230 Or 250 Sprint?

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Pastime67

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My mechanic ordered 230 pistons for a Sprint engine I pulled out of my 1967 LeMans. The engineer at the machine shop doing the machining is telling the mechanic that according to block # 9795066 it needs "250" pistons. I feel it should use the 230 pistons. The 230's were used in 1966-67, and the 250's were used in 1968-69. I can use some help. The head seems to have been reworked. Block looks original.
Appreciate your input.
Bob
 
Bob,

You are correct that the original engine in your 67 LeMans would be a 230, but unless you are the original owner of the car are you sure the engine is original? It is very possible that in the 50+ years sense the car came off the assembly line the engine could have been changed, and it could have a 250 in it now. Post some pictures of the engine and Engine code and I may be able to help you ID what engine you have.

Good Luck
 
Assuming everyone is correct, which I have no reason to doubt, I have a '68, or '69 SPRINT 250. Does anyone have a preferred place to buy the 250 pistons?
Bob
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I am having serious problems with the shop that's doing the machine work on my 250 SPRINT. We have agreed I have a '68-'69 SPRINT but my mechanic is telling they don't want to use the 250 pistons because they feel it would create too much compression and cause damage to the engine or gaskets.
Can someone give me some guidance on this. If I insist, they will void any guarantee on their work.
 
Pastime67 said:
I am having serious problems with the shop that's doing the machine work on my 250 SPRINT. We have agreed I have a '68-'69 SPRINT but my mechanic is telling they don't want to use the 250 pistons because they feel it would create too much compression and cause damage to the engine or gaskets.
Can someone give me some guidance on this. If I insist, they will void any guarantee on their work.
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Just to be clear you have the 4bbl carburetor version of this engine?
Is the macine shop boring out the cylinders for oversize pistons? If so what size?
 
melsg5 said:
Just to be clear you have the 4bbl carburetor version of this engine?
Is the macine shop boring out the cylinders for oversize pistons? If so what size?
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Yes, according to the number 9795066 this is the 250 version. What I don't know ls if I have a head that belonged on the 230 version, and whether they are interchangeable?
Bob
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Pastime67 said:
Yes, according to the number 9795066 this is the 250 version. What I don't know ls if I have a head that belonged on the 230 version, and whether they are interchangeable?
Bob
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That's not what I asked. Both the 230 and 250 had low compression and high compression engines. I asked about which carburetor and what the machine shop is doing with the pistons, standard or oversize and if oversize, exactly what size?
 
The head that was on the engine when I got the car a couple of months ago had the 4bbl and dual exhaust manifold. What I'm waiting to find out is the number on the head. I was told the head looked very clean. I was told they did not have to bore out the engine. That it only required honing. When they took the block apart. one of the pistons was frozen and they had to break it.
 

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Pastime67 said:
The head that was on the engine when I got the car a couple of months ago had the 4bbl and dual exhaust manifold. What I'm waiting to find out is the number on the head. I was told the head looked very clean. I was told they did not have to bore out the engine. That it only required honing. When they took the block apart. one of the pistons was frozen and they had to break it.
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In that case, assuming it's the original head that went with the block it's a high compression, 10.75:1 engine.
Why is the mechanic thinking you can put 230 pistons in a 250 block and what does he think that will do assuming they will even work?
Will the machine shop assemble the engine and give you a warranty?
 
melsg5 said:
In that case, assuming it's the original head that went with the block it's a high compression, 10.75:1 engine.
Why is the mechanic thinking you can put 230 pistons in a 250 block and what does he think that will do assuming they will even work?
Will the machine shop assemble the engine and give you a warranty?
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The engineer at the machine shop knows the 250 pistons go in that block. His concern is that the high compression created by these pistons will be excessive. I told my mechanic to tell the machine shop that this configuration is good for 10.5 compression because that is what I read. You're saying it can handle 10.75:1 compression. I can also relay this information...out of curiosity. what would be considered too much compression?
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Pastime67 said:
The engineer at the machine shop knows the 250 pistons go in that block. His concern is that the high compression created by these pistons will be excessive. I told my mechanic to tell the machine shop that this configuration is good for 10.5 compression because that is what I read. You're saying it can handle 10.75:1 compression. I can also relay this information...out of curiosity. what would be considered too much compression?
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That was a typo on my part. Should have been 10.5. Can the machine shop mill the pistons to lower the compression or has anybody checked for a thicker head gasket?
 
