Checking for decked block on 327

[Michael G.]

Can someone tell me how to measure a 327 engine to determine whether its ever been decked? The engine is apart. Thanks

Mike

[Jack P.]

Re: Checking for decked block on 327

Can someone tell me how to measure a 327 engine to determine whether its ever been decked? The engine is apart. Thanks

Mike

One possible start is , are the engine block stamp numbers visible? If the block was decked without regard to the stamp pad, they may be gone. If the stamp pad has all it's numbers that can be clearly read, this may indicate no decking, or someone was careful to protect the stamp pad.

Jack

[Michael G.]

Re: Checking for decked block on 327

The block is supposedly an unstamped original. I don't know if that is even possible, but after all my years at GM, here in Michigan, I know that many strange things happened to test engines and such in the 1960's. If I can measure the deck height, I'll be sure of whether that claim is true or false.

Mike

[Michael H.]

Re: Checking for decked block on 327

The block is supposedly an unstamped original. I don't know if that is even possible, but after all my years at GM, here in Michigan, I know that many strange things happened to test engines and such in the 1960's. If I can measure the deck height, I'll be sure of whether that claim is true or false.

Mike

Mike,

All GM service fitted blocks and partial engine assy's in the 50's and 60's would have unstamped blank pads. The practice of stamping ID and service numbers on service blocks began in 1969.
Complete engine assy's from that time would have been stamped though.

[Doug F.]

Re: Checking for decked block on 327

take a high resolution picture and post it here, the broach marks don't lie, you'll get plenty of feed back, then you can decide.

[Michael G.]

Re: Checking for decked block on 327

Current owner is, (how do I say this nicely?) a bit stand-offish and uncooperative. Doesn't care if he sells it, doesn't want to be bothered. I think taking any photos in advance of purchase are probably out of the question, but I'm sure I can measure it when I go to pick it up, before I pay.

In any case, I saw it last Friday when I was in Detroit. It has what look to be good broach marks. I've seen a few good and bad ones, but I'm certainly not an expert.

I think deck height has to be measurable, I have lots of good measuring equipment, so I just need to know where to measure from, and how much the measurements should be ( with tolerances). Anybody know this?

Thanks, Mike

[Joe C.]

Re: Checking for decked block on 327

NOMINAL deck height, measured from the centerline of the crank, is 9.025" plus .015" minus .002".

This is not a joke! Deck height often varied from end to end on the decks, with 9.025 (plus/minus a couple thou) on one end, and up to 9.040 on the opposite end! I believe that the holding fixture and/or the violent nature of the broaching process caused the casting to shift in its mounting as the tool was being drawn across the decks.

[Mike M.]

Re: Checking for decked block on 327

i suspect there was so much variation from machined block to machined block, that providingyou a meaqsurement is meaningless. if the block was decked to remove pass car machine assembly data(which usually only requires about .005 thousands to do so), then simulated broach marks applied, we're only taling about .005 to .008inches. a visual inspection of the pad by an experienced broach analyst is the surest.mike way to determine its originality

[Michael G.]

Re: Checking for decked block on 327

I knew tolerances were wide in the 60's (I was a draftsman back then) but I had no idea an engine block deck had that kind of build variance.

Sounds like the only way I can definitively determine originality (I've heard that broach marks can be faked pretty well these days) is if I measure the front of the block relative to the center of the crank and find it to be in the 9.035 - 9.040 range. That would prove that the 5-8 thou of metal hadn't been removed Otherwise (and probably in most cases) there's no real way to tell.

I'll see if I can get some pics next time I'm in Detroit. Maybe that'll give me a warm, fuzzy feeling about this, but I doubt it.

Thanks, everyone for your help.

Mike

[William C.]

Re: Checking for decked block on 327

In the 60's Gratiot auto and others had complete shortblocks for sale @ $250 each, bare blocks available also, these would have been unstamped, certainly possible, especially in the Detroit area.

[Michael H.]

Re: Checking for decked block on 327

In the 60's Gratiot auto and others had complete shortblocks for sale @ $250 each, bare blocks available also, these would have been unstamped, certainly possible, especially in the Detroit area.

I bought a new GM 327 340-360 HP short block for my 57 FI BelAir in 1963. It was $244.41. I still have the receipt.

[Michael G.]

Re: Checking for decked block on 327

In 69 or 70 I paid just over $300 for just such a short block for a SWC I owned then. Got it somewhere in Warren or Centerline. Numbers weren't so important then, so I don't know whether it was stamped or not. It was a fuelly though, so its probably the original numbers matching motor now...

Mike

[Mike M.]

Re: Checking for decked block on 327

i've got two 870 blocks, both with virgin pads, ie , no stamping on their pads. both have stampings on their pan rails. have seen other over the counter 870's with no stamping on pads but all had stampings on their pan rails.mike

[Clem Z.]

Re: Checking for decked block on 327

i've got two 870 blocks, both with virgin pads, ie , no stamping on their pads. both have stampings on their pan rails. have seen other over the counter 870's with no stamping on pads but all had stampings on their pan rails.mike

are there 4 along each pan rail if so that is the air gauge size for the cly bores so the assy people knew what size piston to install.

[Duke W.]

Re: Checking for decked block on 327

Current owner is, (how do I say this nicely?) a bit stand-offish and uncooperative. Doesn't care if he sells it, doesn't want to be bothered. I think taking any photos in advance of purchase are probably out of the question, but I'm sure I can measure it when I go to pick it up, before I pay.

In any case, I saw it last Friday when I was in Detroit. It has what look to be good broach marks. I've seen a few good and bad ones, but I'm certainly not an expert.

I think deck height has to be measurable, I have lots of good measuring equipment, so I just need to know where to measure from, and how much the measurements should be ( with tolerances). Anybody know this?

Thanks, Mike

Nominal deck height is as Joe stated, 9.025", but I'm not sure of the tolerances since I've never seen a fully dimensioned blueprint - just a drawing with nominal block dimensions. However, on average most decks are high, so the tolerance range is probably not symmetrical.

It is a difficult dimension to measure directly because it is the distance from the main bearing bore centerline to the top of the deck. Better shops have equipment to make this measurement, but what really counts is deck clearance since this dimension affects compression ratio, and it is easy to measure with the heads off.

There's no way I know of to precisely determine deck height/clearance with the heads installed.

Duke