Gathering parts.. mild SBF 347

[Old as Dirt]

Anyone guess what RPM range these headers might be good for? Primarys look short.. guessing 1800-7800rpm

[groberts101]

Anyone guess what RPM range these headers might be good for? Primarys look short..

They look just like my brother in law. Too short.. too fat.. and too high strung!

Without actual dimensions, I'd guess anywhere between 3,000 and 8,000 for this "milder build".

[Old as Dirt]

Primary sizes are 1 5/8" stepped to 1 7/8".. The AFR heads flow pretty good numbers.
Think they would be a waste on my engine turning less than 7K?
For the 200.00 CL price, might have to give them a shot.. sure would think they cost way more than that to build.

[groberts101]

Primary sizes are 1 5/8" stepped to 1 7/8".. The AFR heads flow pretty good numbers.
Think they would be a waste on my engine turning less than 7K?
For the 200.00 CL price, might have to give them a shot.. sure would think they cost way more than that to build.

Sure the heads are good.. but I think they will make the engine peakier with the smaller cam you have being worked up for you. I think you may need to shrink that choke ID down a bit to make it more relevant to this combo of parts. Installing headers designed for upper rpm ranges on a 6,000 rpm motor will kill off some of the lower rev ranges torque output. Remember it all has to work together and within the range you want to make most power. What's the minimum rpm range you'd like this motor to pull down to under load?

[Old as Dirt]

That's the thing about a V-Drive boat.. typical run..
Stand on the gas from sitting there, and the rev's jump close to redline as the prop cavitates(burn the prop) and as it get's up on plane.. the prop drags the R's down as it starts to bite.. so, I would say it gets drug down to 4500 from 6500 after the initial hit of the throttle and climbs back up from there.. depends completely on the size of the prop and the pitch.. going to have to play with a few props to find the right combo for sure.. might be a few times it will see 3000rpm while pulling the kids on a tube or ski's.. but that might not be a bad thing managing torque that way..

[groberts101]

That's the thing about a V-Drive boat.. typical run..
Stand on the gas from sitting there, and the rev's jump close to redline as the prop cavitates(burn the prop) and as it get's up on plane.. the prop drags the R's down as it starts to bite.. so, I would say it gets drug down to 4500 from 6500 after the initial hit of the throttle and climbs back up from there.. depends completely on the size of the prop and the pitch.. going to have to play with a few props to find the right combo for sure..

well in that case where the prop is used as the stall speed.. could work just fine.
Could also order up a set of reverse meg's to retune the collectors choke size later on too?

I have pipemax but no more time to run the numbers right now(I have dreams and toys that need tending to as well).. but maybe someone else will chime in with harder learned exxperiences or be able to use pipemax or another calc to help you narrow it all down a bit better. Maybe post up the choke ID as well?

[Old as Dirt]

all good.. I have the Pipemax program too.. don't know the choke #'s.. they are for sale on Craigslist..

[wyrmrider]

They'd be illegal on Bass Lake without Mufflers
hold off on the cam rockers etc

[Old as Dirt]

Considering Bass Lake is 1003.2 miles from here..
We don't have noise limits on the lakes in Eastern Washington.. let 'em rip!

[Old as Dirt]

Larrys program wants 1.749 to 1.874 primaries in a stepped config @ 7200 peak HP with 25.7 to 28.4" primary length.. these headers look shorter, like in the 20" - 24" range.. which just pushes the HP peak further up.. since my peak is figured for 6000rpm.. they are a bit over the top.. dang..

[piston guy]

RPM International I beams with the nut and bolt will do the job for your rpm level. Gram weights in the 560 range. A flat top would give about 9.6 and be cheap gas friendly.

[groberts101]

This is Scats under -$300 rods with minor cleanup. Ford sized journal Chevy pin. 524 out of box.. 514 grams now.. probably end up nearer to 506-508 once all is said and done after they're turned into oil shedding mirrors. Machining spec's were spot on.

2016-04-26 11.56.14.jpg

[wyrmrider]

Do either of you have the big end-small end weights so he can see if his crank will balance?

[piston guy]

They're light enough for that bob weight , BE around 380 as I recall

[Old as Dirt]

RPM International I beams with the nut and bolt will do the job for your rpm level. Gram weights in the 560 range. A flat top would give about 9.6 and be cheap gas friendly.

Thank you.. are you the guy with RaceTec/AutoTec?
Thinking a close to 0 deck/flat top/72cc Chamber will make 9.6CR?