[2BlueLS6's]

Why does FelPro and probably some others restrict the water holes in their head gaskets to BB sized holes........... probably about 1/8 inch? Any reason NOT to open em up some?

 

[Schurkey]

Because they're directing the coolant somewhere else where it'll do more good?

The holes are not random sizes. Other than verifying that you are using series-flow gaskets on a series-flow block; or parallel-flow gaskets on a parallel-flow block, leave the holes in the gaskets alone.

 

[BillK]

Same way the factory ones are. Leave them alone.

 

[2BlueLS6's]

Thanks for the replies guys. It's been a while since I pulled down an original 60's big block, but I just don't recall ever seeing them this small on a factory gasket. This particular one is a '68 model, but I'm going to be doing a '69 L71 and 70 LS6 within a month or so. So the advice is still to use the FelPro gasket with the 1/8" holes on all 3? Incidentally I've had some issues with the '68 engine getting hot, even though it has NEW alum water pump, correct big block radiator (new also) fan shroud properly sealed, new fan clutch and 2nd new 160 degree thermostat (with 1/8" holes drilled to prevent air pockets). Grasping at straws trying to figure reason.

 

[Schurkey]

A '68 is --probably-- a series-flow engine. MOST MK IV blocks are series-flow, but not all of 'em.

Installing a parallel-flow head gasket on a series-flow block can lead to overheating because most parallel-flow gaskets are restricted at the rearmost coolant passages--and those are the only coolant passages a series-flow block has. A few gaskets are set up for both coolant flow patterns; the now-discontinued GM steel shim gasket is one of them (but not the Mr. Gasket steel shim gasket!!)

Two ways to fix that problem: Install series-flow gaskets; or drill three holes in each block deck to accommodate parallel-flow cooling.

http://www.hbassociates.us/gaskets.html

 

[737guy]

My 454 is a 1978 date code casting, has the three holes in the lower portion of the head for cooling, and the 1966 396 heads i am using have them also. Question is, the gasket with the three holes is a felpro 8523 PT1, that has the 3 holes, that is good. In looking at the two pictures in the above post, there is a difference in the two gaskets on the ends also. In picture 2, where the "sort of triangular" water flow opening is, there is another squarish water flow hole below it. In picture 1, the picture without the three extra holes, there is only the sort of triangular looking water flow hole at the rear of the gasket. My 1966 heads and 1978 block both have these two openings (triangular with the squarish hole below) at the rear of the heads & block, behind the 8 and 7 cylinders, but the supposedly correct felpro 8523 PT1 gaskets, with the three extra holes, have only the triangular looking opening, and no squarish looking opening. Sort of a combination of picture 1 with 3 extra holes. Do I open up this supposedly correct gasket that has the three extra holes (cut the squarish looking water flow hole)to allow water flow through both openings behind the 7 & 8 cylinders or leave the squarish hole blocked? Thanks,,,,Thud

 

[Schurkey]

My 454 is a 1978 date code casting, has the three holes in the lower portion of the head for cooling, and the 1966 396 heads i am using have them also.

Far as I know, ALL the heads have the extra holes. NOT all the (Mark IV) BLOCKS have the extra holes. Does your BLOCK also have the holes?

Question is, the gasket with the three holes is a felpro 8523 PT1, that has the 3 holes, that is good. In looking at the two pictures in the above post, there is a difference in the two gaskets on the ends also. In picture 2, where the "sort of triangular" water flow opening is, there is another squarish water flow hole below it.

Yes, without the three holes along the side, you need double holes at the end.

In picture 1, the picture without the three extra holes, there is only the sort of triangular looking water flow hole at the rear of the gasket.

The upper photo is the gasket WITH the three holes; the second hole at the end isn't needed. Having the second end hole blanked directs the coolant to the three smaller holes.

SOME gaskets have ALL the holes--two at the end, and three along the side. The GM steel shim gasket was one of those.

My 1966 heads and 1978 block both have these two openings (triangular with the squarish hole below) at the rear of the heads & block, behind the 8 and 7 cylinders, but the supposedly correct felpro 8523 PT1 gaskets, with the three extra holes, have only the triangular looking opening, and no squarish looking opening.

Yup.

Sort of a combination of picture 1 with 3 extra holes.

Picture 1 (the top photo) DOES have the three holes.

Do I open up this supposedly correct gasket that has the three extra holes (cut the squarish looking water flow hole)to allow water flow through both openings behind the 7 & 8 cylinders or leave the squarish hole blocked? Thanks,,,,Thud

Leave it alone. The end hole is blocked for a reason.

This presumes that your BLOCK has the matching three holes along the side!!! If your BLOCK doesn't have the three holes on each side, you'll overheat under load.

 

[737guy]

Thank you for the quick reply. Appreciate the help. Thud:thumbsup:

 

[70-SS454]

Make sure they are installed "This side up" because they are not side to side symetrical.





'

 

[Wolfplace]

Make sure they are installed "This side up" because they are not side to side symetrical.





'

=
Actually BB gaskets cannot be installed backwards, there is no "up side"

 

[Schurkey]

=
Actually BB gaskets cannot be installed backwards, there is no "up side"

I thought the Gen 5/6 gaskets were "handed"--one left, one right.

Victor makes a "special" pair of gaskets for installing Mark IV heads on Gen 5 blocks; there's separate part numbers for right and left.

 

[69-CHVL]

I just installed a set of 1047's on my GEN6 502, no left or right, and can only go on one way. That is, if you want to use the dowels