Sprite Race Engine Rebuild for Dave L

Started by MiniDave, March 01, 2021, 12:31:53 PM

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MiniDave

Watch this space - it promises to be ugly based on the description!

No compression on #3, and it was blowing out a whole lot of oil, so my guess is a hole in #3 piston.

We need a quick turnaround on this one, he has a race in 3 weeks at Hallet and since he didn't finish his weekend at Houston - it ran great for 2 1/2 days! -  they won't punch his ticket till he runs one more event.

His other option is to pull the motor and gearbox out of his Lotus 7, which is the one with the straight cut gears I built a short while ago, but we'd also need to change the cylinder head as it's aluminum and he can't run that.

We'll see in a couple of days when he hauls it over and I tear it down.....I already made arrangements with the machine shop to slide it in ahead of other work so we can get it right back out again.....but three weeks might be cutting it close, depending on how long it takes to get parts.

Really miss my local Brit parts supplier, Victoria British!

Clancy sold his spare race car, so if this engine runs well I may get to build another for him, he already asked me to build him up another straight cut gearbox so I have another set of gears on the way.
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

cstudep

Sounds like you will at least stay busy for a while! Whether that is a good thing or a bad thing we will just have to wait and see I guess. 77.gif

pbraun

so he needs to finish and drive safe, build a street motor, or minor mods.
Peter
65 Moke
60 Bugeye modified
66 Jaguar XJ13 ( I can wish )

MiniDave

Yes, I have no idea how built up this motor is, what cam it runs or how much head work has been done. I also don't know if he has a wideband on it so he can see if it leans out at higher RPM - which could have caused the piston to burn.

I won't know for sure till I see it and tear it down.

The biggest concern is whether it damaged the cylinder walls.....
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

MiniDave

#4
Well, this engine turned out not to be so dire after all - it still will need major surgery but once I got the head off I expected to see a hole in the piston or the side melted off - none of that happened!

The engine is a bit of a mystery in that the parts list of race parts dates from 2009, and I'm not sure all those parts are still in it. It does still have the $600 flywheel and clutch tho!

For example, 2 of the pistons had pretty good marks on them where a valve has hit, one of the intake valves is different than the others, although it's not in either of the cylinders that have the valve marks on them. One of the pushrods is bent, tho none of the valves are stuck, all the guide look good etc. and one of the 8 pushrods is different than the others! The front two pistons have different markings on them than the back two.

Also, stem seals are on the list, but not on the head....

So, it may have started out pretty racey and has been bodged a time or two over the years.

We're trying to get a set of +40 pistons, if we can't we'll get some +60 and bore the block. If we can get the +40 then we'll just give it a light hone....as long as the cylinders measure out OK, there is no damage to the cylinder walls at least.

The cam is supposed to be a "scatter" cam, but I sure can't see any difference in it other than the lobe width - the cam is undamaged, but several of the lifters are showing damage, as do the rear main bearing, the rear cam bearing and the oil pressure relief valve, which was stuck solid and full of metal bits.

Another interesting tidbit, normally the piston crown comes up to about 5 thou below the deck surface, #1 piston was 3 thou below, all the others were 5 thou over the top of the deck!

The owner is taking the block, head, pistons and cam up to Kent Prather tonight to have him take a look and make some recommendations, but I think it will be a pretty simple rebuild. The owner has no idea about what his timing, valve clearances or air fuel ratio were......so he has some work to do to learn this motor.

Now - the damage. #3 piston - which had the lowest compression - has no tension on the top ring, it has a slight amount of burning damage on the side above the top ring, but nothing else and the top ring was not stuck. #4 piston had a broken top ring, but no other damage, the other two were also fine. Not so bad, huh? However if this engine is running 13-1 compression like he thinks, that will pressurize the crankcase pretty quickly at 7500 rpm!

The engine does have some pretty racy bits on it, like a 4 bolt center main cap, all ARP studs and nuts on the rods, mains and head, and an 11 bolt head.

Should be a fairly easy rebuild, given that I've enlisted the owner to clean all the bits before we put it back together.
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

MiniDave

The owner has decided to see if he can find some 40 over pistons, turns out one of the pistons had a broken ring land under the ring, pretty much like WillieB's engine did. If he can't find the 40's Kent Prather has a set of 60 over he can buy. Still looking for a rimflow intake valve to replace the oddball one.

He's taking the block back up to Kent's shop on Tuesday to do some of Kent's secret modifications (they're not that secret - I told him about them already  ;D ) to make it more durable as a race engine. We're really trying to get it ready in time for the race at Hallet on March 19-21, but that's a big ask if we have to wait for parts. We also need to get the block over to the machine shop either to get honed or bored depending on which pistons he goes with.

I really think this engine has been cobbled up some over the years since it was first built so we're going to straighten it all out - the bones are good, we just need to get everything set up correctly.
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad


MiniDave

Low compression, cast pistons. We need flat top, forged pistons....
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

MiniDave

all righty then, lots done on this race motor, care of Kent Prather (who's also retired but failing at it too :-) )  Today they overbored the oil gallery holes, then threaded them for allen grub screws. They found a couple of bad valves so they changed them all and did a light three angle cleanup of the seats.

