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Topic: C3 Engine Advice

in Forum: C3 Engines


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C3 Engine Advice

Posted: 8/22/05 8:24am Message 1 of 6
ezobens
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Grayslake, IL - USA
Joined: 3/15/2004
Posts: 33
Vette(s): 1969 C3 Coupe. Was an L-46 now a ZZ3 w/M-21 4-speed, manual steering and brakes, 3.70 Posi. Red with Balck interior, non-numbers matching.

I have a 69' Coupe with a ZZ3 small block and a M-20 4-speed with a 3.70 axle.
Being accustomed to driving big-block vehicles most of my life, I am somewhat disappointed with the level of performance of my ZZ3- Mainly low end torque.
I have recently aquired a 400 CI small block from a 71' Chevrolet (4-bolt main) that I am considering using for the basis for the C3. Tentatively, I am thinking about using the 400 short block (with the low comp dished pistons) and putting on the 58cc aluminum ZZ3 heads to bump compression to around 9.5, along with the ZZ3 aluminum intake/carb.
The questions I have are:
Has anyone done this before and what was the result?
What would be the best cam selection for this combination (I want great low and mid range torque- The motor would never go above 5500 rpm)?
Does GM or anyone else make a 153 tooth flywheel for the 400 small block (externally balanced)?
I just put a new 10.5 clutch in about 300 miles ago and would like to avoid having to convert clutch/bellhousing/starter for the 168 tooth flywheel.
Any tips or advice would be GREATLY apprecited!
Thanks,
Elm




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C3 Engine Advice

Posted: 8/22/05 7:10pm Message 2 of 6
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Adams' Apple
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Duncanville, TX - USA
Joined: 11/8/2003
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Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas
Don't know about the configuration of the ZZ3 heads, but the 400 small block uses a different water passage in the block than a 350, and also in the heads. If you use regular 350 heads on a 400 block, it will overheat. You can, tho, drill the correct holes in the heads to match the "steam" holes in the 400 block.
The flywheel should be available from the aftermarket, such as Jegs, or Summit.


Joel Adams
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C3 Engine Advice

Posted: 8/23/05 6:12am Message 3 of 6
ezobens
Former Member
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Grayslake, IL - USA
Joined: 3/15/2004
Posts: 33
Vette(s): 1969 C3 Coupe. Was an L-46 now a ZZ3 w/M-21 4-speed, manual steering and brakes, 3.70 Posi. Red with Balck interior, non-numbers matching.

Joel,

Thanks for the reply!

From what I understand, the 400 block is identical to any other small block except for the rod length, main bearing diameter and siamesed bore configuration- Due to the siamesed bore, additional 'steam' holes were added to the 400 heads. As long as I have the steam holes in the replacement heads, any Gen I small block head will work (chamber volumes obviously would need to be compatable for the compression I am looking for). With the stock 8.5 dished pistons and the 58cc ZZ3 heads, I should get around 9.5 CR- give or take a point or two.

Thanks again!

Elm




C3 Engine Advice

Posted: 8/23/05 11:06pm Message 4 of 6
anips
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sonoma, CA - USA
Joined: 8/9/2002
Posts: 784
Vette(s): 72 LT-1 AC coupe,69 l-36 coupe
I kinda like the 400 idea, you would probley want to go with a new block, you can't bore them very far and if you do they might want to run hot, the 400 in my 79 air cond. pick up came with a four row big block factory radiator, stock compression is 8 1/2 to 1 with a 4.125 stock bore, the only other question other than the steam holes would be is if these heads are the ones you should run,they are a good head but they do have limitations, the small valves, and considerable porting required for engines over 330 hp, because these heads were designed for fuel injection they don't have heat riser passages, for a carburated engine you need a little heat at the bottom of the intake so the fuel stays vaporized, liquid fuel doesn't burn well, in cool to moderate weather you might have driveability problems, although because of all the heat under the C-3 hood they may work fine.


C3 Engine Advice

Posted: 8/24/05 5:31am Message 5 of 6
ezobens
Former Member
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Grayslake, IL - USA
Joined: 3/15/2004
Posts: 33
Vette(s): 1969 C3 Coupe. Was an L-46 now a ZZ3 w/M-21 4-speed, manual steering and brakes, 3.70 Posi. Red with Balck interior, non-numbers matching.

Thanks for the info!

With the amount of heat under the C3 hood, I don't think heat in the intake will be an issue- I usually have more of an issue keeping the heat out ;-) Most of the V-8s I run have the crossovers blocked with no issues.

The reason for the ZZ3 heads is strictly financial and convenience. Since I already have a complete ZZ3 motor with maybe 5000 total miles on it, using the heads from this motor is a 'quick-n-dirty' way of bumping compression out of the 8.5 CR 400. Since I don't really wind these things out anyway and prefer to have my fun from idle to around 4000 RPM, I think the small valves will help in my search for low end grunt. My only quest now is for what cam would be the best for this configuration? A hydraulic roller cam would be trick but too expensive for what I really need. I've been toying with the old Duntov 30-30 mechanical cam idea as well just because I love the sound- But I'm not sure that is a wise decision either.

Thanks again!

Elm




C3 Engine Advice

Posted: 8/24/05 6:54am Message 6 of 6
anips
Former Member
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sonoma, CA - USA
Joined: 8/9/2002
Posts: 784
Vette(s): 72 LT-1 AC coupe,69 l-36 coupe
The good ole 30-30, the last time I used one I was in high school, I think you could have bought the cam and lifters for like 60-70 bucks, with the big valve lash it seemed to beat the hell out of the valve train, if you like the sound of a solid lifter motor how about a good dirt track cam, you need the motor to respond at low RPM coming out of the turns on a heavy track, a cam with maybe 108-110 degs. of lobe separation for good low and mid range torque might be the ticket, or do I dare say it, an RV cam ? a corvette is an RV in a way isn't it? anips38588.8564467593


in Forum: C3 Engines


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