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Discussion Starter · #1 ·
454 .030 over
KB .133 dome hyperteuctics
Stock crank
9:1 compression (estimated)
reconditioned stock rods
1 3/4 heddman headers
peanut port heads
Comp Cams 270H
Edelbrock 750 carb
Ford 9" with 3.50 gears
Street/Strip car
Best 1/4 was 12.85 this year

I bought a nice reconditioned set of 781 heads off EBAY.They have a 3 angle valve job with new stock sized valves and bronze guides and have been milled to clean them up. They are now at 113cc chambers. I have about $500.00 in them after shipping. I know that the larger valves and port work will improve them, but then I will have as much invested in them as a new set of Merlin heads????My winter plans are new heads, cam and carburetor.I have learned a lot on this site and really value the opinions and advise given here.I am looking for 12.0 or better ET. Please advise heads, cam and carb. Thanks
 

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My merlins outperformed my worked 781s right out of the box.

I had a good deal of bowl work and larger valves installed in my stock heads. I went from 105mph to 109mph after the swap. ( had to swap because the larger valves breached into a water jacket and my motor blew itself up!!)

This is on a 414cid motor, so you should see even more improvement if your cam can supply the flow. My cam is a 280/288 hydraulic.

The only main catch-22 is that the merlins come with a large combustion chamber. So, find out ahead of time how much you will need to mill-down in order to achieve your desired compression ratio. They also have a special set of bolts (like 5 or so special ones per head), and require a particular exhaust header gasket, not to mention spark plugs.

So, unless you know a really good head machinist that works for cheap, I say go for the merlins.

"Unless it is very convienent or inexpensive to modify stock parts, you are better off going aftermarket." -Me
 

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Have to tell you, as much of a fan as I am for larger valves, etc., there is apoint of diminishing return. Just the step up from peanuts to 781's is a huge jump. If it were me, and if you are questioning the added money, I'd use the fresh 781's as is and go with some more cam - preferably a spit pattern with about 6 - 10 degrees more exhaust. Your 454 motor is rather mild as is. You can step it up quite a bit before shoveling out money. If money is an object and you can get out of the 781's and recupe the money, then consider the Merlins. Good luck.
 

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If you decide to go with merlins and want a deal on a set that has been freshened with new parts tit. retainers 10 deg loks comp stud girdle and already milled just a little and setup for a solid roller than pm me and we can talk. I am going to afr's. I think you would like either choice. Whatever you decide good luck.

Frank
 
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I went from a set of 049's with bowl porting and stock valves to Merlin ovals and gained nothing on a mild 427.

I would suggest you save your money for a better set of heads.

Merlins are also HEAVY, add about 10 lbs per head.

A set of Canfields, Brodix, AFR's look pretty good after you lift the Merlins.

My vote goes for the 781's on a mild small cube BBC, save your cash.
 

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Jake,

You gained nothing? wow. How mild is the 427? What are you doing here and not camping out on my Transmission thread? ;)

Phil,
Like the others are saying, your current combo suggest the 781 heads are the way to go. There are just more "pros" versus cons for your situation. When I busted my heads, I couldn't afford the downtime fo finding a set of stockers and having them built up. It was my daily driver car for college... but I certainly didn't want to go any slower!! :D So I went aftermarket, and the Merlin oval ports had some good things said from folks here. I also got to re-use my larger valves.

Can you take the car to the track before the swap?
People would love to have some HP/ET numbers to go with the upgrade.
 

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(quote)
I bought a nice reconditioned set of 781 heads off EBAY.They have a 3 angle valve job with new stock sized valves and bronze guides and have been milled to clean them up. They are now at 113cc chambers. (quote)


do you know how much was milled off. i have three sets of 781's right now and all three came in around 119-122cc. seems like you would have to mill alot to get the chamber down to 113.

mike
 
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I hope you don't pull a head and find that you have flat-top pistons b/c you are probably down around 8 to 8.5 to 1 CR!!

Especially with a PP headed P/U core motor!!

You will need a 100 cc head to get decent compression along with .020" thick steel shim headgaskets! The old -206 heads at 96.7 to 98 cc's will get you there as will the newer L-29 P/U heads but they are only smaller large oval port heads.

E-brock's 100 cc "ROVALS" will do you nicely, imho!!

pdq67

PS., and fwiw, pp port heads are only like 200 cc's or so, the L-29's like 230 cc's or so and a true -781 large oval like 255 to 260+ or so intake port sized so there is a heck of a size difference here.

