liquidlounge

iTrader: (1)

This is a really great thread. A couple of questions:
-How many hours would you recommend before injectors are flowed and tested?
-Is there an actual science to runner length for the lower intake? It seems that I have heard/read somewhere that there is. Of course, as the runner is shortened, the powerband moves upwards, but are people cutting these runners to a particular length or just willy-nilly cutting them down and it just works?

jeffswav

I gained about 10 MPH by bolting on a Flux Capacitor. They have been discontinued back in the 80's so hard to find now.

sutphen 30

your not up on the times,,Mr. Fusion is the way to go now.

jeffswav

I have both of them installed in series. Double the power.

CDShack

If you have access to a show called "Engine Masters" on Motortrend TV, they do a whole episode on runner length and where it puts your torque curve. In another, they also examine dual planes vs. single plane intakes as well. That show is a wealth of info, even if you built engines for years.

Their info is generally limited to carb pulls on the dyno, put I imagine the physics are the same for EFI

CDShack

As to your original title about "faster" I had to share: My Machinist has a sign in his shop--"SPEED COSTS MONEY, HOW FAST DO YOU WANT TO GO?"

articfriends

iTrader: (1)

To sum up runner length in a simple explanation, yes, a long runner length dictates the rpms hp peak occurs at. Using a program called pipe max, you can play with runner length and see what happens to that rpm point and the torque.
Heres how I sum up a stock at 502 MPI, 8.8-1 compression, tiny, itty, bitty cam thats about right size for a mild 396, a timing curve at wot/100 map that never exceeds 29.9 degrees and a pig rich tune. you could literally over prop one, run 85 octane and hold it torque loaded way below peak forever and be ok, IE, houseboat, tug boat etc. The overall runner length is about 15.5 inches IF I remember right, one of the common mistakes people make when building one with stock, unmodified intake and throttle body is over camming. For discussion sake, lets say stock there is this nice torque curve from 2800 to 4500 with peak around 3800, hp peak at 5200 (I dont have exact numbers in front of me). You get a big daddy cam, say a 240/246 @.050, you lose a bunch of that bottom end torque/midrange tq and now the tq peak is at 4900. Since intake runner length and size is dictating hp peak, its still done at 5400/5500 even though it has enough cam to actually peak at 6000/6200. You could literally tear intake off on dyno , go to a aggressive open plenum and see hp peak rpm go up 600, 800 rpms. Tq , however would be even lower so not necessarily the answer.
so by shortening the runners some, ie, 2" or so, we give up 20/30 ft lbs of tq in the 2800 to 3500 range and get a higher rpm before intake is yet again a restriction, usually around 5600 on a 502. Since your now gaining rpms,, IF cammed correctly you will also gain hp. BUT on top of gaining hp, just being able to rpm the same prop 200 rpms before powerband drops off should net you a speed gain. This seems to work well on 454/502 mags, it doesnt seem to work as well on 500 efi intakes. Ive seen 454 mages peak at 5700/5800 with modded intakes and still make respectable tq, Smitty

liberator221

articfriends what is your recommended hour interval on injector clean/check?

SB

iTrader: (1)

see here for some ruuner info i posted on a 540 for example:
Dyno sheet

articfriends

iTrader: (1)

Most injectors I flow/clean have never been removed from the boat before and are 18.20. 22 years old. sometimes this goes along with a burned down cylinder. So IMO they need to be done every 2 or 3 years, Smitty