CRG Discussion Forum
Camaro Research Group Discussion => Maintenance => Topic started by: ThinkSS on June 26, 2017, 05:18:05 AM
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1968 L48
Headers
1965 #461 heads (1.94's)
Comp cam XE262H
Cast iron intake, Q-jet
180 thermostat
Temperature outside was 93... although this has happened at lower temps also... in the 70's
Car runs fine for about five miles and then when you come to a stop it stutters and stalls out.
Opened the air cleaner operated the throttle no fuel, only a little vapor.... poured some gas into the carburetor and could hear it sizzle!!
Fuel pump was hot to the touch, so I got a bag of ice and set it on there for about 20 min. Car started after that and I was able to get home. This is happening more than one occasion
Insulated the fuel line near the rear tail pipe with high heat tape, had no impact. Thought that was a problem because it was only a half of an inch away
Here are a few shots under the hood, I have the steel fuel line from the fuel pump to the carburetor and you can see the distance from the rubber hose to my radiator hose, and my steel fuel line to my headers.
I'm not sure what to do here other than perhaps and electric fuel pump. I do not know what temperature the engine is so I will put a gauge on it this week and see if it's running crazy hot. But the car did not overheat at all.
Any ideas suggestions comments?
Thanks everybody in advance
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Here is the fuel line at the radiator
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Your carb is too hot and it sounds like the fuel is boiling. You don't say what intake you have but make sure you have the right gaskets between the intake and carb. Here's a post on the subject from the Corvette forums: https://www.corvetteforum.com/forums/c1-and-c2-corvettes/1978466-q-jet-carb-base-gasket-tech-info-the-hot-slot-manifold-problem.html
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Carb is hot. Not the fuel line. You are cooking the carb.
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I agree. Does not sound like a fuel line problem. Hopefully if you get the correct gasket setup that will solve the problem.
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JMO make sure your exhausts heat riser valve is not stuck in the closed position, and it opens fully when at operating temps (if you are still running one). One other issue that was supposedly recalled many years ago due to fire issues, was blocking off the exhaust passages at the intake below the carb. - simply remove carb., tap the ports and install pipe plugs, reinstall carb., etc..
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Ok... got a break from the desk!!
Stock cast iron intake... the exhaust crossover it is unmodified.
Attached is the gasket set-up.
Are you speaking of the heat Riser valve in the air cleaner?
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There is no heat riser valve in a header system. Is your Ign. timing correct and not retarded? I would also heat shield the metal fuel line where it passes the header tube.
You could also block the heat riser passage in the intake but with this set-up it should not be necessary.
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I would plug that exhaust gas passage on the non-choke coil side of the intake manifold. Heat is flowing thru there.
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Have you ever tried any of those tin block off plates that come in some gasket sets?
Just got this thing put back together to!
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I could try and Advance the timing a bit, right now I believe I'm eight degrees before top dead center on the marker... but it could be less than that I would have to check again
How far Advanced would you suggest I go?
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I could try and Advance the timing a bit, right now I believe I'm eight degrees before top dead center on the marker... but it could be less than that I would have to check again
How far Advanced would you suggest I go?
Go with 36 degrees total. Disconnect and plug Vac. advance before setting total then reconnect.
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Thanks for the tip.
I will get this done in the next few days and report back
Thanks again
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Seat a 7/16" freeze plug in each end of the heat transfer slot under the carb - it will block the heat from under the carb bowl and keep from frying the gas and the carb. It'll also save you from having to pull the intake and blocking the heat passages until you need to do a tear down. First thing I did on the Pace Car L48 when I redid the carb a while back - effortless, and will save the carb and gas from cooking. Use the stainless heat plate you show, or a composite gasket with the plate sandwiched in. Works for me -
Regards,
Steve
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Great idea. Was hoping to not habmce to pull the intake!
Did the plugs seat into the manifold well?
I also think i can advance the timing by a few degrees...
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I mean "have to pull the intake " haha
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I have found that often the exhaust holes for the crossover slot are somewhat eaten up by the exhaust and not round, so the plugs do not perform a true seal. This is why I use a tap with grease on it (when working on an assembled engine) to keep most of the filings from entering the intakes exhaust ports. I simply tap and install a pipe plug, then reinstall the carb with the afore mentioned correct gaskets. Others have also welded them shut, or blocked off the ports at the intake gaskets (when the intake was off or removed). It's your car, hence, your choice. JM2C Timing is yet another possible contributing heat factor.
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During my time of figuring out different issues I did have success with this idea. And that is I had a strange baby crackling sound coming from the carb area after a drive. Took the air cleaner off and put my ear down by the front bowl. I discovered the gas was boiling in the front bowl. This only occurred on hot days above say 85-90 degrees and a longer than normal drive. Purchased a Phenolic spacer and it never did it again. Even with a 30 mile drive at 105 Degrees! I read a few articles that mentioned there really was not much of a performance gain on the 302 with carb spacers. VERY little bonus with a half inch spacer. NO benefit with any other thickness. With that said, I didn't wanna break my intake trying to install longer studs. So I installed a 1/4" with thin quality gasket above and below and the hold down nuts were just near flush with the top of the studs. Nice and sano, changed nothing but what I wanted it to do. No bad visual as it can't be seen when air cleaner is installed. Here is the link. I chose the 4 hole cause the 1/2" one that was discussed that obtained a small amount of power, was a 4 hole. Never knew if it made a difference. I had it running so well I didn't wanna change to the one big hole unit. Hope this helps...D
http://www.jegs.com/i/Canton-Racing-Products/074/85-154/10002/-1?CAWELAID=1710932202&CAGPSPN=pla&CAAGID=44693592161&CATCI=aud-224375369591:pla-176557696391&CATARGETID=230006180039217702&cadevice=c&gclid=Cj0KEQjwp83KBRC2kev0tZzExLkBEiQAYxYXOhw3KgAqGlKsESqlW1m2ddlQYGuChoPTc3kIaYPR2F0aAgN_8P8HAQ
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Bumped up the timing to 10 degrees on the crank... hope to get out for a drive today. I ran the same set up last summer with no issues of the gas boiling in the carb.
