[454C10]

You need more gear and compression for a 500hp 454 in a heavy truck.

The cam you have is already too much for a 2.73 gear and compression in the mid 7's. And tall tires will make that worst. Plus a higher stall converter will be needed.

If you don't plan to increase compression, add more gear and higher stall, then add boost to make your HP goals. And use a smaller cam that matches the gear and stall.

[Horsepoweraddiction]

Originally Posted by cdminter59

Horsepoweraddiction, Can you give me the casting # off the rectangular port heads. I want to find out the chamber volume and port size. I have been looking online but there are too many heads with different size chambers. I was reading a couple articles comparing rectangle ports and oval ports. The oval ports performed better on the low end rpm but the rectangle ports caught up on the high rpm end. If you had them and money is a problem why not use them until you can afford something better?

The head casting number is 3919840 and I like that idea just go with that til I get a set of aluminum heads which I really want. But I know these heads are great. And to 454c10 I'm planning on running a 3.73 and I can probably put a stall in it if I have to.

[cdminter59]

The 3919840 heads are 1967-69 396/375hp, 2.19/1.72 valves, 106.8 chambers. If the exhaust valve is 1.88 they are 1967-1970 427ci heads. Check them out on ebay. Complete they are selling for $1000-$1500. They are a closed chamber head but would work on a 454 with flat top pistons. You would have to check piston to valve clearance. Compression ratio 8.912.

[Horsepoweraddiction]

Yeah I have flat top pistons and I'm sure they will work because the guy I bought it from was planning on putting them on a 454 , And would that campare with a set of the 071 heads? What could I do to get the compression higher?

[cdminter59]

Originally Posted by Horsepoweraddiction

Yeah I have flat top pistons and I'm sure they will work because the guy I bought it from was planning on putting them on a 454 , And would that compare with a set of the 781's heads? What could I do to get the compression higher?

If you could find a set of 781 oval port heads they are open chamber and 113cc. They could be milled but how much??? The compression would still be low at 8.5. I wonder if a set of [10141279 1996-up, Open 100cc Vortec7400] would work like Vortec's do on small blocks. Compression would be 9.4. Another Vortec Casting # 12560241 1998 -up, Closed 100cc Vortec 7400. Close chamber heads that would work are 3872702, 3904390 98.4 cc, compression 9.5. Checkout ebay http://www.ebay.com/itm/1973-1985-Bi...f#ht_500wt_969

[454C10]

781's are 120 to 122cc and make 7.7:1 cr with a set of flat tops.

781's are decent heads but require the use of a domed piston to get the compression up.

[cdminter59]

Originally Posted by 454C10

781's are 120 to 122cc and make 7.7:1 cr with a set of flat tops.

781's are decent heads but require the use of a domed piston to get the compression up.

You know they have to many websites that have the wrong information. I just looked that info up last night on nastyz28.com. 454C10 would you be able give an answer. Will the 454 Vortecs heads work on the early bigblocks with flat top pistons like they do on early small blocks? Anybody else?

[454C10]

I run a set of 781's on my 454 and they are 120cc. So, I didn't need to look it up in this case. I also use a small dome to get it up to 8.75:1. Flat tops are the stock smogger piston in a 454.

I also have a set of 820's from a 73 402, and they measure 112cc. These are also good heads that would increase the compression in a flat top 454.

I heard the votec head will work on old BBC blocks, but I have no experience with those. I also read they are good heads and the low engine output from vortec 454 is due to the poor cam and intake.

[Horsepoweraddiction]

I've found a set of the 781 and i am purchasing them today. for 225$. Good or bad?

[454C10]

the price sounds about right. Maybe a little high. But if they are in really good shape then ok.

I hope you are buying them locally, as they would be very expensive to ship.

[E.Furgal]

I'd have it writen up that they going straight to be magged, and if fail the test you get your green back..

[Horsepoweraddiction]

Yes sir i bought them locally but i found them on ebay, and now i'm looking into pistons, which would be the best budget piston and ring kit? mahle or wiseco? for forged dome pistons. block bored 60 over

[454C10]

You don't need anything special. Just a plain hyper pistons would do the trick.

If you are still planning on using a xe274 cam then look for a piston that will make 9 to 9.5:1 cr i a 454 with 120cc chambers (781 heads).

I recommend the old school 280H cam if you go with a flat tappet cam, as it is less likely to go flat than the XE cam.

[Horsepoweraddiction]

i'm going mechanical roller and would i get more performance with a set of forged pistons ? i 'might' run a small nitrous set up.

[vinniekq2]

I use wiseco forged pistons.
check your heads for flow before buying cam before buying pistons