Max RPM on 3.4 TDC engines

[NateD4]

What's the highest anyone has run a 3.4 TDC/DOHC engine to RPM wise?

Just curious

Thanks

[Schurkey]

With or without engine damage?

[robertisaar]

not that i recommend it, but i've heard of instances of 8000RPM.... IIRC, there were some very specific parts used to do so safely.

not that it is in any way suggested, since you're probably going to kill the transmission with shift speeds like those.... the max a 4T60E is rated for is 6200, i can't imagine the 65E being much if any higher. the 80E.... maybe. the northstars sure do love to rev, i imagine the trans was built to handle a bit more speed than it's cheaper cousins.

manuals.... IDK. the Q4/282 combo is the only other application i can think of off-hand that would be similar to a LQ1/284.

[Superdave]

The 282 gets mad around 6500, max recommended input RPM is 6200. The 284 should be a little better


the 3.4 DOHC has the same rods as all the other gen2/3 60V6's, rated for 7K RPM.

[ga2001532]

What does the 282 do above that rpm? It seems just fine to 6000. Haven't bumped it up yet.

[Superdave]

It's really hard to shift. Both my W41 and stock Cavalier 282's were that way.


Curtis was spinning his to 8K and went through a few.. his engine was pretty wild though.

[ga2001532]

Were these rebuilt or just used trans?

[Superdave]

Just used, my W41 trans was really low miles though.

Not sure if you can get parts to rebuild them or not any more, it's been quite a while since they were built.

[pocket-rocket]

I run mine to about 7k-7,100 on a regular basis when I get to drive it. Why have all that tach and not use it?

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[NateD4]

Im comparing LZ engines and DOHC for rev friendly ess.

Do the DOHCs use hydraulic lifters or mechanical?

Has anyone pushed valve spring forces higher and run them to 8k+?

If so do the belts break?

[robertisaar]

i think it's been suggested(by Ben? it was a very long time ago) that the LQ1 may have been considered to use a solid lifter early in it's development, but the version we all know is hydraulic.

[pocket-rocket]

With a proper balanced bottom end, lighter aftermarket lifters and stiffer springs 8k should be doable and survivable. Maybe we will see this spring. I wouldn't expect to see a belt break from rpm like I would maintenance neglect.

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[Schurkey]

Do the DOHCs use hydraulic lifters or mechanical?

Hydraulic

[NateD4]

What kind of flow numbers and spring rates do the DOHCs usually see/run?

[ForcedFirebird]

The GP has seen 8k, but as soon as the limiter was raised, Ben and I went for a drive and as soon as it hit 8k, it literally blew the exhaust apart at the u-clamp just after the down pipe haha.

Forged/balanced rotating assy, 13* cam timing, lightweight lifters, stiff springs, ported heads/intakes, 75mm TB....

You, know, the engine you are buying, Jon