the head nuts? Haven't checked Haynes on that piece, but any advise it appreciated.
I'm gonna use the copper gasket that I have and see how that goes.
They say in the manual just to run them in by hand, but I double nut them and snug them down to make sure they don't walk out again....but first I chamfer the holes so they can't pull up the top thread above the surface of the block.
The gasket should be marked "Top"
So... the saga continues.
I replaced the head gasket, with a decent copper one that I had. Torqued it down... ran it, torqued again.... ran the piss out of it around town, checked torque.. its good.
Runs the same... lack of power overall and in 4th running up slight inclines, and still regular misfire under load.
Compression check today;
1. 105
2. 90
3. 95
4. 103
Doesn't blow any oil (blue smoke) ever...
Ideas?
Question... Is there a chance that the initial timing of the cam / crank / timing chain wasn't quite right in the beginning?? Could that be an issue? Thinking maybe if its off, perhaps not all the valves are fully closed on compression stroke...
Still Hard to start? For that low of comprssion you probably crank and crank. Jumpering with a strong battery spins it up better too.
Sounds similar to what I had only I had only #2 and#4 low at 90. #1 and 3 were 115ish
Definitley need minimum of 115 IMO. Are you sure the head nuts weren't bottoming on head bolt threads?
Since all are the same I would suspect the combustion chamber volume too large.
Di you check the valves and make sure they are seating properly.
I am sure this is a completely dumb question and I am not trying to hijack your thread, but I am going to go ahead and ask it anyway because I am not super savvy with these engines yet.
Is there such a thing as too much compression on these engines? Or is there anything else you can learn about a "built by someone else" motor based on compression numbers?
I get 150, 150, 140ish, 150. It jumps to about 70-75 on the first revolution and hits the highs listed in about 7 revolutions on all cylinders.
150 is fine. On the engine we built for Dan, it's close to 200....that's roughly a 10.3:1 compression ratio in his engine.
In theory, you can have too much compression - it will cause detonation and blown head gaskets and other internal damage - but it would be way higher numbers than even these.
Diesel engines run between 18 and 24:1 compression ratios for example
Thanks for the info Dave. I was just curious what "normal" was for these engines since a lot of the numbers I have seen were quite a bit lower than what I was seeing. Didn't know where the upper end for these motors generally was or what the normal compression ratio range generally is.
All of my engine building experience in these sorts of things is on V8/v6 motors, motorcycle engines, and old diesels.
I think the 150 range is normal for these engines, with std pistons and such, especially if done cold on a broken in engine. They did make low compression versions of these engines too, for some markets (Canadian for example had 8:1 pistons) I'm not sure if any Mini engines were this low - but Sprites and other A series were for sure.
1098s were I think 8:3
my shop manual (AKD 4935 Leyland) lists compression ratio under Engine Tuning Data for each engine and Model. Although the compression pressure listed doesn't compute very well and is also called cranking pressure.