Decking The Engine Block...
Thread Starter
Instructor
Joined: Dec 2005
Posts: 160
Likes: 0
From: Novato CA
Decking The Engine Block...
I'm considering having my numbers matching engine rebuilt. I'd prefer not to have the block decked. Should this be my decision or the engine builders? Can the determination be done ahead of time as to whether it needs to be done? I just don't want my pad re-stamped and the engine builder can't stop his milling machine.
Any advice would be greatly appreciated.
Any advice would be greatly appreciated.
Melting Slicks
Joined: Oct 2004
Posts: 3,117
Likes: 19
From: Portlandia Oregon
The last 2 engines I had I told the builder not to deck the blocks. 1 was a 1957 283 (bored 12 over), the other 327 340hp (bored 40 over). Both builds were fine. Have his check it and if there is anything really out to tell you. Ask for his recommendations and then post what he said here to get a second, third, fourth ninth etc opinion.
oWEN
oWEN
Drifting
Joined: Jul 2007
Posts: 1,671
Likes: 10
From: california
i would say DONT deck the block. ive seen lots of rebuilds with no decking and they all work fine. ive done lots of head gasket repairs to and even in severe overheats its the head that warps not the block, we would just have the heads surfaced and screw them back together, never a problem. decking a block is mostly done to correct piston to deck hights on hipo builds. save those numbers, youll be fine.
Race Director
Joined: Jul 2002
Posts: 11,593
Likes: 173
From: Clayton NC
Dave
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
Burning Brakes
Joined: Oct 2006
Posts: 797
Likes: 11
There's a 99% chance that you don't need to deck your block. Most GM blocks are with in a couple thou. All the blocks that I have checked are dead on. If your Machinist insist on decking it take the block take it somewhere else. The only time I have a block decked is if I want the piston zero decked. My LT1 block that I used for a Blower motor(wanted the most CCs) was .002" corner to corner. Thats better than alot of shops out there will be able to do.
Race Director
Joined: Jul 2002
Posts: 11,593
Likes: 173
From: Clayton NC
There's a 99% chance that you don't need to deck your block. Most GM blocks are with in a couple thou. All the blocks that I have checked are dead on. If your Machinist insist on decking it take the block take it somewhere else. The only time I have a block decked is if I want the piston zero decked. My LT1 block that I used for a Blower motor(wanted the most CCs) was .002" corner to corner. Thats better than alot of shops out there will be able to do.
Le Mans Master
Joined: May 2003
Posts: 8,876
Likes: 3,556
From: Fernandina Beach FL
2023 Restomod of the Year finalist
2020 C3 of the Year Winner - Modified
Are you going to show the car OR drive it?
If the latter-you can find a junkyard 327 relatively cheap- compared to the total cost of a rebuild -machine it all you want-make it run and look original (maybe even have the machine shop stamp "numbers matching" on the pad) while the original engine sits in the basement or garage.
Richard
If the latter-you can find a junkyard 327 relatively cheap- compared to the total cost of a rebuild -machine it all you want-make it run and look original (maybe even have the machine shop stamp "numbers matching" on the pad) while the original engine sits in the basement or garage.
Richard
Le Mans Master
Joined: Jan 2002
Posts: 8,913
Likes: 283
9.025" is nominal deck height. If the left side is higher then the right, you can deck that side.
I have never seen or heard of a machine shop being able to deck a block and leave the pad. But there is a way to do everything. I would not imagine how you could get the cutter to stop before the pad, and then have it work around the pad, to get the top and bottom. But I guess with C&C machines you could probably do anything.
I watch a computer program run on a block that had the cutting tool moving all over the block cutting away at any and all flat surfaces. I guess it was to lighten the block.
I have never seen or heard of a machine shop being able to deck a block and leave the pad. But there is a way to do everything. I would not imagine how you could get the cutter to stop before the pad, and then have it work around the pad, to get the top and bottom. But I guess with C&C machines you could probably do anything.
I watch a computer program run on a block that had the cutting tool moving all over the block cutting away at any and all flat surfaces. I guess it was to lighten the block.
Le Mans Master
Joined: Jan 2005
Posts: 8,226
Likes: 2
From: Lake Wylie SC
Have the car documented now before doing the rebuild. Still there is no reason why you should not be able to find a builder to deck the block but leave the pad alone.
Unless you are uptight about internal motor parts get the block decked and the motor done right. You can end up with an easy additional 25% of torque and horsepower over what you have now and still have your old numbers left unmolested on the pad.
The only area where you will need to give extra consideration is your head and what your limitations are with your intake and exhaust manifolds.
Almost everyone likes their car more with more power
Doug
Unless you are uptight about internal motor parts get the block decked and the motor done right. You can end up with an easy additional 25% of torque and horsepower over what you have now and still have your old numbers left unmolested on the pad.
The only area where you will need to give extra consideration is your head and what your limitations are with your intake and exhaust manifolds.
Almost everyone likes their car more with more power
Doug
Race Director
Joined: Apr 1999
Posts: 10,866
Likes: 717
From: Beverly Hills/Pine Ridge Florida
Don't do it. It would be a $10,000. mistake.
If you're building a street motor, there's NO need.
The engine has run fine for 40+ years.
Find another shop if they insist on doing it. Chuck
If you're building a street motor, there's NO need.
The engine has run fine for 40+ years.
Find another shop if they insist on doing it. Chuck
Burning Brakes
Joined: Feb 2005
Posts: 894
Likes: 91
Block Squaring vs. Numbers
9.025" is nominal deck height. If the left side is higher then the right, you can deck that side.
I have never seen or heard of a machine shop being able to deck a block and leave the pad. But there is a way to do everything. I would not imagine how you could get the cutter to stop before the pad, and then have it work around the pad, to get the top and bottom. But I guess with C&C machines you could probably do anything.
I watch a computer program run on a block that had the cutting tool moving all over the block cutting away at any and all flat surfaces. I guess it was to lighten the block.
I have never seen or heard of a machine shop being able to deck a block and leave the pad. But there is a way to do everything. I would not imagine how you could get the cutter to stop before the pad, and then have it work around the pad, to get the top and bottom. But I guess with C&C machines you could probably do anything.
I watch a computer program run on a block that had the cutting tool moving all over the block cutting away at any and all flat surfaces. I guess it was to lighten the block.
Before any shops had the "CNC" mill available, it was performed by using both the standard block mill AND the "Bridgeport". They would be "broached" on the block miller up to the pad then placed on the "Bridgeport" to finish the pad area. Numbers remained intact. It was somewhat "labor intensive" but it was "correct".
Now that the "CNC" is in the picture it's a fairly "simple and straight-forward" procedure. Done on the one machine, easily and most accurate!
Thanks, Gary in N.Y.
P.S. It takes all of about 60 minutes to "square" it all up AND leave the original pad and numbers "as-is" from G.M. Remember, not touching the pad leaves the original "broached" area as well here.
Race Director
Joined: Feb 2004
Posts: 11,031
Likes: 2,587
From: Del Boca Vista FL
Melting Slicks
Joined: Aug 2004
Posts: 3,078
Likes: 101
From: Riverhead New York
As others have mentioned, "Decking' is only necessary to cure an out of "True" block. Even so, if such a condition does exist you most likely can reinstall the cylinder head that was on the right side of the block as the mating surfaces are currently compatible. They should remain so in the future. We are not talking about anything but a Naturally Aspirated here. The original numbers on that engine a significant to the car and it's history. Al W.