L28- 3.1 Liter

[gira]

Good Day everyone,

I have a general question about the stroker engines out there. We built one and it recently beat the middle crank bearings up pretty bad without much time on the engine. My belief is we turned it too many RPM's and I want to know from the list if there has been a general consensus of where NOT to go with the RPM's on these engines, or where the harmonics are. This was a professionally built engine with very good parts.

Thanks a million,

Greg Ira

Revtec Race Engineering

www.revtec1.com

[conedodger]

Greg,

I have heard that because of the long crank balance is critical beyond even what we normally consider with these engines. I had heard 68K but I would call Rebello on that... The guy I knew who came up with 68K was not a pro builder. Usually the limiting factor for RPM is valve train so that is why I think balance has to be your issue.

[gogriz91]

John Williams might know 770-806-2926 or he might be able to call Sunbelt?

[MikeW]

I had heard 68K but I would call Rebello on that...

Does this mean 6.8K, i.e., 6800rpm, or does the 68K refer to something else?

[conedodger]

Does this mean 6.8K, i.e., 6800rpm, or does the 68K refer to something else?

Duh... Sorry. I think that answer is obvious.:stupid:

[=Enigma=]

Not so obvious. I thought you were trying to say 6-8k. Why not just type exactly what you thought you meant to say instead of what you think we though you think to say? This way we all think what you meant to say we thought, you think?

[Arne]

Not so obvious. I thought you were trying to say 6-8k. Why not just type exactly what you thought you meant to say instead of what you think we though you think to say? This way we all think what you meant to say we thought, you think?

I thought that you would think that way, Enigma...

[John Coffey]

My 3.0L stroker (same stroke as a 3.1, smaller bore) ran regularly to 7,500 and was hard redlined at 7,999. Sunbelt said if it hits 8,000 the warranty is done and the engine goes boom. The crank was an LD28 crank that was nitrided and lightened to 35 lbs, Carillo rods, JE forged pistons, and an ATI Super Damper.

25+ hours on the bottom end when I had it and the next purchaser is still running it as far as I know.

[mark belrose]

I've still got John Coffey's block, although it's now bored to 3.1L. My shift light is set at 7k and my Electromotive HPV1 limits the revs to 7.5k. I'm not quite as comfortable as John was running it up any higher, and the chassis dyno showed that with my current cylinder there was nothing to be gained up there anyhow. Last year's rebuild showed the main bearings were like new after a season's use.

Greg, is there any chance your block might be flexing? I'm running a stiff ARE pan with larger allen head bolts to inhibit flexing, although I don't know for sure if it's actually helping.

Mark Belrose

[gira]

Great info Mark and John. I am still looking into this to see what the deal is.

Thanks again,

Greg

[Carl Beck]

Hi Greg:

So the questions still are - "where in the RPM range - are the harmonics critical enough to hammer a main bearing" - and/or - "is that the problem area"?

Anyone know what the Factory Red Line is on the LD28? Might be a clue there related to the use of that crank. Lightening and balancing on that crank would also be VERY important {as mentioned}

As I recall, when the cranks started walking around in the early L24's - it resulted in cracked flywheels and blown clutches.. sort of a harmonic whiplash at the end of the crank.

If the center main was the only one hammered - - could have simply been an improperly installed (torqued) center main or cap. Maybe weak main or rod bolts/nuts that failed to hold proper torque.

It just seems that if you ran into a harmonic wall - you'd see more damage than just the center main bearing.

be sure to let us know if you ever find an answer...

good luck,

Carl B.