I cant get my new engine to run smooth. Seems untunable.

[potent rodent]

carb base plate gasket

 

[85K304SPD]

Maybe bad gas?
I had a square with an L98 (aluminum head version) that I drove daily for several years. It ran great until a buddy started messing with the timing. Make sure the timing is right and the gas is good, because it is a high compression engine. I broke and replaced 1 piston, from detonation and broke a second one later that came all the way apart, so I had to quit using that engine until I can rebuild it.
I would pull the heads and check the pistons for broken top ring lands, or at least do a good compression test.

 

[Kurnacopia]

Did you check the fuel line...make sure there's no intermittent clogging of the line in the filter? Filter somewhere you haven't looked yet? inline downstream near the tank? Just throwing out more options....best of luck!

 

[AyWoSch Motors]

Maybe bad gas?
I had a square with an L98 (aluminum head version) that I drove daily for several years. It ran great until a buddy started messing with the timing. Make sure the timing is right and the gas is good, because it is a high compression engine. I broke and replaced 1 piston, from detonation and broke a second one later that came all the way apart, so I had to quit using that engine until I can rebuild it.
I would pull the heads and check the pistons for broken top ring lands, or at least do a good compression test.

Gas is fresh. Timing may be off. If I can get it to idle lower, I'll check it.

 

[AyWoSch Motors]

Did you check the fuel line...make sure there's no intermittent clogging of the line in the filter? Filter somewhere you haven't looked yet? inline downstream near the tank? Just throwing out more options....best of luck!

I blew the fuel line out with air before I out I back together. Only has the one filter, I've looked. It's new too.

 

[AyWoSch Motors]

Okay, so i just went out and capped off every vacuum port on the carburetor.
Still same high idle issue, didnt change.
I also put the air cleaner back on, and sprayed starer fluid around the whole carb and intake. All the gasket seams, throat of the intake, all the vacuum ports, nothing changed. Didnt rev, didnt die out, just still screaming a high idle.

 

[AyWoSch Motors]

I took this video just a second ago. Theres it running. Runs smooth enough, but reving way to high.

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[wanderinthru]

Have you just moved the distributor back and forth?

How did you put the engine in, where did you attach the chain?

 

[AyWoSch Motors]

Have you just moved the distributor back and forth?

How did you put the engine in, where did you attach the chain?

Yes, ive moved it around, seems happiest by ear right there. Wants to die if you either direction. Can chek the timing when its reving high, but if you hold the coke butterfly down a little, you can get it to idle down 700-800 for a few seconds before it dies, and it looks like its still set to about 10-12° which is where i had it set when it was on the stand.

I put the engine in with a chain bolted to the back of the passnger side head and front of the drivers side head, and a safety strap around the pan, why?

 

[wanderinthru]

Yes, ive moved it around, seems happiest by ear right there. Wants to die if you either direction. Can chek the timing when its reving high, but if you hold the coke butterfly down a little, you can get it to idle down 700-800 for a few seconds before it dies, and it looks like its still set to about 10-12° which is where i had it set when it was on the stand.

I put the engine in with a chain bolted to the back of the passnger side head and front of the drivers side head, and a safety strap around the pan, why?

Is it running rich when you hold the choke down?
Far as attachment, just asking questions that hasnt been, information.

Seems it was mentioned, but have you tried a different carb?

 

[AyWoSch Motors]

Is it running rich when you hold the choke down?
Far as attachment, just asking questions that hasnt been, information.

Seems it was mentioned, but have you tried a different carb?

Yes, at first I had my edlebrock AVS2 on it. That carb was originally on the 305 that was in it, and it ran great, but it didnt run well on this engine. It wound idle quite a bit lower than this one, but was really lopsided and wouldn't run sooth. One tail pipe smelled like gas. Found out the previous owner had out in mismatched jets in it to help the one dead cylinder on the 305, so i gave up on that carb.
The one that's one it now, is a Rochester off my friends truck. Ran well we last used, but not now.

 

[85K304SPD]

Worn out throttle shaft bore on the Q jet. Pretty common problem. They suck air around the shaft, and it makes them idle high. PITA to fix, you have to take the shaft out, drill them out and put a new bushing. I've never done one.

 

[Rusty Nail]

I read it all and my last thought is the same as the first.

Valve adjustment / Weak lifter(s)

 

[SquareRoot]

They suck air around the shaft, and it makes them idle high.

Sounds just like my ex.

 

[AyWoSch Motors]

Worn out throttle shaft bore on the Q jet. Pretty common problem. They suck air around the shaft, and it makes them idle high. PITA to fix, you have to take the shaft out, drill them out and put a new bushing. I've never done one.

Hmmmm, that might explain it. Never heard of that.