blown big block street motor....need help

[HOTROD BUILDER]

Hello everyone , I just joined ,my name is Gene and I need some help with a good combination on this bbc motor.

Its a...

454 2 bolt block converted to 4 bolt
bored .040 0ver so its now 4.290
stock steel crank 4.0 stroke
stock reconditioned rods with arp 3/8's bolts 6.135 length
kieth black silvolite flat top pistons 3.0cc valve releif (1.645 comp ht)

Heads are gm rectangular port #3919840 comb cc's 106.8 factory specs, I havn't cc'd them yet

I have a B&m powercharger 250 blower setup(fits under the hood of a 33 ford)

The pullys I have now are 8mm 1.41:1 ratio


I am wanting to run on pump gas most of the time but make as much streetable power as I can without risking destroying the motor.

I am looking to change to forged pistons but I am limited on choices because of the .040 over (this leaves only flat tops with a 3.0cc valve relief) un less i go .060 over then there are few choices.

I was thinking about changing rods to h beams (been looking at eagle stuff)

I am also toying with a stroker crank(4.250) making a 491ci .040 , or 496ci .060

but I was told my blower might be to small for that .

I am also looking at a used set of 325cc pro1 aluminum heads fairly new to help with the static comp ratio problem.

Keith blacks calculator gives me a ratio of (8.6 to 1) .041 gasket with my combination or (8.426:1) with a .053 gasket

cylinder head volume (106.8)
piston head volume (3.0cc)
gasket thickness (.041)
gasket bore (4.380)
cylinder bore (4.290)
deck clearence (.020) calculates to this but I measure .035 maybe becaues of piston rock
stroke (4.0)
rod length (6.135)

As far as the cam I have the B&m cam that came with it no cam card and cant find info from anyone. I guess I will have to degree it to find out what it is exactly

Any thought or ideas woud be greatly appreciated.... Thanks Gene:)

[Awesome Bill]

Hey Gene, welcome to the forum.

Even if your blower was a little small for the 491ci, any boost over zero is a lot of boost. Even 2 lbs of boost will make a huge difference. Keep the compression under 9-1 and 8-1 is better for sure. The 325 used heads are a go any time with even a little more boost. If you run it on the 466, they will still be o.k. with some boost. Over 5lbs will be plenty of power with either of these engines. 500-600hp is a ton of power. I would not worry to much about your rotator now, it is well capable of handling the power limits up to 600. Keith Blacks pistons are very tough and you would have no problems. Watch the heat factor, most gas blower street engines love to run warn because of fuel issues and high egt's.

[HOTROD BUILDER]

Hello bill, thanks for replying. Ii am planning on running at the track sometimes for fun and maybe the hot rod shoot out at indy.So I was looking to pump out maybe 700 hp out of the motor or more if i wanted ,thats why I was looking at changing the rotating Assembly to at least forged pistons and h beam rods. My 34 Plymouth is what i would have it in and I built a tube chassis with a strange strut front end( I used to build nhra pro stock cars) so it had to have a chassis. Its all an all steel car ,and the chassis can handle the power so I thought I would get as much out of this motor as I can and still be street able and I know there is a fine line there,but this car will not be driven on cross country trips anyway. As far as exhaust gas temps isn't this controlled by cam timing somewhat as well as how well it burns in the chamber. I know street motors are not very efficient burning. Thats why I was worried about turning the blower so hard to make boost on the 491 or 496 combination. I am assuming that the hypereutectic Keith blacks silvolites might burn or break the top ring groove with this much heat . Sorry for being so wordy. Again thanks for the help......Gene

[Awesome Bill]

The Keith Black pistons will not let you down. And if you maintain 1200-1400 degree temps @ cruising, this is what kills rings. Any Moly or Hell Fire @ best is only rated to 700 degrees before the coating comes flying off or exceeds 1000 to 1200 hp. Amazingly when run wide open for just a quarter mile, the exhasut gases are usually under 1200 degrees for short times but with tons of pressure and the pressure is what lifts the coating from the rings and into your engines oil. With your application, this could happen from the egts @ cruising. Seen blow by in 1000 miles and people blame it on fuel washing the rings out? lol

Your combination now will handle easily the 700 hp range, even those whimpy rods. Stay off the chip @ all times and it will be o.k. Street engines with a blower are much more efficient with fuel mixtures than any naturally aspirated engines. The blower does mix it up well. But, I have cooked eggs on gas street blowers and this comes from the part throttle condition while crusing and this is why most blower cars run hot even while idling in traffic let alone crusing. Some people have figured it out or put radiators out of trucks to keep them cool but usually nothing works but a trip to the chassis or engine dyno with real loads to tune the carbs correctly.

Either way, if you want a larger engine, the 491-500ci engine would be fine with your block and you will have well over 700 hp with the Dart heads and 4-6 lbs of boost. LOW COMPRESSION around 8-1 is best. You can always change the pulleys, put some race fuel in and go make over 1000hp with just 15lbs of boost with that combination. You will need to correct for the added hp with gear and converter if set up for the 700hp. Usually this is where people don't think about the PACKAGE FOR HP!

[HOTROD BUILDER]

Hello Bill and everyone. What is the Best type of piston ring to run in this blown application above. Since bill you said the Molly rings can lose their coating. Blower drive service suggests stainless steel rings. Give me brand names and all thoughts . Thanks Gene

[Awesome Bill]

Tool steel rings are very hard on the cylinder walls in extreme hp applications but are tuff to beat. The Total seal Stainless Steel Rings are what we use in all turbo, nos, blower applications. I have them on the shelf and we are the eastern area dealer, I can sell just as good if not better than most.

[want-a-be]

Tool steel rings are very hard on the cylinder walls in extreme hp applications but are tuff to beat. The Total seal Stainless Steel Rings are what we use in all turbo, nos, blower applications. I have them on the shelf and we are the eastern area dealer, I can sell just as good if not better than most.


I like the SS rings from Total Seal for the same applications Bill does for the same reasons. I'd give Bill a call and check his priceing out.

Don