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BBC Closed Chambered heads question

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BBC Closed Chambered heads question

Postby Auctioneerhere » Sun Dec 02, 2012 9:50 pm

I have a fresh .060 over 454 with a Northern Auto parts balance rotating assembly. It has Speed Pro flat top pistons.

Looking for advice as to what iron closed chambered heads to use with them.

The block & head package I bought came wit a nice set of fresh 781 heads.

Engine will not see over 6500 rpm.

Just using what we have to put an engine together for my kids pulling truck. {Stock Class}
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Re: BBC Closed Chambered heads question

Postby F-BIRD'88 » Sun Dec 02, 2012 10:12 pm

66 to 69 396 oval port heads with small 96 to 100cc chamber
Gen 6 454 Vortec heads 100cc chambers

Mill to as close as you can get to a 92cc finished chamber size for a 9.5:1 cr on this motor.

Install with a thin steel shim head gasket for max compression

probably cheaper to just replace the flat top pistons to get compression. +25cc dome

or get a supercharger.
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Re: BBC Closed Chambered heads question

Postby Auctioneerhere » Sun Dec 02, 2012 10:20 pm

F-BIRD'88 wrote:66 to 69 396 oval port heads with small 96 to 100cc chamber
Gen 6 454 Vortec heads 100cc chambers

Install with a thin steel shim head gasket for max compression

probably cheaper to just replace the flat top pistons to gt compression. +25cc dome

or get a supercharger.


Been thinking about that, just the fact that every thing is balanced is causing me to look at a closed chambered solution.
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Re: BBC Closed Chambered heads question

Postby F-BIRD'88 » Sun Dec 02, 2012 10:29 pm

Auctioneerhere wrote:
F-BIRD'88 wrote:66 to 69 396 oval port heads with small 96 to 100cc chamber
Gen 6 454 Vortec heads 100cc chambers

Install with a thin steel shim head gasket for max compression

probably cheaper to just replace the flat top pistons to gt compression. +25cc dome

or get a supercharger.


Been thinking about that, just the fact that every thing is balanced is causing me to look at a closed chambered solution.


Well stop thinking about it and ID the pistons by part number , look up the weight and find a piston with a 25 to 30cc dome. (speed pro) Even if you do have to re balance it the new heads are going to cost more than new pistons.
I bet you will find pistons close in weight.
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Re: BBC Closed Chambered heads question

Postby Baprace » Sun Dec 02, 2012 11:35 pm

I'd buy the pistons first, if I remember correctly the closed chamber heads have a slighly smaller valve size when using rectangle ports, on oval ports the valve size is a lot smaller. I have a set of Wiseco .030 with .250 longer rod comp height and 50cc domes that are new in the box for sale for a 4.000 stroke. PM me if interested. $500.00 + actual shipping.

I'm sorry that I forgot about your bore size you are .060, mine are .030, I plead guilty to old age :oops:
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Re: BBC Closed Chambered heads question

Postby robert1 » Sun Dec 02, 2012 11:55 pm

If they are stock replacement flat tops you can't put much cam in it. 244 @ .050 with .550" lift will hit. If you cut the heads it will only get worse.
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Re: BBC Closed Chambered heads question

Postby Pontiac_Puller » Mon Dec 03, 2012 3:29 am

I wouldn't get to carried away with compression. Buuuuuut I can see you wanting more depending what cam you want to run.

I'd vote for weighing your pistons and buying a new set at the same weight with a dome. You could probably save the rings too, but BBC rings are so cheap anyways. This may be the cheapest solution, but it does mean you will have to crack your brand new engine apart.

If you don't want to touch the short block and go for closed chambers, then you want a set of 702s. Very similar ports to the 781s, most came with the same 2.06" 1.73" valves, and of course, a smaller chamber. Rebuild 'em, and have them milled a bunch to get the most squeeze you can. Without doing a bunch of port work they flow much the same as a 781, but most will tell you a properly ported 781 with big valves added will outflow the 702 with the same work done. If it's compression you're after though, it might be worth giving up a little to get it.

It all depends how much work you're willing to do, how much you can do yourself, and what you budget is for parts and outside labor.
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Re: BBC Closed Chambered heads question

Postby Bob Hollinshead » Tue Dec 04, 2012 6:42 pm

F-BIRD'88 wrote:66 to 69 396 oval port heads with small 96 to 100cc chamber
Gen 6 454 Vortec heads 100cc chambers

Mill to as close as you can get to a 92cc finished chamber size for a 9.5:1 cr on this motor.

Install with a thin steel shim head gasket for max compression

probably cheaper to just replace the flat top pistons to get compression. +25cc dome

or get a supercharger.


F-bird, can those Gen 6 vortec heads make any power? And will they work on the older blocks? I have a nice pair here and the port size looks like a large oval but just a little smaller than the 781/049 castings.
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Re: BBC Closed Chambered heads question

Postby F-BIRD'88 » Wed Dec 05, 2012 12:02 am

Bob Hollinshead wrote:
F-BIRD'88 wrote:66 to 69 396 oval port heads with small 96 to 100cc chamber
Gen 6 454 Vortec heads 100cc chambers

Mill to as close as you can get to a 92cc finished chamber size for a 9.5:1 cr on this motor.

Install with a thin steel shim head gasket for max compression

probably cheaper to just replace the flat top pistons to get compression. +25cc dome

or get a supercharger.


F-bird, can those Gen 6 vortec heads make any power? And will they work on the older blocks? I have a nice pair here and the port size looks like a large oval but just a little smaller than the 781/049 castings.


Yes these heads can work very well for you. There was a previous poster who posted some pics of them in ported form.
They go on the gen/Mark IV block with the right head gasket.

But the piston swap is more cost and performance effective.
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Re: BBC Closed Chambered heads question

Postby monte442 » Wed Dec 05, 2012 10:17 am

There are several companies that offer a piston for that combo and all of them use a better ring pack then what you have which will also help with power. Depending on what compression ratio you are trying to achieve, an 18cc dome with the open chamber head will put you in the 9.5-10 to 1 range depending on finished chamber size, deck height and gasket thickness. Giving up airflow to gain compression is the wrong way to go about this.
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Re: BBC Closed Chambered heads question

Postby vincenelson » Wed Dec 05, 2012 10:31 am

Why not use a set of retacnagular port closed chamber heads that have 2.25" intakes and 1.9" exhaust. With a .060 angle mill you can get them down to 96cc combustion chambers.
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Re: BBC Closed Chambered heads question

Postby DaveMcLain » Wed Dec 05, 2012 10:57 am

I've seen 454s done like this before where someone took the low compression flat top piston short block and put on a set of closed chamber heads and it worked well. Sure they don't flow as well as an open chamber piece but for something you're only going to spin 6000rpm or so, who cares. It can run well without a lot of trouble or expense and you already own a fresh 454 why not use it?
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Re: BBC Closed Chambered heads question

Postby Horndog » Wed Dec 05, 2012 11:37 am

DaveMcLain wrote:I've seen 454s done like this before where someone took the low compression flat top piston short block and put on a set of closed chamber heads and it worked well. Sure they don't flow as well as an open chamber piece but for something you're only going to spin 6000rpm or so, who cares. It can run well without a lot of trouble or expense and you already own a fresh 454 why not use it?

X2
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Re: BBC Closed Chambered heads question

Postby Auctioneerhere » Thu Dec 06, 2012 11:49 pm

Thanks for all the advice.
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Re: BBC Closed Chambered heads question

Postby Auctioneerhere » Mon Dec 10, 2012 12:30 am

Anybody have a weight for a .030 piston Speed Pro H661CP

I can't seem to find it anywhere.
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