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Discussion Starter #1
I tried to install my RPM Airgap intake manifold on my 454 and noticed that my merlin 269 heads are missing 2 bolt holes each. hole numbers 13, 14, 15 & 16. Ever get that horrible feeling like the world just came to an end deep in your gut. Stuff thats not "by the book" really gets me down.
I checked a set of old original bbc heads and they have those holes. I also checked a stock cast iron boat anchor intake and they have those holes.
The crossover ports in the middle are open also. Just the gasket covers them
but the intake does not back up the gasket at those ports.
The heads are older 269 World Merlin 1-043D 2.19 1.88 professionally rebuilt..
Whats with these heads? Someone please help.
 

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They omit those holes on just about every aftermarketcyl head although most of those are square ports or big aftermarket ovals
 

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I think also they assume you are using a aftermarket intake which many times is missing those holes as the manifold decks are thick enough you don't need the extra holes.
 

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Discussion Starter #5
I think also they assume you are using a aftermarket intake which many times is missing those holes as the manifold decks are thick enough you don't need the extra holes.
I am using an aftermarket intake. The orange one in the pics is an edelbrock airgap. it has the 4 extra holes but the heads do not. The exhaust crossover is wide open too.
 

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I have seen aftermarket heads both ways. The gap at the crossover is normal, that is a passage to allow air in to cool the crossover passage. It doesnt go anywhere.
 

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Discussion Starter #7
I have seen aftermarket heads both ways. The gap at the crossover is normal, that is a passage to allow air in to cool the crossover passage. It doesnt go anywhere.
So that crossover is left open? The gasket can lay over it without anything backing it?
 

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So that crossover is left open? The gasket can lay over it without anything backing it?

Yup,
That is how every big block in the world is from the factory. As long as the gasket seals the inner passage where the exhaust actually goes through it is fine.
 

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By the way, I think FelPro makes a different gasket that fits better and does not have the extra bolt holes.
 

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dart intakes and gaskets for the dart bbc iron eagles will work for you...
 

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Discussion Starter #13
By the way, I think FelPro makes a different gasket that fits better and does not have the extra bolt holes.
I will search for the gaskets.

Of the dozens of car shows I’ve been to, I’ve never seen the crossover port being open on the edge of the intake.
 

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So the air gap won’t leak if those bolts aren’t used?
It will seal up just fine, just like most aftermarket intakes and heads that don't have those bolt holes.

if you really want those bolts in the heads, you can drill and tap the head to take them if you want to go to all that effort.

Just use the manifold bolt holes as a guide to transfer punch the hole location on the head.

The exposed area around the exhaust crossover port doesn't go anywhere and can't leak anything, oil/crankcase pressure/vacuum/exhaust, so it doesn't matter if the top section is exposed.
 

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Like others said many aftermarket heads dont have those 4 holes. Some ovalport aftermarket heads have them like Brodix race rites even the 294 rec race rite has them and some Edelbrock/GMPP. Most rec aftermarket heads dont have them because theres no rom for them.
They will seal up anyway.

Off topic:
You are workibg on two hyd roller BBC builds? What are the spec on them?
 

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Short answer, the bolts don't matter. Second get a set of performance intake gaskets like the Felpro or Mr.gasket and it will cover the heat riser holes. None of it is an issue.
 

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Discussion Starter #17
Like others said many aftermarket heads dont have those 4 holes. Some ovalport aftermarket heads have them like Brodix race rites even the 294 rec race rite has them and some Edelbrock/GMPP. Most rec aftermarket heads dont have them because theres no rom for them.
They will seal up anyway.

Off topic:
You are workibg on two hyd roller BBC builds? What are the spec on them?
Ok.
I will use this intake then.I will make dummy bolts and cover the 4 unused holes in the intake.

I am building 2 big blocks together at the same time. Bottom end and valve train ar done.On to the rest now.

One is a 468 and the other is a 496.

Im using the same cam for both.: Intake Duration at 050 inch Lift:236
Exhaust Duration at 050 inch Lift:242
Duration at 050 inch Lift:236 int./242 exh.
Advertised Intake Duration:286
Advertised Exhaust Duration:292
Advertised Duration:286 int./292 exh.
Intake Valve Lift :0.600 in.
Exhaust Valve Lift 0.600 in.

The heads on the 468 are merlin 269cc intake that have the 2.19 1.88
and the 496 has trick flow power oval 280 top end kit. 2.19 1.88 and 280cc intake.

the 496 I had decked to 0. I used flat top pistons on the 496.9.0 compression

The 468 got 14cc domes standard deck. 9.4 compression.

I put both ring gaps at .024 top and middle on both for possible future low boost.

496 has forged and balanced crank ,eagle h beam rods and pistons and internally balanced from skip white.

the 468 has forged pistons,eagle h beam, factory cast crank reground .010 under.

this is a fun learning process.
 

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Discussion Starter #18
Short answer, the bolts don't matter. Second get a set of performance intake gaskets like the Felpro or Mr.gasket and it will cover the heat riser holes. None of it is an issue.
Thank you for your help.
I have felpro gaskets now and they do cover the crossovers. But with no intake backing the gasket at the crossover, the gasket does nothing.
 

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The gasket covers the hole. That's all it has to do. Its not under any pressure and the gasket is not going to flex in that small area without prying it with a screwdriver. And someone can correct me if I am wrong since it has been 20 years since I worked on a set, from what I remember on the Merlin heads the exhaust crossover is NOT drilled from the factory. So no hot exhaust is coming up the center either unless you drilled into the exhaust port.
 

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Discussion Starter #20 (Edited)
The gasket covers the hole. That's all it has to do. Its not under any pressure and the gasket is not going to flex in that small area without prying it with a screwdriver. And someone can correct me if I am wrong since it has been 20 years since I worked on a set, from what I remember on the Merlin heads the exhaust crossover is NOT drilled from the factory. So no hot exhaust is coming up the center either unless you drilled into the exhaust port.
The whole point of the air gap intake is to keep the carb cool. If there was hot exhaust being purposefully piped over to the intake would be silly.

I stuck a coat hanger straight through on a stock head of the crossover port.

The hanger would not pass through the merlin 269 head.
 

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