When to resurface spit manifold

I have been having trouble getting my Oliver 70 to run right. I have put on reproduction intake and exhaust manifolds. I pulled them back off and put straight edge I had on it. I put a light behind the straight edge and found a area that had a lot of light showing through. I used a .012 feeler gauge and that fit snug. Can you tighten it up enough to take that clearance out or do I need to take the manifold to a machine shop to true it up? I wonder if this the problem to why I have to put in on full choke to make it run.

Reading your post, I don't see where you say which manifold isn't straight. Maybe I missed it. If its the intake that has a gap, that certainly will cause a problem of low vacuum which will affect fuel to air mixture, cause it to run lean and hotter. If its the exhaust, not so much beyond noisy. As far as torqing it down harder to get it to formed into place, don't go harder than spec, you could crack or break it. Intake manifold vacuum is generally pretty low, enough to cause turbulance to mix the air and fuel, but you absolutely need it. To me, seems kind of odd to have an intake manifold warp because they generally are a cooler part of an engine. I'd say try new gaskets, and Permatex No. 2 (NOT No. 1).

Bottom line is if the intake leaks, gonna run lousy. If exhaust leaks, louder, not worse.

Good luck.

Mark

"When to resurface spit manifold"


Now, apparently.

A new manifold "should" be straight enough to seal. When you put the manifolds on, did you gradually snug the intake to exhaust bolts as you tightened the assy to the head? It all has to tighten as a unit to be properly aligned.

Just wondering, did you static time the engine?
http://www.howacarworks.com/ignition-system/adjusting-the-static-timing

These manifolds were just put on the tractor. The old ones were shot. I have been having fuel problems so I wanted to see how these manifolds lined up to see if I could possibly have a intake leak. I was just wondering if some clearance was acceptable and you could tighten it up enough to seal it. I have seen split manifolds in the machine shop being resurfaced so I thought would ask how much clearance is to much clearance.

Sent mail. Earl

if its the intake that is warped then thats why it is hard starting.
that reproduction isn't made in china is it?
you will need to have it milled to get it straight.

I only remember that if a head had more than .003 warp we resurfaced it. Had to be careful with OHC heads as too much warp would bind the camshaft.

"A new manifold "should" be straight enough to seal."

He said he replaced BOTH intake and exhaust and it is COMMON to have to surface them to get the faces at the same plane, ESPECIALLY with today"s aftermarket replacement stuff.

Have you ever replaced one or both manifolds of a bolted-together set on an in-line engine?

The amount of clearance you are saying is a lot. 012" is enough to cause a significant vacuum leak. That would definitely cause it to run poorly, but perhaps not enough to cause the condition you describe. I suggest that you correct the obvious problems you have found and then re-start with basic engine diagnosis. Overtightening the manifold will only cause more problems than it solves. Take it to a machine shop and have it trued up.

An engine needs 3 things to run:
1) Compression
2) Spark - and at the right time.
3) Fuel/air mixture. Ideal is at 14:1

The condition you describe can be caused by many things:
Ignition timing - could be far enough off to cause your problem.
Valve timing - are you sure that the timing chain and sprockets are lined up correctly? This is another thing that can cause your problem. You can verify with a compression test. If valve timing is off, compression will be low.

I suggest that after correcting any OBVIOUS problems, you return to basic diagnostics. I would start with a compression test. Following that, I would check engine vacuum. Also check ignition timing. Engine vacuum should be at least 22-25" at idle. Ignition timing should be within a few degrees of spec. Most engines will run decent at 5 degrees BTDC.

Make a few basic tests like this and report back. There is still the possibility that your problem could be in the carb, but in order to prove it, all other aspects should be verified.

The easiest way to see if that is your problem is to get the tractor running then spray some carb cleaner around the manifold ports and see if your engine picks up and smooths out. I just had the same problem. If it picks up then you know that's your problem, if not keep looking elsewhere. My Oliver I had to run with the choke out also, then I sprayed it and it smoothed right out. New gaskets and it runs like a top. Let us know what you find.