V8_GRUNT

Hi there guys at the moment i have a stock 351 with single plane manifold and a 600 holley,i put the manifold and carb on about 6 weeks ago, before that it was running the 2v manifold and a 350 Holley, occasionally it would foul up a plug or 2 but recently it has gotten worse, and when it drops to 7 or even 6 it runs like crap (naturally) Now this engine has been great and has it's original internals, i pulled the plugs out today and inspected them, a few of them were wet, but it didn't seem oily, more fuel, is it possible that the carb is over fueling my engine, causing the plugs to misfire and foul? Is it possible that the carb is washing the bores and making oil consumption increase?

The exhaust system has decided to crack as well in the last 2 months where it bends under the car where the fire wall is, because of the twisting motion etc , can this decreased back presssure cause it to run richer as well?

My plans are get a brand new exhaust system in a few weeks and to put a fully worked Clevo in at the end of the year, i just need a few more months out of this one, but there is nothing worse than driving it 1km down the road and then it decides to drop a cylinder, so annoying.

Should i get the car onto a dyno so they can test the a/f ratio and change jets / power valves etc in the carby?

Any suggestions would be fantastic, thanks in advance - Mark

brenx

Over fueling yes. Check the power valve hasn't failed.

Brenden

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XB Fairmont (street car) 11.07@123.02mph.

V8_GRUNT

thanks Brenden, having said that the carby will "explode" or backfire ever now and then under mild acceleration.........isn't that a power valve problem as well??? I think it's time for a re-kit............

CRUISIN

Check this link it should help.Scroll down a little for the power valve and jetting info.

http://www.mortec.com/carbtip1.htm

Another option is to drill 1 small hole thru each of the primary butterflies.
Start with a 1/8 size drill bit, this should be about right.
This will create a leaner mixture at idle. You will have to back off the idle screw a couple of turns. By backing off the idle screw you will be assisting the carby to stay within the idle circuit and prevent overfueling.

paull

This maybe a bit off track but I had the very same problem. It was ongoing for quite some time and what it turned out to be was the factory haul affect ('77 P6 LTD with factory electronic ignition) was slowly dying on me.

I basically ignored it, however, it ended up eating two cylinders and the car is now U/S. Not sure as to why but it was fouling up #1 plug consistently and then #2 & 3. Now, poor old car is dead.

If you don't have the XC factory electronic ignition, please ignore.

Paul

xdclevo

The main thing the drilling of holes do is enable extra air, while still having the correct "closed" position of the butterfly's. If you have to wind the idle out to get to idle properly, you will be running on the intermediate circuit and not the idle circuit.(too much fuel at idle).
To sum it up, tuning can't start until the butterflys are just about closed in the recomended position.

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10.70 @ 125.00 on the black fun top
408 Cube Cleveland.

CRUISIN

By backing off the idle screw I meant to decrease the idle speed.
(Anti Clockwise)
Sorry if that wasn't clear.
You will have to do this as the idle speed will be faster after the drilling mod if the idle screw is left unchecked.

TICK4D

I think it would be more beneficial to tune the new carb instead of just plonking it on and seeing if it will be ok. He obviously doesn't know what jets are in it, and it needs to be set up to your current setup, bodging up the carb is only gunna hurt him long term.

460BBXW

No one seems to mention ,...... v8grunt has just put a single plane manifold on a stock 351 . Bad move . You will have a lot less trouble going back to the Dual Plane manifold, for the rest of the year , till you get your worked Cleveland , use your single plane manifold on that motor .
You will always get a bad flat spot with a Single Plane on a stock motor ( too much air flow , the stock motor can't handle ) pus the diff ratio will be way to high for single plane .
Go back to your original setup , if you foul plugs , (sounds like a High Kilometre motor problem )
Try one stage hotter plug , if this doesn't work , try 2 stages hotter and so on .

V8_GRUNT

Thanks everyone for your comments........much appreciated...........as for the Single Plane Manifold, i was a bit weary of putting it on for that reason........it's a Redline Street Torker, which i picked up cheap for $250 new, not an overly huge manifold, so far the car seems to run fine (power wise) and has a heap more grunt than it did with the old 350 Holley and 2 brl manifold...........i do have a 4 barrel stock manifold at home, do u think it would be worth a try to put that on and experiment? Do u think the stock dual plane may give me more power on a stock engine? If all it's going to cost is another manifold gasket kit and time, i will do it, what do you's reckon?

As far as the manifold goes i will be putting a much bigger single plane on my worked engine later on.........

Has anyone tried to tune their carby's using a gas analyser to measure richness/lean etc?, if so where did you buy it and how much did it cost? Did it work well?

Sorry about all the questions, but i HATE people working on my car and will do almost anything to achieve things myself!!!!

Thanks in Advance!!! - Mark