So much for my "502ci"... - Team Camaro Tech
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post #1 of 49 (permalink) Old Dec 12th, 16, 11:08 AM Thread Starter
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So much for my "502ci"...

As usual, a deal that is too good to be true is... So there were a few things that weren't adding up on my new motor after I pulled the cam to replace it with a cam with a fuel pump lobe. I decided to pull a head to verify a few things for myself and not trust what the builder told my friend. It turns out, everything internal is basically stock GM otc rebuild truck crap. 2.09/1.72 valves, not 2.19/1.88. The cam lift I measured to be ~.462/.462. Yes, that's after multiplying it by the 1.7 rocker ratio... Stock 4.250 stroke so it's a 494ci, not a 502 or 508. I'm out of my mind right now. I do believe my friend didn't know. I'm ready to give the whole thing back, but he offered to set me up with some good aluminum heads and a brand new Howard or Lunati cam of my choice from the "builder". The lower end all looks brand new and it's a seriously beefy 4 bolt main, 489ci. .020 over.
The only thing I'm worried about is that I have flat top pistons. Most aluminum heads have 110-120cc chamber volume. I don't think that would work with flat tops no matter their volume for compression would it?
Considering it's "only" $2,500 for what will end up being a good motor with a little more of my labor, what would you do? I'm thinking the smart thing to do is give them a chance to make it right. What about the pistons though?

Current pistons:



New double roller:

[url=https://flic.kr/p/NT1KYv]

Lower end:


'69 SS396 X66 L34 08D M21 BS
460ci Gen VI 9.75:1 AED 950 carb
241/249 @ .050" .625/.625 110 LSA

Semper Fi!

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post #2 of 49 (permalink) Old Dec 12th, 16, 01:17 PM
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Re: So much for my "502ci"...

I'd get the money back.

Just would never be comfortable going forward.
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post #3 of 49 (permalink) Old Dec 12th, 16, 01:30 PM
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Dave
 
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Re: So much for my "502ci"...

Well it is a four bolt main block anyway (they all are from the one piece rear main seal GEN V and up). Is this a Mark IV block with a two piece rear main seal? Or do you have a Gen VI block with a one piece rear main seal (the Gen V BBC 454 had no provision for a mechanical fuel pump as it was used only in EFI vehicles).

For future information a 502 has 8.2L cast in big numerals on the side of the block. Yours probably says 7.4L. The 502 has a machined boss to bolt on a mechanical fuel pump on the block, and an eccentric lobe on the cam for the fuel pump. They also use a single row timing cover and a plastic ten bolt timing cover that will not accept a double row timing set (can be done just requires reworking a bit, and going retro with a steel or cast aluminum timing cover).

As to your piston's static compression. They are perfect for use with a small 6-71 Roots blower or a couple of Nisan or other four cylinder import car repurposed turbos, but not NOS or a lot of boost from a huge aftermarket turbo (keep it under eight pounds max). Your other option would be closed chambered 90 cc heads to bump up your static compression.

A 454 truck engine uses flat top pistons with open chamber 124 cc heads to develop a wopping 7.4:1 static compression ratio for fear a nitride might be created and kill off those living in California. It was a concession the other 49 states had to make to get any kind of BBC made by Chevy (even though a diesel engine which Californians do love produces nothing but nitrides, and carcinogenic micro carbon soot).

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post #4 of 49 (permalink) Old Dec 12th, 16, 01:44 PM
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Re: So much for my "502ci"...

I have to agree with Vega John, I'd return it. I would just never feel right about it.
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post #5 of 49 (permalink) Old Dec 12th, 16, 03:09 PM
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Re: So much for my "502ci"...

Quote:
Originally Posted by Larger Dave View Post
Well it is a four bolt main block anyway (they all are from the one piece rear main seal GEN V and up). Is this a Mark IV block with a two piece rear main seal? Or do you have a Gen VI block with a one piece rear main seal (the Gen V BBC 454 had no provision for a mechanical fuel pump as it was used only in EFI vehicles).

For future information a 502 has 8.2L cast in big numerals on the side of the block. Yours probably says 7.4L. The 502 has a machined boss to bolt on a mechanical fuel pump on the block, and an eccentric lobe on the cam for the fuel pump. They also use a single row timing cover and a plastic ten bolt timing cover that will not accept a double row timing set (can be done just requires reworking a bit, and going retro with a steel or cast aluminum timing cover).

As to your piston's static compression. They are perfect for use with a small 6-71 Roots blower or a couple of Nisan or other four cylinder import car repurposed turbos, but not NOS or a lot of boost from a huge aftermarket turbo (keep it under eight pounds max). Your other option would be closed chambered 90 cc heads to bump up your static compression.

