Vacuum reading w/ cams

[usmcah-1w]

Just recently installed my speedhut boost/vacuum gauge and at idle it is reading 10 in of vacuum. I have been searching but can not find a definite answer. I do have stage 3 comp cams and recently installed a 2.9 whipple. My idle is fluctuating or surging from 750-1000 when warm and the vacuum readings surge between 10-12 with the idle. Can someone give me a definite answer on what the readings should be?


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[racebronco2]

Did you set the cams per manufacturer recommendation?

 

[usmcah-1w]

They were installed during motor being built so I am assuming they were installed per manufacture recommendation.


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[MG0h3]

I dont have experience with cams in these cars or how extreme yours are but that sounds a bit low. I know Malcolm had some issues with his boost bypass valve fluttering so maybe search for that thread.

 

[04MystiCobra]

Consider posting up how they were installed and the actual specs to get better feedback. Advanced/retarded X amount, straight up, lift duration etc.

 

[cj428mach]

I'd talk to Malcolm, I think he told me when he had his really large cams (may have been stage 3) he had like 8" of vacuum. I believe he ended up going smaller cams and setting them up with a lot wider LSA so the car would run decent.

You probably just found out the one thing no one ever mentions about big, lopey cams is that they really suck to drive. I've dealt with it on other cars and decided to never do it again, after hearing about how the boost dump valve is effected by the low vacuum on these cars i can see it would be a nightmare.

My best suggest is pick Malcolms brain, as he had his blower on and off many times playing with the boost bypass valve to try to get it to work decently on his car. You might save a lot of time and headache. I hope its something you can get to run decently.

 

[usmcah-1w]

I'm pretty sure the cams were installed per manufacture specs. I had a 2.3 whipple installed before and it did have a surging idle when warm but did not know if it was from the cams, vacuum leak or the hiboost intake. I installed the 2.9 whipple and the surging seemed to be noticeable and even died when coming to a stop etc. The 2.3 was never that bad but here recently I got my speedhut boost gauge and installed and noticed the reading was what seemed low to me at 10-12 in so I was thinking maybe a vacuum leak could be causing this.


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[xxjaymanzxx]

I have stage 2 custom cams and it idles 14-16 vacuum

 

[s351]

Turbo car here, with cams my idle vac is between 10-13 depending on rpm my tune needs to be adjusted but when my car idles in the 700's it makes like 9-10

 

[olympic]

I have Crower Stage 4's and vacuum is around 10" at idle.

 

[usmcah-1w]

Mine is reading 10" so I have been searching for a leak the past two days. But since a lot of people seem to have lower readings with cams would this be normal?


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[04MystiCobra]

Depending on the cam duration, overlap etc., how they were degreed/installed (advanced/retarded/straight up) and idle rpm you could be ok. I've always been under 10" with the cams I've run. My current setup is ~7".

 

[04cobraken]

Stage 3 Comps here with 2.9 Whipple and I'm around 10-12in vac as well. Seems to be the norm.