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post #1 of 5 (permalink) Old 01-04-2008, 12:21 AM Thread Starter
Join Date: Dec 2007
Posts: 7

I currently have a low compression 350 short block in my 68 impala. It has the 291 camel hump heads (1.94/1.5), stock (929) cam, rpm intake and Q-Jet. I just converted to a saginaw 4 speed and the car has 3.36 posi out back. The 4 gear is fun, but runs out of steam around 4,000 rpm. I eventually plan on building the original 327 to L79 specs, but in the meantime I'm debating about either putting the GMPP 350 HO cam in this engine or... now you'll know I'm crazy.. I also have a 69 307 short block in good condition. I have thought about "something different" and putting the 291 heads on it, and then going with either the 350 HO cam or the old 097 Duntov solid cam. I also plan on adding headers (car already has 2.5"duals), and would use the rpm intake. I know it's a heavy car and it has A/C, so don't want to get too crazy with the cam.
Also looking for advice on cylinder heads. I have a pair of Aerohead 434 castings with 1.94's, screw-in studs, etc., but feel the 291's are probably a better head. Also have a pair of 487's, but that would drop the cr too low. Just curious of the flow characteristics between the heads.
Looking for any and all opinions.
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post #2 of 5 (permalink) Old 01-04-2008, 02:37 PM Thread Starter
Join Date: Dec 2007
Posts: 7
..answer my own question here, After some thought, drive it as is. Next winter make the 350 a 383 with some good heads (bowtie vortec or edelbrocks). May go back to the turbo 350 trans as well. Saginaw probably won't handle the torque. Sure sign of old age, answer your own questions!
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post #3 of 5 (permalink) Old 01-05-2008, 02:04 AM
Join Date: Jan 2006
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You are going in the wrong direction. You have a big car. It will not move any faster with the gears you have now. I have 4.56 gears in my rear. My street car has 3.73:1 rear gears but it has a 3.08:1 first gear in the four speed box and it will wind to 6,400 with the heads and cam I have installed (this is in a 500 horse SBC 400).

You need one of two things to accelerate. Steeper gears and more of them, or more torque from a bigger, not smaller motor. As to SBC heads, find a buyer for those old camel hump heads that wants to give them a good home in some numbers matching museum piece. Technology has passed them by decades ago. The Vortec head (stock Chevy pick-up truck head found on every 350 made between 1987 and 1995) is what you want, and buy a Vortec single four barrel intake manifold as they bolt up differently than the old heads. Stock Chevy Vortecs will out flow every aftermarket head made (with some simple home brewed pocket porting) up until you get above 0.400" valve lift (how many of us run over 0.500" of valve lift). The new Vortec head has self guying rocker arms (different than the old small block that had a guide plate), and it is limited by the valve spring and seal to a max of 0.420" of valve lift unless you modify the head (machine work usually costs around a hundred). Heads are what make power in an engine by flowing air. The cam determines where in the RPM band the engine will make that power (the valve train also limits how high it will rev).

If you have money to burn buy a BBC and drop it in your car. More cubes makes more power down low where you need it on the street. If you want to hear the motor sing High "C" you will have to start putting quite a bit of money into not only the motor but the drive train to support the shock of the hit from a high winding mouse.

Big Dave
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post #4 of 5 (permalink) Old 01-05-2008, 04:13 PM Thread Starter
Join Date: Dec 2007
Posts: 7
Big Dave,
My mistake, should have put this in the "engine" thread. This car is a daily driver in the summer, and 1/4 mile times are not the #1 priority. I am also more into the nostalgia thing - that was the solid cam / short stoke idea.
I did have a 427 in this car, but pulled it with $3/gallon gas prices plus it makes the car nose - heavy and hurts what little handling it has.
For me, a nice small block that will pull 5,000 - 5,800 rpm and a 4 speed is the definition of F-U-N. - plus the fact that I don't feel guilty about spending the money for gas to drive it to work.
I sold a 72 Chevelle last spring that had an 87 octaine 350, with the afore-mentioned GMPP cam, headers, holley carb, 4-speed and 3.08 gear -a 15 sec car that was fun to drive and got 17 mpg. Probably boring to some, but practical to me.
Got the info I needed on the heads, 434's are junk - terrible exhaust ports. 291's and 487's are about par for flow, just the difference in chambers.
I agree about the heavy car, cubes and torque, and if I was into that, and wanted to spend a lot of money, then there's the 592 BB or 454 sbc and the rest of the drivetrain. Personally, I like the challenge, and get a lot more satisfaction, of doing "something with nothing". I get a bigger grin out of running 15's or 14's with a 327 than 10's with a big block.
We had a guy here in Michigan with a 68 sports sedan like mine running 12.3's with a 327 / glide (and yes, camel hump heads, and... to your point- steep gears). Now that impressed the crap out of me! Most folks thought for sure it was a 427 car.
BTW - the Imp isn't much heavier than a Chevelle or late 70's F-car.
thanks, I do apprciate your comments and post.
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post #5 of 5 (permalink) Old 01-05-2008, 11:28 PM
Join Date: Jan 2006
Posts: 13,007
My favorite SBC is the 377 cid. Thirty over 400 SBC with 350 forged chromemoly crank big heads and a bigger solid roller cam. 4.88 rear gears and a T-56 six speed tranny to row through. That seems to me to be ideal for what you are looking for. Agree the B-body gets progressively bigger and heavier up to 1977 then it only got heavier.

Big Dave
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