730 engine problems

I have a case 730 gas tractor that developed a knock and started fouling the plugs. I cant remember if it fouled all of them or just one or two. The knock is always there whether you are idling down, have the clutch in, are under load etc. It is a fairly sharp metal on metal sound seems to occur every cam rotation. From what we can tell, it sounds as the the noise is from the front cam area ,though its hard to say for sure. The tractor runs rough and will barely move without wanting to die. Anyway we ended up taking the engine apart and could see no obvious sigs of wear which lead us to rebuilding the entire engine. We replaced crank bearings, cam bushings piston pins,pistons, sleeves points, condenser etc. The only things not changed were the valves(which looked alright) and we didnt have the cranked turned. After reassembling and being very hopeful the engine still knocked and fouled the plugs. We had no idea what the problem was. I did some tests and here are the results: compression : 132psi on 3 cylinders and 138 on 1 of them. ( the book says 140). Oil pressure: 45 psi ( book: 40-50). Crank endplay: 0.011 (book: within tolerence). Cam gear backlash: 0.012- 0.018 measured in different spots (book: 0.006 max). As you can see, the cam backlash is way out but after speaking to a couple people, they say this usualy isnt an issue. Upon 2nd disassembly we noticed one of the push rods was shiny all around where it goes through the block/head though i dont think this was the case the first time, hence i"m not sure its part of the problem. We took the engine into case for a quick look but didnt accomplish to much. Now were on our third disassembly. We ran the engine with the cam cover off and though the sound seems to still be in the front cam area there is still no difinitive sign of the problem. We then pulled the crank gear and turned the cam manually with a 500 rpm drill to see if the knock was still there and if the cam was going in and out. From what we could tell, it was"nt. This is where we are right now. We have spent over $2000 on a rebuild and countless hours on this thing over the years trying to figure it out. This is such a simple engine though the problem remains a mystery. Does anyone have any suggestions. PLEASE HELP!!!! Questions: 1.Can backlash cause knocking and effect timing this badly. 2. Can these cams have endplay issues. 3. Can cam endplay effect timing. 4. Do you think the backlash is an issue. 5. Do you think it could be a lifter problem. 6. How much play can distributor shaft have before its an issue.

I can't help but. I admire your tenacity!

Fouled plugs & the knock mey be 2 completely different issues. Did you replace both rod & main brgs.? Did you plastigauge the bearings? Were the Pin Bushings within spec?
As for the plugs fouling, if you are not using Autolite 3116 plugs, give them a try. How's the plug wires?

Did you check the crank size?


I had a ford that the crank wore and the bearings were perfect

Cam gear miss-marked or key sheared? With #1 on TDC, #4 I&E valve overlap should be the same. Overlap means even, EX coming up and Intake going down, valve springs compressed the same.

We have several Kohler 12hp engines on Gravely riding tractors. These gravely Kohlers have dual geared balance shafts for smooth operation. One is a high time engine with 2 over-bores on it. We rebuilt it when we got it and noticed that it made a metallic klinking sound every revolution when operating at low speed. After tearing it down and rechecking our measurements we have determined that this is due to the backlash in the balance shaft gears.
I suspect that the knocking sound you describe is a backlash problem like ours. Also, your distributor shaft should have no noticeable side play between the bushings and the shaft. If it has much at all, then it should be rebushed. This can easily cause missing or rough and inconsistent running.

After thinking about it some more, your engine must be extremely high-time to get that much backlash. It is also possible that some water got into the front cover and rusted the gears, or that one of the gears was soft from the factory. However, if none of the gear teeth seem worn, then it may be that someone replaced the crankshaft gear with a non-case part either because it would save money or because they could not get a replacement.

Assume you pulled and magnafluxed the crank?

same here ,,, hang in there

If you put pistons in it then they are probably hitting the head. I had this happen once. Even after measuring to be sure the pistons were at the proper height. Turned out that after running a bit they would grow enough to contact the heads by a thou or two.

they need to be a minimum of .030 down the hole from the top of the block at TDC

It sounds like your willing to do what ever it takes to fix this tractor.

Was the tractor running ok before it started to knock and foul plugs?

Have you looked at the distributor to see if something didn’t happen to it?

check the distributor for something being bent or twisted.

yes everything was replaced but we did not plastigauge.