The Stovebolt Site Forums The Shop Area The HiPo Shop Carb almost right, but not quite...

Hello

First post from a new member here, and the first thing I should say is that this site is tremendous!

I recently purchased a restored and slightly rodded 71 4WD stepside, and I could not be happier with the buy. However; driveability is not quite where I want it. There seems to be some carb issues, and I'd like to find a simple fix. Carb replacement is an option, as long as I know in advance that I'd be buying a more user friendly carb.

The problem is rough idle, a slight hesitation during idle transition to driving, and dieseling upon shutdown.

I've checked timing (6BTDC), checked for vacuum leaks, checked all ignition... and then set idle mixture with a vacuum gauge according to the manufacturer's (Holley) instructions, and I'm beginning to wonder if this particular carb is just goofy.

The engine is a new 350 (someone said it's a crate, but it doesn't have aluminum heads,) GM electronic ignition, Holley 600/vacuum secondary. It also has a water jacketed spacer between the carb and manifold - I've never seen that before.

Appreciate any and all suggestions.

Paul Domeier
Green71

As far as dieseling goes, you can stop that with a diode on the alternator. For that, and also to consider wiring your engine area the best way possible, check This out.

Holley carbs can get sloppy and troublesome, in my opinion. I put a new Edelbrock on my 350 a year and a half ago ... out of the box and no problems -- wonderful carbs! See This

Alan

Sounds like I'm barking up the right tree. I had a Holley 600 on a small block Chevy many years ago, and never could get it to run just right.

The info on the diode to stop run-on is interesting, and makes good sense. I have an old airplane, and there was a mandated modification to install a diode on the Master power relay to prevent voltage spike when turning power on or off - ignition is separate from the battery/charging system on the plane, but the principle is very similar. I'll give it a shot and see what happens.

I really appreciate the articles you've posted on your site regarding your truck. I was looking at air con retrofits earlier, and saw your super-clean installation of the Old Air system. That's next for the Green 71, but first she needs to run right.

Best

Paul Domeier
Green71

I had a dieseling problem on my Firebird 400 once . It turned out to be the secondaries not shutting off properly for some reason that I forget .

Holly carbs are for race only applications. You'll never get one to run correctly on the street. I would get a Quadrajet or a wanna-be look-a-like carb for everyday street driving. Heck, I would even suggest fuel injection,
Scott

Hey, Paul

I wasn't getting run-on or dieseling with my truck, but I DID notice a hesitation when I turned the engine off. Then, after rewiring my engine area and installing the diode, I noticed a BIG difference -- now, when I turn the engine off it feels so good!

It turns OFF!

I don't like Rochesters any more than Holleys ... they're both argumentative, to me. The Edelbrock is a real honey!

The Green 71 is now a very happy truck. I bought an Edelbrock 600 on the way home from work yesterday.

I pulled the Holley and the weird water jacketed spacer off last night and found... a humongous vacuum leak between the spacer and manifold.

Re-installed the Holley, set the idle mixture and she runs and drives like a Chevy should.

I'll drive for a few weeks with the Holley, then install the Edelbrock just for the heck of it.

I still haven't figured out why that goofy heated spacer was ever installed. It's made by "Clifford." Any ideas?

Paul Domeier
Green71

Sounds like you have an intake manifold heater...pretty common on older motors supposedly improves idle and fuel consumption...I installed one on a '58 235 at the recommendation of Stovebolt Engine Co...I really never noticed a difference.
I also have a GM Crate 350 w/ a 600 Holley...won't let me pass a gas station without saying hello! Plus it tends to load up on idle...I've done a lot research on the GM Crate /Holley issue and it seems the major problems involve that carb...moste guys have replaced them for street use...just bought an Edelbrock 600 as well...good luck

I was told when I bought the truck that it's a cold blooded s.o.b. and that it took at least three minutes warm up before you coud drive it.

I wonder if that was the reason for the heated spacer?

The cold blooded silliness is gone after fixing the vacuum leak (go figure.) It fires up nice and smooth, and away we go.

Air con is next.

Paul Domeier
Green71

Okay, I swapped the Holley out and installed the Edelbrock... and she is SWEET! Idle is smooth as a mirror, and it took all of 5 minutes to get the fast idle, choke and mixture just right.

I am converted. I will never leave the Church of Edelbrock.

Some photos:

http://members.aol.com/padomeier/71chevy.jpg

http://members.aol.com/padomeier/mill.jpg

Paul Domeier
Green71

Nice lookin' ride. We like pictures. What part of the country are you from? I gotta soft spot for 4X4's.
Scott

I'm in the SF bay area.

I just love this truck, but I'm thinking seriously about removing the lift and the big balloon BF Goodrich's. I think it would look a whole lot cooler with stock steel wheels and hubcaps.

Does anyone know where I can find a photo of a stock 71 stepside 4x4?

Paul Domeier
Green71