[Zubair]

Hi Guys

i'm posing this question just out of curiosity,not to stir any form of arguments however all opinions and facts will be appreciated.If one was building a purely
0-125mp/h sprint naturally aspirated V8 for 1/4 mile use etc using a 350 turbo box with around a 4.1 diff ratio would a 377 or 383 work better?I know the torque guys will say torque wins races so 383 wins,and the high revving guys will opt for the 377 saying it has an abundance of torque too.

More importantly what constitutes a 377?406 bore and 350 stroke?Also what heads,intake,cxm,carburettors can one make make use of to build a 600bhp 377 that revs to 7500 rpm+?750 or 850 double pumper Holley?Dart Pro 1 230cc intake port heads?11:1 compresion?

[poncho62]

383....because of the 3 speed auto................Maybe with a 4 speed, the 377 would be better.

There are many more factors involved too...type of car and weight being a couple of them.

[454C10]

A few years ago, I saw a comparison done in a chevy high performance or super chevy magazine. If I remember correctly, there really wasn't that much difference to worry about.

If this engine is going into a small car, like a 60's nova, then build the 377 because the smaller 153 tooth flywheel can be used (internally balanced). The 383 can also be internally balanced but cost more.


Why not just build a 406 with 5.7 inch rods?

[firestone]

Given a choice between the two, I would choose the 377 in pretty much any situation. Assuming the cubic inches are close enough to the same to leave it out of the consideration, the 377 is a more efficient motor. A large bore short stroke is more desirable than a small bore long stroke engine for a couple of reasons. First, the short stroke has a mechanical advantage at higher RPMs. At low RPM, as it was explained to me, there really should not be much of a difference in power. This seemed counterintuitive to me at first, but upon explanation, it made sense. At a first glance, it seems that the 383 should have more low end torque because of the greater stroke. But, torque is figured by stroke * force. The force on the piston is not the same in the two motors. Pressure = Force/Area, so Force=Pressure*Area. Given the same cylinder pressure, there will be more force on the 377 piston because of the greater area that the piston top displaces. Even though there is a shorter stroke, the force is greater, so overall torque should be about the same at lower RPM. At higher RPM, the 377 should make a little more for reasons already mentioned. On top of that, the larger bore of the 377 will allow the heads to flow better due to unshrouding of the valves, and more flow makes more hp. This is all theoretical, and I have seen actual tests done where the smaller bore motor did make a little more low end power, but I think that had to do with other variables.

Given all that, I would still agree with 454C10 that if you have a 400 block I would build a 406.

As far as a motor to do what you are talking about, You can compare to my motor. It is the same idea just smaller.

358 (4.155 bore 3.295 stroke)
Ported Brodix 11x heads
14.5:1 compression
274 282 @.050 ~.660 lift 110 lsa solid roller cam
Super Victor intake
hp 950 carb
made 608 hp at 7900 RPM.

It may be a little difficult to get 600 hp out of a 377 with 11:1, but it should not be a problem out of a 406. A 377 is a 4.155 bore (400 block) with a 3.48 stroke (350ci).

Here is a 406 that I would consider. If you wanted a 377, you could just use the same parts on that but you would probably loose around 40 hp (assuming 1.5 hp/ci for each motor)

Here is the motor. It has the old style AFR Comp 227 heads. The new ones perform substantially better, but don't come out until around April.

408 10:1 comp
AFR comp 227cc heads
262 266 @.050 .638 .639 lift solid roller cam
Super victor intake
Holley 1150 dominator

on pump gas, 620 hp @7000 RPM 537 ft lbs @ 5100 RPM

http://airflowresearch.com/articles/article045/A-P1.htm

Here is an article about the new AFR heads, and some history of AFR

New heads
http://airflowresearch.com/articles/article113/A-P1.htm

History, short, and a good read if you are thinking about these heads.
http://www.airflowresearch.com/about.php

Adam

[bonzipenguins]

I just read a dyno test the other day about 377 v.s 383.The 383 outpowered the 377 up till 3800.They stayed the same till 4500.Then the 377 kept pulling up in to 7000.It peaked at 589 hp.It made 65 more hp than the comparable 383.The 383 had 27 more ft/lbs torque than the 377.At much lower rpms.
In my opinion the 377 is a better race motor.I did build one once for a friend.Real mean but also very unstreetable.Now the 383.Is just much more fun to drive on the streets.Lot's more to give on the low end.Where you need it.

[firestone]

Here is an interesting article about this topic.

From RMRE
http://www.rehermorrison.com/techTalk/53.htm

Bonzipenguins, that is interesting. I wonder if the extra power didn't come from the extra cubic inches to some degree. At a very low RPM, the 377's mechanical advantages (mainly having to do with friction)really have not had time to shine. 27 ft lbs at 2000 RPM is 10 hp. It seems reasonable to me that the extra 6 cid could give the 383 a nudge toward gaining 10 hp. I cant remember all of the details of the test that I saw, but the smaller bore motor made a little more low end hp in that case also, I cant remember what the size difference was though.

