7610 again... head gasket and injection pump question

I hate to keep bugging you guys about this 7610, but I guess I need to quit looking over it so closely. I noticed when I topped the fluids up, the coolant was a quart or two low, and no signs of it in the oil. I steam cleaned the tractor really well and ran it to temp and found it is leaking externally from the head gasket just above the injection pump where the corner of the head is. A little background on the tractor's engine: It was rebuilt by a good ford mechanic after it punched a valve through the head (top part of the valve broke off) with a used head that was completely rebuilt at a local machine shop. Has just over 2000 hrs since that rebuild. I check the torque on that head bolt in that corner and it didn't spin when the wrench clicked at 110lbs. Is this a common leak on these engines? The tractor has never gotten hot enough to boil over that I have been aware of and it doesn't miss or show compression in the cooling system, just a small seeping of coolant in this one spot.

Also, the tractor is low on power and tends to have some unburnt fuel in the exhaust, quite a bit when cold, but still some haze when up to temp. It is also pretty down on power for something that should be closer to 90-100hp. It has a hard time roading a 14ft dump wagon in 8th gear that weighs about 4-5000lbs, something our 6610 can do well. I talked to the guy I use to do my injectors/pumps now, and he said he thinks the pump may have been set/slipped and is timed a little retarded. How do I check the timing on a Simms pump? The CAV on the 6610 is easy with just loosening 3 bolts and twisting it, but this one doesn't look quite as easy. The injectors only have about 500 hours on them. I bought a new set so I would have the old set to send off to get rebuilt when the time came.

Thanks in advance!

Hurst

I probably should have clarified on the head gasket question. Does it just sounds like a bad gasket in that one spot?

They're somewhat know to weep or leak on that side of the engine... Yours is probably at the point it ought to be replaced if it's leaking that much. I doubt if it's losing any compression on it tho...
Low power could be anything from the timing being off to a restricted fuel line or filter... or a bad lift pump.. although they usually take the staggers if they're actually starving for fuel.
IIRC, timing you check by removing the plug on the rear of the pump and install a timing pin/pointer. You then observe timing on the flywheel through the cover plate below the starter. Should be 17 deg on that engine I think... Adjustment is made on the drive gear.

Rod

Rod is correct, those engines can and do leak traces of coolant, although in my experience it's usually the right rear corner where I see it. The problem is exacerbated when you work it hard without warming it up first. This is almost never a big issue if you don't mind putting a little water in it once in a while. In short, I wouldn't fret about it - it's certainly not a compression issue.

As for pump timing, the spec for that engine is 25 degrees BTDC. To check, remove lower rad hose, idler pulley, and front cover plate. Rotate engine until the two timing marks on the pump line up EXACTLY. Check your marks on the flywheel. You should be at 25 degrees plus or minus 2 degrees.

If that checks out, and you still suspect timing, it could be worn bearings in the pump. In that case, the easiest way to confirm is via a process called spill timing. Let me know if you're up for that, and I can post some directions. Other reasons for low power include fuel starvation of one form or another.

This pump doesn't have a removable cover on the rear of the pump shaft. It just has a stamped steel cover pressed into it. Does this come out or is there another mark that needs to line up on these pumps to time them? I saw a 9700 the other day and it had a tach drive coming off of this same area of it's 6-cylinder simms pump, just to clarify where I am talking about on the pump. If that's it, do you just make a pointer out of some key stock and slide it in the slot?

I don't think it is a fuel restriction, because the tractor can smoke like a freight train. I put in a new air filter last year and it didn't bring down the smoke. Turbo isn't losing any oil and spun freely when I checked it without any play. No boost leaks I could find. I adjusted the valves, and a couple were a little on the loose side of their specs, so fixing that helped smooth the idle a little, but still smokey and not as much power as I feel it should have.

Hurst

I should also mention the pump just crossed 2500 hrs since its last rebuild.

I agree that the right rear corner is the most common leaking point on the 268. Mine is leaking there right now... probably about 2L a day or so. It's probably weeped for 5-6 years until she broke her belt last summer at full power and had a good boil.. and the lid's been leaking ever since. Another job to do once the weather breaks.

Rod

The timing is checked exactly as I specified in my other post. Do NOT try to pry the cover off the rear of the pump.

Where exactly are the two timing marks on the pump you are talking about? I know on a roosa master pump there's a little windows you take off and line up 2 marks there. Is there something similar for the Simms pump once you have the engine set at 25 deg. BTDC?

Hurst

Yes. As I said in my first reply, they are behind the plate behind the idler pulley behind the lower radiator hose.

Once you get the plate off, you'll find a stationary slash mark, and one that moves with the drive hub. Line those two up EXACTLY, and by that I mean, dead nuts on. Make CERTAIN that you're turning the engine in the normal direction of rotation when you do this. Then look at your flywheel and see if you're at 25.

The cover plate that bern is referring to is labeled as number 44 in this diagram. The marks are behind the plate at the front of the pump.

Sean, thanks for the diagram! that
clears it up quite a bit. Each of these
tractors are just a little different
Lil

Best,

Hurst