[Nick915]

Trying to learn about carbs so bought an vacuum gauge to adjust the idle mixture ratio. Here is what I am getting at idle. Any ideas or is this reading ok? Gauge is from Harbor Freight so maybe it is bad?

Setup:

Engine fully warm, idle set to 800-850 rpm. Gauge hooked to small port underneath in front of carb. Engine (from what I am told) is a ZZ4 shortblock with Edelbrock RPM heads, intake, and assume the matching cam. Carb is Holley Street Avenger 670. Mixture screws are 1 full turn out.

Engine runs good and doesn't seem like there are any issues. Just checking things out, learning, and tinkering with it.

 

[CorkyE]

Looks like about 22 inches of vacuum. Someone else may have another opinion, but I'd leave it alone. Don't create a problem where you don't have one.

 

[Nick915]

Looks like about 22 inches of vacuum. Someone else may have another opinion, but I'd leave it alone. Don't create a problem where you don't have one.

Thanks for the advice! I just assumed it would have less vacuum due to the performance parts that are installed on the car. I guess the cam they put in is on the small side then.

 

[SoCal805]

2 words....walk away.

That is very good vacuum. If you wanted to check the gauge accuracy, use a Might Vac, with gauge, and compare readings to the HF gauge. FWIW I have the same HF gauge. My motor however only makes 16hg with a 220/224 cam at idle

 

[jcabuilder]

If it ain't broke don't fix it!

 

[ilikeike]

Looks like you have a good pump/engine.
I’m envious, I’m lucky to get 10”~12”.

 

[BillDini]

If you have an economy cam or stock cam its ok. I would suspect the gauge is off in that case. Incorrect timing can also cause that condition. 20 is normal for most stock engines. My stock L79 runs at 16 psig and my 71 350 with a roller cam that is hotter then stock idles at 15. Also rpm affects vacuum.

 

[Nick915]

If you have an economy cam or stock cam its ok. I would suspect the gauge is off in that case. Incorrect timing can also cause that condition. 20 is normal for most stock engines. My stock L79 runs at 16 psig and my 71 350 with a roller cam that is hotter then stock idles at 15. Also rpm affects vacuum.

I just assumed with all the other performance mods that were done (ZZ4 shortblock, Edelbrock heads/intake, Holley carb, TKO600, 3.73 gears) that a nice cam would have been put in too. Guess they stuck with a real mild cam. Car runs solid just always want more power.

Would love to get it dyno tuned but is tough to find anyone around here that can work on carbs and has a dyno.

 

[fairfax1000]

I just assumed with all the other performance mods that were done (ZZ4 shortblock, Edelbrock heads/intake, Holley carb, TKO600, 3.73 gears) that a nice cam would have been put in too. Guess they stuck with a real mild cam. Car runs solid just always want more power.

Would love to get it dyno tuned but is tough to find anyone around here that can work on carbs and has a dyno.

Don’t sweat the more power details. But if you want it, put a big block in it and call it a day. A lot of people would love a car that runs solid.

However, this might help because they use a ZZ4 to bolt on stuff for more hp-they got +110 more.

Small-Block Chevy Bolt-Ons - We Add 117HP To The ZZ4 Crate Engine - Hot Rod Magazine

Follow along as we add 117HP to our GMPP ZZ4 crate engine with an assortment of small-block Chevy bolt-on performance parts including an intake manifold, carburetor, chamshaft, and cylinder heads - Hot Rod Magazine

www.motortrend.com

 

[SoCal805]

As long as the added timing from the VA along with mechanical advance that comes in as RPM increases does not provide too much timing to cause detonation, that all is good.

If it did than a VA stop plate should be considered. Otherwise if all is good and car runs good, leave it alone.

IDK what cam pairing Edelbrock has with those heads but given the vacuum the motor makes I suspect a 218/22 cam, possibly smaller.

With 20hg, I am sure power brakes are happy

 

[Nick915]

Otherwise if all is good and car runs good, leave it alone.

IDK what cam pairing Edelbrock has with those heads but given the vacuum the motor makes I suspect a 218/22 cam, possibly smaller.

With 20hg, I am sure power brakes are happy

Not an expert but you are probably close on the cams specs. I definitely wish the car/motor was a little more "rowdy".

 

[BillDini]

Not an expert but you are probably close on the cams specs. I definitely wish the car/motor was a little more "rowdy".

I would suspect this cam is used.

Chevrolet Performance Parts - 10185071 - Hydraulic Roller Camshaft -G.M. ZZ4 Crate Engine

Pace Performance offers the best pricing on products offered by Chevrolet Performance Parts. Including 10185071 - Hydraulic Roller Camshaft -G.M. ZZ4 Crate Engine.

paceperformance.com