Hey guys
I have a 350 punched 30 over with 435/456 cam, Edelbrock manifold, flat top 9:1 pistons and MSD Ignition...Question is I have a Holley 600 vac.secondaries but the motor seems to starving for fuel with this carb.....Can this Carb. be rejetted for this motor or do I go get a 750cfm? also vaccuum secondaries or mechanical......

I'm not real clear on exactly what cam you have on this engine and you don't mention what heads. But 600 cfm should be fine if it is a fairly mild engine. There are a couple cheap things I would try before switching carbs anyway.

1. Try using a lighter spring in the secondaries. Just pull the round cap off the back passenger side of the carb and swap in a lighter spring - they make a kit that sells for around $10 if I remember correctly.

2. Rejet the carb if the mixture is off. Are your plugs sooty and black all the time? (too rich) Or are they bright white and clean? (too lean). They should be a light tan color. You can change the fuel mix by changing jets. Of course you want to make sure the float levels are set right and the idle mixture screws are set right before you swap jets out.

Finally - specifically, what is the car doing/not doing that you don't like? You say starving for fuel but do you mean that the car misses or bogs? Does it happen at high RPM, off the line, etc.

Hey Eric68,
The heads are stock and had total rebuilt...valves, springs, seats etc..The Cam is 209/274 DUR. 435"/456"....
As far as what the motor is doing, It's a fresh rebuilt, it has less then 20 minuts on it so I havent taken it out driving. The motor is idleing great its when I rev it over 2000 rpm it bogs down and starts to backfire through the carb (Checked power valve, its working)...Also #8 cylender header tube glows a faint orange...
I'm not getting any smoking out of the exhaust, matter of fact I can put my face behind the tail pipes and no burning of the eyes.. Hope this info helps out......

Check your plugs and check for the conditions Eric told you, BUT...

Sounds timing related to me...

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79' Z28 4-spd- built 355, TRW 10:1 forged flat tops, WP SportsmanII heads, Crane Energizer 230/230 duration .480"/.480" lift, Edelbrock Victor Jr., Holley 750cfm, Dynomax headers, dual 3" flowmasters :) 3.73 Posi 10-bolt

Joesmith69,
I have the timing set at 12 deg.
I'll check the plugs to see if they are sooty/blacken...
I'm just getting conflicting story's
My friends are telling me I "hafta" go with a 750cfm and Ramchargers are saying rejet the 600...If I know forsure the 750 would work with this engine combo,I'd buy the carb and just sell the 600. Damn Carbs can be a pain in the @$$.

Have you double checked your valves? You may have one that is too tight - the cylinder that is making the header glow maybe? Make sure you follow the break in procedure for the cam carefully - you could wipe a cam lobe if you don't.

Yes, could also be timing - that's what I was kind of thinking initially, and is why I asked exactly what the symptom is.

There's more to the timing issue than just setting the initial timing. The advance curve will affect your midrange power quite a bit - especially if the mechanical advance mechanism is sticking or if it was "recurved" with the wrong springs. I once had a sticking mechanical advance and the car would fall on its face at 3500 RPM and then run like a banchee above 4000 RPM.

With stock heads and a mild cam your 600 is fine. Everyone tends to think bigger is better when it comes to carbs. In reality a 750 would probably be too big for your engine and you would wind up having to jet the 750 leaner to make it run right.


[This message has been edited by Eric68 (edited 03-20-2002).]

a lean condition or vacuum leak causes your headers to glow
shane

First, the 600 should be just fine on your motor, the 750 will be way too much!
Sounds to me like you are getting way too lean as you suspected and that can cause a lean mis-fire which is what I think is coming back through the carb. Also, a lean condition will heat the headers so they glow also. You didn't say which model or list # (the number stamped on the front of the choke airhorn), but you should be able to rejet it just fine.

You indicated 12 degrees advanced at idle, but what about at 2,000 rpms where you said it has problems? If the mechanical advance is too much, the timing will jump too high and cause problems.

One other thing you mentioned was the Edelbrock manifold... is it a square-bore or spread-bore type? If it is a spread-bore, do you have an adapter plate for the Holley carb on there? You need it!

Check those plugs! Then let us know...

Good luck,
Bill C.


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Bill C.
Colorado Springs, CO

68 Camaro... someday!
71 Chevelle SS
70 Nova

OK guys, I found the problem,
Snap-on timing light.....
I had a friend come over today to check out my problem and he saw I was using a Snap-on timing light and he told me that they show incorrect readings when using a MSD ignition.
So I called MSD and they confirmed that. He went home and got his Autozone light and holy crap, that motor came to life!
Thanks for all your replies http://www.camaros.net/forum/biggrin.gif