melsg5 said:
That was a typo on my part. Should have been 10.5. Can the machine shop mill the pistons to lower the compression or has anybody checked for a thicker head gasket?
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Just spoke with the mechanic and he told me milling the pistons would bring another set of problems such as balancing. The gasket that was on the 250 was a thin metallic gasket and this was creating their concern on compression. The mechanic sez the gasket that came with the gasket set is about 3.0Mil (1/8?). He tells me he can order whatever size gasket the machine shop will need to get the correct compression.
I wonder why they previously used the thin metallic gasket?
 
Pastime67 said:
Just spoke with the mechanic and he told me milling the pistons would bring another set of problems such as balancing. The gasket that was on the 250 was a thin metallic gasket and this was creating their concern on compression. The mechanic sez the gasket that came with the gasket set is about 3.0Mil (1/8?). He tells me he can order whatever size gasket the machine shop will need to get the correct compression.
I wonder why they previously used the thin metallic gasket?
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The machine shop would balance the pistons by weighing them. Thin gasket is used to raise compression. Does this mechanic normally do business with the machine shop or you picked the machine shop?
 
Pontiac was very optimistic with the compression ratio's of these engines, the 1 bbls were about 8.9 to 9.0 to 1 CR and I have never seen a 4bbl engine with an actual static compression ratio of more than 10.1 to 1. So I run the thicker felpro head gasket, not the stock this steel stock type and they run fine on 93 octane unleaded, but I do not know what the fuel availability is in your area.

And while you can bolt a 230 head to a 250 block with no issues, if you use a 4bbl 230 head on a 250 block with stock pistons you will end up with a static CR of around 13 too 1! way to high.
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cammerjeff said:
Pontiac was very optimistic with the compression ratio's of these engines, the 1 bbls were about 8.9 to 9.0 to 1 CR and I have never seen a 4bbl engine with an actual static compression ratio of more than 10.1 to 1. So I run the thicker felpro head gasket, not the stock this steel stock type and they run fine on 93 octane unleaded, but I do not know what the fuel availability is in your area.

And while you can bolt a 230 head to a 250 block with no issues, if you use a 4bbl 230 head on a 250 block with stock pistons you will end up with a static CR of around 13 too 1! way to high.
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That is my concern. Since my 1967 LeMans was an original 230 Sprint and they later used a block from a '68-69 250 Sprint, they may have used the original 230 Sprint head and 4bbl manifold on the later model 250.
I have a good 1967 non-sprint OHC 6. Can I use the block to make it into a Sprint using the components off the 250? Would I need to swap cranks? Is this getting too complicated?
 
melsg5 said:
The machine shop would balance the pistons by weighing them. Thin gasket is used to raise compression. Does this mechanic normally do business with the machine shop or you picked the machine shop?
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Mechanic uses this machine shop. I agree with Cammerjeff that I might have had a 230 Sprint head on a 250 block, and the 13.0:1 estimated compression is what's causing their concern.
 
Pastime67 said:
Mechanic uses this machine shop. I agree with Cammerjeff that I might have had a 230 Sprint head on a 250 block, and the 13.0:1 estimated compression is what's causing their concern.
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I thought nobody has checked the head casting number?
 
melsg5 said:
I thought nobody has checked the head casting number?
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I personally don't have knowledge of that one way or the other. I will personally be calling them to find out, but the machine shop is very adamant of the high compression with the current parts.
 
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