Engine Head spigot hole to big

[dd-ardvark]

I have a pair of New Old Stock 914 2L heads that were cut to 112mm spigot hole and the chambers were never opened up, so the head registry is still there. This is the surface that a stock 94mm, and After-mkt. 96mm barrel would rest against in the head. The heads will be opened up to 115mm that of a 103mm steel, same as 100-102mm http://www.lnengineering.com/nickies.html cylinders outside dia.

I want to use these heads with NOS 98mm Mahle/Okrasa/Oettinger aluminum cylinders, that have an outside barrel dia. 106mm. Yeah, 4mm, REAL thinnnn cylinder walls, but a good machine shop can make spacers for the outside of these cylinders without to much of a problem. They will be 4.5mm+/- thick.

A little background: I've done this on type1 motors using steel on cast steel cylinders, and it was an interference fit to the cylinder. Case in point, 88mm slip-in cylinders, this is a thin walled barrel (stock 1600 outside dia.) and the head spigot hole was 101.5mm, cut for 90.5-92mm barrels...To answer your question this was done just as an exercise in bastardization at it's finest. No, we didn't plan on the motor living for any great length of time, it was an old tired engine to start with, and the motor only lived for about 6 weeks, and died after it swallowed a small Gremlin. We knew it had, because HE kept knocking on the case real loud... Anywho, when the heads where pulled, no leaks at the cylinder and head were evident, discounting the one that the piston was slapping against.

Question: Should I make the spacers an interference fit to the cylinders (pressed on), or to the heads (pressed in).

Question: Should I even be concerned with an interference fit.

Also: My thinking is to make the spacers of aluminum this time instead of steel, to coincide with the aluminum cylinders. Keeping in mind both the head and cylinder are cast aluminum.

Question: If you agree to the aluminum spacer, what type/grade of aluminum should be used.

Either way I will be using LN-Engr's. Head Stud and Hardware Kit because of their research into the thermoexpansion differences between aluminum and steel.


Calling all bastardization experts and or real ones, your thoughts please. dd-ardvark

[Massive Type IV]

I'm really confused here...what are you trying to do size wise??

[dd-ardvark]

Sorry about thank Jake, guess it was a little long winded. Here's the simplified version of the same question.

The head has been bored out to fit a 103mm cylinder.

The chamber in the head was never cut out bigger.

Question: Can a cylinder of stock dia. with a spacer be put back into this hole.

[Massive Type IV]

If the cylinder head was unshrouded for the biger bore, you can't go the other way!!

[dd-ardvark]

So my question is still, should I press the spacers on to the cylinders or into the heads, or should I even be concerned with an interference fit? Another words, have the spacers made to just drop into place.

[Bugzilla]

Wanna sell 'em?

[dd-ardvark]

Hey bugzilla

Na! I'm going to keep the heads and parts I've collected. I'll get this motor together before this years out.

Just as a side note: You asked a question on the shoptalkforums as to what the rods were in the motor that you've acquired are. Well, I've got a set of Chevy 350 rods and they appear to be pretty close. Take one down to your local Napa store and set it next to a brand new rod and have a look for yourself. About the only thing I can see from the photo is the they appear to have been cleaned up (polished).

[Bugzilla]

Fair enough!

I am sorta in the market for a set of performance heads that will go on a 103 register, so I don't mind finding some already cut. I'd like to put that big motor back together, but do it RIGHT this time. Thanks for the info on the rods, BTW.

Of course, my preference is to buy the whole lot from Jake, either in kit or turn-key form. But I'll still have a bunch of parts left over, and that would be a SHAME to just let 'em sit around!

~Troy

[Wally]

Hello DD,
After reading your thread several times..., I think I understand now (?). IMO the Alu rings you want to use will neither contribute to structural strenght for either the head (when you press them in there) or the cylinder (if you press them onto those). Very possibly be dangarous because of weird stresses that might appear due to the fact that tiny differences in thermal expension or thermal conductivity can occur, even with a similar grade aluminium. Since Oettinger made the Nikasil set, you can better trust that the design was good, than to try tinkering with it yourself.
So, why use a 'fill-up' anyway. In an original set-up, the cylinders don't have an interference fit either. Now your inteference is just a bit bigger. If you want to use the rings anyway, into the head seems a little safer than onto the cylinders IMO. Its not ideal, but you want to use those heads, so be it.
FYI, I also have a NOS Mahle (Oettinger?) Nikasil set, but of 103 mm. It has 5 mm wall thickness at the top and I also just ordered LNengineerings head stud set (same minds?).
Good luck,
Walter

[cnavarro]

This works great- Bugzilla want's your bored out 2L heads and I have a set of 2L heads for sale that haven't been bored out yet that are getting new valves and guides put in as we speak at Headflowmaster :-) Although my set of heads have been thermal dispersant coated (they now appear black) and have ceramic coated intake and exhaust ports :-)

Anyone one else want a set of head studs so that I only have to make one trip to our "freezer" warehouse (heat's out and it's about 5-10F inside), since i'm heading over there to pack up Wally's set?

Just kidding...

Keep warm folks!

Charles Navarro
LN Engineering
http://www.LNengineering.com
Aircooled Precision Performance

[Bugzilla]

Originally posted by cnavarro
...our "freezer" warehouse (heat's out and it's about 5-10F inside)...

Is that what you call your "Optional Cryogenic Treatment"?

hehe

~Troy