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ddhens 11-09-2007 01:18 PM

406 rebuild questions...
 
I’ve been lurking/reading here for a while now, but this is my first post. I recently bought a ’73 Vette that I’m going to restore that has a 406 small block. The previous owner said he mainly ran 1/8 mile with it. When I rebuild the motor, I’d like to make it a little more mellow for street driving. The car does run great and the compression check ranged from 162-172. Can I get away with just a milder cam kit? I called Comp Cams. They suggested a 12-211-2 or maybe a 12-240-4 (to help with the vacuum). Maybe I should also be looking at swapping out the single plane intake? I’ll never take it to the strip…only around town weekend driving. I appreciate any help…

Here’s the current setup...

406 small block (1970 400 +.030)
9:1 compression (per previous owner)
Speed Pro 7066P pistons
Competition Cams 12-214-4 (http://www.compcams.com/Technical/Se...umber=12-214-4)
Rhoads Lifters
Victor Jr. 2975 Intake
Holley 800 CFM #4780-2
Open chamber (smog) heads 2.02/1.60
HEI dist, Accel Supercoil, MSD 6AL
Headers
Super T-10 trans.
3.70 rearend

oldbogie 11-09-2007 05:38 PM

Quote:

Originally Posted by ddhens
I?ve been lurking/reading here for a while now, but this is my first post. I recently bought a ?73 Vette that I?m going to restore that has a 406 small block. The previous owner said he mainly ran 1/8 mile with it. When I rebuild the motor, I?d like to make it a little more mellow for street driving. The car does run great and the compression check ranged from 162-172. Can I get away with just a milder cam kit? I called Comp Cams. They suggested a 12-211-2 or maybe a 12-240-4 (to help with the vacuum). Maybe I should also be looking at swapping out the single plane intake? I?ll never take it to the strip?only around town weekend driving. I appreciate any help?

Here?s the current setup...

406 small block (1970 400 +.030)
9:1 compression (per previous owner)
Speed Pro 7066P pistons
Competition Cams 12-214-4 (http://www.compcams.com/Technical/Se...umber=12-214-4)
Rhoads Lifters
Victor Jr. 2975 Intake
Holley 800 CFM #4780-2
Open chamber (smog) heads 2.02/1.60
HEI dist, Accel Supercoil, MSD 6AL
Headers
Super T-10 trans.
3.70 rearend

Ya know the Rhoads lifters calm the cam a bit, I'm not so sure I jump in and change it, especially with a manual gear box behind the engine, you can manage the RPM range a lot easier that with an automatic. A performer dual plane air gap would probably build up some bottom end, that could let you get away with an axle gear ratio reduction without hurting street performance and pick up cruising mileage from a tank of gas. Or put a T56 in it for the OD and leave the 3.70s.

Overall this sounds like a nice combo, I wouldn't rush in to make changes.

Bogie

F-BIRD'88 11-10-2007 05:52 AM

pass on the 305H cam and rhoads lifters.

Instead use a Comp Xe284H-10 12-250-3 cam and conventional hyd lifters.
Consider using a RPM type manifold. Will give up but a few few top end ponies but add a lot of mid range torque right where you'll be using it the most.

This combo will make plenty of power yet will drive a lot lot nicer.
Trying to tame a big race cam with rhoads lifters is snot going to work for ya.

if you were to swap the old smogger heads for a AFR 195 Eliminator head, you would think you'd bolted on a afterburner.

reuse the 800cfm carb
swap to a RPM hi rise dual plane manifold
swap the 305H cam and lifters for a Comp XE284H-10 can and hyd lifters
change the cylinder heads A brodix IK200 is a very good head also.
I could not find the specs on your pistons. If flat top use a 70cc head.
if dished use a 64cc head.
With the ignition timing set up properly, your power brakes will function fine.
it will still have the bad boy idle but will be a lot nicer to drive overall.
It will be much faster.

ddhens 11-10-2007 02:34 PM

Thanks for the feedback. I couldn't find any info on the pistons either, but the po definitely says they're flat top. I really hadn't planned on swapping out the heads at this time at $1000-1500, so I'll probably just look at the cam and intake for now. And, if I was going to be doing much highway driving the 3.70s would have to go...but for around town they're ok.

F-BIRD'88 11-10-2007 11:03 PM

Quote:

Originally Posted by ddhens
Thanks for the feedback. I couldn't find any info on the pistons either, but the po definitely says they're flat top. I really hadn't planned on swapping out the heads at this time at $1000-1500, so I'll probably just look at the cam and intake for now. And, if I was going to be doing much highway driving the 3.70s would have to go...but for around town they're ok.

Don;t change the gears. A motor with a cam like that will not be happy with a lower gear. 3.70's are your best gear overall for what you use your car for.
If you want to slow the hwy cruise rpm down a bit go to a taller 28" tire P235-70-15


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