Milwaukee Midget

[Milwaukee Midget]

I O -

There is a trick that Fordboy has used in the past on this combination which incorporates drilling additional water passages - actually steam vents - in the face of the head and into the deck of the block.  This gets better cooling to the particular area where it's getting hot.  The reason I didn't incorporate that trick was because I was using the MLS gasket.  On the Cometic, the outer faces are embossed around the water and oil passages, and I didn't think we could get a clean hole punched through the 3 layers - at least clean enough to ensure no leaks.

If I go to the Coopers copper gasket, leaks won't be a problem, and perhaps I'll look at that.

[Crackerman]

On the retorque, you did it with a hot engine. I was always under the impression that this is a not so great practice. The expanded, due to heat, metal will relax when cooled, unloading the bolt/stud and losing clamping force. Many higher hp diesels i have seen with a failed headgasket after replacement had a hot retorque after replacement.
I like to give the engine a heat cycle or two, then do a cold retorque. That way, as expansion occurs, it only clamps harder if the studs dont deflect.

I may have the wrong ASSumption on this one, but i also lost a new headgasket the only time i did a hot retorque. Changed it up and havent had issues ever since. (Aluminum head, iron block mitsu 4g63 around 250hp/liter) granted aluminum grows much further than iron.

[jacksoni]

It's my understanding with the Cometic MLS gaskets ( I use them too) that in addition to the deck (and head) surfaces be flat, but also exceedingly smooth in preparation, nearly polished, for best seal. I have been reusing mine with a spray of copper coat with no issues so far.

[Geo]

Yes, different gaskets need different surface finishes.  Jag needs semi smooth, Mercedes needs semi rough.  A heat cycle without running anywhere and then a cold retorque has always worked for me.

Geo

[Milwaukee Midget]

On the retorque, you did it with a hot engine. I was always under the impression that this is a not so great practice. 

Right you are.  Thinking back, I don't recall retorquing the head after the dyno session.

[Interested Observer]

So, Chris, the following is one person’s take on the gasket issue, for what it is worth..
I was somewhat concerned that you were inclined to launch off on an O-ring solution, involving machining, new parts, a whole new and largely unproven setup, when you already have a pretty simple, well-performing configuration that survived the dyno and quite a number of runs with only a single minor leak between cylinders.  And that with a bit of a murky torque/retorque history.  The Cometic gasket seems to be a rather well engineered piece, with the embossed ribs helping to concentrate and apply the preload where it needs to be--in the seal areas.  I am not sure if the actual construction is exactly as per the illustrations in the Cometic catalog, but the concept seems correct and the success of their approach seems to be well accepted across many applications.  Due to the narrow seal width it may not be the kind of gasket one would want for something you were going to put 100,000 miles on, but for relatively short term use it seems fine.  Also, it would appear that it is amenable to being “enhanced” in the bridge area between the cylinders if that proves to be needed, by adding some thin shim stock between the two outer sheets--further biasing the contact loading in that region.


Secondly, it seems like you may be itching to incorporate Fordboy’s steam vent technology and copper gasket.  While this certainly could be done, and may be just the ticket for a 30 minute road race, is it really needed for a one and a half minute blast down the salt?

I'm actually having difficulty getting the engine above 180 - it's running super cool - at least as far as the water temp is concerned.

It doesn’t seem that you are really getting that hot, and I just see more machining, special gaskets, liberal and necessary application of sealing compounds (a mess to deal with), and the movement of the clamping force back to the immediate area surrounding the head bolts instead of between the cylinders.  The solid copper gasket would be considerably less compliant than the embossed, multipart Cometic.

Stick with what you’ve got!  It works!

[Milwaukee Midget]

Well - we may . . .

Another issue on the horizon is the potential of doing something to increase compression.  It's a huge headache on small capacity engines.

We needed to come up with a widened lobe center angle and an unusual cam lobe in order to make what we're running work.

Just a reminder for those who are following along, MAX that can be tolerated:


 
Fordboy

We're in really good shape, considering we’ve got .0065 pop up on the pistons and that I shaved the head .060.  Additionally, the cam Dema built actually has more lift than the SPVP-5 it replaced.  Cam is dialed in at 105.25 degrees.

Piston clearances @ plotted points

Intake –
TDC   .091
5 ATDC   .071
8 ATDC   .064
10 ATDC   .061
12 ATDC   .060
15 ATDC   .063
20 ATDC   .076

Exhaust –
20 BTDC   .100
15 BTDC   .087
12 BTDC   .085
10 BTDC   .087
8 BTDC   .089
5 BTDC   .096
TDC   .115
5 ATDC   .144


[/quote]

Now this was calculated with what was advertised as a .027 gasket -

I'd ordered up a pair of their steel 3 piece head gaskets.  They were advertised at .027, measured up at the fire ring at that, but by the time I put the torque to the studs, they crushed down to .0225. 