A 454 truck engine uses flat top pistons with open chamber 124 cc heads to develop a wopping 7.4:1 static compression ratio for fear a nitride might be created and kill off those living in California. It was a concession the other 49 states had to make to get any kind of BBC made by Chevy (even though a diesel engine which Californians do love produces nothing but nitrides, and carcinogenic micro carbon soot).

Big Dave
Looking at the pictures, I think I see the "spider" that holds down the dogbones for the stock roller lifters, so judging by that, it's a Gen VI, and therefore also a 4-bolt main and a one-piece rear main. It also has the mechanical fuel pump boss, which means it is a 454 block. If it does in fact have the 4.25" stroke, then you have either a 489 (.030 overbore) or a 496 (.060 overbore). Probably why they were calling it a "502", although the latter has the stock 4-inch stroke and a 4.5" bore. That being said, you can make plenty of power with a 489 or 496, if you put some decent heads and a healthy cam in it. You could probably find a GM ZZ502 cam as a takeout, and add a set of the AFR 265 oval heads and have a real stump puller. Even with the flat tops, the AFR's are available with 110 cc chambers, which should yield a pump-friendly 9.6:1 CR, or thereabouts.

Depending on how they want to work with you, you still might have the makings of a good street motor. What are the casting numbers on the heads?

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post #6 of 49 (permalink) Old Dec 12th, 16, 03:11 PM
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Re: So much for my "502ci"...

Also, there are double roller timing chain sets available that will clear the stock aluminum 6-bolt timing covers. I used one on the 489 that I built for my boat.

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post #7 of 49 (permalink) Old Dec 12th, 16, 03:53 PM
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Re: So much for my "502ci"...

If the honeymoon isn't good then chances are the marriage won't be much better. I would get my money back. Way to often being kind hearted I have given people a second chance and got burned. My dad also said when you bend over for people you put yourself in a vulnerable position.
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post #8 of 49 (permalink) Old Dec 12th, 16, 08:17 PM
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Re: So much for my "502ci"...

So basically you have a short block that needs pistons. If he will give you a set of alluminum heads, then buy some pistons to get you where you want to be, should be at least 10:1 with the alluminum heads.

With the new slugs, you are now into it for $3,000. Check out what blueprint is at on a 496 short block for comparison

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post #9 of 49 (permalink) Old Dec 13th, 16, 06:54 AM Thread Starter
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Re: So much for my "502ci"...

Quote:
Originally Posted by Larger Dave View Post
Well it is a four bolt main block anyway (they all are from the one piece rear main seal GEN V and up). Is this a Mark IV block with a two piece rear main seal? Or do you have a Gen VI block with a one piece rear main seal (the Gen V BBC 454 had no provision for a mechanical fuel pump as it was used only in EFI vehicles).
This is a Gen VI 8.0L 489ci block bored .020 to 494ci. I'm trying to keep it relatively stock looking, so no turbos or blowers.

Quote:
Originally Posted by Vega$69 View Post
I'd get the money back.
Just would never be comfortable going forward.
Quote:
Originally Posted by RSSSfanatic View Post
Looking at the pictures, I think I see the "spider" that holds down the dogbones for the stock roller lifters, so judging by that, it's a Gen VI, and therefore also a 4-bolt main and a one-piece rear main. It also has the mechanical fuel pump boss, which means it is a 454 block. If it does in fact have the 4.25" stroke, then you have either a 489 (.030 overbore) or a 496 (.060 overbore). Probably why they were calling it a "502", although the latter has the stock 4-inch stroke and a 4.5" bore. That being said, you can make plenty of power with a 489 or 496, if you put some decent heads and a healthy cam in it. You could probably find a GM ZZ502 cam as a takeout, and add a set of the AFR 265 oval heads and have a real stump puller. Even with the flat tops, the AFR's are available with 110 cc chambers, which should yield a pump-friendly 9.6:1 CR, or thereabouts.

Depending on how they want to work with you, you still might have the makings of a good street motor. What are the casting numbers on the heads?
Gen VI 489ci 8.0L block. The heads are nothing special stock 489 heads with 2.09/1.72 valves.

Quote:
Originally Posted by RSSSfanatic View Post
Also, there are double roller timing chain sets available that will clear the stock aluminum 6-bolt timing covers. I used one on the 489 that I built for my boat.
This motor was all together when I got it, so the timing chain fits under the stock cover.

Quote:
Originally Posted by 1971ls6 View Post
So basically you have a short block that needs pistons. If he will give you a set of alluminum heads, then buy some pistons to get you where you want to be, should be at least 10:1 with the alluminum heads.
With the new slugs, you are now into it for $3,000. Check out what blueprint is at on a 496 short block for comparison
After doing some thinking, these are my thoughts as well. A Blueprint 496ci is $8,095 through Summit. Just the short block is $3,695.
My friend is the middle man and I decided to give him a chance to make it right. I have no interest in talking to the builder because the ending of this would be very different... My friend has set it up so I'll be receiving a set of aluminum heads and the new cam I want.
I might put new pistons in and I might not. I want to take some measurements first and see where I am. If I'm over 9:1, I'll leave them for now. I just don't want to spend anymore money right now....
Thanks a lot for all the comments guys. I appreciate the feedback.

