706 not getting fuel to 2 cylinders

Cory Schmidt

Well-known Member
Just finished a complete overhaul of a 706 with gas engine. Have it timed fairly close(best we can tell), the valves clearances are fine. The problem is that cylinders 3&4 are not firing. Tested spark and compression both fine. So that leaves fuel. When running wires were pulled off the plugs and the rest had a effect, but 3&4 didn't.
 
order is set as well. even tried to flip just those wires no effect. checked through all. all in place. it runs fine on the other four. If you still think that's my problem what should I try.
 
I'll double check the order it is cast right on the block so I know it. had the manifold ground when engine was stripped and with a new gasket that idea was out for us. but never hurts to check
 
blew air from spark plug hole back though intake valve lots of air out of carb. attachment hole
that means no rag
 
Do you have the correct intake gasket installed? There are two styles of gaskets, the early ones were a piece of metal with sealing rings around each port. The later ones were a one piece composite style. They do not interchange!
 
Cory, just went through this on a 560. After I did all the trouble shuting good compression, good spark, no fuel. vaccume leak. found the round metal ring not seated right. It was damaged and needs replaceing, I removed it and reset manifold and she runs sweet now. I was surprised how little of a leak would stop the 2 cyclinders from fireing at all. oldiron29
 
Many times a plug will fire out of the tractor, but under compression it won't fire, or will fire if you hold the plug wire away from the plug. I'd try new plugs.
 
pulled manifold off the gasket look like a new gasket should. Since it was off we took a depth gauge to the bosses on the head and the counter bore in the manifold. the bosses were around 1/16inch longer than the bore (including the gasket). we figure this is our problem. I'll try to post later when we get that fixed and if it helped. Thanks for the suggestions everyone.
 
The rings to guide gasket are only used in the end cylinders and not middle two. On the gaskets, early models used same old gasket the trucks and 560 used. When we started having all kinds of problems with intakes leaking, IH came with a ribbed metal gasket that had asbestos embossed material on the intakes. They also came with the plated grade 8 bolts and hardened steel washers. Those good washers are no longer available. The ones they subbed to now are not a good fit. The new combination did a real good job but you had to split the manifold before installing as intake part of gasket is thicker. Many will fit gasket packages use the old style gasket and when you start mixing and matching gaskets and manifold you have to know what is going on. If you machine the manifold all in one piece and don't split it you have to use the gasket that is same thickness all the way, intake and exhaust. I hate those gaskets as they ruined more than a few engines in their hay day.
 
it is one of those one piece ones. the same type we used last time we rebuilt. Had no problems. we think this time since we had it and head ground the shop we had do it forgot to mill something so the boss/rings on the head stick out to far and when tightened the manifold would pull tight on the ends and not in the middle
 
Milled the rings down a little on the lathe. Tightened the manifold back on. Purrs like a kitten again. Again thanks for the help.

Note to others: be sure to check measurements on things that go into others to ensure a good fit
 

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