[DorkMissile]

Well,
Tore my LT1 down today, and was able to pull the #1 bullet out of it as I wanted to check the weight on the piston, rod, etc.....

I ended up throwing the #1 & #2 rings in the bore at 1" below deck

#2 ring took a .018" feeler
#1 ring took a .012" feeler all the way, a .013" feeler about 1/3rd the way across the ring gap

I was pretty lucky that given I was running boost (8-9lbs) but with E85 & Meth. Can see in the #7 bore where there is a little bit of indication that the ring was bottoming out. No ridges on anything, so i think I will be safe without boring it.

I was curious if GM might have started opening the ring gaps up over time (my car is a 2018) but it looks like mine is just as tight as earlier engines.

[gotswap]

need to measure at top, middle and bottom of the can. End gaps on N/A cars are generally tighter than with forced induction or N2O

[laynlo15]

Nope just on the Lt4s

[Eldi Z]

Originally Posted by DorkMissile

Well,
Tore my LT1 down today, and was able to pull the #1 bullet out of it as I wanted to check the weight on the piston, rod, etc.....

I ended up throwing the #1 & #2 rings in the bore at 1" below deck

#2 ring took a .018" feeler
#1 ring took a .012" feeler all the way, a .013" feeler about 1/3rd the way across the ring gap

I was pretty lucky that given I was running boost (8-9lbs) but with E85 & Meth. Can see in the #7 bore where there is a little bit of indication that the ring was bottoming out. No ridges on anything, so i think I will be safe without boring it.

I was curious if GM might have started opening the ring gaps up over time (my car is a 2018) but it looks like mine is just as tight as earlier engines.

So seeing such tight gaps, would you do it all over again and run on the SBE with the ECS Novi setup? Would you reduce boost, or remain as you are?

What are your plans now that you are already inside the engine?
Forged Pistons?

[DorkMissile]

Well I knew what I was getting into, and my tuner has been down this road on the LT1. His advice from the beginning was the only way he was going to tune it is if I ran E85 and Meth. And not really for additional fueling, but for temperature control.

Had I wanted to stick with Gas, he would have kept me at 600hp - the rings can't take the heat without bottoming out on the gap.

My intent is to switch to 6.125" Rods, forged pistons, and throw in a cam. Will also go to TriMetal bearings

[wnta1ss]

Yeah that is tight, but not as bad as some have been found to be. When I first heard about someone finding top ring gap in a factory LT1 at .009" I thought WTF, as using the top ring gap normally specified for an NA engine would mean .018" on this bore. We've heard of them being as bad as .007" too, ouch.

[laynlo15]

Mine broke the 1 and 8 cylinders ring land. We set the gap at Manley's recommendation plus a thou. My engine builder does a lot of blower motors so he's always cautions on the loose side when boosting.

[TJay74]

While the ring gap is an issue, cylinder temps and cylinder pressure from boost and ignition timing also contribute to the ring gap issue coming to head. Like the OP that is why I asked to keep my tune on the conservative side and at 650rwhp. I think I could even get to 700rwhp, but like the Op I think I am going to address it correctly when I swap in a cam in the future.

[laynlo15]

Tjay, good idea but the problem is some of us don't stop at that? Ha

[KingLT1]

Originally Posted by Eldi Z

So seeing such tight gaps, would you do it all over again and run on the SBE with the ECS Novi setup? Would you reduce boost, or remain as you are?

What are your plans now that you are already inside the engine?
Forged Pistons?

I don't believe he had a failure...he is simply tearing it down and upgrading for the next round of mods. I would do the same if tearing it down for a cam...imo it only makes sense to do drop in rods and pistons along with a cam. If these engines didn't have shit afm lifters and you could simplly pull the front cover and drop a cam mild cam in with a bigger fuel lobe, then I could see doing just a cam but that is not the case on these engines. That being said, The SBE will handle some power on boost with the correct fueling and tuning. His ring gaps are tight but actually not that terrible from what I have seen some report.

[DorkMissile]

Correct - I pulled the engine for two reasons. Update to forged pistons / verify ring gaps and to swap cams.

FYI - my car was dyno'd at 700whp during tuning, on E85 & meth, and I ran it that way for a year, about 8000 miles. And I put it thru it's paces. I did 500 miles in one weekend at Brainerd Intl Raceway for PowerCruise. 1 mile long pulls on the front strait from a rolling start at over 170mph. I usually go thru 2-3 quarts of meth in a weekend of running around on the street, I went thru 7 gallons in 3 days there.

#7 cylinder to me looks like the ring had bottomed out, but not enough to break the land. You can see in the cross hatch where the finish polished / smooth and where there is no hatch, about every 30 degrees radially around the bore.

I am waiting for some parts to show up before I tear it the rest of the way down, so just understand this is just checking one pair of rings out of one cylinder. I would doubt that .012" isn't going to be the tightest one I see.

[Eldi Z]

Good information here. Another important thread is taking shape here!

[oldman]

I will also point out that many people who "broke a rod", in all probability bottom a ring gap and then the rod broke..Just my opinion of course. I think I went with my piston card +.002, probably too loose, but I'd live with a little oil loss vs a engine failure. Don't remember off the top of my head if the card called for .018 or .020 top. .022 seems a little wide so it probably was .018 and thus I ran .020. Sorry it has been a while.

[DorkMissile]

Well - pulled the rest of the pistons out, but haven't checked any more gaps as I am just focusing on the build.

I know as with the LS engines, the GenV engines seem to have problems in #7 & #8 cylinders first, and here is a pic of my #7 bore. When I see these radial spots left by the top ring, to me it looks like the ring gap was bottomed out.

FYI - note my car runs on E85, with meth, and still has a little oil in being pulled thru the catch can (hence the build up above the rings - it looks like the oil really likes to stick to the aluminum part of the bore in the cylinder above the sleeves)