Muncies vy Turbo v6

[Muncie]

Its l67 with ported Ecotec heads, reverse top swap i guess you would call it.

So l67 rods etc

[immortality]

What compression did you end up with?

Going with less compression on a daily driver is going to make the motor a bit more lazy when not on boost. GM made that compromise with the L67's, stronger rod/pistons but lower compression and then they advanced the cam timing to try and get some of that by closing the intake valve earlier.

I'd like to try some higher compression pistons in a L67 but so far I've only found very expensive forged pistons. A mate has suggested just using a stock L36 bottom end to get the 9.4:1 CR which would work better with a cam I just bought.

[vlad01]

It should be fine with low to moderate boost, but you need to make sure there is zero detonation, the L36 pistons are very fragile (very high silicon content) and also vulnerable by it's piston and chamber design (lands very high up and thin, large open champers prone to det and little squish that gives lands little protection from det) . Even mild det in an NA breaks them at a drop of a hat unfortunately. But with no det, they take it just fine and it will like you said, run a lot nicer than the L67 bottom end.

The rods are thin too, but they should be fine as long as there is no shock from det or pre-ignition, probably a few 100 hp and they will be fine.

I'm pretty sure that Richard Holdener got 1k hp on one of these on his dyno with nothing special, I can't recall if he gapped the rings or not, but gapping them is more of a solution for sudden heating from det, if there is no det at all, then gapping is less of an issue. Probably a good idea to do it anyway.

[Muncie]

The rod difference L67 quite a bit beefier, I have already run this combo before I had an oil pressure issue on first start and hurt a bearing it ran for a bit before spinning main 2.

Light came on dash for about 10 seconds then went off again damage was done didn't fine the cause just pulled engine back out.

No noticable off boost difference with l67 bottom end instead of ecotec they drove about same.

[immortality]

The rod difference L67 quite a bit beefier, I have already run this combo before I had an oil pressure issue on first start and hurt a bearing it ran for a bit before spinning main 2.

Light came on dash for about 10 seconds then went off again damage was done didn't fine the cause just pulled engine back out.

No noticable off boost difference with l67 bottom end instead of ecotec they drove about same.

With the roller lifters it shouldn't hurt it to pull the plugs and crank the motor to build oil pressure before firing it up.

My mate had the Comp Cams XP Hot cam in his L67 and his biggest complaint was it been lazy down low off boost.

It should be fine with low to moderate boost, but you need to make sure there is zero detonation, the L36 pistons are very fragile (very high silicon content) and also vulnerable by it's piston and chamber design (lands very high up and thin, large open champers prone to det and little squish that gives lands little protection from det) . Even mild det in an NA breaks them at a drop of a hat unfortunately. But with no det, they take it just fine and it will like you said, run a lot nicer than the L67 bottom end.

The rods are thin too, but they should be fine as long as there is no shock from det or pre-ignition, probably a few 100 hp and they will be fine.

I'm pretty sure that Richard Holdener got 1k hp on one of these on his dyno with nothing special, I can't recall if he gapped the rings or not, but gapping them is more of a solution for sudden heating from det, if there is no det at all, then gapping is less of an issue. Probably a good idea to do it anyway.

He beat up on the L67 pretty hard, the L67 can take a lot of abuse which is why I'd prefer higher compression pistons for that rather than put in a L36 bottom end.

But take what Holdener does with a grain of sand, no real comparison with a engine fitted in a car, he ran the engine cold, he ran e85 but real lean, lean enough the exhaust was glowing with EGT's peaking at about 1400°F IIRC.

[Muncie]

I'm going to run this thing in NA as I dont have tune I'm happy to throw at new engine. My old 500k ecotec took 9psi with me tuning it with fuck all knowledge for 12 months. I got greedy though gave boost controller 3 clicks when I should of done just 1 and broke a piston.

Its got a 2500rpm hi stall so you can get it off line alright even if it is doughy down low its not my daily more of a mid week cruiser and weekend drag toy.

[vlad01]

Wow, yeah I forgot how flimsy the NA eotec bottom ends are. I'm so used to seeing the Buick ones and hadn't touched or looked at the ecotec ones for years.

I know the rod is thin, but what stands out is how ridiculously thin that wrist pin is. It was almost a fad where engine builders and OEM went thinner for less weight to help engines live longer at higher RPM, but over the years they realised it made things worse by allowing the pin to flex and bind up in the small end and piston simultaneously, which then would causing failures, small end or piston or both.

So now the trend is going back to the old days of hefty pins, where modern pistons and rods are more than light enough that the pin's weight doesn't matter, but their rigidity certainly does!

I didn't know that back when I last played with those engines, it's funny how your eyes go somewhere new when you revisit something with much more wisdom and understanding.

The L67 pin looks like just an average one to me, not even beafy, where the NA one looks like it's made from paper. Back then, I would have said how damn thick that L67 pin was and thought the NA one was normal haha.

[Rhysk94]

Wow, yeah I forgot how flimsy the NA eotec bottom ends are. I'm so used to seeing the Buick ones and hadn't touched or looked at the ecotec ones for years.

I know the rod is thin, but what stands out is how ridiculously thin that wrist pin is. It was almost a fad where engine builders and OEM went thinner for less weight to help engines live longer at higher RPM, but over the years they realised it made things worse by allowing the pin to flex and bind up in the small end and piston simultaneously, which then would causing failures, small end or piston or both.

So now the trend is going back to the old days of hefty pins, where modern pistons and rods are more than light enough that the pin's weight doesn't matter, but their rigidity certainly does!

I didn't know that back when I last played with those engines, it's funny how your eyes go somewhere new when you revisit something with much more wisdom and understanding.

The L67 pin looks like just an average one to me, not even beafy, where the NA one looks like it's made from paper. Back then, I would have said how damn thick that L67 pin was and thought the NA one was normal haha.

Stock L36 blocks have gone 600+.
Its all on the tune.
Which 98% of the time is why they go tits up.

[immortality]

Wow, yeah I forgot how flimsy the NA eotec bottom ends are. I'm so used to seeing the Buick ones and hadn't touched or looked at the ecotec ones for years.

I know the rod is thin, but what stands out is how ridiculously thin that wrist pin is. It was almost a fad where engine builders and OEM went thinner for less weight to help engines live longer at higher RPM, but over the years they realised it made things worse by allowing the pin to flex and bind up in the small end and piston simultaneously, which then would causing failures, small end or piston or both.

So now the trend is going back to the old days of hefty pins, where modern pistons and rods are more than light enough that the pin's weight doesn't matter, but their rigidity certainly does!

I didn't know that back when I last played with those engines, it's funny how your eyes go somewhere new when you revisit something with much more wisdom and understanding.

The L67 pin looks like just an average one to me, not even beafy, where the NA one looks like it's made from paper. Back then, I would have said how damn thick that L67 pin was and thought the NA one was normal haha.

I believe the weight reduction was all in the name of efficiency, to reduce rotating mass and gain economy. It's the same reason why the ECOTEC has the same bore and stroke but 1" less deck height.

The Ecotec pistons have ridiculously thin top ring lands, I've seen a few popped off when the rings butt up.

[vlad01]

Yes, the whole architecture of the last gen of 3800 was in the name of weight reduction, efficiency and emissions. It was the first maybe the only pushrod engine to achieve ultra low emissions spec I recall, right at the end with the last 3800 L26 US variant.