Thursday, January 11, 2007

Shovel Head Gasket Tip

Since I have been on the subject of Shovelheads lately (drag racing stories) it came into my mind to give a tip on torquing Shovel head bolts. This is a trick that was taught to me by Dick Conger over 25 years ago while I was working for him in his Harley dealership in Pueblo Colorado. If you are sharp you may note that is somewhat similar to the factory torquing sequence for Evolution head bolts, but Dick taught me this before the Evolution was even born!

I say that it is similar to the evolution torque pattern, in that it tightens down on each side of the oil drain hole first and then goes to the opposite side. The idea is to put a good tight squeeze on the drain hole first, since that is generally the source of head gasket failures on a Shovel. Of course it is far different from the Evolution sequence in respect to torque steps, as the Evo sequence is more concerned with cylinder distortion.

A little lube on the threads as well as under the head of the bolt will help keep your torque readings accurate. And don't forget, you also want to reach the torque setting of your wrench while it is still moving, because it takes more torque to start a bolt moving than it does to turn it. For that reason it helps to plan ahead so that you don't run out of room to "swing" your torque wrench just before you reach the full torque reading.

I know some will say that you don't need a torque wrench for Shovel headbolts. I even talked to a tech at S&S recently (who will remain nameless) that said he doesn't use one for Shovelheads. My only answer would be, that of the thousand or so Shovel engines I have torqued using this method, the failure rate has been zero, or very close to it. Happy wrenching!


Anonymous said...

I have heard that there is improvements that can easily be made to the crank breather gear port (opened up)(match ported?)on the shovelhead motor , can you give some insight as to this modification(if it is true)?And is there big gains by doing so....?


St.Lee said...

Hi Billy, there is a modification that can be made, but it is not so simple. Couple of things to consider; the breather window in the cases of early motors (including generater shovelheads) was a rough cast oval hole which was obviously smaller than the window in the breather gear. Those would definately benifit from opening them up. Later cases had holes that were roughly rectangular, but still not very precise. Size of the window is important, but timing is even more important. The breather gear rotates CCW which means that grinding on the bottom side of the case window will make the opening event earlier and grinding on the top side will make the closing later. Unless you have a degree wheel and know how to set it up properly, it is probably not a good idea to change the opening or closing sides. You can still make the hole square, though, and open the ends of the hole to match the width of the window in the gear. My rule of thumb is to "blueprint" the breather timing (that is take the opening and closing sides to maximum S&S specs - open 10 degrees BTDC - close 75 degrees ABDC) on 88 inch and larger motors. On smaller strokers I just square off the opening and never put a degree wheel on it. For stock rebuilds I do neither except on request.

Another option is the S&S breather gear (which will run you about $80) which has the increased breather timing built into the window on the gear. This eliminates the grinding and possible contamination (if your cases are not apart)

The whole idea is to relieve excess crankcase pressure. Excess crankcase pressure would obviously rob horsepower, but I can't give you an estimate of how much. The bigger the displacement, the more air needs to move when the pistons come down, so with the same breather opening a larger motor will have more crankcase pressure. Excess pressure can also lead to blowby (oil consumption) and oil carryover (oil out the breather) If you are not experiencing either of those symptoms, I probably would not advise taking your engine apart just to modify the breather.

Anonymous said...

That explains alot for me.I have a cone 74" shovel..and its "stock as a stove",other than some mild port work and dual plugged.
From hearsay and such it was explained to me as a big gain in power.After your explaination,I feel its not so necessary for me to do.
I guess its everybodys thing ,to make more power,but,its just me and the wife ...taking those weekend rides...
But my 75 Ironhead chop...I would like to build a fire in lol
Thanks for your response!

Anonymous said...

New technology reed valve breather
made by S&S available in stock bore
& .030 oversize. I'm rebuilding a
.010 overbore 74" shovel right now
with mild headwork, an original
440 sifton cam, S&S "B" with a
Power tube, using a voes &
a programmable ignition,2 into 1
collector exhaust. This is a fun
project for me. owned this
bike in several forms since 1985.
I think the Old meets new will work
just fine. S&S says that if you are
using an isolated primary that this
reed valve will work well.If you
are still circulating engine oil
through the chain case, it's not a
good idea.

charl Hill said...

I have recently torn down and rebuilt my 77 shovel. I had a machinist true up all of the surfaces. also i had to have the cylinders honed to .070 because of a broken piston ring from the previous owner. anyway i put in new keith black pistons and now they are coming out above the lip of the cylinder about .025 and are hitting my heads. what to do now? thicker gaskets? will that get me far enough? or do i have the heads shaved now?

St.Lee said...

Were the cylinders trued up also? Or do you mean ALL the surfaces, like the base gasket surfaces on the crankcases?

I would think the best place to make it up would be on the base gasket, since it is not subject to the pressures of the head gasket. Maybe even a thin stroker plate if needed. Ideally you would like the stroker plate and/or extra base gasket to add up to the same amount removed in the truing operations.

Another thing to consider (may not be related to your problem) is that if the heads were shaved, the counter bore in the head should be cut the same amount deeper so that the firering on the cylinder does not bottom out on it before the head gasket compresses completely. Depending on where your piston is hitting, this might solve the contact problem without altering the base gasket.

charl Hill said...

Thanks Lee I had all of the surfaces trued. crank case cylinders and heads. so i think i will try a stroker plate. because the biggest gaskets i can get only add up to .025" and that is leaves 0 clearance piston to head. thanks man. I am just opening a shop and getting into the bobber world. I am more schooled in newer harley's so it is always a learning experience with the older mods.

charl Hill said...

where do you get stroker plates?

St.Lee said...

S&S used to sell them in a variety of thickness'.but I don't think they have them anymore. I normally just cut them out of sheet aluminum when I need them.

mike said...

i have blown rear head gasket twicein less than a 1000 mi,rear cylinder runs hot,any ideas?

St. Lee said...

Hi Mike, the first thing to do might be to deal with the "running hot" issue. Timing and lean carburetion may be good places to look. Once you have addressed the heat issue, the head gasket problem may go away, but it may also be due to other issues such as gasket surface condition or the headbolt inserts that are cast into the head may have "pulled" some, so that they are proud from the gasket surface. If they are you will need to have them countersunk to about .010 below the surface.

Anonymous said...

Hey Lee,

Thanks for the Shovel push-rod adjustment and head bolt torque I somewhat recently rescued a 76 Shovel from a hillbilly's yard & I am just about ready to bolt down the heads.

Leaving the very best for last, thank you so much for placing all the Glory where it belongs - to God the Father and His Son - our Lord Jesus Christ.

May God continue to bless you!


Will said...

Love your blog! I've been doing a lot of research into rubber gaskets and this has really helped. Thank you!