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My 66 small block 350 h.p. is fouling the R43 AC plugs so much that new ones will only last 200 miles before fouling. The plugs are "wet" after removing them and the only way I can get the car to start at that point is to sand blast them. What brand and heat range is most appropriate for this car? The car has transistorized ignition and I read that "they can be inferior to conventional ignitions for firing fouled plugs or loaded- up engines" -- sounds like my problem Thanks Bill
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Re: Fouled plugs
Start with an analysis of your driving style and the plug heat renge. 43s are much to cold of a plug for "crusin' around town" or duty that primarily involves short hops on and off a trailer. Try a set of 45 heat range plugs and your problem should disapear, assuming you don't have other engine problems. If that doesn't do the trick, I'd start looking at the basic engine, Carburetor, and Ignition system all as possible problems, but start with good ignition wires and a hotter plug first. -
Re: Fouled plugs
In addition to Bill's advice to try hotter plug and verify ignition wires, this might be a signal to run compression check and trickle down. If you're leaking oil into combustion chambers, it may be time for cylinder head/piston work....Comment
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Re: Fouled plugs
Bill's right - 43's are far too cold for normal street driving. 45's or 46's should work, and Champion RJ16YC's are even better - far less susceptible to fouling than AC's, for some reason. AC's are great for originality, but in my experience, Champions are far better for performance and reliability - I got tired of disassembling ignition shielding and switched to Champions (maybe that's why so few cars surface with the shielding intact?). Haven't fouled a plug or had a miss since, and my '57 270 has always run rich.
JohnComment
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Re: Fouled plugs
Just another thought, Bill mentioned sandblasting as a means of cleaning plugs to tet back running. In my experience, that also makes the plugs very prone to fouling again because of the roughening of the porcelin caused by the abrasive cleaning process.Comment
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Re: Fouled plugs
It would be a good idea to pull the plugs and read them before they foul lots can be learned about your engine this way.Comment
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Re: Fouled plugs
Bill,
Excuse my thoughts if they are off base, but it does not seem right that the plugs are coming out wet. Can you tell if they are wet with oil or gasoline?
If oil, maybe your valve stem seals are worn.
If gas, perhaps you have a leaky carburetor. I assume you have a Holley, and I can vouch for the fact the Holleys can dump the float bowl down the intake manifold after the engine cools down. I had all three carbs leaking on my '69 tri-power, and it would lead to plugs wet with gasoline almost immediately and fouling the engine oil within a few starts. If your engine oil smells like gasoline, it is not a good sign. I am still not totally certain of why/how this happens, but I have been told that this problem can occur on both 2 bbl. and 4 bbl. Holleys and that it's probably caused by warped metering blocks/metering plates inside the carb. This problem can be solved by eliminating the warpage, or by buying new carbs. I chose the latter, since my car is a driver, and I can always get the original carbs rebuilt at a later time.
Good luck.
Joe Peplinski '69 L68 Conv.Comment
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Re: Fouled plugs
in 1967 the big blocks with tri power leaked down and we found it was caused by pressure in the fuel tank when the vette was not running. we drilled a small hole in the gas cap and this seem to solve the problem. after you drive your vette for a while shut it of and remove the cap to see if there is any pressure in the tank.a lot of vettes lost the bottom end because of gas in the oil.Comment
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Leaky Carbs (was Re: Fouled plugs)
Clem,
Thanks for the input, but residual fuel pressure was definitely not my problem. Neither was the other most suggested theory, engine heat induced fuel perculation.
To prove this, let me tell you about an experiment I ran while trying to solve the mystery. With the engine cold, I disconnected the coil and I cranked the engine to fill the carb float bowls, with the float level correctly set. Then I removed the carbs from the engine and sat them in buckets on the ground, being carefull not to tip them in the process. 2-3 hours later gasoline was leaking down the walls of the carbs from the area of the main nozzle, accelerator pump, and air bleed areas, well above the idle transfer slots and throttle plates. I have a witness to this test, if you doubt me.
My only theories of what was going on involved capillary action and/or vapor pressures inside the carb passages, but they are at best unproven theories. I've had no such problems since switching to the new carbs. Maybe one day I'll plane the metering plates and metering blocks to be true again on the original carbs and see if that solves the problem, but for now I just want a reliable driver.
Joe PeplinskiComment
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Re: Leaky Carbs (was Re: Fouled plugs)
the front and rear carbs have nitrilfil floats, did you ever check to see if these floats were heavy(gas soaked) if the floats were heavy they could sink in the fuel level and cause the gas to be forced from places you discribed.Comment
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Re: Leaky Carbs (was Re: Fouled plugs)
Clem,
While I never looking inside the secondaries, their fuel levels were right on every time I checked them (often while searching for the cause of this problem). I did rebuild the primary once myself, and I had all three carbs professionally rebuilt (to no avail.) before I found this site, and started to get some clues to what the problem was and that this was not unusual behavior for Holleys. Based upon the advice I got from this site, and a summer lost to chasing this problem, I decided that new carbs were the right choice for me at that time. Thanks for the input.
JoeComment
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Re: Leaky Carbs (was Re: Fouled plugs)
Clem,
I re-read you post an noticed I didn't put together a full responce. In my case, all 3 carbs leaked, with the primary probably being the worst of the bunch. I know the primary has a brass float, and thought the secondaries did, too.
As for bottom end damage caused by gas in the oil, yeah I was worried about that. In fact it was the gas smell in the oil that eventually lead me to discover the carb leak problem (after changing the fuel pump to no avail. - what a job). Luckily, I only had a few hundred miles on the car when I found the problem. After that, I don't think I got more than perhaps 100 miles and/or a few starts between oil changes until I put new carbs on it. First sign of a gas smell in the oil and it was changed.
Thanks again.
JoeComment
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Re: Leaky Carbs (was Re: Fouled plugs)
joe i have some of these orignial carbs here so i will try your test and let you know what i find out.thanks for the tip. clemComment
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