SBF Dirt Track build questions

[frnkeore]

I ran some numbers and your giving up lb per ci, running a 347 ci engine

The 361 = 6.44 lb/ci, the 347 = 6.798 lb/ci. If you can afford a after market block, then you should run a 4.11 bore x 3.40 stroke, that equals 361 ci. Then add the best flowing heads you can afford.

The intake will take some experimentation, using the 1850 carb. A Parker Funnel web might be best for max hp but, but, I would try as many manifolds as I could get my hands on, to get the torque where it's best "for you" at corner exit. Victor Jr, Super Victor, will be the upper rpm, along with the PFW, next step down will be the Edel Torker and Weiand 7515. The dual planes Edel Air Gap or Weiand Stealth would give you the most corner exit control, to start with.

[englertracing]

Heads heads heads, its all about the heads, if you don't get them right the rest is irrelevant, bore and stroke combo won't matter a lot with the 1850.

Larger bore generally helps the heads....

[fordified]

Heads heads heads, its all about the heads, if you don't get them right the rest is irrelevant, bore and stroke combo won't matter a lot with the 1850.

Larger bore generally helps the heads....

In what way? I assume he's going to run a 1.84 intake valve. Even a 2.02 requires no more than a 4.04 bore. At .250 clearance from the bore wall a valve typically doesn't see that wall. The majority of the flow wants to go to bore center, not the wall side.

[BCjohnny]

Heads heads heads, its all about the heads, if you don't get them right the rest is irrelevant, bore and stroke combo won't matter a lot with the 1850.

Larger bore generally helps the heads....

Yes, and for any given capacity means a shorter stroke crank which, all things being equal, can be lighter with a lower MOI

Piston speed is also more conservative for any given rpm, so less frictional loses, which tend to go up as a square of rpm

I also wouldn't run it at the capacity limit either, at some stage you'll want to refresh the bores ....... assuming you don't grenade it in the meantime

[fordified]

For a 348” engine at 5500 rpm?

Calculate the piston speed with a 3.4” stroke.

[Krooser]

I recently got the green light from the wife to step up from production based dirt racing to a class similar to a DLM chassis with a 361 cube limit for two valve iron production based motors.

361 cu.in 1088kg's 2398.62lbs min weight
347 cu.in 1070kg's 2358.94lbs min weight

Is it worth the effort to go for every last cube over obtaining off the shelf rotating assembies?

When asked this question, I always ask back, "What are the fast guys running?"

Budget is a consideration.

Second question I ask, "How much are the fast guys spending? Can you afford to be in contention for the win or just have fun racing in the back?"

Fast Fords are Far and Few Between, those kind of details are generally closely kept.

I know with the Chev crowd I have heard of some big dollar motors people are pulling out the chequered book for. I spec and assemble my own motors and have been doing my own cylinder heads since the last century.
I don't have a big chequered book but I have a PHD (Poor Hungry & Determined). Struggling at the back is no fun (why I am asking here) running with and occasionally beating chequered books is my buzz.

Call Clements or Cornett Engines....their Fords win most of the Lucas/WoO championships.

I know those are unlimited 900 hp motors but their advice would be helpful...

[hoffman900]

Bill Carlquist (Bill-C) on here builds nasty small Fords for road racing and circle track. This is very much in his wheelhouse and I would reach out to him.

[stealth]

Just my 2c.. which means nothing. but...

Why not start out with a combination that's a proven winner. No matter the brand. If SBC are winning, start there and when you have a winning ride, then start working your way to the weeds with a non-conventional combination.

You'll get much more satisfaction if you have a chance to win. You'll know it's your driving skills that need work if losing instead of chasing a car issue.

Best of Luck..

[RCJ]

For cubic inches build what is cheapest, get the best pro built carb and the best head. The carb is your restriction so litewieght parts and low friction will help.