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It's not likely that your freeze plugs caused the problem that occurred. If the plugs fell down, they would simply fall into the exhaust crossover - there is no connection to the intake runners. If the plugs came loose and got sucked upwards from engine vacuum, they would simply hit, and be retained by, whatever gasket you had covering them under the carb. Unless you dropped something else down the intake during the plugging operation, the problem that occurred may be coincidental to the hole plugging operation.
Yes, I see your point. there was a distinct pop pause pop then smooth running for a while then the catastrophic clunks. It was just idling when it happened. I was very careful about the manifold opening, Stuffed with a rag while working etc, even checked it before putting the carb back on. Maybe a washer rolled down inside out of view. Anyway, I checked and the oil pan is full of coolant. so time for a new motor. Once I get the engine out I'll pull the heads and see what I can see. Which won't be too soon.
Originally Posted by lars
It's not likely that your freeze plugs caused the problem that occurred. If the plugs fell down, they would simply fall into the exhaust crossover - there is no connection to the intake runners. If the plugs came loose and got sucked upwards from engine vacuum, they would simply hit, and be retained by, whatever gasket you had covering them under the carb. Unless you dropped something else down the intake during the plugging operation, the problem that occurred may be coincidental to the hole plugging operation.
I checked and the oil pan is full of coolant. so time for a new motor.
That's really tragic. Sorry to hear of the bad news. Makes me sick to hear about it, so I do know how you feel right now... With any luck, you may be able to sleeve the broken cylinder, save the engine at a reasonable cost, and end up with something better than you had before.
That's probably what I'll do tomorrow. Pull the carb and have a look. Not sure which way I'll go on this, leaning toward a crate engine. Money is an issue so venturing into a rebuild might not be the best route for me.
Welp, the expansion plugs are still in place where I put em. That leaves me dropping a nut or washer down the intake which I was very careful not to do but people make mistakes or the engine failed from some other reason.
researching engines, looks like S and J have a rebuilt 327 for 1200 plus shipping. Probably go that route.
I'm betting you had a completely unrelated, coincidental failure of the engine not due to anything you did - it was just that time... You would have noticed dropping hardware down the intake. You can stop flogging yourself, and take comfort in the fact that the engine broke in your garage and not on the road 200 miles from home...
It serves no purpose. There is a crossover passage between the secondary throttles connecting the cavity for the hot idle compensator plenum and power brake vacuum port in the carb baseplate to manifold vacuum, so no gasket hole is needed:
Got it, thanks. I ordered the stack on Amazon (they actually show it as things that tend to be ordered together). It wasn't on there when I got it and I couldn't figure out the weirdness I was experiencing until I read this article.
Quick side question that may or may not be related (probably a little off subject): I looked up the number on the side and looks like I have a quadrajet made that was originally on a manual trans but I have an automatic. It has a fresh sticker saying it was rebuilt by Holly (though it doesn't work well, floods, etc). Are there any issues using a quadrajet originally made for a manual trans on an auto trans situation?
If you have as Q-Jet "remanufactured" by Holley, you have a complete piece of junk that needs to be thrown in the trash. Get rid of it. It is not usable or rebuildable - it has been completely hacked and destroyed. E-mail me for my paper about those "rebuilt" hacked carbs. The Holley rebuilts are some of the worst - right there with Uremco...
The difference between the manual trans carbs and the auto carbs is primarily in the throttle lever: The auto trans carbs have provision for the tranny kickdown cable attach point on the bottom of the lever. The M/T carb often have the bottom of the lever cut off with no kickdown provision. But that's not your problem - the problem is that Holley-built carb. It's not serviceable.
No, you cannot use Q-Jet gaskets on a Holley or AFB.
This original thread was originally posted on the C3 Forum, and was re-posted here on the C1/C2 Forum as general info for the members since a lot of C2s have been converted over to Q-Jets. A lot of members here on C2 also own 1st generation Camaros, which use Q-Jets with hot slot manifolds. No factory C2 Vettes were ever equipped with Q-Jets, but used similar manifold systems with the Holley and AFB carbs.
Lars
I'm just now becoming aware of this hot slot manifold issue on my 68 L36 Corvette. Not sure to use the tapped socket head plugs or the freeze plug methods. I grateful that this Forum does exist to capture this information for the benefit of us enthusiasts. Thank you Lars for the original 2014 post that still rolls on today.
I did discover that the original Q-jet 7028216 has been replaced by a 69 Q-jet. This Hot Slot fire event may have happened to a previous owner of this Corvette. I see pitting in the Aluminum Intake manifold around this hot slot and the intake was poorly repainted. I'm now into final stages of restoration and have spent over 4 years of looking for this original carburetor. Anyone now where to find the 7028216? Thank Ya'll.
Lars,
I found your 2019 post and was wondering; I'm having this same issue on my 63 300/327 and was wondering if you would know the gasket installation for this model. I also have a carb spacer installed. Is that even necessary? Photos would be great if your still around to answer, My spacer also has the heat slot.
Note, this is an AFB carb setup.
07-28-2018, 05:44 PM
