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I know a lot of people have asked if the DOHC heads can be used on a pushrod block, and we have been told "no", but I am one of those people that likes to know the "WHY" part. You know what they said about curiosity and the cat? About how it killed a couple of hours!!!!!
I needed to remove the head on my 3.4 DOHC that I am getting ready to rebuild, so I figured that this would be a good time to do some comparing with the 3100 block I had sitting next too it.
Just so you know, I have a 1999 3100 SFI block (physically the same as the 3400 with the exception of the BORE). I also have a 1994 3.4 DOHC. Both are in really rough shape, but these pics will show how they interplay with each other.
First set of pics is of basic comparisons, second set of pics is of a 1994 3.4 DOHC head on a 3100 SFI block, and third set of pics is of a 3100 SFI head on a 3.4 DOHC BLOCK.
One thing I would like to point out in these pics is that I KNOW that I put the REAR DOHC head on the FRONT of the 3100, but that should not matter. For the 3100 head on the 3.4 DOHC, the rear head is on the rear bank, but once again, it does not matter. Just wanted to point out that I am aware of this before anyone pops in about it.
This is all REALLY cool.
First of all, some basic pics.
This is a bare 3.4 DOHC block:
And this is a bare 3100 SFI block:
One of the biggest NOTICEABLE differences is the OIL VALLEY. The 3.4 DOHC does not have lifter holes, and it has a cover on it. When the engine is ASSEMBELED, the valley is actually OPEN to the air, and not sealed off like the 3100. The 3.4 DOHC has that cover on it to keep anything from getting in there.
Here is the cover on a 3.4 DOHC:
This is me holding the cover in place on a 3100 block:
Now for pics of the DOHC items on a 3100 block.
First of all, this is a 3.4 DOHC HEADGASKET on the 3100. Sorry it is so blurry, but the items I want to point out, I have more pics of.
This is the first glaring difference (other than the oil valley). as you can see, half of the coolant ports are OPENED UP to the exterior of the block. If you go up to the first 2 pics, you can see the coolant passages around the cylinder. The 3.4 block is thicker and has an extra cooling port.
Now this is the 3.4 DOHC HEAD on a 3100 block. The coolest thing is that it DOES BOLT RIGHT UP. I only have 2 bolts holding it in, but they are the same fitment.
Now for the inconsistancies.
First of all, this is looking at the INSIDE area of the engine. The 3.4 DOHC has oil passages to feed the oil back into the block. This is not really a problem on the 3100, however you would have to make a cover for the lifter ports that also allowed the oil return for the heads.
This is the underside of the 3.4 head on the 3100 block from. You can see that it overhangs too much, and the coolant passages are exposed (you will REALLY see this later on in the 3100 head on 3.4 DOHC block pics)
Here is a closeup of the exposted coolant port.
Now here is a HUGH problem. Here is an exposed OIL PASSAGE for the head. You can see that the 3100 block has NO provision for this at all. Keep in mind that the 3.4 DOHC has to flow a LOT more oil than the 3100 because of the overhead cams, so if you were to attempt to make something, keep that in mind.
Lastly in this set is just a standing back pic of the 3.4 DOHC head on the 3100 block.
Now for the last set of pics. A 3100 head on a 3.4 DOHC block.
Once again, just like with the DOHC head on the 3100 block, it bolts right up. I don't have a headgasket to show the comparison, so this is just the head on the block.
Remember that oil passage I told you about? Here it is again. The 3100 head only halfway covers it.
Remember those coolant passages that the 3.4 has, but the 3100 does not? Here they are exposed on the block. The head does not fully cover them, so this is a MAJOR problem.
And here is the oil valley feed holes in the 3.4 DOHC block, but the 3100 head does not cover them.
I know that a lot of people know this already, but some people are like me and want to know the WHY and not just take someones word for it.
I needed to remove the head on my 3.4 DOHC that I am getting ready to rebuild, so I figured that this would be a good time to do some comparing with the 3100 block I had sitting next too it.
Just so you know, I have a 1999 3100 SFI block (physically the same as the 3400 with the exception of the BORE). I also have a 1994 3.4 DOHC. Both are in really rough shape, but these pics will show how they interplay with each other.
First set of pics is of basic comparisons, second set of pics is of a 1994 3.4 DOHC head on a 3100 SFI block, and third set of pics is of a 3100 SFI head on a 3.4 DOHC BLOCK.
One thing I would like to point out in these pics is that I KNOW that I put the REAR DOHC head on the FRONT of the 3100, but that should not matter. For the 3100 head on the 3.4 DOHC, the rear head is on the rear bank, but once again, it does not matter. Just wanted to point out that I am aware of this before anyone pops in about it.
This is all REALLY cool.
First of all, some basic pics.
This is a bare 3.4 DOHC block:
And this is a bare 3100 SFI block:
One of the biggest NOTICEABLE differences is the OIL VALLEY. The 3.4 DOHC does not have lifter holes, and it has a cover on it. When the engine is ASSEMBELED, the valley is actually OPEN to the air, and not sealed off like the 3100. The 3.4 DOHC has that cover on it to keep anything from getting in there.
Here is the cover on a 3.4 DOHC:
This is me holding the cover in place on a 3100 block:
Now for pics of the DOHC items on a 3100 block.
First of all, this is a 3.4 DOHC HEADGASKET on the 3100. Sorry it is so blurry, but the items I want to point out, I have more pics of.
This is the first glaring difference (other than the oil valley). as you can see, half of the coolant ports are OPENED UP to the exterior of the block. If you go up to the first 2 pics, you can see the coolant passages around the cylinder. The 3.4 block is thicker and has an extra cooling port.
Now this is the 3.4 DOHC HEAD on a 3100 block. The coolest thing is that it DOES BOLT RIGHT UP. I only have 2 bolts holding it in, but they are the same fitment.
Now for the inconsistancies.
First of all, this is looking at the INSIDE area of the engine. The 3.4 DOHC has oil passages to feed the oil back into the block. This is not really a problem on the 3100, however you would have to make a cover for the lifter ports that also allowed the oil return for the heads.
This is the underside of the 3.4 head on the 3100 block from. You can see that it overhangs too much, and the coolant passages are exposed (you will REALLY see this later on in the 3100 head on 3.4 DOHC block pics)
Here is a closeup of the exposted coolant port.
Now here is a HUGH problem. Here is an exposed OIL PASSAGE for the head. You can see that the 3100 block has NO provision for this at all. Keep in mind that the 3.4 DOHC has to flow a LOT more oil than the 3100 because of the overhead cams, so if you were to attempt to make something, keep that in mind.
Lastly in this set is just a standing back pic of the 3.4 DOHC head on the 3100 block.
Now for the last set of pics. A 3100 head on a 3.4 DOHC block.
Once again, just like with the DOHC head on the 3100 block, it bolts right up. I don't have a headgasket to show the comparison, so this is just the head on the block.
Remember that oil passage I told you about? Here it is again. The 3100 head only halfway covers it.
Remember those coolant passages that the 3.4 has, but the 3100 does not? Here they are exposed on the block. The head does not fully cover them, so this is a MAJOR problem.
And here is the oil valley feed holes in the 3.4 DOHC block, but the 3100 head does not cover them.
I know that a lot of people know this already, but some people are like me and want to know the WHY and not just take someones word for it.
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