Engine Pad and Block Machining

**Gene M.** · February 24, 1999, 05:21 PM

Re: Engine Pad and Block Machining

Mike, Don't do it, if the surface is flat enough to seal the heads. The squareness to the mains does not matter. If you want to retain all the original unquestionable stampings to this car DO NOT RESTAMP IT. This engine if un square to the crank has all ways been that way within normal manufacturing tolerances, and functioned for over 30 years. There is no rearon to surface a deck other than to achieve flatness to seal the head gaskets. Even this can be done with out machining the area where the stampings reside on the deck. You will destory the value of your car by defacing the stamp pad. If you find it necessary to mill for flatness, mark the edge that the head and gasket terminate and only mill to that line so appearance of your pad area will remain intact. These are my feelings on this topic, the car belongs to you so do what ever you want.

**Chuck G.** · February 24, 1999, 07:37 PM

Re: Engine Pad and Block Machining

Don't do it Mike. I think that this would be a MAJOR mistake that will seriously devalue your car. Your engine has been together and run fine for 30+ years. If the "decks" aren't 90 degrees off the CL of your crank, so what. I don't think that you're looking for incremental increases in horsepower. Chuck Gongloff, Baltimore, Maryland

**Gary Schisler** · February 24, 1999, 09:13 PM

Re: Engine Pad and Block Machining

I wouldn't do this for any amount of horsepower or other gains you might get out of it. Many of us only dream of an original engine let alone a "matching numbers" one. When I had the engine on my 66 rebuilt, the builder and I both agreed that machining the stamp pad would not be necessary. This is not the original engine, but someday, somebody might be interested in the un-molested pad. Rethink this with your rebuilder and ask for alternatives. Besides, unless you are going racing, what advantages will the "blueprinting" give you?

**Richard E.** · February 24, 1999, 09:35 PM

Re: Engine Pad and Block Machining

Mike:One more vote against taking a chance of messing up a ID pad. I talked to my engine builder, as well as a race engine builder friend. On builds good stock 327 engines, the other builds 800-1200 HP dragster engines. Both agree that unless a head was leaking because of a bad block, don't even mess with it. My race engine friend thinks of matching the deck surface to the crank journals only because of the criticality of matching TDC on all eight. But then he also spent over $1000 for a set of rings!! Cheers--Dick

**Dick W.** · February 24, 1999, 09:35 PM

Re: Engine Pad and Block Machining

Mike, the horsepower that you might gain by decking the block would more than be offset by the loss of value to your car. If you must deck the block for whatever reason, there are a few machinists that will take the time to set the block up and only cut the surface that the gasket and head cover, leaving the machine code, VIN, and factory machine marks on the pad intact. You may have to hunt for this type of service, but it would be well worth it

**Joe L.** · February 24, 1999, 11:35 PM

Re: Engine Pad and Block Machining

Mike----

VERY FEW engines actually require block decking during a rebuild. Performing this operation to achieve "squareness" with the crank centerline is absolutely unnecessary for a street engine; this is a "racers-only" machining operation. As far as gasket sealing goes, very rarely is a block deck "warped" enough to require machining. This can be checked with a precision straight edge. When I checked mine, it was perfect. If you use a good composition head gasket, like Fel-Pro Perma-Torque Blue #1003, minor surface irregularities will be no problem. I do not recommend the use of stock-type steel shim gaskets.

A lot of times, I believe many unnecessary machining operations are performed. Block decking is one of them. Cylinder head surfacing is another(they can be checked just like the block). Crank grinding is another; many Chevy cranks show virtually no wear and micro-polishing is all that's required. Grinding crank journals weakens the crank; why do it if the crank doesn't need it? Another unnecessary machining operation is cylinder over-boring. Use the smallest overbore consistent with oversize piston availability for your engine, if you need to oversize at all. Most machine shops are set up for .030", so that's what they do. Most 4" Chevy small blocks have .020" oversize pistons available. If your engine only needs a .020" overbore, why go to .030"? Just to make the machinist's life a little easier?

**Alex Gilmour** · February 25, 1999, 02:04 AM

Re: Engine Pad and Block Machining

I wouldn't deck the block if it were my car. Since I drive my car almost daily, I am going to look for a 4-bolt main 350 that I can build and make appear like the stock 327 (ie stock manifolds, carb, etc). I am planning to "pickle" my matching numbers/never bored 327/300hp engine on a stand along with my matching number tranny until that day I decide to chase that elusive Top-Flight award.