The distributor was bumped over the winter so i hope that is the problem.. although i like the idea of blocking the ports. Just don't want to take the intake off... again..... haha
What i would like to do is get to 36 degrees total timing but i gave no tach to see if i have ended the mechanical advance
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Bumped up the timing to 10 degrees on the crank... hope to get out for a drive today. I ran the same set up last summer with no issues of the gas boiling in the carb.
The distributor was bumped over the winter so i hope that is the problem.. although i like the idea of blocking the ports. Just don't want to take the intake off... again..... haha
What i would like to do is get to 36 degrees total timing but i gave no tach to see if i have ended the mechanical advance
Depends on how much advance is in the distributor now but likely it isn't 26 degrees. Probably more like 20 so you'd only be at 30 total now. You should get a timing light with built in tach to find out when you're timing is all in and how much advance your distributor is providing. The timing on my stock L30 with original iron heads running 93 octane pump gas is best at 14 initial, 34 all in at 2800-3000 rpm and vacuum advance restricted to 11 degrees from manifold vacuum. That puts it right on the edge of detonation at WOT but it runs great and stays cool all the time.
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Hmm... yes i see. Right now the distributor is cast iron with a pertronic ignition module... probably the stock internals other than that.
Its cool out today so no issues with my drive. I will set it up to 16 degrees in the crank and see how it goes..
Thanks for the direction
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Great idea. Was hoping to not habmce to pull the intake!
Did the plugs seat into the manifold well?
I also think i can advance the timing by a few degrees...
The plugs I used were fairly deep - very snug fit in the holes at the end, no deterioration in the holes at all. They're not going to move of leak for a century or two - just start the plug in the hole, drive it down with a round punch until it seats nearly flush with the top of the hole.
As noted, you can also insulate the base of the carb with risers, but I like using just the gasket combo as it's not noticeable at all.
Regards,
Steve
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Hmm... yes i see. Right now the distributor is cast iron with a pertronic ignition module... probably the stock internals other than that.
Its cool out today so no issues with my drive. I will set it up to 16 degrees in the crank and see how it goes..
Thanks for the direction
I wouldn't do 16 initial unless I knew what my total would be with that and you can't know that until you map your advance curve. It's important you set it up right to avoid detonation. I was suggesting that 10 is likely still a bit low and you may need to dial in your vacuum advance to get the proper advance at idle which will help with your hot carb issue by keeping the engine cooler. L78 steve was suggesting that may be your issue back in post #7.
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Also, if you have your vacuum connected to full manifold vacuum at idle, I guaranty that it will run cooler at idle. Look up Johnz's article on here about timing and vacuum. I have all my cars that have a distributor set up that way. I have a 302 with headers and drove it in heavy traffic last week when it was 100 out and it never got close to overheating.
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I did not see where you verified the engine temp. Engine coolant circulates through the intake to cool it.
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Hello everyone i have been away from the car as I'm out camping... before i left i put 22 degrees at the crank... car ran great and much more pull than at 10 degrees. I dont know what i have for vacuum, I will take a picture and post it when I return where the vacuum line is connected at the carb...
I have no idea as to what the internals of my distributor are currently...
Can i tell by pulling the cap and rotor and inspecting?
I did pick up a tach from a buddy so I can see where Im at 3500 rpm. I do have the dial on my timing light so I can set that to 36 degrees to be at zero on my timing mark. That is a goal correct?
Thanks again for the help as I'm new to the hobby.
Have a great 4th everyone!
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You can measure the circumference around the outside of the balancer with a cloth measuring tape. Divide the circumference measurement by 10 and use that measurement to place a new sharpie mark on your balancer. It will be that distance, clockwise to the right from the timing slot mark on the balancer. The new sharpie mark is now at 36 degrees before top dead center. You can disconnect/plug the vacuum advance, hook up your timing light, rev the engine and watch for the timing to stop advancing. when reving the engine does not advance the timing any more, you are at full advance. You are shooting for lining up the new sharpie mark on the balancer and the zero on the timing tab while running the timing light. Once you have that reved up and lined up, you lock down the distrbutor hold down. 36 degrees is full centrifugal advance. Hook the vacuum advance back up and see how it drives. No special timing light required.
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Fantastic!
Just got back so looking forward to getting dialed in
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If the distributor is in the motor you can still get a small mirror and peek under mount where the advance weights sit to see how much your particular distributor's advance slot will allow it to add as it spins up as it is usually stamped as something like 'CW22' - meaning 22 degrees of cent. advance - like a 302 distributor would have in it..
That should give you a better idea of how much initial or crank advance you can use to get to where you want the total to end up.
The amount can also be changed if necessary, by using a limiter on the pin that locates in the slot itself to change the movement or by using an 'old school' trick of brazing up part of the slot to limit and make the travel shorter and allow more initial if so desired..
Using Higher octane gas or running a higher compression setup with pop up pistons generally requires more timing verses a lower compression and flat tops, but an engine with 34 -36 total without or before vacuum advance added is relatively a safe number to shoot for with a mild setup depending on how quickly the weight springs used allow it to come in..
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Good to know i can inspect the advance.
Between looking at the distributor, measuring the balancer, and using my light with a dial and tach, i should be able to get it to 36.
I know im on the dartboard just looking for that bullseye