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Discussion Starter · #14 ·
I was hoping to get more agreement on what to do. I am sure I have the KB pistons with .133 domes. I may be mistaken on the chamber size of the 781s.I am at work and the specs are at home.I am thinking now that the paperwork said 118 CC chambers. Should I mill them more ???? Am I going to see much gain installing the heads "AS IS" ??????. I hate to replace new valves. I am considering the Voodoo 61202 cam. No one has said anything about what cam will work best ???? Thanks---- Phil
 

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pdq67 said:
I hope you don't pull a head and find that you have flat-top pistons b/c you are probably down around 8 to 8.5 to 1 CR!!

Especially with a PP headed P/U core motor!!

Thats what happened to me. I was going to do the head swap and get a pair of Race Rites, pulled the head off and had flat tops and -236 Peanut Port heads. Needless to say that motor came out of the car, and I found a new motor for less then the heads and a cam.

Which leads me into the Merlins. I have a set of the Merlin Cast Iron Heads on my 468. I bought the motor from someone, so they are on the car and don't think they have been milled, but I know I have domes pistons to put me at 10.5:1. They perform very nicely. The motor has been in for only a few weeks, but they pull very nicely off idle and make good power. About 1.5 times what my old 8.0:1 Peanut Port 454 made. I know the gain is not just the heads, but they are a big part and I do reccomend them.

jakeshoe said:
Merlins are also HEAVY, add about 10 lbs per head.
What makes them so much heavier? I would think if anything they would be lighter, but never compared the two.

Chris
 
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BB_Mike said:
Jake,

You gained nothing? wow. How mild is the 427? What are you doing here and not camping out on my Transmission thread? ;)

Phil,
Like the others are saying, your current combo suggest the 781 heads are the way to go. There are just more "pros" versus cons for your situation. When I busted my heads, I couldn't afford the downtime fo finding a set of stockers and having them built up. It was my daily driver car for college... but I certainly didn't want to go any slower!! :D So I went aftermarket, and the Merlin oval ports had some good things said from folks here. I also got to re-use my larger valves.

Can you take the car to the track before the swap?
People would love to have some HP/ET numbers to go with the upgrade.
MY 427,
~9.5-1, Had a Comp 270H on a 112 LSA, WORN out, 049's. old Edel Performer intake, 800 Q-jet, 1 3/4" headers, open exh, ran a 8.25 1/8th. and 12.94 1/4.

Same except freshened, RPM Q-jet intake, same carb, headers, stall, gears, but Merlins, and a Crane 284 ([email protected] on a 112), 4 degrees bigger, and it still won't break a 8.15 with 2 different converters....
BTE gave me 1 that was 1000 rpm too much, the 2200 Summit it had turned 8.20-8.30.


The heads were worth nothing on that mild of a combo, might have been if I twisted it over 6500?

I'm a little busy now,
convoying from north to central Iraq, had some "problems" today.

So I may not be avail for a day or two.
 

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The World heads have thicker gasket surfaces - I suppose for a number of reasons, but most likely to allow the flexibility to take a healthy cut off them if needed. My suggestion - seeing as how you have intentions of changing anyway - get the current heads off (at least one anyway) and see what piston is in there.
 
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Phil,

What do you want to know b/c of your bump??

I am sure everybody will be glad to help if you come back and be more specific.

The reason the Merlin ovals are quite THE cheap cast-iron head is b/c W/P's opened up both the good and the bad ports so that they are the same cc if not mistaken.

AND I REALLY wish they would sell a 290 cc true large oval intake ported cast-iron Merlin head with a 90 cc combustion chamber that used stock valve train stuff!!

YOU talk about a stock flat-top pistoned 454 P/U motor winner, imho!!

I'd buy a set in a heartbeat!! To heck with my old -206's!!

pdq67

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10 Posts
Discussion Starter · #20 ·
454 .030 over
KB .133 dome hyperteuctics
Stock crank
9:1 compression (estimated)
reconditioned stock rods
1 3/4 heddman headers
peanut port heads
Comp Cams 270H
Edelbrock 750 carb
Ford 9" with 3.50 gears
Street/Strip car
Best 1/4 was 12.85 this year

I bought a nice reconditioned set of 781 heads off EBAY.They have a 3 angle valve job with new stock sized valves and bronze guides and have been milled to clean them up. They are now at 118cc chambers. I have about $500.00 in them after shipping. I know that the larger valves and port work will improve them, but then I will have as much invested in them as a new set of Merlin heads????My winter plans are new heads, cam and carburetor.I have learned a lot on this site and really value the opinions and advise given here.I am looking for 12.0 or better ET. Please advise heads, cam and carb. Thanks


Everyone has a different idea. PDQ67 talks like the Merlins are not that great.What about putting the stock refurbished 781s on with a new cam ,springs, and roller rockers ???What cam?? Voodoo 60203 ?? Perhaps a SOLID ??? I need vacuum for the power brakes.How about some cam advice for these heads ? I am still looking for help. I have not made any decisions.
 
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