Thread: carb problem or?

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small block ford, edelbrock performer intake, just a run about pickup.

anyway, got most all the lil kinks worked out with the truck but I noticed that the driverside bank runs 500degree egts for each cylinder.
Pass side runs 700 on average.

Jets are matched, engine runs and drives perfect. If it was one cylinder I'd think it was valve leakage.... plugs are all gapped the same and in good condition.
The carb appears to be functioning well, but why would the pass side be leaning out? Manifold air draw perhaps? Manifold vacuum is 18inch so no air leaks that I know of.


Any suggestions appreciated!
Thanks folks.
Drew

Is this at idle? Idle screw adjustment. Proper adjustment may require one screw to be out 2 turns while the other is out 1 turn.

What was used to measure these temps with? Is it a hand held device or something in the exhaust system?

handheld IR gun. I use it alot at work with EMD and Detroit engines. It isn't 100% accurate but it's pretty darn close.
I'm used to balancing an engine with both exhaust gas matching and firing pressure....

I'll mess with the idle screws when I get back on land (3weeks). Any other suggestions? I'm looking for ideas so when I hit the house, I can hit it with ideas.

Thanks guys!
Drew

I was hoping you would say thermocouples

A stab in the dark - many Ford 302/351 engines used heads with EGR ports or holes in the exhaust port that allowed air to continue the combustion process, if necessary, in the exhaust system for emissions control. If for instance a head was changed at some point in the engines life, one ended up with those holes and the other didn't, you might have additional air flow right at that port. The heads could even have the same base part number and be a different configuration. Also, those heads often (but not always) had a hump about 1.5" up that exhaust port (again, with or without an EGR hole). I had 2 sets of DO0E heads - one set had the holes and humps, the other didn't - just holes. If that ends up the problem, I'd probably just remove any hump and forget about the temps at the header where I assume you are checking. If you are really worried, possibly check the actual head temps instead. As far as those EGR holes, plug 'em with HT epoxy or just ignore 'em.

Let us know what you find

well this has long tube headers (1.5 primary to trans crossmember, 2 1/4 rest of the way) So I was checking an inch from the exhaust port. A Pyrometer would be nice, but either buying 8 of em or moving the thermocoupler around 8 times would stink.

I didn't even think about egr stuff (this is a 1976 engine/vehicle). All the smog stuff was diabled and kinda just left hanging in place when I took ownership. Where exactly would this egr port be located? I'm sure I could find it if I had the motor in front of me.

Interesting idea about one head being changed and the other not.....
Dang thing runs great, so I am not overly concerned, it was just something I had rattling around in my head, so figured I'd ask.

Man I hate being at work for a month, Caterpillars are not nearly as much fun to work on.

Drew

You will have to pull the headers loose to check inside of the exhaust port. You can feel the hump and a hole for air to mix with the exhaust gasses. Probably what I would do is to find a contact gauge and just find out what the head temps are if you have that concern about differential. Just a word about those '76 heads - they are close to the worst ever used on a Ford as they were trying to reduce emissions and Hp to meet the fuel crisis so they made the valves smaller and reduced the compression ratio. I don't have my book of specs close, but not their best choice. A nice pair of iron GT40P from a 5.0 Explorer/Expedition would add new life to the 'beast' and the base for my Avatar's engine heads. (I had a '76 F250/460 that was a California truck - now, ya wanna talk emissions junk that disappeared)

Cat diesels are a great power plant - if you want to watch a lump of yellow iron all day.

Originally Posted by IC2

many Ford 302/351 engines used heads with EGR ports or holes in the exhaust port that allowed air to continue the combustion process, if necessary, in the exhaust system for emissions control. If for instance a head was changed at some point in the engines life, one ended up with those holes and the other didn't, you might have additional air flow right at that port. The heads could even have the same base part number and be a different configuration.

Beautiful assessment. I never would have considered that.

me neither tech. and that is one of the many reasons I asked this question in this forum... great minds.

Cat diesels are a great power plant - if you want to watch a lump of yellow iron all day.

Perhaps that was true 20 years ago. The c32 engines are a nightmare. They are too new for the Tech's to know anything about, and I believe they already discontinued them.

On another note, I had no real intentions of keeping these heads long term, just getting a vehicle running to get it outta the shop and running around more before I spend anymore time on it. When I get home, I'll pop the headers loose and take a looksie

thanks again,
Drew

You can probably just look at the front and back of the heads---the air tubes attach to an point that on the other end has a plug / adapter for the bolt hole for accessories--sort of like a caterpillar thread insert----

Originally Posted by jerry clayton

You can probably just look at the front and back of the heads---the air tubes attach to an point that on the other end has a plug / adapter for the bolt hole for accessories--sort of like a caterpillar thread insert----

Jerry - my recollection since I no longer have any of those vintage heads (they all went to the scrap yard)is that it was all internal, fed from the carb heat passage (but then CRS has ......now what were we saying?)

Carb heat passage was exhaust forced across by a valve at the head of one exhaust pipe--the passages your referring to had fresh air pumped into them from an air pump---passages went from end to end---accessories were fastened to front of heads with an adapter---pipes were hooked to rear of heads---

I'll let ya all know when I get home Aug 19th.

Thanks again, 25 heads are better than one.
Drew

forgot about this thread.

for a conclusion:
When I got this truck it didn't run... sounded wretched, knocking and the like.
I'd gotten most of the kinks out, but without a good fuel mixer it was hard to get it set perfect.

the reason one head was hotter than the other was exhaust valves.
Someone at some point did a valve job. From the keeper to the top of the valve stems was a distance of .200 on almost all the valves.
three exhaust valves on the passenger bank were a distance of .380!!!!
So aside from the angle being crazy, I'd wager the exhaust valves were being held open slightly.
due to this being a daily driver I did the sensible thing, I ground the ends down to .200
I expected the seats and valve faces would have been worn down but it runs well now with no smoke, so good enough for now.

thanks for everyones help,
Drew