Head Oil Transfer Dowel Question

Hello All,

I am in the process of replacing my HG to stop a oil leak at the transfers. I've just finished reading SecaMaverick's "Frustrated-head gasket leak early after top end rebuild" thread. I have my head off and noticed the oil locating transfer dowels are "shorter" than the combined depth of both recesses in the head and block. If you look at the first picture in SM's thread you will see one of the dowels sitting higher in the seal. When I push the dowels up in the head they will bottom out at around 1/4". When I bottom them out in the block there is only about a 1/8" left above the washer. Would the dowels sitting too low contribute to oil leaking at these transfers? If so, this may have also been some of SecaMaverick's problem.

Thanks,

Gary

 

Shouldn't. The dowels are locators; the o-rings around them do the sealing.

 

BigFitz,

Not being argumentative or a smarta$$ and you did say "Shouldn't". I agree, the washer will seal the bottom of the dowel into the block, but if a space is left from the top of the beveled dowel to where it will flush with the head which would put it right at the bottom of the diagonal oil ports in the beveled recess wouldn't that allow oil to seep down the dowel? There was a considerable difference in the amount of oil leaking once the oil heated and thinned at higher rpms. Also, the other two locating dowels sit higher in the block than the oil locator dowels when bottomed out and all four dowels are the same length. I was going to send you a PM, but if this is the case it might help other members...including me.

Thanks,

Gary

 

rocs82650

If I have this drawing correct this is a cutaway of the area I think you are asking about, it is the oil feed to the camshafts "750 YICS SHOWN". (others can comment if they see anything or I have this wrong) the steel locating dowel / oil path is in the purple color, the seal ring is in green, head gasket is the thin black edge.

You are correct the dowel is shorter than the space allotted by the drilling in the head and cylinders. The rubber seal (elongated o-ring) however is longer than the space allowed causing it to be compressed into the provided cavity. In the picture the seal (green) looks like a rectangular cross section only because of how it is squished into the available space between the head and cylinders.

From what I can see the seal (elongated o-ring) is doing all the work keeping oil from leaking to the outside.



FlyGp

 

FlyGp,

You do nice work. You're drawings are very clear. I'm waiting on a order from Len including a HG and seals. I have the head off. Flashlight in the cavity shows the bottom of the diagonal oil transfer ports on my 650 actually finish in the bevel of the top of the dowel cavity. I don't want to repeat myself or mislead other members. When I get my order I'm going to push the dowels all the way up, probably use Rick's paint brush/copper sealant method and see what happens. I used Indian Head the first time. The head didn't leak prior to me doing the top-end and the only place it leaks is at the transfer ports. Once it's all back together and I can run it in the higher rpms w/o getting oil on my pant leg and boot I'll report back on this one.

Gary

 

rocs82650

You are absolutely correct about the diagonal oil port angle, thanks for pointing this out. I just checked the head I used for measuring and creating the drawing and the port is absolutely as you describe, Looks like I have some rework to do.

FlyGp