Gen VI HP approximation????

Bought a Model A with a GenVI 454 crate motor and mechanical fuel pump, 600 edelbrock, stock heads and pistons (I ran the #'s off the heads and block). It Idled smoothly and I wanted the "thump". So, I put in a CompCams TH 283 Thumper cam, roller lifters (it had a flat tappet cam for some reason) and roller rockers.
I got the thump.
The engine really came to life. Assuming the orig. set-up was around 300hp? What HP and torque would you expect this has?
I realize a Dyno is the only true method, but I live in a rural area and haven't found a dyno yet. I'm just looking for you experienced BBC guys to give me a guess. My guess was around 350hp 420 torque just by the way it runs out.

Any help??????

i would not know why anyone would use a flat lifter cam in the mark 6 engine when towers are casted in the block for the stock roller lifter hardware ? if i was you i would of looked in to this abit more as in the long run could be better set up in the with roller cam .are you sure what you have is not a mark5 block? as all them were flat lifter cam engines ? what heads do you have ? most older bbc till mark 5 used a small oport head small valve dual valve spring rotators intake and EX so if it has the mark 6 heads on it the big O port with no heat EX cross over. but has 16 valve spring rotators that need to be dealed with any spring more then a stock GM valve spring is used . so two sets of rotators eliminators are needed . with no head work then it about what you said maybe abit more on tq carb is to small to see any max power numbers but will work ok at low RPM for the street . so if head work was done maybe more hp .with headders i would say mid 350 hp to 400. with some head work and bigger carb . the 330 hp marine engine was a bone stock 454 with a marine cam flat Hyd cam was about 500/500 223/223 @ 050 and 114 lsa roller cam a abit less lift 483/483 224/224 lsa115

Don't have any idea why they had a flat tappet cam in there other than maybe to steal the roller cam and lifters for another engine before he sold it to me?
It is a MarkVI with MarkVI oval port heads. I had to put the 7/16 ARP retro stud kit for my roller rockers and have CompCams beehive springs to match the cam 547/530 227/241 @50
In hindsight, I should have just upgraded the heads to begin with.


Thanks for your reply.

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Originally Posted by upolka2

Don't have any idea why they had a flat tappet cam in there other than maybe to steal the roller cam and lifters for another engine before he sold it to me?
It is a MarkVI with MarkVI oval port heads. I had to put the 7/16 ARP retro stud kit for my roller rockers and have CompCams beehive springs to match the cam 547/530 227/241 @50
In hindsight, I should have just upgraded the heads to begin with.........

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i just built a mark 6 engine much like yours but a roller cam with roller rockers . i did a geat deal of work to the mark 6 heads . i am not sold to write off the stock heads but on even the stock mark 5/6 heads i use the ARP 7/16 top stud 3/8 bottom or if a hi spring rate i drill and tap heads to the old mark 4 rocker stud 7/16 to 7/16 tops. done many of the 5/6 engines over the years . but done more of the mark 4 blocks. i still find them of value .the mark 4 blocks. i still like them in my build ups getting harder to find with stock bores or not pass there life .but pass over the mark 5 blocks it has no value to me.i like the 6 just for the fact that the block is a roller block. most all my builds i find that the roller cam is a better out come

I put in the compcams roller lifters and roller cam. I bought the factory GM retainer set to hold the lifters in place---so it now is a full roller motor. I completely agree with you about the roller cam. Thanks for your input. I was just curious what kind of approx HP that I had.

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Originally Posted by upolka2

I put in the compcams roller lifters and roller cam. I bought the factory GM retainer set to hold the lifters in place---so it now is a full roller motor. I completely agree with you about the roller cam. Thanks for your input. I was just curious what kind of approx HP that I had.

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shows i am slipping i am a dealer for comp cams but i do not use there thumpers cams i would of knew by the comp number of cca11-600-8 if i used them:). smart move on your part to go roller .make sure you have the right length push rods in the engine