Topic: 38 vanny head gasket

[dgraham225]

Have a couple questions, not a mower build but a mud motor build lol. First, what's the compressed thickness of the stock briggs mls gasket for the 38ci motor? I was told around 0.030 but want to confirm this. Secondly, where can I find a copper (or?) 0.040" thick head gasket? Long story short, had to deck block 0.023 to get it back straight, had a nice groove blown between the cylinder wall and head bolt hole. Stock piston is now flush with the deck. Heads have been shaved (bps iron mountain heads). I thought I'd have enough clearance with the stock mls gasket but evidently not, piston end up slapping exhaust valve within the first hour of run time. Don't have the time or money to get too extensive as its middle of duck season. Any suggestions? I figure a thicker head gasket should get me by if I can find one

[Rocket Ron]

I keep .043 copper in stock.    Ron.

[dgraham225]

Good deal man, I'll give you a call tomorrow after I pull the head and check things out

[dgraham225]

Ever seen a seat fall out? Valve didn't get bent, looks fine. Keep in mind these are bps iron mountain heads, I'm told oversize valves? 1.086" exhaust valve.

[BIG AL 202]

YES! YOU GOT LUCKY! MOST OF THE TIME THE PISTON DOESN'T LOOK TO GOOD WHEN THAT HAPPENS!

[Rocket Ron]

Woniinder If iT is still under wartt? I beleave I'd give them a call Cause yu'll be need'n a nother one of them.

[dgraham225]

Naa no warranty lol, it's been a couple years and a lot of hours. Seat isn't hurt at all either as far as I can tell, went back in place without a terrible amount of effort
Everything looks concentric as far as I can TELL anyway thus far. What are your thoughts on that? Any way to help keep the seat from coming out again?

Piston is fine, small scar but not terrible. Block is bad though, so looks like I'll need another one afterall.

[BlueShamu]

What the heck!?!?😳

I've seen a lot of mixed reviews on the IM's...that's for sure. Some guys have them on their MM's and swear by them. Others will cuss them up one side and down the other!

I've read that the trick to getting IM heads to hold together is to use all BPS components...don't mix and match Manley Valves, PVT cam, IM heads type thing. If you running IM heads, get the rest of their performance parts to go with it....just what I have seen written out there on one of the mudmotor forums....Bonjour! 😳

[dgraham225]

No telling man, from what I've been reading, looks like this is more common for a briggs than I would've thought. Hopefully i can get by with the same seat/valve and the head doesn't have to be reworked and all that.

[George Herrin]

If it was done right from the start it would have lasted. it didn't have enough press fit or it would not have come out. It prolly wont stay now you can try peening it back in but more than likely it will need to have an oversized seat (OD) put in it

[dgraham225]

I was afraid of that.  I hate to take a chance destroying it all once I get another block and swap everything over.  Sounds like I got REALLY lucky this time.

[BIG AL 202]

YES YOU DID! TIME TO PUT IN OVERSIZE SEATS. YOU MY CONSIDER REPLACING ALL THE SEATS. DIFFIDENTLY CONSIDER IT, CHEAPER THEN A ENGINE! 

[Cromwell C4]

If it was a grass cutter you could just knock it back in and use a punch in a few places and it would probably last the life of the engine. But in a performance or racing motor, i wouldn't even try it. Get a new oversized seat put in, blend it back into the port and do a nice valve job. It can be done for less than $100.

[dgraham225]

yea we dont turn the RPM's you guys do, mud motors typically top out at 46-4700.  but they live a hard life, lots of WOT running for longer periods of time.  I figure i better get this taken care of lol, who's my best bet to send it to?  Few guys around my area mess with these heads but its duck season, doubt I could get it done in the time frame i need.  I appreciate yalls help!

[redline]

Out of curiosity, are those a recast head, or just a worked over Briggs casting?