[crm318]

The other day, I took my GTO for a cruise. It ran well, but near the end of the drive, on a 60 mph highway, it got up near 230° for a very short time. A week later, I started it up and it would barely idle until warm (90° out here) but it eventually ran decent. I also installed an aluminum radiator during that week. Today, it wouldn't idle without feathering and steady pedal. I installed a new Cliff Ruggles Quadrajet and it still has the same symptoms. It even puked a little gas on start up. It acts as if there is a vacuum leak, however, I blocked off all vacuum sources to the carb and sprayed starting fluid around the base with no variation in rpm. At idle, it has an unhealthy lope and it won't even run in gear without getting on the stall. Sun Tuned distributor is set at 12° degrees initial and 32° total. 5.5 psi to the carb. Could I have burned something up on or in the engine for the short time it was at 230°? Seems unlikely, but I am stumped.

[tom s]

Have you rechecked the timing?Sometimes if not tight they can retard themselves.Tom

[hurryinhoosier62]

Originally Posted by tom s

Have you rechecked the timing?Sometimes if not tight they can retard themselves.Tom

X 2.

[crm318]

Yes sir. 12°. I also made sure the hole down bolt was snug.

[72LuxuryLeMansLa.]

I'm no expert but could it be a lost lobe on that HFT Cam?

[SA74SD]

You may have a failed head gasket. I would suggest doing compression test and check radiator for signs of gasket failure.

[STEELCITYFIREBIRD]

It even puked a little gas on start up.
Explain more.^

Does It run normal off idle,also running under load? (cruise )

Any new mechanical noises?

Any idea why it got hot? What does it normally run rolling?
Possibly detonation/damage from a load of poor fuel?

Not clear if only has this issue @ idle /low rpm only.
Ether terrible for pinpointing vacuum leaks, too volatile, propane works well.If simply closing the choke manually cleans it up then a vacuum leak. idle mixture screw adjustment a distinct possibility?



Myself plugs out, see what they say.

If it will run at higher rpm, Turn up the idle and pull one plug wire at a time and replace, note if no RPM drop, weak hole and where to look deeper.Also note if you have a nice fat long spark, make that coil work hard.

Could it be as simple as a leaky set of plug wires? Runs bad on damp days.

Need to determine if you have a dead/weak hole/s if a few are they grouped by the intake divide, adjacent to each other ,or are they all affected.

[steve25]

Puking gas at start up is a sign of retarded Cam timing , or the firing order being wrong, and both will make for poor idle and low Vacuum!

[Gary H]

I'd pull the plugs first, if anything's going on with an individual cylinder the plugs should show it. If they're all dark, you've got a ignition or fuel issue. If one is extremely clean compared to the rest it probably is the head gasket. Do a compression test as well.

[STEELCITYFIREBIRD]

Originally Posted by steve25

Puking gas at start up is a sign of retarded Cam timing , or the firing order being wrong, and both will make for poor idle and low Vacuum!

Possibly an exhaust valve not opening........ hopefully not a scrubbed lobe.

The plugs should be very telling.

[crm318]

Here are the plugs. They all look decent (#2 is a bit dark, but not bad) but #7 looks suspiciously clean. I did just put on a fresh set of rebuilt heads with Cometic MLS Head Gaskets C5711-027. No oil loss and the coolant is clean and full. Cylinders were in perfect condition when I replaced the heads.

Compression test at 190° temp:
1) 127psi. 2)125psi
3) 127psi. 4)135psi
5) 140psi. 6)135psi
7) 123psi. 8)123psi

[STEELCITYFIREBIRD]

Pull the plug wire on #7 and see if it is doing any work....rpm drop. Clean #2 up before it goes back in...or move it to #7. Go from there. Most are pretty low #'s, valve adjustment too tight?

[SA74SD]

Those cranking numbers do seem low. After you do the suggested test for a weak/dead cylinder, do a leak down test. I suspect you will find one or more not sealing up good. Good luck and do let us know what the actual cause is.

[crm318]

Well, at this point, I would assume that if there was a flattened love, there should be metal particles in the oil filter. I just purchased one. I'll put it on the morning and cut open the old one.

[72LuxuryLeMansLa.]

Originally Posted by crm318

Well, at this point, I would assume that if there was a flattened love, there should be metal particles in the oil filter. I just purchased one. I'll put it on the morning and cut open the old one.

Do you have any noise in the valve train?

[crm318]

No valvetrain noise at all.

[Kenth]

I would check valve/rocker adjustment.
I like 1 turn preload with standard 951 lifters from zero play at pushrod.

[crm318]

Well, I figured I would put on one of my old plug wires on the #7 and it is back to normal. So much for the brand new Taylor Cable wires. I took it for a cruise and the Cliff Ruggles carb is amazing. I will borrow my buddies more competent Snap On compression tester and continue my investigation. I'll keep y'all posted.

[72LuxuryLeMansLa.]

Originally Posted by crm318

Well, I figured I would put on one of my old plug wires on the #7 and it is back to normal. So much for the brand new Taylor Cable wires. I took it for a cruise and the Cliff Ruggles carb is amazing. I will borrow my buddies more competent Snap On compression tester and continue my investigation. I'll keep y'all posted.

I'm glad it was a cheap fix.

[crm318]

I was able to get my hands on a Snap On compression tester and the numbers jumped up from 147 to 155 psi. My old tester is going in the trash...