Pulling truck engine "again" BBC

[Walter R. Malik]

Looking forward to the 2020 season, it looks like this guy is gonna have me do a new short block for this pullin truck. It will be a new aftermarket block in a bigger bore shorter stroke. I'm thinking 3.625 stroke and a custom piston with enough bore to get it to the 473 cube limit.

It will have custom dome to get compression up more, gas ports, thinner rings maybe 1 mm 1mm 2mm, etc.
It's currently 462 cube with 4.280 bore 4" stroke.

What kinda power improvement could one expect with a nice new big bore short stroke short block, with the same cam, heads, intake etc on it ?
More comp, 11 more cubes, etc.

Randy

If you can run it a bit higher in RPM, the shorter stroke, lower piston speed will help ... at the same RPM, the results will not be much different if the RPM level is pretty much limited by air intake. I have used a 4.470" bore x 3.760"; (a Mercruiser 502 block), for a customer who wouldn't know how to tune a chassis if you drew him a picture; like most of those type people, all he can say to another team who is always ahead of him with a lesser engine I built, is he needs more power.

[swampbuggy]

Randy, what are the cylinder head rules ? Mark H.

[randy331]

Randy, what are the cylinder head rules ? Mark H.

Any iron head made by GM.
Porting/welding allowed.

Randy

[swampbuggy]

10-4, well that certainly limits your possibilities on the big bore short stroke engine as far as power production. Mark H.

[randy331]

10-4, well that certainly limits your possibilities on the big bore short stroke engine as far as power production. Mark H.

Everyone is limited by the same rules.

But, what can be done to the heads is very open.

Says no port plates, but it doesn't say you can't weld up the intake surface on the head so the ports can be raised without using a port plates.
We could move the valves in the heads, weld the chamber etc. One could get creative if the budget is there. But that stuff gets expensive fast. Moving the valves wouldn't be free, then send the head off to Jesel for a custom shaft rocker. Weld and raise intake and ex ports. Lots of machine work. $$$

But, it does sound like he's gonna do the aftermarket block, bigger bore short stroke for next season.
I was down at his shop over the weekend and heard it from his WIFE too that the money for it should be in the budget for next season. lol
She just needs to get beat once by the right truck and the budget will go up !! LOL


Randy

[swampbuggy]

Yeah Randy the thought came to mind about welding and relocating ( like the Super Stock guys do ) . I would think that would be a PITA with cast iron . Certainly would be very time consuming and expensive for sure. Mark H.

[Walter R. Malik]

Yeah Randy the thought came to mind about welding and relocating ( like the Super Stock guys do ) . I would think that would be a PITA with cast iron . Certainly would be very time consuming and expensive for sure. Mark H.

Brazing the floor of the exhaust port for a much better port shape is very common for those cast iron heads.

[PFC1]

I have brazed the floors of the BBC heads up. Makes for big improvement. You can make a lot of power with the rectangle port heads w/o moving valves around. Personally, I think there are better places to spend money unless one has an unlimited budget.


Oh, and no I don't want the job doing it just in case someone asks.