[megatrek]

I got a set of BB heads casting # : 2899943
I was told they came off of a 413 out of a motor home. The valves measure 1.50 and 1.88. I'm just looking for some addtitional info on them.

 

[Evildriver-3]

It's either a 361 or 413 truck head, that's it

 

[Chump]

2899943 71-77 361, 413 (Truck)"

 

[megatrek]

Thanks guys.

 

[Evildriver-3]

ON behalf of myself and Chump Your Welcome

 

[Bummo]

1.50 ex? Pretty small. Intakes not great either. What is the CC on those heads? If its any bigger than about 73 its gonna be tough to fill at the higher revs. Very low speed, torque head, but you might be happier with something else. I put a small valved head on a 400 cheby once for torque and it was pretty disappointing.

 

[megatrek]

I was thinking about putting them on a hot 383 short block I had, but with those small valves I may keep em' till I build me a truck motor. Got em' real cheap so not big deal if I got to sit on em for a while.

 

[Evildriver-3]

1.50 ex? Pretty small. Intakes not great either. What is the CC on those heads? If its any bigger than about 73 its gonna be tough to fill at the higher revs. Very low speed, torque head, but you might be happier with something else. I put a small valved head on a 400 cheby once for torque and it was pretty disappointing.

You need to read the stroke and combo's post and you will see why that sucked, small motors and torque don't always work with the so called small port high velocity BS theory.

How a motor breaths and what it needs to breath is dependant on the lower end and it's RR.

 

[chrysler300le]

Smaller valves don't make more torque. I don't know who thought up that theory. Bigger valves make more power all around not just up high in the rpm range. Since they allow for more cylinder filling at low rpm's too and more fuel to be compressed, bigger valves will also make more torque.

 

[Bummo]

Small valves / small ports on intake will generally mean that the mixture will be able to maintain or recover a good velocity into the cylinders. Yes, big valves/ports will flow more (by area) but if the mixture is moving so slow into the cylinder it works against you. Of course the ports etc cant be too small or it wont fill the cylinder either. There is a compromise. The post I started about some cid sizes ie some piston to stroke combinations being just plain better than others was really about the 3 togeather...port and valve plus cylinder plus stroke...whats a good combination...not just bigger on everything. But it kinda was worded so it ended up being RR only. Oh well.

 

[Evildriver-3]

No it seems everyone is missing what dictates port and intake choices, you really need to understand Rod Ratios and it's effects and then you will understand where to use a small port head, you wouldn't use a big port head on a 318 for a torque motor, you wouldn't use a open plenum on a 318, you wouldn't use a big carb on a 318, you don't use a "big cam", Same as you wouldn't on a 440 for a truck built for torque, why because it can't get them to work together at a low rpm, why you ask? because the RR sucks for low end, so there is only so much you can do to increase low end with a motor and a big RR.
If you look back there is a post that i made that is going to prove this theory, im going to take a big huge port big huge cam motor and we'll see how it pulls like a freight train at low end.