My $0.02

Alex

'66 A/C Coupe

**Jack H.** · February 25, 1999, 03:19 PM

Re: Engine Pad and Block Machining

This is a frequent and valid point of consideration. You're between a rock and a hard place. If you deck the lid to achieve a quality engine rebuild, there's simply no way you'll preserve the factory original broach marks (forget about the numbers for a minute) unless you have the machinest 'stop short'.

It's 'iffy' if the 'stop short' method can be done satisfactorily -- without leaving a ridge or step line that will give you problems with valve cover and gasket seal. You can try, but it's your call....

Now, on the issue of restamping. That's also your call. The Catch-22 is NCRS does not condone the practice, so we can give you no official help. Plus, if judges determine your restamp is improper, you'll lose points.

There are shops here and there with the skill and experience to do a good job. Some, so good it's impossible to tell from the original without use of destructive agents (acid wash, magnaflux, Etc.). But, again, we cannot help you.

Now, you confuse me. If you have the original engine, why on earth would you ask questions regarding font, size, placement? If you've got the real McCoy motor, take an impression, photograph, Etc. You have the pad dimensions, so you've got the one and only template of originality for that car/engine -- use it, don't ask us!

Then, if you do restamp, be prepared to tell the truth, make a declaration on your judging sheets (judges cannot use owner declaration in their on-field evaluation of your car) and support your position with the evidence you have -- photographs of original pad complete with broach marks, font, placement, Etc. A reasonable buyer or judge will understand why you did what you did (quality vs. originality tradeoff during the restoration process).

**Joe L.** · February 25, 1999, 04:45 PM

Post Script

One other point I guess that I should have mentioned at the risk of confusing the issue even more: as I stated, machining operations to establish "squareness", of the block deck surface to the crank centerline are usually not necessary for street engines; original production tolerance machining, which should not have changed significantly in service, should be adequate. However, very, very, rarely an engine may have slipped through that was not machined to production standards and tolerances with regard to the parameter at issue. If this occurs, it can, ultimately, result in an improper fit between the cylinder head and the intake manifold. This, in turn, can result in high oil consumption due to the vacuum extraction of oil from the lifter valley into the intake ports. This problem CANNOT be corrected with any intake manifold gasket or sealers; it can be corrected, however, by angle milling the intake manifold. So, the long and the short of it is, it's not a bad idea to CHECK the relationship between the block deck and the crank centerline. However, unless this measurement reveals a condition of serious departure from production dimensions and tolerances, don't deck the block. It is HIGHLY unlikely that such a condition will be found in your engine.

Also, I'd like to add a comment relative to block decking which "stops short" of the stamping pad. Most automotive machine shops use a rotary broach to machine deck surfaces. I do not understand how, using a rotary broach, a machinest can "stop short" of the stamping pad without failing to "cut" a portion of the deck surface which needs to be machined. Other machines can be used to surface blocks and heads, but few, if any, machine shops are equipped with them due to extremely high cost.

**Mike Grady** · February 25, 1999, 08:42 PM

Re: Engine Pad and Block Machining

Many thanks to all for taking the time to respond to my post. You've all certainly given me a lot to think about.

**Dick W.** · February 26, 1999, 10:23 PM

Re: Post Script

Joe, the machinist that I use also has a vertical mill and the tooling to deck a block. I have had several blocks done without disturbing the pad area. I am sure there are other shops or machine shops that could perform this service. He is not inexpensive. It cost several times what a normal block decking costs.

**Joe L.** · February 27, 1999, 04:23 PM

Re: Post Script

Dick----

Thanks for the info. Some time ago, I tried to locate a shop in this area(San Francisco Bay Area)for a friend that needed to have his block surfaced. His "numbers" were deeply stamped and I told him that I didn't think that the light "cut" that would be required would remove them. Nevertheless, he wanted his pad to be "untouched". He and I checked around all over the area and could not find an automotive machine shop that didn't use a rotary broach.

If it ever comes up again and, at that time, I still can't find anyone who can do it, I might just recommend a long, cross-country trip for somone's block.

jc · February 28, 1999, 01:33 AM

Re: Engine Pad and Block Machining

Don't do it. there is not that much added power, if you wanted more power, I've got a 4 bolt sitting in in my garage you can rip up. Find one at a junk yard, deck it and restamp it to your number etc. hence you have to maching numbered motors.

Engine Pad and Block Machining

Engine Pad and Block Machining

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