[bonzipenguins]

im not sure but I read the article in a chevy high perfromance book.And have had experience with both motors.The hp,and torque numbers were better on the 383.Up until 3800.Then the 377 started waking up.My buddy I built the motor for lives in L.A.So I bet its a pain to drive that thing.
62 nova
377 12.5:1
4 spd M-22
3.73 gears with a powertrax diff.(we had 4.88.But we changed it after we saw how quick that motor got up.)
Custom ground solid cam 300/300 ,250/250, .600lift, 106 lsa
Pete Jackson(Noisy)gear drive
Edelbrock E-Tec 200 heads
Harland Sharp 1.6 roller rockers
Victor jr. Intake,And a Mighty Demon 850cfm carb.(He later had another guy put Mechanical Fuel injection on)
The motor easily got to 7000+ rpm.In between gears.

[Bob C]

Originally Posted by bonzipenguins

im not sure but I read the article in a chevy high perfromance book.And have had experience with both motors.The hp,and torque numbers were better on the 383.Up until 3800.Then the 377 started waking up.My buddy I built the motor for lives in L.A.So I bet its a pain to drive that thing.
62 nova
377 12.5:1
4 spd M-22
3.73 gears with a powertrax diff.(we had 4.88.But we changed it after we saw how quick that motor got up.)
Custom ground solid cam 300/300 ,250/250, .600lift, 106 lsa
Pete Jackson(Noisy)gear drive
Edelbrock E-Tec 200 heads
Harland Sharp 1.6 roller rockers
Victor jr. Intake,And a Mighty Demon 850cfm carb.(He later had another guy put Mechanical Fuel injection on)
The motor easily got to 7000+ rpm.In between gears.

I built a similar 377 for a Camaro. The guy took it down the road and came back and said he wasn't impressed. I asked what he shifted at and he said 5500. I told him to try it again but shift it at 7000. He came back with a very large permagrin. A 377 is very impressive at higher rpm.
Bob

[coldknock]

So is a 406 with the correct combination of parts to make it scream. There's just more volume to work with.

With the 4-something gears I'd say an even shorter stroke, like 3.25" in the 400 block would be fun and help slow the piston speed a bit. The car can't be a pig or it'll just suck no matter what engine goes in it.


Larry

[bullheimer]

yeah, 406 or bigger all the way, Unless!!! YOU have a real light car or geared from hell with 4.56 or better to get that little 377 off the line. or just like the sound of shifting at 7000!! i have a 400 too, i am going for a stroker out to 415. everything i read in chevy high performance says forget the 377. same thing as a DZ 302 but bigger. they were a blast to drive.

[Zubair]

Am I correct in assuming the 377 is a 400 with a 350 stroke?
If so what is a 406 with a 350 stroke?Will that not work better?
also you guys state to go with longer gear ratios or diff ratio as the motr spins up so fast,I would have thought to go with short gearing to get it to spin up even faster as thats what one is looking for,something that revs like a bike.

[SAATR]

A 406 is simply an overbored 400, it's the same motor.

[zipper]

I just had to get in on this one since i currently run a 377" in a 3253lb 1980 Malibu with 5.43 gears. I personally love the performance of the 377's but they have draw backs and the biggest factors are weight and gearing.
my car was weighed at Memphis MSP. on certified scales, it will run all day long in the 10.50's @ 124mph and 6.50's@ 106mph in the heat(100 degrees) on alcohol with a toilet bowl. The engine would run better with 6.00/6.20 gears in the 1/8mi.
i would say that a 388"er might run 1 tenth better with this much weight, however a 406" junkyard motor, with brodix heads and 6.20 gears i ran 6.26 in the same car. I run an electric shift PG with a 5500 stall and pro brake, but the 406"er broke a rod bolt, so in went the 377" motor.
Now the big surprise!! before i put this motor in a lead sled, i put it in my friends 1850lb dragster, it went 5.16 in the 1/8mi and 8.23@ 158mph in the qtr. so weight deffinately matters. He built a 434"er and it only ran 4.98 in the same dragster.
So yes 377's are heaven sent but they have no torque, but you can't break them and they run forever. I do have to admit i have the wrong cam in the engine at this time it's 6.65in and 6.85ex a little big for this much weight. It would be better with the 6.30x6.30 cam i had in the 406"er.
But why not build a b/blk for the truck? they're cheaper to build for torque and work much better for the weight of the truck.
Enough said i've written a book here.

Zipper

PS, i've got a 434" with hilborn stacks on an engine stand just haven't put it in yet, hope to run 5.70's with it.