Sorry to hear of your troubles Frank, hope you can make it to Cresson...
Sorry to hear of your troubles Frank, hope you can make it to Cresson...
FMR pics.
jb
massive blowby with 13:1 compression looks like you were burning a LOT of stuff with too much heat. If you had to choke it to kill power, that probably didn't help. Could have been running VERY rich and was washing down the cylinder walls. those bores "appear" to be able to be cleaned up. Figure a .020 overbore might work, but you are back to new pistons/rings at the min.
Flat tops in 324 cube motor is pretty high compression.
I will post later this evening...just realized I am late for work!
Ah, fugg it.
I measured the piston to cylinder clearance according to manleys instructions at 0.010 - 0.014. Should be 0.003 - 0.0035 and certianly no more than than 0.005, or am I wrong?. FMR
That just sucks Frank... Keep us posted!
DD
I read this same line in SHM's engine building book...if the pistons were truly that far undersized, they either wore away a lot of material or were letting the oil by and that was causing the smoke. Are you measuring the piston diameter above the top oil ring or below the rings. Only thing that sticks in my mind is how far the pistons will get exposed at bottom dead center from the skirt bore. If they installed standard stroke skirts, the pistons will cock to the side a little at BDC and could start chewing up the piston. Now that I think about it, I need to verify my sleeves can accept a stroker setup! Maybe the motor was setup with hypereucraptic piston tolerances instead of for forged pistons which grow more?Originally Posted by cobra132
Taking a harder look at the pictures, I see a LOT of detonation burning the top of the piston...ie, pitting. I also see a LOT of burned oil as if you were getting blow by or sucking it in through the intake/PCV. I have had motors that I put 3k miles on and still looked like fresh clean pistons. Something is not right in the a/f mix and getting a lot of oil into the cylinder.
As for the sides of the pistons..., they look like they got hot and expanded too much in the bore. Given the compression of 12.7+ (guessing), you needed 100 octane or even 104 depending on the timing curve. If I run less than 98..I have problems. I never saw the inside of my motor in November 2006, but it died with just one session of 93 octane and the pistons were toasted but the block was fine.
Any idea what the water temps where during the practice session? I don't have any experience with the Darton Wet Sleeve setup. Mine is a dry sleeve so my water jackets are all still aluminum with no water hitting the sleeve. The reason VT originally sold me on this was even heat disapation around the sleeve and more block strength to cope with solid engine mounts.
There are 3 or 4 theories on what happened, but I know you are going to hate my next suggestion. Send the pictures to the engine builder and tell him the scenario and ask questions of "what could have caused this?" SHM has built enough motors that they should be able to say "Yep, that was XXXXXX." within about 5 seconds.
None of the above probably helps but might get you going in the right direction.
Worst case, I personally would use the stroker crank, stroker rods and some stock bore pistons in the original block, setup for 11.0:1 compression and put the smaller cams back in with an aggressive tune and race fuel. If the big bore is salvageable, Call Steve down at Houston Performance and start a dialog for rebuilding it. You might just be a set of pistons/rings/bearings and some machine work/assembly away from being good to go. Steve has built enough motors and rebuilt Joe Johnson's 5.4 in his 2000R. He knows what he is doing. If that doesn't work, I can get you in touch with HPP and who they are using here in DFW. They seem to split machine work between Houston Performance and a local shop in Fort Worth depending on the build. In all honesty, any shop familiar with small block chevy's should be able to build a mod motor. They are zero balanced and basic engine building techniques apply for boost or N/A.
Call me if you need to vent (214-364-0420) or need some basic advice about combos. I don't claim to know a lot about what tolerances work best for a road race motor but these motors STOCK can take a lot of abuse on track and in general. I will say you have had some bad luck since the beginning and it makes me sick to think I could be in the same boat. Maybe we can narrow down the common failure and I am leaning towards tuning??? But that's just me making a SWAG...
Ah, fugg it.
:idea: Richard Painter may know a thing or 2 about mod motors.
jb
DSS Racing is the answer
I know the former national champ in AIX uses them and Wayne has one of their engines in his AI car that has lasted for years and years (not a mod motor). SHM has not been great for several of my friends in the past. Shouldn't someone have to cover the cost of this? Unless your tune was too lean it was not your fault. I don't see lean doing all this. Some of it yes but not all the skirt damage. Looks like lots of blow-by
JJ
Jerry, hasn't it been YEARS since that car has even seen the track?!oke:
Ah, fugg it.
Yes it has. but they still built a motor for that car that lasted for years and I know several Lightning guys around the country that have run their Mod motors and had great luck with them.
Jerry, hasn't it been YEARS since that car has even seen the track?!
Also the 2007 AIX National champ (Chris Griswold) is a big fan. I'm sure there are other good engine builders but I KNOW these guys are good. From what I've seen and heard in the last few years I would not spend a dime with SHM. JMHO.
JJ
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