I've got a 35 gtr which I had a cam and heads put on it. Ever since then my case bolts and exhaust bolts have been backing themselves loose and falling out. I've tried everything I can think of to keep them in and nothing works. The motor runs great and I've tried several different props. The only thing I can think of is the cam is possibly out of balance.

Has anybody had anything similar happen. I can make a hunt without the bolts backing out.

loctite won't work?

Put studs in the block

I've used locktite and studs. They r still working themselves loose. Anybody else seen this happen.

And the threads r still in decent shape. I did have to drill and tap one hole but the rest r in decent shape.

Try ARP bolts maybe? What color loctite did you use?

Does sound like something may be out of balance though. Must be some pretty bad vibration to keep shakin' those things loose.

No experience with this particular situation. However, couldn't you drill and tap with steel heli-coils?

Aluminum is notorious for not "locking" bolts/studs do to not being able to really tighten everything down. And with bolts in areas like that you dont want to use red loctite if you ever have to take the bolts out.

But couldn't you drill and tap for heli coils, use steel/stainless heli coils with red loc tite, then bolt it down as normal with blue loc tite?

Also, when I use loc tite I always wait a lot longer then they say before using the motor just to try to make sure everything sets up. If you go the helicoil route, I would red loc tite the heli coils and let that set for 24 hrs before messing with the bolts.

Sounds like something is out of whack... lots of hours on my heads, mikuni, cam, and exhaust and my case bolts are still as tight as when I put it all back together.

Get it like you want it and weld them bisches

Cam is not the issue. Get a balanced prop and swap out your bottom pulley to a 48. Take some load off the engine.

Make damn sure that the threads are clean for the loctite to work!

I put arp studs in mine and it was the worst mistake ever nothing but problems with them backing out. I put my stick one back in and no problems

I've tried all combos of studs and loctite as suggested. nothing has worked. I'm running a gt extreme with an open floor, just a box for the drivers seat. I'm running no more than 3850 rpms. It runs like a champ but bolts r falling out whether it's me or 5 guys. Whether I run it wide open or at 3600 rpms. I love the performance with the cam and headwork. It fits my needs. A stock motor doesn't quite cut it. With that said I would rather cut my loses and fix the problem rather than deal with this while trying to enjoy my hunting season. Whether it's my motor, the prop, shaft, cam, or another critter I just want to solve the problem. Any one else in the wide, wide world of mmt have any input.

You wanna try a stock cam and see if the vibration goes away?

I was guilty of running it on the ragged edge a time or two just to see what the motor was capable of, but also knew it would not hold up at long intervals at those rpm's! When I said it would do it all day long, I meant at any given time the motor would give me 5500 rpm's! For a 1/4 of a day! Lol

All 3 of my motors have the same set of studs in them taken each time from the previous motor !! Any how I never had a problem with s loose stud or any crankcase problem except for the 100 hour leek!!

i have had a stage 1 from calen for a little over 100 hours now. i am just starting to have this problem so i brought it over to calen last week and asked him to figure out what the deal is with it.....im thinkin its a bent shaft. only weird thing is i do not have any bad/extra vibration. it went so far as to shear one of the crank case bolts clean off and backing some of the other misc. bolts that are on the motor. once calen figures it out i will report back.

Since soooo many people are modifying these 35 briggs and having issues with them afterwards as the case and guts just aren't up to the task, it would be nice if go-devil, gatortail, mud buddy etc. would talk briggs into just making a reliable 45 to 50 hp engine right out of the crate. And beefing up the case, crank, bearings etc to handle any potential mods with relative ease up to about 70 hp/ 75 to 80 ft/lbs of torque.

then people would just mod those engines and have other problems. I don't really see B&S that worried about the mudmotor industry considering it is maybe 5% of there engine sales

Emissions are too strict once you go over 1000cc...

Bolts shearing off is the cover moving on the block. Heat and vibration are the culprtit along with too small of bolt for the cover. Torque is being applied to the cover through the bearing surface on the cover. More load and rpms and more load applied. Metal grows when heated and shrinks when cooled. Add all of these factors in and you have backing out bolts, sheared bolts and cracked covers or blocks. I have seen numerous motors do it with out a cam swap and just bolt ons. The cam is not the problem.

im thinking either my prop is not balanced (which i find hard to believe b/c i been running it for some time now without these issues) OR i bent my shaft.....like i said i been running my stage 1 for over a 100 hrs now and i am just starting to have these issues. not sure what the contributing factor is.

I've talked to plenty of people over the last couple of weeks who have had the bolts back out and shear. Some have had stock engines. Some have engine mods, from various manufacturers. No one has pinpointed for a fact what the problem is. I'm leaning towards drake1 point of view. They aren't built like tanks. We r running them beyond what they were built for.

Had the same problem with an EVT stage 1 ( Heads intake carb) which are all bolt on mods. I got some nordlovk washes and red locktite and never had a problem with the state 1 again. Also can you get a true torque on a GTR with the powerhead on the outdrive? if not you might be looking bolts due to bolts not being torque right.


Once they get loose they will break if you get down on it.

I forgot to mention that when I built several airboats in the past I ordered some bolts from a place called AIRCRAFT SPRUCE that had holes drilled right through the heads of the bolts. Once you torque the bolts down to specs I would run stainless welding wire through all the bolts and presto no more lose bolts due to vibration. Airboats have alot of vibration at times with the wind changing direction through the prop and bolts were coming lose and trying to drill those holes was not easy so I found some at the place mentioned. I suppose you could get a machine shop to do it also. good luck.

I think I might have found something that atleast would contribute to my issues. Last night I was going fishing and when I started the motor. It idled great but as soon as I gave it gas it would only run on one cylinder. Then after a minute or two it warmed up and ran like normal. So today I pulled the plug on the side that was missing and the gap of the plug was huge.

My thinking is it was creating incomplete combustion and occasionally missing (that I didn't notice). And possibly causing a "balance" issue. Does this make sense. I have not pulled the plugs since I had the work done since it only has 20 hours and it still ran "great". So I hope I get a little more get up and go and solve my bolt issue.

An unbalanced motor may not have noticeable vibration, but it can back out bolts all over the motor. If u put the wrong harmonic balancer on a car engine, u can have the same issues that r being discussed here. Sounds like an internal balancing issue. R these welded and ground cams balanced before being sent out?

If u get a high rev V-8 balanced and blue printed, all of the intervals r balanced. It would seem reasonable that some of these welded and ground cams r out of balance, causing some of these issues.

Honestly do you think they are doing it? Doubtful... its a lawnmower motor bro...Thats the mentality. THis is a small market already and peopel bitch abotu high prices anyway so add balancing on top of that.. then the price goes up more!