CyprusMustang

I just changed head gaskets and had the heads ported as I was getting pressure in coolant and overheating. Turns out a piece of head gasket went out and was leaking.

Anyway I had the heads pressure tested for cracks and Vaccum tested for leaky valves turns out all ok.

I install them back to the car and car doesn't ovwrheat anymore and coolant flows nicely. However I'm trying to get the idle perfect and I cant. I always had an issue with the idle. I purchased a vacuum guage from here but it's in bar and reads .0 to .8. The needle bounces rapidly back and forth from .6 to .7 which is 17.5 to 20.5 inches Hg.

I played with the timing and it seems to run best at around 16-17 degrees on the balancer.

There is a mid range cam installed, it's a 302 with edelbrock 600 carb, slightly higher aluminum intake manifold, it's been bored over once and has Patriot long tube headers.

Not sure what else I can test or try out. Any ideas guys?

barnett468

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plug the pcv port non the carb.

plug the distributor vacuum hose.

set timing to 12 btdc.

if you have a holley set the gas level so it is just below the gas inspection holes when it is idling.

adjust the fuel mix screws equally so the engine reaches the highest idle.

report results.

erratic vacuum is often leaking valves.

CyprusMustang

This is where I am now. All ports plugged, timing light is out and set at 12 starting point and idle is as best as possible. Yes it says that an erratic needleeqds to leaving valves but I had mine vacuum tested and all came out fine.

What now?

barnett468

well i check my own valves so i cant say much else . . in your case i would have checked them myself after the shop tested them just to be certain.

it can also be caused by valves that are adjusted too tight.

possibly an air leak.

67mustang302

If it has a cam, the idle won't be completely stable. Especially with more overlap.

CyprusMustang

My valves are torqued down so they are self adjusting. Question though, could this be due to longer or shorter push rods?

barnett468

you need to do this . . loosen rocker bolt until you can just get a .002" feeler gauge between the rocker and the valve stem tip.

count how many turns it takes to tighten the bolt . . if the bolt is fine thread and it takes more than 2 turns until its just barely snug, it is a little too much . . it may be ok but it may not . . it depends on your lifters.

if it takes 3 turns, it is definitely too much but again, it may be ok but it may not . . it depends on your lifters.

any more than 3 turns is ridiculous.
.

CyprusMustang

But that means it would be misfiring ... No? I don't have a feeler guage. Need to find one.

barnett468

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no it does not necessarily mean it would be misfiring.

CyprusMustang

I would have to do this while each cyl is at the top of compression stroke right?