Replacement Engine: Street vs Raced with low compression

[Adam L.]

I blew an engine endurance racing and have been stressing out about the options (my failed engine was a fully refreshed forged build with all the reliability upgrades which lasted for about 30 hours, but don't have the budget for that build again)

Option 1) Street Engine w/130k runs and drives no problem

Cold
#1 190 / 25% leak
#2 190 / 30%
#3 190 / 30%
#4 190 / 20%
#5 185 / 30%
#6 180 / 20%

Would presumably need at least the welded oil nut, and leak #s suggest maybe a head refresh?


Option 2) Raced engine lightly prepared (presumably welded oil nut) but seller doesn't have a lot of details and one cylnder is down on compression ~25% off

Price is roughly the same for both. Not sure which one is better then the other?

I also see one on ebay for 2k which is lower then typical but salvage with unknown health...

Any advise? Whats the minimum budget for a race ready engine?

[aeronaut]

Tuff call, I think you'll have to assume engine work on all of them until you get one and run your own tests and tear into them. Buying engines you can't inspect before purchase is a crap shoot, unless from a very trusted source.

Those leak down numbers on option #1 look consistent across the cylinders, which tells me there's a small chance they could be low due to user error or the leak down tester isn't a standard one.
Welding an oil nut with the engine out of the car is trivial, so not sure why that's even in the decision equation.

Knowing nothing else, I'd probably go with #1. None of them feel plug and play. Assume work needed on any of them, and hope for a pleasant surprise.

[pbonsalb]

What failed on the fancy race build? What bore, stroke, rpm limit? Presumably something was done wrong, or are people doing the sort of racing you do only getting 30 hours out of a motor?

[Adam L.]

What failed on the fancy race build? What bore, stroke, rpm limit? Presumably something was done wrong, or are people doing the sort of racing you do only getting 30 hours out of a motor?

a year + back we did a full refresh including the e46 pan and dual pikcup pump, 11:1 86.5mm JE Pistons + rods + decked head with new lifters and Schrick Camshaft Set 264 / 256 degree and all other maintenance items like the chains, tensioner, vanos... I also crashed the car after that and didn't make it to nationals but that's a whole other story. It had been about 30 hours on the engine prior the failure a couple of weeks ago, and there were some signs from oil analysis that the bearings might be going but I didn't maybe look at the signs as closely as I should have in part because we had some conflicting data (oil report after that showed 0). It was estimated it would last 60 hours and 30 hours was so much shorter but who knows what the crash did, there was always an alarming about of sparkle/metal in the oil, the engine seemed to be ticking louder more recently... hindsight is always 20/20

AFAIK connecting rod broke. Data didn't show any oil pressure/temp or obvious issues. This was the first enduro I particpated in. We made it 1.25 hours out of the 3. Engine note changed and power was down. Oil pressure stayed ok but engine temp shot up quickly then the rod went through the block

For the replacement engine I'm thinking of doing the bare minimum which I believe would be (I'm not a mechanic so any advise is appreciated)

Street Engine w/130k runs and drives no problem
Cold
#1 190 / 25% leak
#2 190 / 30%
#3 190 / 30%
#4 190 / 20%
#5 185 / 30%
#6 180 / 20%
Head was recently refreshed on this engine, but a little unclear why the leak% are as high as they are

+

ARP Rod Bearings and Bolts
VAC Competition Dual part-number VAC-HVOP-S54-N- a bit unclear if this then requires the S54 pan and related dual tubes, dipstick too? believe so
Rear main seal
Mishimoto 68c lower temp thermostat

Main bearing cap bolts? 11 11 1 735 525 ?
unlcear if replacing the oil chain is a critical refresh item as I gather that starts to get pretty deep into the dissasembly?
Anything I am overlooking?

in any case I gather tearing down more of the engine to do things like piston rings seems to have less value as costs spike pretty quickly in part because of the requirement to take the head off to do rings? ...

-Adam

[Adam L.]

I called VAC and answered some of my own questions...

Oil Pump Options
A) shaft and sprocket VAC-OPUK-M50 $199.95 + $150 baffle = $350 or +500 to include a new pump
B) 1,299.95 for VAC improved new s54 pump + s54 pickup tubes, s54 pan, dipstick... = ~$2k

There somes to be some conflicting opinions of what pushes the need for the A versus B when road racing..?

[pbonsalb]

Stock rods and rod bolts regularly hold 500+ rwhp on turbocharged examples of these motors. I don’t think ARP bolts would have made any difference in your case. I would guess you had an oiling issue. Any indication of a spun bearing — rare, loose oil pump nut — common, failed oil pump pickup tube brazing — common? Did the builder cap off the piston oil squirrels or leave them in place? I would think they would help with cooling on an endurance motor. Were you running an rpm limit over 7000? Doing so on an S52 seems to decrease reliability due the long stroke crank. Also, the S54 pump flows less than the S52 pump, but can be modified to fit an S52 pump rotor to increase output.