396 heads - Chevelle Tech
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post #1 of 15 (permalink) Old Apr 24th, 17, 5:22 PM Thread Starter
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Mike
 
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396 heads

I have been stalling quite awhile in finishing my engine. Reason being I was convinced my idea for using open chambered 781 heads on my 396 was a great build. I bought high dome pistons (L2242 nf60) and the heads which were already rebuilt. Sent the engine to the shop and now was selecting a cam when I got cold feet. I even asked many questions on this forum and posted threads. Bottom line is I am insecure about this build. Don't want to get the car done and mess up the engine. I am thinking of getting different heads. This is a street car which I want around 400+hp. A basket case that is now almost done. Any suggestions? I thank anyone who can talk sense into me.

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post #2 of 15 (permalink) Old Apr 24th, 17, 5:53 PM
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Re: 396 heads

Zero deck the block and take a bit from the heads(781's) to get yourself at around 10.5:1 and you shouldn't have any trouble seeing 400hp+
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post #3 of 15 (permalink) Old Apr 25th, 17, 12:50 PM Thread Starter
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Re: 396 heads

That massaging of the head is the problem. Where ? It apparently is not a piston to valve issue but is a piston to chamber wall or something else. Thats my worry.

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post #4 of 15 (permalink) Old Apr 25th, 17, 1:01 PM
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Re: 396 heads

It is. Usually the piston dome hits the chamber on the outside edges. I used the old 2287 piston in the 781 castings and had to clearance the sides of the chamber.
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post #5 of 15 (permalink) Old Apr 25th, 17, 2:52 PM Thread Starter
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Re: 396 heads

That is why I think I'll replace the heads. Good likelihood I won't get it right. The bores are different shapes so I think it is a risk. So I am thinking of getting closed chamber heads but I have these high dome pistons and don't want more than 10.5 compression. Any suggestions on heads would be appreciated.

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post #6 of 15 (permalink) Old Apr 26th, 17, 4:34 AM
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Re: 396 heads

those pistons won't work with OC heads at all. they'll hit the heads hard around the edges of the dome. This is not related to the height of the dome, it's the shape where the dome meets the deck of the piston that's wrong.

This is old news.

Just FYI, I had this trouble on a stock 396 with stock original 66 396 heads. Those were supposed to be stock replacement pistons, but they hit the heads in several places on all cylinders.

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post #7 of 15 (permalink) Old Apr 26th, 17, 6:30 AM
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Re: 396 heads

Sorry for the confusion OP, I thought these were an open chamber piston
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post #8 of 15 (permalink) Old Apr 26th, 17, 9:01 AM
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Re: 396 heads

Now I'm confused.

I ran L2242 nf60 (39CC dome) in a zero decked 396 with milled 118CC 781 heads with no clearance issues

'66 SS 396 #'s match/ POP - Aztec Bronze / Bronze Interior
'66 Malibu 454 Cortez Silver / Maroon Interior
'37 Chevy Coupe 235 Straight 6 - Cabana Cream`
'55 Chevy Gasser - 427, 4 speed
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post #9 of 15 (permalink) Old Apr 26th, 17, 4:15 PM Thread Starter
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Re: 396 heads

And thats why I am confused. Dream 66, sounds like you had no problems with this set up. Do you remember what cam you used?

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post #10 of 15 (permalink) Old Apr 26th, 17, 4:38 PM
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Re: 396 heads

Lunati 20110549 Hyd. Roller

232/242 578/595 -112 LSA

The machine shop did have to re clearance the exhaust reliefs in the pistons by .080 due to oversized valves But there were no clearance issues with the dome and head.

Head gaskets were .035 compressed and the "zero" decking was .007 for an .042 quench and 10.4 nominal static compression.

Here's a pic of the clearanced area
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'66 SS 396 #'s match/ POP - Aztec Bronze / Bronze Interior
'66 Malibu 454 Cortez Silver / Maroon Interior
'37 Chevy Coupe 235 Straight 6 - Cabana Cream`
'55 Chevy Gasser - 427, 4 speed
'72 Cutlass Supreme - Gold/White

Last edited by dream66; Apr 26th, 17 at 5:10 PM.
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post #11 of 15 (permalink) Old Apr 26th, 17, 5:18 PM
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Re: 396 heads

I should add that I would not select that cam for street use. Too lopey. It liked 2,800rpm and above.

'66 SS 396 #'s match/ POP - Aztec Bronze / Bronze Interior
'66 Malibu 454 Cortez Silver / Maroon Interior
'37 Chevy Coupe 235 Straight 6 - Cabana Cream`
'55 Chevy Gasser - 427, 4 speed
'72 Cutlass Supreme - Gold/White
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post #12 of 15 (permalink) Old Apr 26th, 17, 8:35 PM
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Re: 396 heads

I would still use the 781 heads.

Ray

http://s30.photobucket.com/albums/c3...t=DSC01615.jpg
Best pass so far 9.034 at 148.10, 1.242 60'
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post #13 of 15 (permalink) Old Apr 26th, 17, 8:50 PM
James
 
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Re: 396 heads

been looking to use 781 heads on my closed chambered pistons aswell . heres a couple pictures where head was done for cc piston from what i can tell .




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post #14 of 15 (permalink) Old Apr 27th, 17, 9:23 AM
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Re: 396 heads

I used these pistons with the 781 heads. Had them done with 2.19/1.88 valves on a .060 396 and made 500 hp with them.

https://www.summitracing.com/parts/trw-l2287f60
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post #15 of 15 (permalink) Old Apr 27th, 17, 11:14 AM Thread Starter
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Re: 396 heads

Thanks Dream 66. That cam is more radical than what I was considering. I thought something along the lines of lift under 530 and duration @50 of less than 230. And an LSA of 112. Also, I kept the smaller valves in the 781. If this combination will work I will order the cam kit and go forward and have the shop grind off what is needed for a proper fit.

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