Question for the Ford guy's

[a70eliminator]

What do cyls. 3 & 7 have in common? I clean plugs and go for a run and find these two plug fouled while all the others look nice mocha tan, did it twice and and even swaped some plugs yet still 3 & 7 foul out fluffy black. Oh this is for all you ford guys 351weezer good comp, 145 best 135 worst fouls 3 7 plugs during idle is when it;s happening.

 

[skyking897]

Re: Question for the Ford guy's

Just covering some basics here. You know the Ford cylinders are not numbered the same as a GM and the 351 has a different firing order than a 302? Just asking, don't take it the wrong way.

On edit. #5 is front cylinder on the left bank and #7 is the third on the left bank.

 

[The Hammer]

Re: Question for the Ford guy's

Failing injector modules?

 

[a70eliminator]

Re: Question for the Ford guy's

Just covering some basics here. You know the Ford cylinders are not numbered the same as a GM and the 351 has a different firing order than a 302? Just asking, don't take it the wrong way.

On edit. #5 is front cylinder on the left bank and #7 is the third on the left bank.

Number 3 is the 3rd cylinder left bank
number 7 is the 3rd cylinder right bank
Front cylinder on left bank is 1
Ok got it now sorry, it's number 3 and 7 that are fouling.

 

[Shamus O'toole]

Re: Question for the Ford guy's

carberated correct..are the plugs oil fouling or fuel fouling?

 

[EddiePetty]

Re: Question for the Ford guy's

..... 5 & 7 foul out fluffy black....... during idle is when it;s happening......

The "fluffy black" indicates unburnt fuel. I agree that it sounds like dripping injectors. Switch a pair around and see if the problem follows.

Edit: Disregard...having a Chevy moment here.

 

[a70eliminator]

Re: Question for the Ford guy's

They are carbon fouling, holley 4160 I've just went through set the floats all new needle&seat sets all the gaskets. for some reason it's just the center plug on both sides.

 

[Shamus O'toole]

Re: Question for the Ford guy's

hmmm....not sure on this one. 2V or 4V heads? In other words was this motor factory equipped with a 2 or 4 barrel carb??

 

[a70eliminator]

Re: Question for the Ford guy's

factory 4bbl, I'm hoping these a common link between these cyliders, something in form of a vacuum leak because I can't seem to get the idle air adjuistments to respond like they should, mainifold vacuum is low and steady @14psi., once I accelerate out the idle range I can feel those two fouled plugs come to life after one or two missed, then smooth power again.

 

[bgiese]

Re: Question for the Ford guy's

if I remember right there is a exhaust gas crossover in the cast iron intakes that warms the area below the carb, if that becomes clogged it will foul out the center plugs, might be something to check had it happen on a 70's 351 one time.

 

[a70eliminator]

Re: Question for the Ford guy's

Good thought yes it's there but not sure how it effects 3 & 7 although they are both in that area. I'm going web searching off the site for a bit thanks,

 

[a70eliminator]

Re: Question for the Ford guy's

Didn't get around to any more research, this has come on suddenly, dwell is 29* timing 10* pulled carb and checked float heights, inspected everything and reassembled using a re-new kit with needle valves power valve ect.
#3 and 7 continue to foul, the exhaust crossover shouldn't effect anything as I used to seal them off on the bigblock. I sprayed some carb cleaner around the intake ports and couldn't detect any change. I'll keep at it even if I have to pull the intake. I haven't checked for a wire problem other than visual, the wires have only 1 season on them I doubt it's an issue.

 

[funk6294]

Re: Question for the Ford guy's

I am assuming it still has the factory cam?? You say that the idle airs do not respond and that the vacuum is low. Could it be the carb idle is adjusted so the plates are above the idle transfer slots. That may explain why they have little to no affect??? If that is the case it could be dripping fuel from the boosters and dumping raw fuel down the intake, which the 3 and 7 are the first two downhill cylinders.

 

[skyking897]

Re: Question for the Ford guy's

I see you changed your post to read cylinders 3 & 7, if thats the two cylinders you have problems with, check the distrubutor cap. Better yet change it. 3 & 7 are next to each other in the firing order on a 351.
1-3-7-2-6-5-4-8

 

[Shamus O'toole]

Re: Question for the Ford guy's

if the cap was the case wouldn't you feel the miss while running? I've kicked this around to some friends and haven't gotten any real responses as to what could cause this.

 

[pcosky]

Re: Question for the Ford guy's

I am assuming it still has the factory cam?? You say that the idle airs do not respond and that the vacuum is low. Could it be the carb idle is adjusted so the plates are above the idle transfer slots. That may explain why they have little to no affect??? If that is the case it could be dripping fuel from the boosters and dumping raw fuel down the intake, which the 3 and 7 are the first two downhill cylinders.

I have to agree with Funk6294, take a good close look at how the carb is adjusted and make sure no raw fuel is getting out the secondary venturis nor the vent tube.

I don't have a lot of marine experience but I used to drag race Fords with Holley carbs and those two cylinders are the shortest intake runners from the secondarys of your carb. If it were a double pumper I'd tell you double check the linkages on the carb and the accelerator pump adjustment but the 4160 is a Vac secondary so that won't apply here...A small fuel dribble caused by the needle and seat not sealing due to a bad float (even a new float) can give you headaches.

Pete

 

[a70eliminator]

Re: Question for the Ford guy's

Thanks for all that great input!
The primary throttle plates are just barely into the transfer slots, and the secondarys are closed all but just off the seat so they don't stick.
I can adjust the fast screw out till the primarys close and engine stalls so I don't think the secondaries are letting anything by.
I like the distributor cap theory of the 3-7 firing and I do have another cap so I'll try it.
I also just bought an intake gasket set, even though I'm not convinced it's leaking.

 

[a70eliminator]

Re: Question for the Ford guy's

Turned out to be the carburetor after all, I slapped another carb on She's purring again.
I still can't put my finger on what's wrong with the original one, I even swapped floats, I've been tinkering with holleys since the 70's but this one was a stopper, I went as far as removing the core plugs in primary metering plate, I'll sit down with it over winter in my basement and get to the bottom of it but for now I'm going boating.
Pcosky you were exactly right about those two runners, I think my problem may be that thin tin between the secondary metering plate. it had a little pitting going on, fuel is definately getting somewhere it shouldn't, and it's not the float level.

 

[KRH1326]

Re: Question for the Ford guy's

I am not at home, so can't double check myself by looking at an intake manifold.

I know that you had a carb problem, but the reason, IF I REMEMBER CORRECTLY, is because in a stock marine intake, those two cylynders have the shortest, downhill and common passage to carb(with all of the over/under turns).

Any excess will show up there first.

 

[pcosky]

Re: Question for the Ford guy's

Turned out to be the carburetor after all, I slapped another carb on She's purring again.
I still can't put my finger on what's wrong with the original one, I even swapped floats, I've been tinkering with holleys since the 70's but this one was a stopper, I went as far as removing the core plugs in primary metering plate, I'll sit down with it over winter in my basement and get to the bottom of it but for now I'm going boating.
Pcosky you were exactly right about those two runners, I think my problem may be that thin tin between the secondary metering plate. it had a little pitting going on, fuel is definately getting somewhere it shouldn't, and it's not the float level.

Holley makes a metering block for that carb to do away with the metering plate on the secondary side, money well spent IMO.