Stamp Pad Preservation during Rebuild

[Keith B.]

Many of you know that I'm currently having my factory L-36 rebuild to stock specs and have had to direct, educate, and oversee my mechanic every step of the way as I'm paranoid of perserving the stamp pad. He understands that now and so does the machinist...it will not be decked. SO...

Are there any other steps to be taken before the block is "Hot Tanked", will this disturb the stamp/broach area, I would think not but I see in the archives that some have covered the stamp pad during hot tanking, etc.

Any other steps or precautions are appreciated, I only have one chance at not screwing this up !! Thanks.

[Michael H.]

Re: Stamp Pad Preservation during Rebuild

Many of you know that I'm currently having my factory L-36 rebuild to stock specs and have had to direct, educate, and oversee my mechanic every step of the way as I'm paranoid of perserving the stamp pad. He understands that now and so does the machinist...it will not be decked. SO...

Are there any other steps to be taken before the block is "Hot Tanked", will this disturb the stamp/broach area, I would think not but I see in the archives that some have covered the stamp pad during hot tanking, etc.

Any other steps or precautions are appreciated, I only have one chance at not screwing this up !! Thanks.

Be very careful when selecting/purchasing the rear cam bearing. This part is unique to 65 and 66 big block and, for some reason, very few engine builders are aware of this critical item today.
I can't even guess at how many times we've heard the horror stories of "NO OIL TO THE LIFTERS" in the last few years just because the wrong bearing was used.
Make sure he compares the new one with the one he removes.

Don't fall for the align bore/hone procedure.

If in doubt about anything the builder recommends, check with the people here before agreeing.

[Chris E.]

Re: Stamp Pad Preservation during Rebuild

I had my block "hot tanked". Here's what it looked like after the cleaning process. It actually wound up uncovering a slight double stamp.

[Tom H.]

Re: Stamp Pad Preservation during Rebuild

You should not encounter any issues with your pad during a rebuild or hot tank.

[Chuck G.]

Re: Stamp Pad Preservation during Rebuild

Not many, if any shops use the old "hot tank" with sodium hydroxide anymore.

Most have a gizmo that looks like a huge dishwasher. Your block is suspended by a chain, and then power washed in the device.

I haven't seen a hot tank for decades here in Maryland. EPA, OSHA, etc.

Chuck

[Terry M.]

Re: Stamp Pad Preservation during Rebuild

Used to be some places that baked the cylinder case, and other parts, in an oven-like device. A lot hotter than your kitchen oven, though. I don't know how common that is any more, or what it might do to the pad area. It might be best to ask your machine shop exactly what they do before you commit to their process.

[Chris E.]

Re: Stamp Pad Preservation during Rebuild

I did notice a slight rounding off of the stamp pad support area, but the pad surface appeared to be undamaged. (see my pic above)

[James W.]

Re: Stamp Pad Preservation during Rebuild

Many of you know that I'm currently having my factory L-36 rebuild to stock specs and have had to direct, educate, and oversee my mechanic every step of the way as I'm paranoid of perserving the stamp pad. He understands that now and so does the machinist...it will not be decked. SO...

Are there any other steps to be taken before the block is "Hot Tanked", will this disturb the stamp/broach area, I would think not but I see in the archives that some have covered the stamp pad during hot tanking, etc.

Any other steps or precautions are appreciated, I only have one chance at not screwing this up !! Thanks.

Keith,

A couple of questions for you;

Will your mechanic be the one and only person working on your engine?

Does he have employees that he will delegate different machining/rebuild duties to during the rebuild process?

Why I ask is because when I had an L78 engine rebuild performed the machine shop owner and I met to discuss the rebuild and my expectations. He was very knowledgeable regarding the L78 rebuild and mentioned the required grooved cam for proper oiling. I stressed to him that in no way was the engine block stamp pad to be touched. This meant no block decking or any other block to head sealing surface cleaning/prep work by hand or machine was to be performed on the block especially in the area of the pad. We had this discussion with the engine setting between us on an engine stand as I pointed at the stamp pad showing him the broach marks and stamps and explained to him the reason why this area must not be touched. He said he understood the problem was that he was not the only person who worked on the engine. We even went so far as to put about three layers of duct tape over the stamp pad surface before disassembly with "Do not remove" written on it with a Sharpie marker. During the engine disassembly which he delegated to one of his employees the employee used a sanding long board with 80 grit paper to remove the old head gasket material from the block surface. You can imagine what this did to the original factory broach marks. The message regarding the stamp pad surface was not given to the other employees as to its importance.

I would stress that if the machine shop/engine builder owner is more than a one man operation, be sure that if possible YOU have short meeting with the shop owners and all of the employees that will be working on your engine. I'd be sure that they are all in attendance at the meeting to stress that the block stamp pad does not get touched.

In the attached pictures, on the left is the stamp pad before the engine rebuild, the factory broach marks are clearly visible. In the two pictures on the right after the "accident" you can still see some of the original broach marks, but I am willing to bet that during flight judging that it will get a deduct for the broach marks. The more you zoom in on the pad the better the original broach marks can be seen. Maybe if the judges use a 10x magnifying glass they will be able to see them better. I figure this little accident cost me 38 originality judging points.


Good luck and I hope this helps.


James West

[Patrick H.]

Re: Stamp Pad Preservation during Rebuild

When the motor in my 71 was rebuilt, I took off from work to be present for each part of the rebuild operation. I watched every bit of what happened to that motor.

Of course, I was documenting it for my series in Vette Magazine, but I still found that it was beneficial to be there.

Patrick

[Chris E.]

Re: Stamp Pad Preservation during Rebuild

Tell the shop owner that you will deduct the amount of value lost by damage to the stamp pad from the final invoice. Since the value lost usually ranges from $4-10K, that should convey to the shop owner that you expect the rebuild to be free.

That'll get their attention.

[Ronald R.]

Re: Stamp Pad Preservation during Rebuild

I had a simular problem with mt 1970 ZR1, the shop used a buffer on the old gasget residue. I got hammered upon judging. At this point what should you do? Try to resore the marks ( mine are barely visable) or leave them alone. My stencils were judged correct but I lost for lack of broach marks??
Ronnie

[Ronald R.]

Re: Stamp Pad Preservation during Rebuild

PS I( had onother car, a 1966 450 HP cpe. with a blown head gasket and an eroded block. The marks and numbers were perfict!. i found a local shop tht decked the block up to the pad. This looks perfect after the head is on. I think I did the best thing, any comments or better ideas?
thanks RDR

[Joe R.]

Re: Stamp Pad Preservation during Rebuild

Keith,

As you may have read, I am rebuilding a L-72. Some of what I'm about to mention is covered above. Anyhow, here's what's unique about this engine and what to watch out for.

The cam for 65 - 66 only has to have a groove ground in the rear journal for proper oiling of the lifters. And the rear cam bearing must be the three hole design for 65 - 66 as well for the same reason.

Make sure you use the second design valve springs. The first design was very prone to breakage. The part number for an engine set of valve springs is GM #12371061. It includes the valve spring, retainer, and seal. It is still available from GM today.


Joe

[Jim R.]

Re: Stamp Pad Preservation during Rebuild

Make sure you have him use the steel frost plugs also, a step i forgot on my 65, my builder used the popular brass. point deduct!

[Jim R.]

Re: Stamp Pad Preservation during Rebuild

Oh yah also the correct intake gaskets.........