7610 boost pressure

What is a 7610 supposed to run for boost at full load? It has the pump turned up 1/2 turn. Mine is putting out around 8psi at full load and
no signs of a boost leak anywhere, but I feel like that is a bit on the low side. I always thought 1 psi per 10 hp or so was around normal,
so I would expect this tractor to have closer to 10 psi of boost pressure. I'm measuring at the test port on the intake manifold. It's also
very slow to spool up compared to my Allis with a 301 turbo engine. That motor seems to come to life around 13-1400 rpms, this one seems to
need to be closer to 17 or 1800 rpms to build boost. It's the same tractor I replaced the thermostat in, retimed the injection pump, and
adjusted the valve clearance, all trying to figure out why it falls flat on its face with a load.

Hurst

(reply to post at 19:51:57 05/23/15)

Click to expand...

Do you hear it whistle at low RPMs? have you removed the air discharge tube and felt for play and free movement? The bearings on my 9000 got coked up and the shaft was hard to turn. I removed the oil fittings and sprayed WD-40 in it while turning by hand until it ran clear from the bottom. After that I was hearing it whistle where I never had before. 1/2 turn of the smoke screw is not significant.

From the IT manual 7000s 12 LBS later tractors 15 lbs.

Try checking with the air filters removed.

Mine usually runs 12-13 psi as best I can remember but it's a while since I checked it. You do realize that it would have to be checked under full belt to be a meaningful figure....
1/2 turn of the smoke screw would probably give you the better part of 10 horse depending on where it was before you turned it. Be very careful turning a 7610 much more than that. The engine will only take it until it gets hot and cooling capacity is rather limited on those things...

Rod

I'd be checking for a fuel restriction from the sound of it. Low fuel = low boost.

I just wanted to update everyone on the tractor. After all the different things, I finally got to the bottom of the problem. 3 or 4 years ago, I had an injector that was leaking at a defect in the body (small pit or crack, hard to tell, but the fuel was coming out of the bore in the cylinder head and changing the nut didn't fix it). So, I ordered up a set of 4 new injectors and installed them. Thinking back, that was probably the last time the tractor ran decently. The other day, I took my 4 old injectors and installed them all back on the tractor (they had around 2000 hrs on them from the last rebuild), found the one that was leaking, removed it and installed that nozzle into one of the new aftermarket injectors that I purchased several years ago, and sent it on its way. The tractor runs like it never has in the last few years! It pulls our 20ft woods batwing no problem, 4th and 5th gear, up rolling hills without even thinking about bogging down. I need to look at the stamp on the aftermarket injector nozzles, but I have a funny feeling that the nozzle is not the correct type. The tractor doesn't smoke anymore either! The old injectors had Delphi nozzles, so they should still have some life left in them.

Thanks for everyone's help through all of this!

Hurst