383 vs.350

[Guest nosz350]

I'm trying to get some info back on 383 or 350.which you is the best?i've heard a bunch of bad things about 383.

[Guest Night_rider_383]

If The 383 is done right its far better than a 350. 383's will run more to build than a 350 cause of the need for a 400 damper, flexplate, stroker crank, machine work, My self i always use 6.0'' rods to keep the rod/stroke ratio in the ok to good range. With the 3.75'' stroke and the 5.7'' rods the rod/stroke raito is a not to good 1.52:1. With the 3.75'' crank and 6.0'' rods the r/s/r is 1.6:1. The 383 aint a engine you want to build for pure race unless you got the money to speed to build for power up high. The 383 is a great street engine cause of the big block type torque it can make down low and mid range. The 350 is cheap and can be built for power and torque as well but in my eyes nothing beats a 383 for a great street/strip engine. If your looking for something to drive every day and maybe race alittle, and you don't wanna put alot of time and money in it i would go 350 but again i will say the 383 is a @*&% of a torque engine and would be the best bang for your buck if you dont mind putting alittle more into the engine at the start. Just my two cents.

[Guest Fast Frog]

Nothing bad about a 383 cept maybe too much power!! I've had one in my Z for over 5 yrs with no problems! Four of those yrs it had supercharger on it!

[MYRON]

Bobby, Remember that car doesnt weigh much.

gobs of torque is great, but if you cant put it to the ground it is useless.. build the bottom end strong and then put a power adder to it.

You rode in my car and it was just a 355ci

with stock crank and rods with a CR of 10.2.

0-60 in 4.5 and 1/4 mile speeds pushing 120

aint to shabby for a 355 c.i.!!

[Kevin Shasteen]

I'm glad this came up; I personally have no experience in owning/building nor using a 383 but have always wondered about choice of rod/pistons w/the 3.750 stroke.

 

Of all you guys that are using the 383, 400, 406, 408's which incorporate the 3.750 stroke...which rod/piston choices have you made & what kind of durability have you found.

 

My questioning arises from specifically from the 6" rod which will require a piston compression height of 1.130 after a .010 Block Deck Height clean up that still allows the piston to remain .010" below Block Deck Height. To me that 1.130 piston compression height is rather thin/pushing the brink; but then again I've never ran w/a 383(?).

 

The 5.7" rod in a SBC w/3.750 stroke requires a piston comp.height of 1.425 which allows .015" removal from the block deck height & your piston would still be .010" below block deck height.

 

The 5.565" rod which is the factory rod for the 3.750 stroke uses a piston comp.height of 1.560 and also allows .015" removal from the block deck height and again allows the piston to remain .010" below the block deck.

 

So; again-everyone out there using a SBC w/the 3.750 stroke; what rods/pistons have you chosen & what kind of durability have you seen....also I'ld like to know what your compression ratios were along w/the intended use of the engine (street only or street/strip or strip only?).

 

Thanks for the thread-good info!

 

Kevin,

(Yea,Still an Inliner)

[Guest Fast Frog]

Kevin:

 

I'm using 400 rods(5.565").

[pparaska]

...and if you're going to be buying rods, why not build a 350 with 6 (or 6.2 possibly?) inch rods to get the rod/stroke ratio in the (better) 1.7-1.8 range. Broader torque curve (improved breathing characteristics, etc.), less road angularity, better detonation resistance (for the same static compression ratio).

 

Good Forged rods in longer than 5.7 length are not very expensive. Nor are pistons to run them.

[DavyZ]

Good point Pete! Yes, the next motor I build will have 6 inch rods minimum length. I envision a 355 Chevy with lightened Scat crank, 6 inch rods, aluminum heads, 10:1 compression, etc, etc. Man, I can dream larger than my wallet anytime!!!

 

David

[Kevin Shasteen]

I've read quite a bit on this rod/ratio stuff & it seems there are some good points & then there are those who get miffed about it.

http://www.headsuperview.com/gklass012101.html

is an article written by George Klass...FFW Tech Director.

 

He recounts the actions of Reher-Morrison Racing Engines who built a 500cu in engine for the puropose of testing different engine combo's whereas the only variables were different connecting rods & piston comp.heights....the outcome was that there wasnt any difference on hp/torque.

