327 help

[prairiehotrodder]

a customer brought me a 327 chevy today that wouldn't run right in his street truck. I'm just about out of ideas on whats wrong with this thing. It idles fine and starts good but when you rev it up it won't go past 3000 rpm. Same problem whether its in park or driving down the highway. It sputters and flutters and won't go beyond that rpm.

Its a virtually unknown engine as far as whats inside. He bought it as a fresh rebuild. Its got camel hump heads (461) and an rpm intake. A 750 holley (3310) and a stock HEI. I did a compression test and got 180 on every cylinder. I dropped in a brand new MSD HEI and nothing changed. I put a 12 volt jumper to the dist and nothing changed. Tried 3 different carbs nothing. New fuel pump, checked plug wires. Re - adjusted all the valves. One valve ( #5 exh) sticks up a bit higher than the rest but it still seals. Any suggestions ? The customer is wondering if the timing chain is on wrong. Its not loose. I'm out of ideas.
Brian

[Cobra720]

Check valve spring pressure, battery, air cleaner.

[af2]

Power valve...

[GARY C]

I have had spark plugs do that, they get fuel fouled and then they get (Hot Glazed) or something like that and they appear to be fine.

My 382 SBC drag engine did it twice and at about 4000/4500 it would lay down so bad you would almost bounce your head off the steering wheel.

EDIT, it is called High Speed Glazing if memory serves correct.

[pastry_chef]

timing chain on wrong could do it.

[travis]

Serious exhaust restriction? Crushed pipe, clogged muffler, etc.

Plugged fuel tank sock, crushed fuel line? Maybe rig up some temporary way to monitor fuel pressure. Weak fuel pump? Flattened fuel pump lobe?

Dead valve springs? Bad plugs or wires?

Maybe hook up a vacuum gauge and see what’s going on.

Any idea what kind of cam?

An incorrectly installed timing chain could certainly do it too.

Wrong balancer or timing pointer? Maybe timing isn’t where you think it is?

[jake197000]

ck exhaust back preasure.dont remember if chevy used double wall y pipe but other gm cars did.ran into collasped inner pipe a bunch of times back in the day.i would think if timing chain was on wrong it woulnt idle right.shoot a litte carb spray in carb when its doing it that will tell you if ist lean.put it on a scope if you have one.hope you get it.you will eventually.

[fdicrasto]

Sounds like plugged or restricted exhaust system. Should be easy enough to drop exhaust and check it then.

[Ericnova]

Check the metal contact finger in the center of the HEI rotor. It has been found on several forum boards, and MSD now sends tech notes about it with their ignitions, caps, and rotors....the metal contact bent down so far it doesn't even contact the carbon button in the bottom of the distributor cap.

Bend the finger up where it should be, problem gone. Might be your problem if the rotor went off the stock HEI and onto the MSD test HEI.

With the proliferation of offshore made parts, you can't take anything, even simple parts, for granted anymore. Closely inspect everything.

[peejay]

Check backpressure for sure. Easy to do, ram a 1/8" NPT to 3/16" brake line adaptor into the pipe near the manifold, stick about 6" of brake line on it, and then a 6' length of vacuum hose to your favorite vacuum/pressure gauge. Should never see over 1, maybe 2psi at WOT unless it has a turbo and you're checking pre-turbo.

Since there is no airflow through the hose, you only need six inches or so of hardline, hot gases won't get into the hose.

When you're done, remove the NPT fitting and thread in a plug or just weld it shut.

[F-BIRD'88]

Hei needs a ground wire from engine to firewall.

[Tuner]

Broken valve spring?

[Geoff2]

No, HEI doesn't need a grd wire from engine to firewall.

[midnightbluS10]

Did this truck have a running engine before this one? Can you supply an auxiliary fuel source to bypass everything in the truck to verify its not fuel related?

[F-BIRD'88]

No, HEI doesn't need a grd wire from engine to firewall.

It does if you don't want to fry your shifter cable.
Or go fast. Without a engine -body ground strap
The shifter cable becomes the intermident ground path.
Poor diz perf. Fried shifter cable.