I am Installing a set of Merlin cast iron heads on a 454 block (74-78). I am .030 overbore, and using 1037 Fel-Pro head gaskets. The gasket instructions refer to three cooling port holes in the block, stating. "If these holes are not present,in your block, they must be added" "2-1/2" holes and 1 (front) 5/8". My block does not have the two rear holes , and one partial front hole. Has anyone encountered this?

The short block is complete, with heads pistons installed, and oil pan on. I feel I can accomplish drilling the holes with the use of a vacuum, and magnet to draw drillings away from the finished block, while protecting it by masking.

If anyone else has been there, how did you handle it?

If it's on the engine stand, flip it over and drill upside down. Those holes are present on the 14015445 blocks and provide additional circulation. I don't know that I've ever seen any running temperature difference, but I'd drill 'em if the Merlins call for them.

I'm looking at the instructions dated rev 03/94 for installing my Merlin ovals that I got back in '95 and the paper say's to use Fel-Pro #1017-1 or equivalent headgaskets with NO mention of drilling any holes in my '75 454 P/U block...

What's going on?? I mean, after all these years I got this big sucker together and so, NOW reading here, do I need to take her back apart and drill these holes????

pdq67

PS., the sheet does explain how to drill the cross-over heat riser if wanted.

As well as to use headers so that the head isn't heat-soaked by the thicker Merlins and stock cast-iron exhaust manifolds b/c heat soaking may increase exhaust valve guide wear due to temperatures being higher vs stock...

Pretty sure the 1037's are GenV gaskets. A MarkIV motor would use the 1017 or 1027. I am running 1017's on my 402 motor and the matchup was perfect. You may want to double check the application.

The 1037 fits all three blocks but has the large cooling hole in the rear blocked.
The holes should be drilled on all Gen IV blocks with the 1037 gasket.
They are not required with the 1027 & 1017. The holes are one 1/2" between the first cylinder & second cylinder, one between the second & third & one 5/8" between the third & fourth just below the middle head bolts.

It's the difference between Parallel cooling flow, and series cooling flow. It has nothing at all to do with what heads are bolted on. Every big block head I've seen already has the matching passages cast-in. Any Mk IV can be converted to the later/better style coolant routing, if it wasn't built that way to begin with, but I don't think you could convert a Gen series engine to the older system. (And why would you want to????)

ALL Gen V and Gen VI, and SOME Mk IV have/had parallel flow. Most Mk IV used series flow.

Either one can work well, but in my opinion, the parallel flow is very slightly "better" for keeping the temperature nice 'n' even within the engine.

Yes, all it takes is the appropriate head gasket, and perhaps drilling some holes in the block deck to change coolant flow within the engine.

I've been suggesting that a series flow gasket, mistakenly installed on a block that does not have the extra holes, would be a chronic overheater, and nothing would fix it short of different gaskets or drilling some holes.

Tough way to get a thread started, but thankful someone pointed out the difference. What would be nice is if someone has a picture identifying the aforementioned holes.

Guys! My error. The gaskets I am fitting up are 1017, not 1037! Same issue still applies.

(Use the "Larger Image" buttons on the Summit website)

http://store.summitracing.com/default.asp?target=partdetail.asp&part=FEL%2D8523PT%2D1&FROM=MG

That should be the link to a parallel flow head gasket. Note 3 extra small holes between cylinders, (they look like extra head bolt holes) and only one smaller coolant hole at each end of the gasket in line with the cylinder openings.

http://store.summitracing.com/default.asp?target=partdetail.asp&part=FEL%2D8180PT%2D2&N=110&Ntk=KeywordSearch&Ntt=Chevy+Head+gasket

should be the link to a series flow gasket. Note NO extra smaller holes between cylinders, and two large coolant holes at each end of the gasket in line with the cylinders.

Is there a Fel-Pro headgasket number cross reference or what b/c I'm having a slight problem finding the 1017-1 and 1027 gaskets on the Summit site???

Are they now the 8180PT-2 and 8523PT-1, (whichever numbers match the other "older" numbers??)...

AND I assume Mr. Gasket .020" steel shims, PN 1131 are OK too for either application the other two can be used in??

pdq67

I'm too cheap to use the "performance" gaskets, so the ones I linked to are the "rebuilder" ordinary-kind.

The Summit numbers are FPP-10171 and FPP-1027.

The Mr Gasket 1131 steel shims are for the older, series flow routing of a MK IV. (NOTE: Summit's photo is NOT the 1131 gasket--I think the photo is of a small block gasket!) The GM 14015351 steel shims are for parallel cooling a MK IV.