Low engine vacuum. Poor idle.

[hurleygo3]

I'm in need of some help. I'm having issues with getting my motor to idle. Specs are 2000 block, 7120 head, Harlan Sharp, banks header, rockers hesco 274 cam. Running the 2000 stock injection. Issue is it runs great off idle. Won't idle when hot. Afr at idle is about 10.5 and has very little vacuum 10-11. I think the issue is the low vacuum causing issue with the MAP sensor. Would advancing the cam help? Or should I put the stock cam back in? Would a MAP adjust help this issue?

Looking at this adjuster.
https://splitsec.com/wp-content/uploads ... r_inst.pdf
H-274

274
224
108°-112°
480
Hi-performance street - fair vacuum - healthy exhaust sound

[Cheromaniac]

The low vacuum is definitely playing tricks on the MAP sensor but even the Hesco H274 cam should produce more than 10-11"Hg of vacuum at idle.
You almost certainly have a vacuum leak so I think you should start by searching for the source.

[hurleygo3]

I spoke with Bennie at Hesco. He also said that cam should be running more vacuum.

[SilverXJ]

Vacuum leak or some other problem. Did you degree the cam in? Did you check push rod length? The MAP adjuster won't fix your problem.

[cruiser54]

Are you running a catalytic converter?

Could you have an exhaust restriction? There's a vacuum test specifically for that.

[hurleygo3]

Ended up pulling motor and installing a stock one for the race. Push rod length was good, no vacuum leaks, exhaust is wide open. Cam was not degreed. Cam timing is going to get checked here soon. Possible it was one tooth retarded. Should know here soon.

[SilverXJ]

That is what I think it is.

[hurleygo3]

Well. I'm still having the same issues. I installed a new stroker build and I'm still having the vacuum issues. Low bouncing vacuum. 6-8"
This is a new new build but used the same head and same cam. 7120 head with cambers cleaned up and a Hesco 274.
Motor runs good, has a flashed ECM. But it heats up when you get into it. Runs cool at ides or cruising.

[christuned]

Did you degree the cam ? What is the intake centerline ?

[hurleygo3]

Did you degree the cam ? What is the intake centerline ?

It came in at 116*
Hesco calls for 108-112

That is with the cam installed straight up. Compression is 150 across all cylinders.

[jeepxj3]

1 tooth is how many degrees?

[christuned]

Did you degree the cam ? What is the intake centerline ?

It came in at 116*
Hesco calls for 108-112

That is with the cam installed straight up. Compression is 150 across all cylinders.

The cam being that retarded is a problem, did you use a stock replacement timing set or a roller set ? Do you have a specific part number ? You definitely want the cam in the 108-110 ICL range.

Also 150 cranking compression is low, getting the cam timing corrected should bring that up a bunch.

[hurleygo3]

This is the chain I'm using. Closes double roller.
http://www.summitracing.com/search/bran ... leSwitchNo

Hesco also thinks the cam is one tooth retarded. Hope to move it tonight and redegree.

[jsawduste]

Mike, cut and pasted from your link.

UPC:
750385701459
Timing Chain Style:
Double roller

Maximum Advance/Retard at Camshaft:
2 degree

Maximum Advance/Retard at Crankshaft:
4 degree

Several options here. Plenty of ways to install it and very possible to have it retarded. My 14 inches is with it advanced 4 degrees. Same setup as the dyno sheets.

[christuned]

Mike, cut and pasted from your link.

UPC:
750385701459
Timing Chain Style:
Double roller

Maximum Advance/Retard at Camshaft:
2 degree

Maximum Advance/Retard at Crankshaft:
4 degree

Several options here. Plenty of ways to install it and very possible to have it retarded. My 14 inches is with it advanced 4 degrees. Same setup as the dyno sheets.

Did you degree it when installing, if so what did it come it at after you advanced it four degrees?