 

I've also read where the old rule "There's no substitute for Cubic Inches" makes the rod/stroke ratio argument a moot one(?). So why did Reher Morrison choose to argue his point by building a large displacement engine to make his point(?) when large cubic inches allegedly counters his countering of his test???

 

I've also found an excellent article on the web where as the writer gives all the arguements: timing, cyl.pressures, dwell time and piston accel (well worth reading); it is:

http://www.chevytalk.com/tech/engine/rod_angle.html

 

In that article he makes a valuable point on rod length regarding its angularity in relationship to the piston/cylinder. He claims that any rod angle more than 18* ("*" being Degrees) is hazzardous to an engine and will result in excess cyl.wear due to ecess thrust to the piston. He also gives a formula for calculating piston angle-it is as follows:

 

Stroke/2 = Answer/(Sin(Con.Rod Length))

 

Take a 350; its stock stroke is 3.48 w/5.703 rods...working the above formula gives you the answer of:

 

Rod Anlge = 3.48/2 = 1.74/(Sin(5.703))

 

Rod Angle = 1.74/.09937

 

Rod Angle = 17.51*

 

Now take Davy's 355/6" rods; it works out to be:

 

Rod Angle = 3.48/2 = 1.74/(Sin(6.00)

 

Rod Angle = 1.74/.10452

 

Rod Angle = 16.646

 

Now take the 400; its stock stroke is 3.750 w/5.565 con.rods...this gives you an angle of:

 

Rod Angle = 3.750/2 = 1.875/(Sin(5.565))

 

Rod Angle = 1.875/.09697

 

Rod Angle = 19.33*

 

(Note-This explains why many engine builders talk about the 400's excessive cyl.wear)

 

Now lets take a stock 454 w/6.135 con.rods & working the formula gives us the following:

 

Rod Angle = 4.00/2 = 2/(Sin(6.135))

 

Rod Angle = 2/.10687

 

Rod Angle = 18.741*

 

Now, for you Ford guys; take the 5.0; it has a stock stroke of 3.00 w/5.090 con.rods:

 

Rod Angle = 3.00/2 = 1.5/(Sin(5.090))

 

Rod Angle = 1.5/.08872

 

Rod Angle = 16.907

 

Take the 5.8W block that has a 3.50 stroke w/5.956 Con.Rods; this gives us...

 

Rod Angle = 3.50/2 = 1.75/(Sin(5.956))

 

Rod Angle = 1.75/.10376

 

Rod Angle = 16.865*

 

As always-I've enoyed this thread!

 

Kevin,

(Yea,Still an Inliner)

 

[ June 07, 2001: Message edited by: Kevin Shasteen ]

[Guest Anonymous]

Don't you have to notch bottom of the bores or something with 6" rods? I seem to remember there are Long and Short rod 383's and the longer one required some notching?

 

Regards,

 

Lone

[Guest nosz350]

Thanks again for the info guys.I think i will build a rock soild 355, myron a power adder will be no problem when i got all NOS i need in may back room.Here is a long term goal,have a car(1970 datsun Z)that i can take to a car show and win something,then turn around acruise 100 or so miles and see my good old pal Myron in Conroe(with the A.C. on ).and also be able to go to the track and run in the hi 9s- low 10s on the bottle. WHAT A GOAL!!!!!!!!!!!

[Guest Night_rider_383]

Just my thoughts on this and parts i'm useing. Sometimes the bigger c.i.d engine wont come out ahead. Like you take the old small journal 327's. Given all of them had stock forged crank and rods. 2.30'' mains, 2.00'' rod journals. 5.7'' rods. 3.25'' stroke and 4.00'' bore. We all know and read that larger strokes builds torque and larger bores builds horsepower right? With that said the 327's had the small stroke and large bore. Light bottom end, and small journals. Well this adds up to a small cid engine that can run with large sb's and a few bb's on the top end of the 1/4 mile if the engines is some what useing the same parts is used. Like c/r, head flow rates, etc. But the bigger engine will kill off the line and down the 1/8th mile. It's kinda like looking at a small block race a big block most of the times the same block comes out of the hole faster, leaving the big block at the beams but after the 1/8 mile the big block hits hard and comes right past the small block. Thats cause the bb uses the same strokes as most of the small block's are just alittle bigger and bore sizes alot bigger than sb's

 

Usein the fact "light makes right" and the small journal rods will spin up faster this is what im useing for my 383 build

 

Callies 4340 forged light weight knife-edged crank. with 2.45'' mains, 2.00'' rods, 3.75 stroke

 

Manley 4340 forged h-beam rods, 6.0'' lenght, 2.00 journal, profiled for stroker engines.

