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Old 09-24-2010, 12:35 AM
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As was said already, the problem will be with the extremely large chambers which could easily be 122 cc's and will make it necessary to use a domed piston to achieve a decent static compression ratio.

Boring to a larger bore size piston will help, as will a longer stroke crank. Both will increase the cubic inches which raises the static compression ratio. I'm sure you know this, but I like to spell it out for others who may be reading this thread.

A professional engine builder that I know will not build a BBC with a flat tappet cam unless the buyer signs a liability release form. He says he has had too many of them roached in the BBC. Therefore, I would use a retro-fit hydraulic roller in such a motor, based on his experience.

The 049 heads may not be the whiz-bang performers that you perceive them to be. They're pretty mild.

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Old 09-24-2010, 02:01 AM
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Quote:
Originally Posted by techinspector1
As was said already, the problem will be with the extremely large chambers which could easily be 122 cc's and will make it necessary to use a domed piston to achieve a decent static compression ratio.

Boring to a larger bore size piston will help, as will a longer stroke crank. Both will increase the cubic inches which raises the static compression ratio. I'm sure you know this, but I like to spell it out for others who may be reading this thread.

A professional engine builder that I know will not build a BBC with a flat tappet cam unless the buyer signs a liability release form. He says he has had too many of them roached in the BBC. Therefore, I would use a retro-fit hydraulic roller in such a motor, based on his experience.

The 049 heads may not be the whiz-bang performers that you perceive them to be. They're pretty mild.

I agree on the retro roller cam, with the oils today it's just not safe to run a flat tappet cam.

As for compression that kind of depends how much HP you want to make. If you want 450hp then 9.5-10:1 compression is going to be needed.

The 454 I built for my '71 GMC has dome pistons and a hydralic roller cam. The dome on the piston is small, but it does give me 10-10.5:1 compression with the 781's head that I am running. The 781's have some of the largest oval ports that came in GM BBC heads. I installed 2.19 and 1.88 valve and had a little pocket porting done to them. As for the cam it's a Comp Cams Nitrous grind, NX279HR, it has 279/294 duration and .537/.541 lift on a 113 LSA, 2000-6200 power range. I figure this setup is good for 450-500hp.
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Old 09-24-2010, 06:24 PM
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Good info on the cam most of the proublems people have that I have read are with flat tappet cams. I figured the 049 heads would work really well in a street motor gonna change to 219 188 valve and do some mild work hoping to only spend a few hundred bucks. Aftermarkets would be nice but the are about 1500 to 2000 and a lot are rect and a little more then I think I need. I have been told the 049 are more then enough for my application. 450 to 500 is my goal I think that would be a great engine and be a lot of fun. Around 500 tq would be great and I don't think it would be to hard to handle on the street. As always thanks for the info and any advice is always welcome
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