finally finished my heads, cam, etc install on my new to me 80. i have a whopping 7.5 inches of vacuum @ idle now. car runs great, idle sounds awesome & revs faster than any hydraulic cammed engine i've ever heard. idles at 850rpms.

even though the vacuum is low, the brakes work fine. however, the headlights wont open without help. how much vacuum is actually needed to operate the headlights? do any of you guys know where i can get an electric vacuum pump?

i also have a distributor problem to overcome. i have way too much advance. im getting 35* in the distributor. in other words , if i set it for 12* initial , i have 47* by 3000rpms. not sure whats missing in there, but it has definately been modified.

quick recap of everything i did ... did the performer rpm e-tec package minus edelbrocks heads. i used my own modified vortec heads. also installed the accessory drive system off a 94 chevy truck, which i must say is pretty sweet.

what it had ( i discovered upon tear down). engine had been rebuilt some 30,000 miles ago. found true .030" over flat top pistons and double hump heads. the heads b.t.w. had accessory bracket holes drilled thru them. emphasis on the word "thru". wonder why it had an oil leak or two. :lol:

sorry for the long post. please give me all your comments , advise, etc.

 

If it has the HEI distributor, there is a bushing on a pin in the advance mechanism that limits the amount of centrifugal advance. It sounds like the bushing is gone. That is too much advance of any set up. You can install a bushing or braze up the slot it rides in.

That vacuum sound awfully low for a Performer RPM cam. You might check with Edelbrock to see if that is normal.

There are vacuum reservoirs you can install to help overcome the weak vacuum. There may be vac pumps, but *I* am not familiar with them. Good luck, and...

RACE ON!!!

 

edelbrock advertises 10"-12" of vacuum. i dont really know what could make the vacuum low other than the cam though.? its not jumping around like the valves are not seating. very steady.
the cam is an unusual grind though.
308 int.-318 ex. advertised.
234 int.-244 ex. @ .050
.488 int.-.510 ex. lift.
112* lobe sep
107* centerline

 

I didn't look up the specs on the cam before I commented. I was under the impression it was milder than that. With Edelbrock's spec of 10"-12", you are not near as far off as *I* was thinking. Good luck, and...

RACE ON!!!

 

Sounds hot!!!!!
:rolleyes:

 

Anybody remember Rhoders lifters? I think they used to bleed off at low rpm and help tame out the cam. I remember they helped my buddies big block GTO but they clicked at idle. Just a thought.

 

I used Rhodes lifters when building my 383. Never had the opportunity to dyno the engine but my logic was they may help broaden the torque curve. Mine don't click. Your buddy may need to reset valve lash with the engine running. An old pair of cut-out valve covers will help keep oil off the exhaust while doing this.

Lowcountry Corvette
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