low buck 454

[prairiehotrodder]

I picked up a TBI 454 that has been recently rebuilt with .030 over speed pro Hyper pistons (stock style dish) and its got low miles and looks mint inside. It has the Gen ? whatever block with 4 bolt mains. Sorry i never understood roman numerals.

Anyways i had a plan to build it into something fun. Here is what i'm thinking :

Edelbrock #60439 performer RPM heads with the 100cc chamber. These should give me 9.4 CR
Comp 11-602-4 thumper cam (hyd flat tappet) 243 / 257 .522 / .507 107 LSA
single plane intake
850 holley
2" hooker headers
78 malibu with 4.10 gears, 3200 pounds, 4000 stall

Will this make 500 hp ? Maybe mid 11 's ?

[GRTfast]

My big block original build was 9.5:1 with a comp cams thumpr hydraulic roller with a little bit more lift and duration. Brodix race rite bb2R heads. Rpm Airgap, 850 Holley. Made 494hp 532tq

I’d guess you’ll be close.

[Ericnova]

I think you need to run your compression ratio calculation again.
I don't know what dish you have, but putting these number in for a flat top piston - 4.280"bore x 4.0" stroke, 100cc head, 2cc dual valve relief flat top, piston to deck .040"(undecked stock block w/rebuilder piston), .041" x 4.370" head gasket(common Fel-Pro composition gasket) and it comes out to 8.75:1 compression ratio for the H661CP "rebuilder" height piston, and 8.9:1 for the H625CP piston that is closer to stock height(piston .025" down at TDC).

If it really is a dished piston(Speed-Pro/Sealed Power do not show a dish hyper, only a dish forged) compression ratio is going to be even worse.

[wyrmrider]

the intake/ exhaust ratio is really bad with that cam spec
way too much exhaust
you will loose expansion ratio
hot exhaust
and gas efficiency will suck
any quench?
post up revised compression

[F-BIRD'88]

Roman numerals 3 III 4 IV 5 V 6 VI 7 VII 8 VIII 9 IX
10 X 11 XI

you will want to know the gen# of the block to get the right head gasket..

[F-BIRD'88]

The cr with a dish piston and 100cc heads will be way lower than 9:1. A flat top gives 8.8:1

[prairiehotrodder]

4.280 bore
4.00 stroke
.039 thick head gasket
4.370 bore head gasket
i measured the piston was .010 in the hole
and i guesstimated a 5 cc dish

The piston is a H518 CP which i believe is a hyperutectic. This piston info claims a 1.625 compression distance.

The block deck has not been resurfaced,


I guess i screwed up somewhere, because even the above specs give me 9.06 -1

[prairiehotrodder]

So i went and re-measured my deck clearance. Here is my method and results. I must have done something wrong the first time.

I put the dial indicator on the deck of the block beside the outer edge of the piston and zero it. Then slide it into the bore and bring the piston up. It stops going up at .034 . then i rock the piston top to bottom with my fingers and it goes to .017. The math is .034 - .017 = .017 Then .017 /2 = .0085
Then .017 + .0085 = .0255

That .0255 should be my deck clearance.

Feel free to correct me if i am wrong.

[prairiehotrodder]

Well from your help and a little more thought i decided those pistons don't have much potential for performance. I think i might just change pistons. The speedpro H693CP should just slide right in. It has a 1.64 compression height and a 22 cc dome. If i used them i could run the cheaper Edelbrock E-street head with a 110 cc chamber and get around 10.3 CR.

Brian

[Ericnova]

if we use your number, .0255" for the piston to deck, and your 5cc valve relief, then the calculator I'm using(Wallace Racing) says 8.82:1.

If we figure it with 5cc relief and use the given 1.625" piston compression height and an undecked block, then it drops to 8.60:1.
1.625" height and undecked block gives a piston down the bore .040" @ TDC.


When you checked the piston in the bore, did you make sure the side you measured .034" on was also rocked clear over on that side??

What calculator are you using, maybe we can spot why it is coming out different than most of us are figuring??

Generally though, as a rule...if you aren't supercharging or turbocharging it, flat tops in a BBC under 565 cubic inch are just bad news....you can't get a head chamber small enough to make decent compression.

If it is as fresh as you say it is, buy a set of domed Hypers and stick them in, you can even transfer the rings if you are desperate and careful you don't break one or spring one out of shape...put them on the new pistons right back in the same bore they were in before.
Or you can brush hone and re-ring.
Pick something with a 10-12cc dome and use the 100cc head, or go to a 18-24cc dome and a head in the 112cc+ area.

Well, I see you arrived at the same conclusion I was typing out...

[prairiehotrodder]

thanks Eric

this is the calculator i use :

http://www.csgnetwork.com/compcalc.html


I'm sure its correct and any errors would be due to me. I did not rock the piston down at the beginning. That will be the why i get higher CR than everyone else. I should have done that.

[af2]

This should put you close.

https://www.summitracing.com/nv/parts/s ... /chevrolet

[1980RS]

I picked up a TBI 454 that has been recently rebuilt with .030 over speed pro Hyper pistons (stock style dish) and its got low miles and looks mint inside. It has the Gen ? whatever block with 4 bolt mains. Sorry i never understood roman numerals.

Anyways i had a plan to build it into something fun. Here is what i'm thinking :

Edelbrock #60439 performer RPM heads with the 100cc chamber. These should give me 9.4 CR
Comp 11-602-4 thumper cam (hyd flat tappet) 243 / 257 .522 / .507 107 LSA
single plane intake
850 holley
2" hooker headers
78 malibu with 4.10 gears, 3200 pounds, 4000 stall

Will this make 500 hp ? Maybe mid 11 's ?

My flat top piston 461 wit mild ported peanut port head went 11.70's@111mph. Air Gap, 850 Mighty Demon and 1 3/4" headers and a CC 282S cam. The 2" Hookers slowed the car down by 2 tenths. You should be able to run easy 11's with that combo if you can get it to hook.

[prairiehotrodder]

Thanks guys, i'm glad you helped me get this figured out. I bought the H693CP .030 pistons with a 22cc dome. For a relatively low buck motor with the Edelbrock E-street heads now i feel like 500 hp is attainable. I've built plenty of 8.0 - 1 CR BBC 454's and i know they can be fun but i decided to step up my game a little with this motor.
Now to choose a cam. I want to run stock rocker arms if i can. Anyone know what lift they will handle without problems ?

[F-BIRD'88]

The old stock mark IV bbc rockers were good for 550" gross lift.

Long slot type are not expensive

Any dome piston ,when used with a edelbrock head you must verify piston dome to chamber clearance
especially the 100cc eddy head.