'69 SS396 X66 L34 08D M21 BS
460ci Gen VI 9.75:1 AED 950 carb
241/249 @ .050" .625/.625 110 LSA

Semper Fi!

"The galleries are full of critics. They play no ball, they fight no fights. They make no mistakes because they attempt nothing."
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post #10 of 49 (permalink) Old Dec 13th, 16, 07:05 AM
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Re: So much for my "502ci"...

Good thing you decided to pull the cam.

Couple years ago I bought a 427 from a builder in Calif. was doing a Yenko Clone.

Motor came and the oil pan we'd agreed was part of the deal was not installed. Guy said it wasn't part of the deal however I had email it was.

Well with the pan off I get to looking and discover it was not a 427. Wrong crank from the GM 6223 427 crank. Was a Scat crank and the engine was a 496. As I looked further other thing were not as agreed.

Ended up in court. He lost. All because he wanted to screw me out of a $40 oil pan
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post #11 of 49 (permalink) Old Dec 13th, 16, 07:10 AM Thread Starter
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Re: So much for my "502ci"...

Quote:
Originally Posted by Vega$69 View Post
Good thing you decided to pull the cam.

Couple years ago I bought a 427 from a builder in Calif. was doing a Yenko Clone.

Motor came and the oil pan we'd agreed was part of the deal was not installed. Guy said it wasn't part of the deal however I had email it was.

Well with the pan off I get to looking and discover it was not a 427. Wrong crank from the GM 6223 427 crank. Was a Scat crank and the engine was a 496. As I looked further other thing were not as agreed.

Ended up in court. He lost. All because he wanted to screw me out of a $40 oil pan
Yes, we were both very lucky. If it weren't for my friend being the middle man, he'd probably be getting the motor back out of pure principle. He probably figured no one will ever know because the motor still would have had a ton of torque.

'69 SS396 X66 L34 08D M21 BS
460ci Gen VI 9.75:1 AED 950 carb
241/249 @ .050" .625/.625 110 LSA

Semper Fi!

"The galleries are full of critics. They play no ball, they fight no fights. They make no mistakes because they attempt nothing."
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post #12 of 49 (permalink) Old Dec 13th, 16, 08:53 AM
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Re: So much for my "502ci"...

As far as I know, GM never built a 496 CID motor in the older Mark IV/GEN V/GEN VI configuration. They built this platform in a 396/402, 427, 454, and starting in the 80's, the 502 CID. To get a 496 out of this configuration, you generally add a stroker 4.25" crank and bore a 427/454 block to 4.060".

The "496" that GM produced was in the newer LS-style platform, which shares few if any parts with the "old school" big block Chevy. Is this what you have? I'm confused when you talk about a .020 overbore on a GM 496 block.

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post #13 of 49 (permalink) Old Dec 13th, 16, 09:00 AM
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Re: So much for my "502ci"...

Are the pistons forged or cast (my guess)? If they are cast, they might be OK for a mild street cruiser, but if you are planning to bang on it very much forged would be a better choice.

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post #14 of 49 (permalink) Old Dec 13th, 16, 09:49 AM
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Re: So much for my "502ci"...

Quote:
Originally Posted by RSSSfanatic View Post
As far as I know, GM never built a 496 CID motor in the older Mark IV/GEN V/GEN VI configuration. They built this platform in a 396/402, 427, 454, and starting in the 80's, the 502 CID. To get a 496 out of this configuration, you generally add a stroker 4.25" crank and bore a 427/454 block to 4.060".

The "496" that GM produced was in the newer LS-style platform, which shares few if any parts with the "old school" big block Chevy. Is this what you have? I'm confused when you talk about a .020 overbore on a GM 496 block.
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post #15 of 49 (permalink) Old Dec 13th, 16, 10:43 AM
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Re: So much for my "502ci"...

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Originally Posted by 1968 Z28 View Post
Last Big Block truck engine....8.1L Vortec Engine Specs
Correct Jerry, but my understanding is that this is a different block and heads than the "old school" BBC that most of us are familiar with. Someone correct me if I'm wrong. Heads have basically the same exhaust port arrangement, but intake arrangement is different. Can't swap Mk IV / Gen V / Gen VI heads, cam, crank, etc., to the 8.1L Vortec blocks. The 454 and 502 were the last of the original platform.

Someone correct me if I'm wrong.

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