So i closed my season on a lean #7 cylinder, which made me tear into my engine sooner then expected. On inspection of my heads i noticed little cracks on the head between the valves. Im positive they werent there before installation. Im also switching around intake setup and have the chance to go to a rectangular port head. Ive searched for about a week now seeing no one really put a rectangular port head to the test of high boost. Many that see 10-12 psi, but im looking at 24-28 range. So who has put a LS3, LSA, LS9 head to the test? Would notice a power gain in the lower at lower boost levels with these heads? Or should i stick with my 317s?

Background on the car: 370, GT55-94, 25 psi average, E85, 1/2" ARP studs, LS9 gaskets . Current heads are hand hogged 317s that held up to over 75 20-28 psi passes, and probably hundreds of street pulls.

 

The LSA and LS9 head would be much better than the 317s. Since you are setup for it, Id rock the LS9 because of the 1/2 head bolts. It will take a little machine work, but youll be happy with them.

We run 19-22 psi on the ZR1s with out issue and getting pretty crazy with the tuneup and water temps ( 25-27* timing and AFRs in the 13s on a road course)

Id stay FAR away from the 821 or 823 LS3 castings.

 

Thanks man, i was hoping someone could shead some light on this! Anyone else?

 

I thought the 823 heads where the head of choice for boost, if not whats the casting number (5864 or something like that)

 

i think what he is getting at is they will lift before the lsa or ls9 heads.

does anyone know why this happens on the l92/ls3 heads compared to the 317s?

 

Ill be cutting some heads apart tomorrow

The LSA and LS9 heads are also a much better material.

The 317 vs the LS3, I have not the slightest clue. I have one of those too, Ill cut apart.

 

Often detonation will cause that.

 

My future plans definitely have the lsa heads included in them and have for a bit now. Seems to be the best bang for the buck going at the moment. I thought i read there's a minimum bore required of either 4.00 or 4.030. Can you confirm that as well Louis?

 

I wouldn't run the rectangle port stuff on anything under 4.065" personally, but that is only my opinion.

 

It needs a minimum of a 4" bore. Yes, larger bore is optimal, but there is no issue with a 4".

 

With boost or nitrous I agree 100%.

N/A is another story for another part of the forum....

 

Totally agreed. Unshouding in any case is good, but if he already had a good shortblock, a little shrouding is still going to fair much much better over the cathedral setup.

 

Great to hear! thanks guys.

 

I'm in for Louis's findings on cuttingthe heads apart.

 

I plan on using my 823 castings on a turbo set up. I have wanted to know what the deck thickness was compared to a 317 head myself.

 

Bump for results from the heads being cut apart

 

I got the ls3s cut apart last night and Scoggin dickey delivered the LSA head yesterday. Probably have everything cut apart on Monday.

 

Sounds good.

 

From the old beat to death L92 head threads seems like if you try and machine them to run 1/2" studs they break super easy under a decent amount of boost. I'm running standard diameter ARP studs and will see how far i can push my L92's with the GT-88

 

In for pics