bbc help

bbc advice

Can any one suggest a good rotating package to run in a 4.5 bore 10.2 deck bbc to make a safe 1500hp or so i have a bowtie block, aluminum heads, a hi helix 1471 and want to run my 2400lbs door car in the mid to hi 7's also open to some cam spec suggestions and spring pressure specs. am i better to run a shorter stroke like a 540 combo or a 572 combo? thanks for any advice. i am really hoping to make some safe power with what i have

 

bbc

540-557-572 a few choices. 4.25 4.375 or 4.5 stroke all good combos 12.1 compression.

 

Bbc ci

A 4.5 Bore and 4.125 Stroke will get you a 526ci. This is the Miner Brothers combination. Remember you have a blower, you don't need 948 cubic inches. The shorter stroke will be easier on the rotating assembly. Use .400 longer than stock rods.
Good Luck

 

You need to watch the stroke if your running aluminum rods. I had to make more room on the pan rails even with a Merlin III block on a 4.25 stroke. I run a 4.530 with 4.25 stoke (548 ci) with a 14-71 standard helix mooney. I started with 9.5 compression. With a 14-71 you can make all the compression you want. Plus it easy on parts. We run low 7's at 5000 ft air, all day long on a very safe tune. But I'm also in a 2000 lb altered.

 

I also vote for the 4.125 stroke and the longest rod you can put in it.
The less CID the less you have to spin the blower to make use-full boost that will not heat the charge.
It takes power to spin up the blower. More blower RPM the hotter the outlet air temperature. These both cause large para-static losses.

Using that big of a bore allows unshrouding the valves in the chamber to increase actual air flow in and out of the engine.

Large bore increases surface area for PSI on the piston to push it down.

Short stroke with long rod allows less ignition advance although the big bore will need more so that will about balance out.
Get the valves off the seat fast with high ratio rockers and you can reach your goal without using huge lift numbers that kill valve springs. It is actual air through the valve while off the seat for the duration that fills and expels the cylinder not a max flow at max lift.

Yes you can get more actual power with less boost and have a longer lasting engine.

This is the short very story version of this combination.

 

What heads are they? at what lift is the peak airflow?

You can destroy any rotating assembly no matter how expensive it is, just give it enough fuel and not too much timing.

I don't get too caught up in strokes or rod lengths...

Explain your blower, pie opening?, LF?, billet rotors? etc...

 

Blower is an oddy's worked bds pie opening hi helix, heads are rhs 360cc runner nothing done to them cam is .652 lift with 1.7 was going to go 1.8 rockers. 300 in 308 ex duration 114 lobe separation, I know this not an ideal set up but i am trying to make work what i have, i want to make my 2400 lb door car do mid to hi 7's until i upgrade my whole motor package.i have the makings right now for a 572 combo but am worried about the stroke. i do plan on running conservative timing and lower boost until i upgrade.should i not worry and run the 572? will it make me enough power to run mid 7's?

 

BBC Helped

I opted for the smaller bore on my deal (4.500 540) for the fact that if you loose a piston or something there is lots of meat left for overboring. Plus when you get up to a 4.600 bore it gets difficult to put o-rings in. Bores are getting pretty close together. IMO

The rest sounds pretty good.

Corey

 

my motor is the 4.5 bore 4.5 stroke, callies crank i just need to upgrade my rods and pistons as they were steel carrillo's and brc dished pistons for a blown gas application which brings me to my first question is 572 a safe combo or should i de stroke it to a 540 or less? i don't want to run a ton of rpm as my valvetrain and cam are limiting factors i believe.

 

bbc

We had less stuff than you and went 7.60@3100lbs with 526 inches and a glide. 7.80 with a 468. I like the 540 myself. Super strong crank with huge torque and decent piston speed to 9000. Call Bullet and get a known good cam.Get a decent fuel system and make 30lbs of boost and it will fly. Like somebody else said the stroke bore etc doesn't really mean that much.Run at least 350 psi on the seat springs depending on how much rpm and get expensive lifters and rockers. We run Isky lifters and used to run Comp steel rockers with conventional heads.
If you buy a cam or parts from Oddys they will hold your hand until it runs. We learned a LOT from Jim when he ran Chevy's but had to regrind the cams because the valve action got too fast.
Be prepared to pull timing on the hit...a bbc will hit hard.
Mike

 

Call Billy at Oddy's and do what he tells you. I have a 526 bowtie block dart 360's short deck isky rockers and not even a stud girdle he built in 1997 it sit in the corner till 05 put it in a 2750lb car big street tires with a ssi d HH 35 , went 4.25 at 169 at 4000 ft air ,, he said it made about 1780 when he did the work with a BDS 14 HH at 30 over I think Oddy's is the best on the Chevy combo they have a lot of exp with them 716-674-2500 I will say your block is your weak link, that combo can make enough power to push the crank out of the block