The next size available was the .036.  Assuming similar gasket crush, I lost probably .2 CR due to this, and I'm fighting for every single point I can find.

The head is maxed out, but even with a notched piston, the best I'm likely looking at is 13.6:1 and still have safe piston clearances.

But seeing as I have a few thousandths more to the plus due to the thicker gasket, I might be able to make up some of it with Rimflow valves, which have a thicker head, and provide better flow and anti-reversion properties.

Much to take into account.

Or I could just start on a destroked DOHC K-series MG/Rover 4 and be done with it. 

[fordboy628]

Midget,

If you recall, the retorque done @ TNT was on a "basically" cold engine, it was not hot, by any stretch of the imagination.   Perhaps warm or tepid is the proper adjective, as we pumped cool water through the assembly to facilitate a "cooler" retorque.

In my experience, the discoloration you are seeing is due to heat concentration between the siamesed #2 & #3 cylinder bores.    It is why I drill the extra "steam" holes.   They have been indispensable for 30 minute road race sessions.    BUT, Interested Observer is right, you probably don't need them at the temp/run time for your application.

I am not opposed to the Cometic gasket, it has held up better than I expected, although at the price of slightly lower C/R.    Simple, working setups are preferable to complicated, untried solutions.

In my experience, you NEED more static/dynamic C/R at the low V/E your engine makes.   I still think the most cost effective way to higher static C/R, is a set of "domed" pistons, fitted to the current cylinder head assembly.   As opposed to a "small" chamber special cylinder head.   A small dome, combined with the Vizard "slot" or notches, opens up more choices for alternate camshafts/camshaft timing.   Your checkbook, your choice . . . . . . . . .

Once the complete cylinder head has been flow tested with the inlet manifolds, you can make an intelligent choice based on: information . . . . .     OR, you can have my ex-partner pick a head based on how it "looks" to him . . . . . . . . . 

Just my 2 cents.

Off to pay my homage at the grave of Edgar Allen Poe with a toast of absinthe.   Back in 10 days, unless I end up in the Arkham Asylum.    GO BEARS!!!!
 
Fordboy   

[Milwaukee Midget]

yaah - go bears dare, aina hey . . .

All possibilities are on the table.  I need to calculate the pop-up I can get by with and maintain the valve-to-piston clearance, and still allow enough variance so we can rock the cam a degree or two without crashing into things.

A friend of mine showed me how to do that! 

Absinthe?  Nevermore . . .

[gkabbt]

yaah - go bears dare, aina hey . . .

All possibilities are on the table.  I need to calculate the pop-up I can get by with and maintain the valve-to-piston clearance, and still allow enough variance so we can rock the cam a degree or two without crashing into things.

A friend of mine showed me how to do that! 

Absinthe?  Nevermore . . .

Been there done that and as you said.....Nevermore!     

[Dean Los Angeles]

180 degree coolant temperature is way too low. The whole idea it to retain the heat of expansion and use it to push the piston down. The hotter the coolant the better.

Simple formula, run it until it melts, then back off a little. 

A lotta years ago I saw an interview with a famous AMA dirt track tuner. His rider won the race by a wide margin. The interviewer said that is was an almost perfect race.

The tuner's response? "Hell no it wasn't near perfect. Perfect is when you cross the finish line a lap ahead of everyone, The frame splits in two, the engine explodes just as it runs out of gas, and the rider dies of exhaustion. That's perfect."

[Milwaukee Midget]

180 degree coolant temperature is way too low. The whole idea it to retain the heat of expansion and use it to push the piston down. The hotter the coolant the better.

Absolutely - the Smokey Yunick approach.

I was surprised as to how cool the thing ran at Bonneville.  My previous experience had been not being able to keep it from overheating.

Seems like that's no longer an issue.

 

[grumm441]

I'm not sure I would use a copper gasket
there is too much area to compress
With the Cometic gasket you have more localised pressure around the fire ring
G

[Jack Gifford]

... I'm not sure I would use a copper gasket
there is too much area to compress...

See my post #3230 to this thread. I apologize for being repetitive, but there doesn't seem to be a very widespread understanding of traditional O-ring/copper/receiver-groove functionality.

[Peter Jack]

I wouldn't use a copper gasket without a proper O ring setup.

Pete