Exchanging Heads on 18hp's

[samo_ott]

Does anyone know if I can put a later 18hp head (early 60's) with a thermostat in it on my older 1958 18hp FD that does not have a thermostat? Will the cooling holes line up? I know I could take both off and check but was hoping someone might know.

I just got the FD and it has a stripped plug hole and I have a spare head lying around so was wondering if it would fit. Thanks...

 

[1946Zephyr]

Re: Exchanging Heads on 18hp's

Sorry, but No you can't. You have to stay with your year of head. Your engine has a completely different cooling system, than the one with the thermostat.

 

[Chinewalker]

Re: Exchanging Heads on 18hp's

That is correct - they won't swap. The block is cast differently to accomdate the t-stat head...
- Scott

 

[samo_ott]

Re: Exchanging Heads on 18hp's

dang, I was hoping all the 22 cube engines were the same...

 

[F_R]

Re: Exchanging Heads on 18hp's

"all" 22 cubes are not the same, even year for year. The 18, 20 and 25hp motors have different combinations of pistons and heads to get the various horsepowers.

 

[samo_ott]

Re: Exchanging Heads on 18hp's

duh... ya, of course!

 

[cc67]

Re: Exchanging Heads on 18hp's

You might try a heli-coil. I've used them on motorcycle heads before with no problems.

 

[samo_ott]

Re: Exchanging Heads on 18hp's

There already is one in it. But when I took the plug out the heli coil came with it. But it also screwed right back in again. Problem is the HC was solidly attached to the plug and the plug was as old as the hills... Close to original! So I want to change the plug and I'm not sure how I can get the HC off the plug without buggering up what is currently working... So I was just hoping to swap with one of my other heads as I did recently with my '54 25hp 35.7 cube engine but I guess it' wont be as easy... I'll have to see if I have another head... As it is now I cant even check the compression in that cylinder... I'm not a big fan of HC's although they do serve there purpose...

 

[cc67]

Re: Exchanging Heads on 18hp's

I always used red locktight on the HC and never had one back out. Maybe you could have it welded and re-taped. Another problem usind different year heads is the cowl mounts would be different.

 

[freddyray21]

Re: Exchanging Heads on 18hp's

A new helicoil should screw right in as well. Sounds like someone got locktight on the plug not the coil.

 

[Sea18Horse]

Re: Exchanging Heads on 18hp's

Or maybe it's a solid insert and not a helicoil at all. The solid inserts are junk in my opinion for this very reason. True Helicoils installed properly don't come out.

Cheers...............Todd

 

[samo_ott]

Re: Exchanging Heads on 18hp's

Interesting. How would one know the difference? Can one tell visually?

 

[hammerhandle]

Re: Exchanging Heads on 18hp's

my fathers 67' 20hp had that solid type spark plug insert, the insert wasnt just the wire part like a heli-coil with its own special tap for the threads, but a larger nut like shaped self threading plug and then the spark plug threaded into that.hard to describe but wasnt very big. i dont know where he got it at but i know he had it in there for years and never had a problem with it. i will ask him the next time i see him. hope that helps alittle samo.

 

[rjezuit]

Re: Exchanging Heads on 18hp's

Some inserts are solid with a larger thread on the outside and the original size tapped on the inside, kind of like a threaded plug. True "helicoil" brand inserts are coiled stainless steel of diamond shaped cross section. If you tried to thread the plug in without the insert in the plug, it should not go in. The helicioil is like a spring. You tap the head with a special propreietary tap and when you insert the coiled insert it "grabs" since the pitch opens up when it is installed. This allows the plug to thread in correctly, but also causes the helicoil to stay in. There usually is an installation tool and a drive tang on the helicoil that you break off when you are done installing the insert. Look here.... http://www.emhart.com/products/helicoil/standard.asp Rick

 

[jbjennings]

Re: Exchanging Heads on 18hp's

Steve,
I know someone who has an extra '57 18hp head. But you probably won't want it because I know for a fact he owns a couple of mercs and it may be tainted with bad merc juju.
check your email....
JBJ