He also supplied the owner with new push rods, gasket sets, rod and cam bearings and a few other bits and bobs. main bearings are on the way and will be here Fri I'm told.

He also decided to go with the 60 over pistons Kent had, so we'll be sending it off to be bored and finish honed tomorrow - I'm hopeful my buddy at the machine shop can slide us in and get it done by Friday afternoon, he said he thought he could but if he's slammed he may not be able to get to it as quickly as he hoped.

They also balanced the rotating assembly, so once all the stuff arrives it should be an easy assembly process.
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

MiniDave

OK, the block and old rods/pistons went to the machine shop today, I'm hopeful he can get it done by Friday, but we won't have rings and rod bearings till Monday, so that will slow things down a bit too.

Kent apparently found a lot of things wrong in the head, bad valves, one seat that needed to be recut and so on. He also said no two lobes on the cam were the same lift, so a new cam will be in the works for the next time it gets torn down. :(

This engine definitely shows signs of detonation, and it has been bodged together with an assortment of oddball parts, two pistons that were different from the other two and so on, but if you want to piss with the big dogs you have to lift your leg as they say, so he's buying the good stuff and he'll get more as the season goes along. The pistons he got from Kent were forged and 70 thou oversized custom made pistons - the max you can do without offset boring the block. Kent has used them for years, so they're a known quantity....that's the kind of stuff you need to do if you're going to win races - and Kent's engines win races - and championships.

I don't know how many races a season he's planning to do (or can afford to do!) but this will get him thru the weekend and get his license punched.

Funny thing is, he went racing without checking the timing, fuel ratio or pretty much anything before he hit the track! I wonder if he even checked his tire pressures! Oh well, you learn you grow! ;)
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

pbraun

Hummmmm  more fun!  71.gif 11.gif
Peter
65 Moke
60 Bugeye modified
66 Jaguar XJ13 ( I can wish )

MiniDave

Surprisingly, my guy got the Sprite block bored and finish honed this afternoon, tomorrow he'll hone the wrist pin holes in the pistons and I should be able to pick it all up tomorrow. He did us a real favor getting it pushed in ahead of some other work, but he said he had a opening pop up in his schedule, so he slid us in and got it done.

I still have lots of things to do to the block before it's ready to assemble, and if the bearings and such come in for the 998 I'll build it up this weekend first. I'm still waiting for the transmission and head to come back for the 998, so all I can do is the block build up on it for now.

We won't have rings or rod bearings for the Sprite motor till Monday at best, so it will wait till then, but I should have everything ready to go together, so it will be a quick assembly and into the engine stand for a lite break in, retorque and re-adjust of the valves.

Then he can haul it off and drop it back in the car, but the actual break in will happen when he hits the track. Kent says he can run the first session on the break-in oil, keeping the revs below 6K, then drain and change the oil and go for it in the second session.

I'll have pics when everything comes back to me.
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

MiniDave

#12
The block came back from the machine shop pretty clean, but I still spent a good part of the day using a scotchbrite pad on all the bearing surfaces, running a tap in every hole - some of which were really crudded up - and getting rid of the last tiny bits of red RTV (man I hate that stuff!)

Once it was all clean and ready I went ahead and installed the new cam bearings - by the way, 998 and 1275 cam bearings are different after all. I never paid a lot of attention to how since they use the same camshafts, but since the block is smaller, the rear cam bearing on 998's is about half as wide as those used in a 1275, and the middle bearing is smaller too. That's the only difference that I can find.....

With the cam bearings in I cleaned out the lifter holes with a rotary wire brush just to make sure they were completely clean and slipped the new lifters in, then installed the cam and oil pump.

There's not much more I can do in the block till the piston rings and main bearings get here, but I have plenty to do on the cylinder head yet. I'll lightly reface the rocker arms as we're going to reuse these standard arms, then Kent supplied us with a "competition" rocker arm shaft, so I'll install that and get them all set up.

I've already cleaned all the main parts, but I'll still need to clean up the threads on all the bolts.

I'm hopeful that the rings and bearings will hit today, but if we don't have them by Monday there's little to no hope of making the race next weekend. If we do get it done I'm thinking of going, it's only a four hour drive and I have a lot of friends going, I could help Clancy with his sales efforts too. He's taking his trailer - he's developed a gig to go to the races and sell parts and such - he's a Griot's dealer, Milwaukee Fuel tools, and lots of specialized Sprite race parts, including the transmissions I build for him. I applaud him for his entrepreneurship!

A few shots of the cam tool in action - thanks again to WillieB for making the last bushing I needed to complete the set. The paint marks help me align the holes in the bearings to match the oil ports in the block. You also have to watch to make sure the bearing doesn't rotate as it's going in - I've had that happen a couple of times.
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

Willie_B

Glad to see that it does the job.

