L29 head compatibility

[ADS-454]

The GM Performance 454HO crate motor uses the 12562920 heads. These heads are available at various places online. All of them include the note that they will not fit on a L29 motor. What is the reason they will not fit?

 

[yevgenievich]

They are large open chamber heads. On l29 will severely lower compression

 

[Schurkey]

Rectangular intake ports won't be sealed with the oval-port L29 intake manifold 'n' gasket???

The pushrod guideplates in the HO heads are set-up for thicker pushrods than the L29 uses???

The bigger valves won't clear the valve reliefs in the L29 pistons???

Accessory bolt holes in the front of the heads use larger bolts? 7/16 vs. 3/8?

 

[Scottm]

L29 heads have conventional 'full size' oval port intakes, like the 049 head of the early 70's. It's a lot of work, but after grinding the swirl ramps out of the ports, L29 heads flow about 290 cfm on the intakes. That's enough for 600 hp, but you will never get that with the stock intake. I am working on my truck again and posting in my thread, with lots of head work and flow testing:

99 L29 454 build

I made a few posts on my 454 rebuild and hop-up in the general vortec thread that really should be in a new thread, so here it is.. My 97 K3500 extended cab dually has 230,000 hard miles, so I bought a L29 7.4/454 from a rolled suburban to rebuild and swap in. It allegedly had under 20k miles...

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