Billet alum head for diesel tractor puller?

[tstom]

Would be interested in opinions on whether a solid billet aluminum head would live on a John Deere diesel puller engine. The pull lasts about 40 to 50 sec.Occasionally they have to rerun in a "pull off" tie breaker
They now run a ported stock cast iron head that has the water jackets filled solid with block filler (grout)and don't seem to have much trouble. These are serious pull only engines with 120+lbs manifold pressure, 5000 rpm,roller cam, etc.
The head is approx 48"x8"x6"

 

[swall]

You are considering alumimum because----?

 

[tstom]

Ease of machining... What other options should I consider?

 

[MikeHalloran]

I've seen forged aluminum billets that big turned into high pressure hydraulic manifolds. The alloy may have been 2024-T3 or -T4. For some reason, we had to section one. Witnesses reported a lot of noise from the bandsaw, and that the two halves bowed about 2" as internal stresses were relieved.

You may have some trouble with distortion as you machine the part and relieve stresses that were locked into the billet. One way to deal with that is to finish the head bolt holes early, and lock the workpiece down to a strongback, or fixture and machine it cylinder by cylinder.

It's really a joy to machine 2024-Tx; it produces beautiful curled chips, and you can run most tools as fast as your spindle will go. It's very strong, too

Mike Halloran
Pembroke Pines, FL, USA

 

[MikeHalloran]

OR, you could slow down the CNC machine a bit, and start with a billet of iron or steel, since weight reduction is not a priority on pulling tractors.



Mike Halloran
Pembroke Pines, FL, USA

 

[EHudson]

It is far easier to keep valve seats in an iron head.

 

[stout1]

I disagree that weight reduction is not an issue. Pullers are always trying to reduce weight of the engine, frame and other places in order to put the weight where they need it to hook better. We used to build a lot of pulling engines at a shop that I used to work at, we even built billet AL heads for a V12 Allison (I think that was what it was for) but it must have been built pretty well since we never had it come back in with problems. We never did do an AL head on a diesel so I'm not sure how that would work out but I would think that you shouldn't have any problems with it. The cylinders will have to be o-ringed if their not already though. Good luck.

 

[tstom]

I hear of guys using steel billet heads and questioned why alum. won't work
Stout1 is correct in that the overall weight may not be a concern but where it is placed is important...so lighter parts allow more flexibility in weight placement how ever that is not my main issue I just am not thrilled about carving a complete cyl head out of steel

They tell me their ex temp is usually around 1800* I don't really see seat retention as a problem if the interference is correct I have seen computer traces from Top Fuel cars that have temps approaching this range (run time much shorter) How close would egt reflect in cyl temps?

 

[brngrhd]

i know that rick kippley made a head for a pulling tractor out of aluminum and it worked very well. if your into pulling i'm guessing that you might know who rick kippley is. i don't see any reason that you can't do it.

 

[patprimmer]

It should be OK.

Valve seats do sink back into aluminium heads under the seat pressures you need for high rpm blown alcohol motors (9000 rpm, 40# boost SBC at 1500 HP with over 300# on the seat).

I don't know what seat pressures they run on diesels, but I would think cylinder pressures and temperatures are higher than alcohol motors.

I think tractor pull motors run really high boost, so spring pressures might be high despite relatively low rpm.

The valve seat problems occur if the inside rad of the port is to close to the valve seat and so reduces support, and if the heads have started to go soft. The extra heat in a diesel motor might send the heads soft earlier.

For thermal stability you might need a T6 grade of aluminium as lesser heat treated grades shrink on repeated thermal cycling. I think the Si level also impacts on thermal stability.

Of course even mild steel will be more stable.

Another problem with aluminium is that it expands more than steel or iron and therefore does not have a good consistent grip on the gasket and is more inclined to pull studs. Having said that, many people successfully run aluminium heads.

If I went aluminium heads, I would "o" ring the heads with receiver groves in the block.

When I raced air cooled VWs I actually used thiner head studs with bigger threads so they stretched a little when stressed by expansion. This overcame the stud pulling problem that was very common with high output VWs.

Regards

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[Fabrico]

Is that a 2-valve or 4-valve configuration? I would think a 4-valve would be harder to make but better at taking a beating.

It sounds doable. But I would be in great fear of running it for too long though. Having a bulk of the initial heat coming from high EGT should keep the seats tight. But heating up the head and then putting around could go the other way. Also the head will loose strength as it gets hot. A second or third run in a short period of time might waste everything.

You might also consider having a very simple new iron head with your name on it poured somewhere.

 

[tstom]

Was planning a 2 valve design to keep rockers simple and be able to transfer Jesel type rockers to this design

Pat is correct that high spring pressures are needed however the cyl.bore size is 5.120" so this allows me room for seat inserts with a beefy o.d. and still have the needed valve size

The cast iron idea is interesting but I don't know anything about designing a casting Is cast iron billet available this large? or at that point would it just be better to use mild steel?

brngrhd, not really into pulling just engine building and machining but it's good to know someone has done it

Thanks guys,

Tom

 

[swall]

I would find a local gray iron foundry and go talk to them. On the low end of tech, they could pour you a
"rectangular log" of gray iron. On the high end of tech, you could have a styrofoam pattern CNC machined and the foundry could make a "lost foam casting". Between these two extremes would be having wood patterns made with varying levels of complexity and cost.

 

[thundair]

I noticed no one has mentioned the heat loss of an Aluminum head. All things being equal (dimensionally) a cast iron head will produce more HP and be more consistent.

I did not look it up but I seem to remember 2024 had stability problems over 300* F.

If you do use Aluminum I would start with a 356 T7 cast and try to get a foundry to double the silicone and 4% cooper.
Matl Gurus please keep me honest.
But if you are going to cast I would suggest Meehanite or CGI casting.

A simple pattern could be made to give you all the spring pockets and cover lip and combustion chamber rough in.
I think you could do all of those without cores which is the most expensive in pattern making.
Just bring the pattern maker the head and tell him the material you want to cast it out of, and that you do not want any cores.
He will calculate the shrink, and cast the part so that you can finish machine it or CNC complete.

http://www.machinedesign.com/BDE/materials/bdemat6/bdemat6_2.html

Cheers

Cheers

I don't know anything but the people that do.

 

[swall]

Thundair--your proposed modifications to 356 alloy chemistry results in what is close to 390 alloy, which has been used for blocks and pistons. Don't know about heads.

 

[tstom]

I think I am leaning away from the alum ....This will be too much work to have to redo it 3 pulls into the season...while that may or may not happen the aluminum was my idea. The customer wants steel so I don't think I'll talk him out of it. I didn't realize cast iron would be an option for a single part run but as I said I don't really know anything about it I will check the local availability Thanks again to all
Tom

 

[IceStationZebra]

If I ran aluminum heads I would definitely use a thermal coating on the combustions surface.

Also, is there an alcohol head available? Maybe you could get them to make a version with a flat combustion surface and a different material. Not the best option, but may be an option.

ICZ