I am thinking about using fast burns on my 77 L-48 350... these are low compression motors that hardley push any AIR.... If you have used these heads on your factory 350 and have any dyno numbers please report them with other mods....

If I keep m orginal l-48 block I am looking for 300-325 rwhp so I will need to make a 375-400Hp 350. This way I can keep up with modern day cars and run low 13s

 

Fast Burns are too big for what you want to do, imo. I would use Vortecs instead. The FB heads have a 210cc intake runner and are really suited to high-RPM 350's or a bigger cube small block like a 406. I ran home-ported Vortecs on my 0.060"-over 400 (413) in my '77 Z28 and hit a 12.15 on drag radials, launching from a dead idle. With more RPM on the launch I could have no doubt hit an 11.90. The motor was a budget rebuild with KB hyper flat-top pistons, unported RPM intake, cheap Crane Blazer cam and lifter kit (234/244), home-modified 3310 Holley, 1 3/4" cermaic coated Hedman headers and dual 3" exhaust with race Flowmasters. I think it was CHP magazine that did a build-up on a junkyard 350 with stock Vortecs, Comp hyd cam and 750 Holley, and made 395HP or so on the dyno. Vortecs have tremendous low-lift flow #s (even better than the FB heads) and thats what makes them so deadly with an under .500" lift street cam.

 

that is a ver good point I will not have over .500 lift on my camshaft... so low RPM are important... but so are flow numbers across the board. I LIKE the AFR 195 the best... AWESOME low in flow and mid range...perfect for what I want...but the smallest chamber they have is 68cc... I need to go smaller than that to build compression.

I have a stock headed L-48 with smog 78cc heads and comp 270 cam....it makes about 8.8 compression. Trying to get to high 9's or low 10's with my compression ratio... w/o swapping out pistons. Block has not been cut orginal standard bore.

 

that is a ver good point I will not have over .500 lift on my camshaft... so low RPM are important... but so are flow numbers across the board.

Low-lift flow @s are important for a wide-torque band from the engine. The valve hits peak lift only once in the cycle, but traverses the lower lift ranges twice. Vortecs have fantastic flow numbers right through .500" lift, stalling (in unported form) around .550".

The Vortecs have a 62cc chamber. You should hit somewhere around 10:1 CR with them. You can also use a FelPro 1094 .010" steel shim headgasket to help with compression and a bit better quench.

 

CHeck out this link.

http://purplesagetradingpost.com/sum...%20Fast%20Burn

YOu can see the vortec are only better at .200 The rest of the time the AFR have the better flow number. It is just the darn chambers? I figure I maybe at 9.5 at beast with a 68cc from a 78cc chamber.

 

I think your compression calculations are too optimistic. I'd figure closer to 8.4:1 for a stock-headed motor. Consider, too, that the factory put .015" shim gaskets in, and if you pull the heads, you'll surely do at least .028 (a shim isn't sealing without milling the block deck). Expect about 9.5:1 with the 62cc Vortecs.

You can get a set of Vortecs for $600, tops. You'll pay twice that, at least, for the AFRs. Are you going to get twice your money's worth? If you intend to really build this engine someday, the AFRs may be a decent choice. But, if you intend to call it quits here, then go with the Vortecs.

Comp XE268, Vortecs, and matching RPM manifold for Vortecs, is about as good as you'll do, without tearing into the short block. You might get low 13s out of it, in that '77 Vette (keep in mind, those Vettes were even heavier than the Camaros of that year!).

Todd

 

I'm not arguing whether or not AFR is the better head - you started this thread asking about Fast Burns for your application, not AFR's.

 

Your guys are both right....I did start with fast burns and the vette is a 3500lb car....

I have been ttrying to research all these choices on the net to make the best call and heads... and I the future I will out grow the vortecs. I have seen some impressive numbers but I really am looking closely at the flow numbers from .200-.500

http://purplesagetradingpost.com/sum...%20Fast%20Burn

see this link...

as for compression I justed checked factory is only 8.5 to 1

so I need to figure out what will get me just over 9.5 to 1 or 10 to 1 w/o getting pistons.