After putting on 58cc aluminum heads with 190cc runners, 2.02/1.60 valves, a Weiand team g single plane intake, a comp cams 286magnum & stainless 1.5 roller rockers The .030" 327 will not idle below about 1,200 rpm and only can give it WOT above 3,000rpm. I plugged the gauge into the manifold vacuum port and left the ported vac line going to my distributor on. The gauge read about 10"-12" at best and shot up to 20"-25" when revved (normal?).
Did I use the gauge right? Also I know of at least 3 places the intake is leaking from, This weekend I will pull the single plane and replace it with a dual plane edelbrock eps, on top of low vacuum I don't think the single plane is helping. By putting on the dual plane I think it will solve the no idle below 1,200 rpm.
What do you guys think about the intake swap, and about the current vacuum readings? Did I use the gauge correctly?

Someone once told me, big cam and heads on a 327= no idle. I believe that is complete b/s, I know of people running around with bone stock 282" motors with comp cams 292magnum and bigger...

If you got vacuum readings, you used it correctly.

Yes the vac will rise when piston speed increases and load stays at nil. The time period in milliseconds for overlap to occur also decreases when revved, so reversion decreases some. That's why engines with larger cams smooth out at higher rpm. Mine smooths out around 4k. Might even HAVE vacuum then:D.

Update
I had the timing set around 16-18 initial at idle (1,200rpm) So I remembered reading about using a vacuum gauge to set idle timing and mixture, I began playing with the mixture screws and was able to lower the throttle to a much more reasonable 800-1,000 (oscillating) and when I lowered the rpm to 800 I noticed the vacuum gauge held steady at 5" which is very low, So I then advanced the dizzy more (i'm assuming since I dropped the idle rpm the advance went with it) I didn't use a timing light but I'd say I'm around 8"-10" of vacuum at 800rpm ball park guess is initial timing is around 16-20* (is this okay?). Not bad but when I turn on the head lights the idle goes down even more, goes to around 700 and oscillates to around 900 slowly. I will pull the single plane intake and replace with better gaskets a dual plane and report back. Though there's vacuum leaks and the idle oscillates, It's better than it has been, but we will see if this holds out.

Also I had to turn the mixture screws out quite a bit and can wiggle them with my hands (back and forth), Is there a possibility they could pop out while driving?

[quote=ace's68;10631

Someone once told me, big cam and heads on a 327= no idle. I believe that is complete b/s, I know of people running around with bone stock 282" motors with comp cams 292magnum and bigger...[/quote]

Define no idle.How is a 283 with a 292 magnum bone stock?A big cam and big heads will have an effect on idle speed.the low port velocity and reversion issues will result in lower manifold vac numbers and have a weaker signal underneath the carb..all adding up to an increase in curb idle rpm to crutch it.

John, you really can't guess about timing, put the light on it. If you know you have vacuum leaks, fix them first. The vacuum gauge will read very high when decelerating (after you blip the throttle, as the revs are falling back to idle)

Define no idle.How is a 283 with a 292 magnum bone stock?A big cam and big heads will have an effect on idle speed.the low port velocity and reversion issues will result in lower manifold vac numbers and have a weaker signal underneath the carb..all adding up to an increase in curb idle rpm to crutch it.
Meaning not at a reasonable idle speed on a modded car 700-900, not talking 1,500rpm like dragsters idle. lol.
I can see how you got confused when I said bone stock 283 with a 292 cam. I mean everything else on the motor is original, stock parts other than throwing too large of a bump stick in it. Many people around here do there engine matching by what sounds good, example, throwing a 292 in every ones stock motor.

I bet when I put the dual plane on the manifold vac will rise and will be better at idle and more steady. Your right, big ports, big cam, big single plane= more idle speed to bring up vacuum, which is why I will be switching to the dual plane.

John, you really can't guess about timing, put the light on it. If you know you have vacuum leaks, fix them first. The vacuum gauge will read very high when decelerating (after you blip the throttle, as the revs are falling back to idle)
I will have the correct gaskets and timing tape at my disposal in less than a week, So I will be able to fix the leaks, hopefully, it is hard due to the heads being milled and the block decked (intake does not fit well) and will know the timing at idle and all in.

I will have the correct gaskets and timing tape at my disposal in less than a week, So I will be able to fix the leaks, hopefully, it is hard due to the heads being milled and the block decked (intake does not fit well) and will know the timing at idle and all in.

I have had to hog out the boltholes in intakes. It's not a crime:). In fact some intakes come from the maker with oblonged holes. Do a dry fit before you make the end seals, and look in the carb flange towards the intake ports. You want that to be a smooth intersection. Probly can't see it on the dual plane though.

I have also had to hog out intake bolt holes.

Milling heads / block doesn't change any angles, it only puts the boltholes in the heads lower than the boltholes in the intake. Hog out the intake holes until the bolts will screw in without toughing the edges of the holes, things will fit much better.