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I have a GenV 454 that is getting worked over. Aside from the usuall machining I'm replacing the heads. It is going into a 66 chevelle. Used for street application only. Only racing it should see should be some goof who thinks his Ford Focus GT is hot poop. Basically I want a quick car that won't be spinning much past 6000 rpm. It will be bolted to a Tremec TKO 600, 12 bolt with 3.73 gears. When we place new forged pistions in it a compression ratio of 9.5:1 will be the target. I haven't figured out cam selection yet but I'm sure a duel plane intake with an 850 carb will what I select based upon previous posts. I also don't know if that carb size is to big for my intentions considering many posts recommending that seems like a strip recommendation. I will have headers and MSD ignition as well. I've searched the forums alot and found recomendations for the Mark IV blocks but little on the after market heads for street application. Please help

Here is the heads I'm considering.

1. BB-Chevy Merlin III Cast Iron Cylinder Head
269cc Oval Intake Ports
119cc Combustion Chambers
2.300'' Int/1.880'' Exh Valves
1.550'' Valve Springs, .650'' Max Lift for Hydraulic Roller Cam
Assembled, Sold Individually

2. BB-Chevy Merlin III Cast Iron Cylinder Head
320cc Retangular Intake Ports
119cc Combustion Chambers
2.300'' Int/1.880'' Exh Valves
1.550'' Valve Springs, .650'' Max Lift for Hydraulic Roller Cam
Assembled, Sold Individually

3. BB-Chevy Dart Iron Eagle Cylinder Head
308cc Intake Ports
119cc Combustion Chambers
2.25'' Int/1.88'' Exh Valves
1.550'' Springs, 145lbs @ 1.900''
.660'' Max Lift
Assembled, Sold Individually

4. BB-Dart Chevy Iron Eagle Cylinder Head
345cc Intake Ports
119cc Combustion Chambers
2.30'' Int/1.88'' Exh Valves
1.550'' Springs, 195lbs @ 1.900''
.690'' Max Lift
Assembled, Sold Individually

So please offer any assistance
Thanks to everyone who helped me with the machine shop question last week, big help!!!

Mike Dettloff
 

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Out of the heads you listed I like the 269 cc ports for your combo.
 

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Just repeating what I have been told when building my 454. was told the Merlin 269 oval pots are decent heads but you can get just as much good flow for a street motor with a set of GM 781 oval port with larger 2.19/1.88 valves and some mild port work. This you can have for about $800 compared to the Merlins in the 1200-1400 range. Just a thought.
 

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049/781 Heads. More than enuf potential to do what you want.
2.19/1.88 valve and bowl blend

Or if you need to buy aftermarket stuff...Oval port all the way. Brodix RR oval would make a great head in aluminum. Or the merlin in iron.
 

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049s or 781s will work well, cam in the 240/250 range on a 110, it should run 11s easy.
What ever you do, dont do option 4 - or the focus will drive right around you... your car would be a turd ;)
 

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Yup, my car had a 9.5:1 454, 781's, [email protected] cam, on a 110. ran 11.50's all day long on pump gas.
Now it's a little different :)
 

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If the aftermarket heads have raised ex. ports there may be header issues with sparkplugs
 

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Not to steal the thread but what kind of converter/gear would be used to make a 9.5:1 454 with a cam like the one mentioned above run 11.50s?

Planning a similar build myself, I'll be using 781s.
 

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Yeah I missed that V....thought it may be a typo and forgot to put the I before the V.
Its MARK IV and GEN V VI

;)

Be sure to check that the merlins isnt just a replacement MK4 head. It need to fit your newer block.

I would consider Ovalport Brodix heads instead. It will be lighter, more power. easier to port, better sell value. And you know that you did the right choice instead of changing them after a few years. ,)
 

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I guess I'll play devils advocate a little. No doubt, that the 269 cc merlins or modded stock heads would be a better combo for right now. But, i don't buy into the absolute assumption that a little bigger head would be a bad thing.

Just look at the chevy crate motors like the 454ho and 502 ho. That's pretty much the worst combo....small cam, 8.75:1 compression and iron rec port heads. Yet still they make good power.

Now, take that Iron eagle 308 head that's been designed to have high velocity ports , not to mention a superior combustion chamber design, and put it on a more suitable 9.5:1 454 with good cam. I think you'd have a real ripper on your hands. Also, you'd have a better casting than the World Products merlin head. Lastly, you'd have a head at the end of the day that would "grow" with you if you wanted to make it a 496 or run some more compression/cam down the road.

Just my opinion,

Bill
 

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I'd stay away from raised exhaust port heads if i were you. my heads have .625 raised ports,and it was murder trying to find a header that worked.I tryed three sets till i massaged a set to make them work. in the process i ruined a 200.00 set also. 66's with bbc"s are a tight fit when it comes to headers. Also the rpm ,rpm air gap is the the highest intake that will fit under a stock 66 hood. You will have to use a drop base air cleaner to make it work.
 

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