No get up and go.

[chrisb9259]

Any idea why I don't have a lot of power? 350 motor hei dizzy holley quad carb. I've never driven one before but yet I'm sure there should be more horses. Any suggestions? And the timing is at around 8

[demian5]

Pull some plugs and post up some pictures. And post pictures of your carb and distributor with the air cleaner off. Could be the advance in the dizzy not moving or too tight of springs. Could be tall gears in the rear end. Could be a tired motor. Could be the heat flapper on the air clear hanging closed and drawing only hot air into the engine. Could be a 307 and not a 350. Could be a number of things.

[p0508]

Timing is around 8!?!

Your total timing in a 350 HEI should be 34-36

I'm assuming you checked the timing at idle and you have 8* initial.

But agree with above, without seeing the motor it could be MANY things.

[Steeveedee]

Did you just buy it? Or has the performance degraded over time?

[chrisb9259]

yes sorry. i just bought the truck about 3 months ago. the inital timing is 8 at idle. when i bought it it wasnt running at all due previous owner not really taking care of it. but said there was around 5000 miles on the motor. when i got it home. i changed the dizzy, spark plugs, plug wires, changed oil, transmission fluid leak, and some random leaks. i will take pictures tomorrow.

[rpmerf]

5000 miles on the motor. What do you know about it? Stock rebuild? Crate engine? Compression ratio? Camshaft? Stock intake? Stock exhaust?

Drive ratio plays into this. Larger tires, lower rear ratio make you accelerate slower. TH350 and TH400 have a steeper first gear than the 700R4 and 4L60E. Makes it feel slower off the line.

Check for vacuum leaks.

Check the valve lash.

Get the timing set to 34-36 all in. Should be all in by around 2500 RPM. This should get you a base of around 14-18*. Vacuum advance should add about 10*-12*.

Make sure your carb is in tune. Might take a bit of trial and error. An A/F gauge makes this easier. Make sure the linkage is correct and WOT on the pedal equals WOT on the carb.

Jack it up and make sure you don't have sticking brakes or a bearing going out causing additional parasitic loss.

When you say it feels like it should have more power, do you mean part throttle, wide open throttle, all around?

What is your weather like? I know my cars feel like they are down on power when it is 95*+ with 60%+ humidity and the air feels like soup.

[68 P.O.S.]

Since timing is your truck’s baseline, it has to be setup correctly first before you move on to other things like the carb, etc. Start with verifying top dead center with a piston stop to ensure your timing marks are accurate and the harmonic balancer outer ring hasn’t slipped. Once verified, advance your initial timing to about 12 degrees to start with, just to make it run a little better while you keep working on it…it’ll feel like a small victory lol. Do not set total timing yet, you have to set up your distributor correctly first before you can do that. Which HEI are you running, GM or aftermarket? How many degrees of mechanical advance does it provide? How many degrees of vacuum advance? Has the original power wire for the distributor been replaced with an HEI friendly one? After these numbers are determined we can figure out the distributor curve. New mechanical advance springs will likely be needed to ensure the engine fully advances between 2500-3000 rpm. The vacuum advance needs to be restricted to provide no more than 15 degrees. Once the distributor is curved, you can set the total timing to 36 degrees, where SBCs run best, and then connect the vacuum advance to the manifold vacuum port on the carb.

For the carb, since you say the PO didn’t take care of it, I’d pull it off the engine, clean it out thoroughly, throw a rebuild kit at it, and get a carb calibration kit to fine tune it to your truck. Before you put the carb back on the engine, using the idle adjustment screw, adjust the butterflies to square the transition slots to ensure the engine only idles on the idle circuit of the carb. If you don’t do this, you’ll be chasing a rich idle with some drivability issues. Having the transition slots squared also puts your idle rpms very close to where it needs to be when you put it back on. Once back on the engine, fire it up and adjust the idle mixture screws for best vacuum with a vacuum gauge.

Other things to check: Fuel system…check for kinked, clogged, or deteriorated hoses, clogged filter or sending unit, or bad fuel. Vacuum leaks…check around the intake connections and the carb, brake booster & check valve, trans modulator.

[garyd1961]

New motor with 5000 miles on it and the previous owner neglects maintenance lets truck sit still then sells truck. I would check for flat lobes on the cam.

[demian5]

Do these things then get back to us:
Compression test (pull all plugs first).
Idle with a vacuum gauge hooked up to manifold vacuum - Whats the steady reading? Does it bounce around at all?

Did you check any of the items I listed or are you looking for a definite answer/ It is not because your timing is at 8 static. Advance it to 14 and try it again for the heck of it.

Sounds ike a few things, get started.

[chrisb9259]

These are the pictures. The only thing I know it's not stock exhaust.

[chrisb9259]

I have already rebuilt the carb. The heat index was 116 today. I will try advancing the timing a little more. I will do a vacuum test and get back to you guys. Thanks for all the input and for the advice. What exactly do you mean by putting the butterflies back square? I'm pretty sure I didn't do that when I put it back on. I know all the fuel lines are good and new ethanol free gas is in it. I really need to check the vacuum. And to be honest you lost me at distributor curve and the technical jargon.

[68 P.O.S.]

Here’s a very good thread by Gregski that goes in-depth on how he tuned his Holley using an A/F gauge. It’s a long thread, but has A LOT of great info with pics that will really help you out. http://67-72chevytrucks.com/vboard/s...d.php?t=713728. Post 37 is where he begins to talk about the transition slots. Post 156 has 2 good links to articles written by a GM Engineer that thoroughly explains timing and the distributor curve.

What's the make & model of that distributor?

[68 P.O.S.]

Originally Posted by garyd1961

New motor with 5000 miles on it and the previous owner neglects maintenance lets truck sit still then sells truck. I would check for flat lobes on the cam.

Good catch. Initially I thought it said 50,000 miles. You're right, at 5000 miles that sounds a little suspicious...it very well may be a flat cam lobe or 2.