MiniDave

#14
It's a bit fiddly on the inside bearing, but it works perfectly!

Today - it's raining outside so I'm down to cleaning things up and a little paint here and there.

Oooooh........shiny!

It's just good ol Rusty O'Leum as this is a race motor and I'm sure it will be torn down frequently - in fact I'll bet I'll be tearing it down again this fall for a new cam, some better rockers and some hardened seats and a good race valve job, plus a few other tricks of the trade.
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

MiniDave

Oops, found this today.....

This goes hand in hand with the bent pushrod and the "crop circle" in the top of the piston. Funny that they ran it like this because, look how far out the adjuster is to compensate for the bent pushrod.

Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

MPlayle

Looks like it was also compensating for a bend in the rocker arm.


gr8kornholio

Something oddly satisfying about tapping holes.  It's so nice when you can thread your bolts smoothly all the way in. 
I am the GR8KORNHOLIO! Are you threatening me?

Saussie Aussie 1965 Australian MK1 Mini.
"Beavis" - 07 MY/MY MCS, B/MY Konig Daylites, JCW sideskirts, TSW springs, TSW lower rear control arms -- Exploring the country with new friends since 11/09.

MiniDave

#18
The owner knew that his engine was running pig rich, but when he tried to adjust the mixture (done by raising or lowering the jet on a SU carb) the jet wouldn't stay up. On looking at it I could see that the choke linkage was holding the jet down and that it was bent in all sorts of weird ways - that's how the choke works - it drops the jet down to richen the mixture and the return spring in the linkage draws the jet back up and holds it against the adjuster. So I took the link off and reconfigured it and viola! now it works! I had to straighten the bend on the end where it attaches to the jet, square the first bend coming off the linkage as it was only about 60*, then re-bend the jet end in a different place to shorten it. It was actually a little tough to do as this metal is pretty stiff, I couldn't bend it with pliers, I had to use a hammer and the vise. Which tells me someone bent it that way to begin with, and/or these carbs have been messed with like everything else on this engine so far.

One more thing off the list.

Still waiting for main bearings and rings so I can build the block. The head is done, I rebuilt the rocker arm assembly with a new shaft and refaced the surface of the rocker that hits the valve, so the head is ready to go on when the block is done. This rocker assy is a short term solution, when we re-do with the head later in the year or post season with new hardened seats and new valves we'll put some new roller tip rockers on it.
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

MiniDave

Well, as often happens when you want to get things done quickly....parts orders get screwed up and sent to the wrong address and so on ....bottom line rings and bearing won't be here till Thursday at the soonest, so there's no way we can make the race at Hallett this weekend. Too bad, since it's close enough I might have been able to go....still might but it's unlikely at this point.

The next race is at Gingerman, in Michigan, towards the end of April, so that gives us more time for break in and tuning. I won't be going to that one, it's more like a 10-12 hour drive and if I felt like I could do that I would be up for the Texas run.
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

Scargo

#20
Dave...

I assume the race at Gingerman that you mentioned is the VSCDA event over the May 1 & 2 weekend. (There is also a drivers school there the last couple of days in April.)

If this engine being built for Clancy, I have to ask if he is also planning the run in the VSCDA Sprite/Midget Racing Series season finale at Grattan Raceway in Michigan in mid-August. The reason being, I will be there and if Clancy will be there as well, I will look for him.


MiniDave

No, THIS black engine is for another guy, so that he can finish his school at Gingerman (now - he was going to finish at Hallett this weekend) but Clancy also wants me to build HIM an engine, for the weekend at Gingerman. That one's a long shot, as all he has is a block, crank and rods at this point.....I have a head he could use but it's just a stock 12G940 head.

I don't even know if he has a car to put it in.

I also need to build a transmission for it.......
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

Scargo

#22
Dang ....you were too too quick on the rebuttal. Now go back and look at my revised line of questioning.

MiniDave

#23
Too quick on the keyboard!

Yes, he will be at Grattan, that's one of his every year races. He no longer drives, he's set up a business selling parts and tools to racers now, however they (Gingerman) were looking for a "school car" that they could rent out for that weekend and I think that's how this one came about....I still don't know if we're going to build it yet.

I'm limited on how much I can accomplish right now, a few hours a day seems to be my limit.

He has a new trailer that I haven't seen yet but as you get closer to the event I'll make sure you two meet - he's hard to miss, he's 6'4" and I bet anyone you ask in the paddock will be able to point him out!   77.gif

He sells some slick adjustable lower control arms to allow changes in camber and caster both

Edit: we're not going to build the Gingerman car now, maybe later in the year for next season.
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

MiniDave

#24
Well, I got a call this morning that the rings we've been waiting for finally came in, only they're wrong. So, another delay....good thing we're no longer trying to make the race this weekend with this engine.

Edit: Just got a call back, turns out the rings are right, the package was labeled wrong! I'll get the new rings tomorrow, so I can carry on with the build. Now I need to get the other engine out of the stand so I can load this one in when I'm done with the assembly.
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

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