headers glowing red

[Jody Lang]

Is it a Q Jet with primary metering rods?

[Greg Reimer 7376]

Back in the early/mid '70s, the era of the most horrible performing cars on earth, a guy backed his '74 Cadillac out of his garage, got out to close and lock the door, and he left his car running on fast idle-around 2000 RPM or so. The phone rang, he ran inside to take a call, which lasted about fifteen minutes, and the car ran at that speed the whole time. He got off the phone and came out to find the cars' exhaust manifolds, the Y pipe, and the head pipe to the muffler cherry red hot. He panicked, shut the engine off, whereupon it dieseled like crazy for several minutes, and then backfired and quit. He had no idea that a by product of retarded ignition timing and a late closing camshaft was excessive exhaust heat. He's lucky he didn't burn the whole place down. Set the timing to 36-38 degrees at 3000 like everybody says, and I bet you find that the engine's idle improves significantly as well. Good luck, let us know what happens.

[njk53]

Agreed too little timing. SBC should stand 40 degrees of total timing. But, all engines are different set it at 36 degrees and raise it in 2 degree increments.

[henrys57wagon]

Thanks again guys As far as the primary throttle plates go what size hole do you have/ recommend, ours are 1 in each primary plate and 1/8" dia?
The throttle plates are well past the idle slots and am wondering if I should drill another hole in each primary plate to get the plates back to where they allow the idle circuit to work? Or keep increasing the size of the one hole?

Originally Posted by Jody Lang

Is it a Q Jet with primary metering rods?

We are still running the front metering rods. The car will be mainly a street car. We have kept our 69 Stocker engine but with a 2800 stall and only a 373 street gear in it now, but LOVE how the engine performs on the street

[Greg Reimer 7376]

Originally Posted by henrys57wagon

Thanks again guys As far as the primary throttle plates go what size hole do you have/ recommend, ours are 1 in each primary plate and 1/8" dia?
The throttle plates are well past the idle slots and am wondering if I should drill another hole in each primary plate to get the plates back to where they allow the idle circuit to work? Or keep increasing the size of the one hole?



We are still running the front metering rods. The car will be mainly a street car. We have kept our 69 Stocker engine but with a 2800 stall and only a 373 street gear in it now, but LOVE how the engine performs on the street

Sounds like a 1/8" air bleed hole through the primary throttle butterfly is about right. if you have the proper static initial timing, the engine's idle characteristics would improve to where no further mods were necessary.

[Herbie Null]

piston at TDC - ON THE COMPRESSION STROKE, I know you have probally checked this. I had this happen to me 1 time, engine ran but headers got cherry hot. I was in a hurry and had the distributor on TDC #1 set on the wrong stroke.

[Jody Lang]

I don't think you can get away with that much timing with that low of a stall. Breaking motor in with that much timing wont be a problem. Driving on the street I think it would detonate.

With the primary rods in it (which is fine) with no load on engine the rods are down in the lean or big part of the rod. Just not enough fuel is getting past the rod/jet for the raised RPM.

As a quick fix when breaking cams in I've just ran some duck tape across the choke area to richen it up. Cherry red exhaust will be gone. Don't forget to remove duck tape after break in.

[henrys57wagon]

Thanks again guys.
We finally got back to the Nova. I took the carb apart at home and cleaned/ blew it all out. We put the carb on and set the timing to 36# at 3000. The headers glowed so we put the old HEI back in ran it up and set the timing to 36 and the header glowed!!!!

We took the carb off and went to put the spare on but were missing a plug for this carb so I said lets put the 1st carb back on and see what happens.
Well low and behold everything worked fine??????????

So with the throttle plates drilled with a 1/8" hole the plate is above the idle slots and idling at 1100 in neutral, dropping to about 800 in gear.

What if we drill another 1/16 hole in each plate or would you recommend opening up the 1/8 hole to 3/16? Thanks, Henry.

[Alan Roehrich]

I'm not sure you should need a 3/16" hole in the throttle blades to get it to idle.

[Dave Noll]

Originally Posted by henrys57wagon

Thanks again guys As far as the primary throttle plates go what size hole do you have/ recommend, ours are 1 in each primary plate and 1/8" dia?
The throttle plates are well past the idle slots and am wondering if I should drill another hole in each primary plate to get the plates back to where they allow the idle circuit to work? Or keep increasing the size of the one hole?

Not trying to contradict anybody, & mine doesn't have a q-jet but to get my 351C with a 2bbl Motorcraft to idle decent, I currently have a 1/4" hole in each throttle plate. & it adjust's correctly now. But my cam is probably too big.