larose481

Just getting ready to put the heads on and noticed a coolant port above #7 cylinder just to the left of the head bolt dowel that is open in the block and there is a port in the gasket but not on the Gen 4 heads. The factory Gen V heads matches the port configuration of the block and the gaskets that Cometic speced out for this conversion are actually Gen V gaskets so naturally the port would be there. Question is, do I need to drill this in the head or can anyone that has done this conversion without drilling give me some feedback. On the opposite side this would be on #2 cylinder as well. Any help soon would be great as I am waiting to put these on. Think I answered my question as I have looked at every head manufacture out there and all BBC heads don't have this port in them and can be used on either block, just different gaskets.Thanks

larose481

Just subscribed so here are pics.

larose481

Anyone have any thoughts? Would love to bolt these on.

sonicss42

Make sure you do your research. There is some issue with GenIV heads on a Gen V block and I recall there is a special head gasket which is made for this.

larose481

I had Cometic spec out the gaskets I need and I have done a carbon transfer between the head and block and the clamping area between the two is the same as the original Gen V heads so I hope it will be fine.

FIXX

did you deck the block?? their is soppose to be a super smooth surface for the cometic gaskets..i havn't seen anyone having any luck with this conversion..

Borgie

Are those factory iron heads? I know if you run a Gen V block and use aftermarket heads (they are a gen mark 4 variant cooling jacket) and the proper head gasket it's not an issue. Plenty here have done this, however, I'm not sure of the exact differences between a factory Mark 4 and a aftermarket style coolant passage regarding heads. And as noted, cometic MLS gaskets require a certain RA to seal properly.

larose481

Block has been decked and heads milled. Borgie, these are a factory head 781 castings. They appear to have the same coolant port configuration as an aftermarket head based on the heads I have looked at. So the port that was in question on my original post, I think I am ok. Now as far as the differences on the factory vs. aftermarket for this conversion, I think aftermarket heads do in fact run the same coolant port location as the stock Gen 4 heads but the actual port openings in the casting is smaller on the i.d. to help with any mis alignment of the coolant ports. Also, they look to have more material towards the lifter valley which might aid to this type of conversion. Now, I took the Gen V gaskets that I took off of this which still had the impression of the coolant port outlined in the gasket and then put alignment dowels in the new Gen 4 heads and layed the old gaskets on the heads. I then took a small hammer and tapped around the coolant ports to leave an impression on the gasket. I pulled the gasket off to compare the location on the two coolant ports and both of them were in the same location as far as the amount of material to be clamped on the lifter valley side which is where the issues are. Lastly, the new cometic gaskets lay right to the edge of the block and the head and the heads match or overhang slightly into the lifter valley. I am having a hard time believing that these would not seal the same as the original Gen V heads that were on there as they have the same clamping area. Not sure why some people say they do this conversion all the time and no problems and others say they have never seen it work. I personally have never done it.

1BIGJIM

Do a search, you will be able to read for hours. Here is one thread.

http://www.offshoreonly.com/forums/g...54-please.html

larose481

Thanks, 1BigJim. I have read every post including that one on this conversion that I could find as well as hours of other posts on other forums. Once again, soulnds like some work and some don't. I see that the Felpro 1037 for the 4.250" bore is what most are running or the 1047 for the 4.500" bore but was looking for an MLS gasket as this is supercharged. Felpro speced out the 1071-041 and Cometic said the C5817-040 is used for this conversion when I talked with both. Is one better than other, not sure but I chose the Cometic. Felpro did specify the only thing to look for is a minimum clamping width of .186" between coolant port and lifter valley. This same dimension is called out in posts by other members as well as published in the How To Build Gen V/VI book. I am sitting at a minimum of .305" or more around ports. Here is a couple pics of the layout. You can seen the Gen V impression in this Felpro gasket that I was running and then the new circular impression of the Gen 4 head after transfering as previously mentioned. All ports lay out the same as far as overall location.