quest for 340 at 450hp

[74340]

Well John cope used to or maybe still does build racing 904 and 727 transmissions ...

The primary reason why people or some people choose to go with a 904 is because it weighs less and less rotating Mass... Typically worth about 2/10 on a quarter mile versus a 727... Both transmissions are great and a 727 is probably better in stock form than a 904... But the 904s can be built to handle power

 

[74340]

Engine

 

[74340]

904

 

[Russ Knight]

904

View attachment 114813

Thanks!

 

[74340]

I ended up going with the Hays converter about a 32 to 3400 RPM stall

 

[Russ Knight]

Can't wait to see how it turns out!

 

[TIMINATOR]

IMHO Not anywhere enough cam and intake for those heads and headers. I have built .100 over 360s with Comp Cams 262 @.050 solid roller, Victor Jr. Intake, ported 2.05 valves in 340 X iron heads, 800 dp holley, and it was .3 quicker and up 4+ mph with 1 5/8" street headers rather than coated Hooker 1 3/4" race headers in a 72 Challenger. Ran 4.10 gears, 3000 stall 904 out of a motor home with its low gearset.
Easy 11.40s @ 118 thru dual 3" exhaust and Dyno Max 3" mufflers on old Hoosier 275-60 15 treaded street tires. Drove it everywhere and 35 miles to the track. I believe yours would run faster with ported 2.02 irons with that small F.T. cam and dual plane intake on yours.
I tried LD4b and perf RPM dual planes and strip Dominator intakes before the Victor with that combo. Keep in mind that was in Phx, AZ in the summer at over 100 degrees temps about 20 years ago.
I still have the motor on a stand in the garage. Got a mild 440 /727 2500 in it for now. Building a 512 alum headed solid roller motor next, mebbie a shot of squeeze too!
I just bought alum heads for the 360 and am looking for an A body for it and want to get it in the 10s. I still have all of the intakes, both sets of headers, and a Comp 255@.050 solid roller and the low gearset 904, and just bought a transbrake for it. I may just have to buy a stroker for that too!
TIMINATOR

 

[TIMINATOR]

1 7/8" headers are race only deal. They will kill all the torque below 4500 rpm. Bad choice for your dual plane intake and small FT cam.
You really want about 260 @ .050 and a Victor Jr. Intake with those headers.
A better street combo would be 1 5/8 headers, dual 3" exhaust with crossover at about 14"" past the collector and a hyd. roller cam of 240° @ .050. A low gearset from the later trans is also a nice addition.
Easy 11 sec. 1/4 mile and good street manners too.

 

[74340]

There are plenty of reasons.not to put long tube full length headers on your car ... Such as fitment ,cost ECT... But losing torque even on the low end even on a close to stock engine or even stock engine is not one of them....


I haven't put it on a Dyno yet but I can tell you right now there's certainly no shortage of torque with this combination...

 

[TIMINATOR]

Was the 1 7/8" a misprint?
1 5/8" on a street small block works great, but 1 7/8" drops the bottom end torque.

 

[74340]

Was the 1 7/8" a misprint?
1 5/8" on a street small block works great, but 1 7/8" drops the bottom end torque.

It wouldn't matter if it was a 1 and 7/8 or 1 5/8 header ... You're not going to get a drop torque... If I took the stock manifolds off of stock and for some reason put 1 7/8 headers on it would gain torque... ( Even on a stock engine) ( From stock manifolds) And the difference between 1 and 7/8 and 1 and 5/8 would probably be about the same between each other but it certainly wouldn't drop in torque...

 

[Steve340]

With the stall you have it is going to get up to the RPM were the larger header is no real issue - more of an advantage in the upper RPM range anyway most likely.
I found exhaust diameter was critical playing around with 750 CC motorbike engines.
The smaller the engine the more critical sizing becomes.
However the V8 motor is a pretty forgiving old beast so just fit what you have it will go fine.

 

[TIMINATOR]

Header tube diameter, tube length, collector diameter, and collector length will all affect torque and horsepower production. Larger diameters will "rock" the torque curve around point of peak torque favoring HP and diminishing torque, while smaller diameters and longer lengths favor torque while diminishing HP. This is well documented fact.
Raising the stall will mask the lower torque production and allow you to see the HP gain.
Just because you don't see the reduced torque with a higher stall convertor, doesn't mean it is not happening. This is why high stall convertors exist.
TIMINATOR