 

JE forged pistons 4.030 bore, -28 cc dish, 1/16th, 1/16th, 3/16th'' rings, (dished to keep c/r down for use with a blower)

 

Block deck. Pistons .010'' "in the bore"

[DavyZ]

Kevin, I currently have a 350, but since I have been posting on this board, I have come up with every engine combo and have considered what would be "ideal" for a Z.

 

I first thought a 383 would be the hot ticket since the prices for 383 cranks have come down to very reasonable levels and 350 blocks are soooo easy to come by. But there are 383 combos that are better than others, like the 6 inch rod--that would be the best one IMO from the research I have done.

 

I then considered a destroked 400: down to 377 with a 350 crank or even to 350 ci with a 327 crank. But finding a good 400 sbc is getting much harder nowadays. This type of engine would rev, give you decent torque, and have very sweet compression with pump gas. Plus the factor is greater when they realize what the motor really is.

 

After considering all of these and the relative costs. After reading one of David Vizard's books, the 355 can be made to give an incredible amount of hp and torque for the cubes--and rev really well for a decent price. I figure with a lightened Scat crank and some decent heads, etc., 450 hp is really nothing for the motor...

 

A "simple" build that included lots of torque w/o throwing too much cash in the motor would be a near stock 400 or a 383. The 355 has decent torque although not as much (do we need more torque?). Each engine has slightly different characteristics--it just depends on money and what you want your car to do. I am totally convinced there is not a "wrong" choice in the bunch. Bigger is not always better, but neither is too small. Just my $.02.

 

David

[pparaska]

Night rider, that sounds like a sweet motor.

I used to hear good things about the smaller journals having less bearing speed and better wear (smaller radius = shorter circumference, and less distance travelled by the bearing for each revolution) I believe the Chevy may have gone to the larger bearings to give the crank more meat. But the Small journal 327 crank is a pretty strong piece as it is. Kept below 6500 rpm, most stock crank/rod 327s stay together pretty well.

 

I also think that the guy writing the stuff about rod angle is making a bunch of jumps in logic that I can't buy off on. There's alot of interesting stuff there, but I am having trouble going along with major parts of it.

 

JMO,

 

[ June 08, 2001: Message edited by: pparaska ]

[Guest Anonymous]

The 327 is still my fav. motor, it was 'the' motor of choice in dirt track racing out here in the late 60's, early 70's. These motors ran alcohol with mechanical hilborn injectors (like to have a set now to convert to EFI but can't afford it... ) and compression ratio's around 12.5 to one (might have been higher). As I recall they were dry sump and most in my area were setup like sprint cars but the body styles were a bit different. Although I had never seen a dyno run with one of these on it, they had to be putting out a easy 500-550 hp. These engines were generally ran all season with maybe a occasional tear down if something broke, but usually just change the oil in the sump. I know the engines were spun to 6500 (sometimes higher) routinely. Power was transfered through old three speeds often (or in and out boxes later). The sound the 327 made with a set up loooong collector sprint car sidepipe like headers (uncapped back then) was pure music. They would literally explode out of the corners and to watch a good driver on a clay track keep it pointed in the right direction was incredible.

Sorry for the trip down memory lane, but I felt the 327's virtues needed to be mentioned. Strong tough motor, great HP per displacement.

 

Regards,

 

Lone

 

PS: If you've never been to a dirt tracking event, try to go sometime. Seeing a pack of sprinters or mods coming out of turn 1 sideways on a green flag is sure to get the addrenelin going.

 

[ June 08, 2001: Message edited by: lonehdrider ]

[DavyZ]

Hrm, maybe you and I should catch a race sometime, eh Lone? I think they have dirt races at Altamont, but I'm not sure and I'll have to think about that. What tracks are in Sac?

 

David

[Mike kZ]

I know I've mentioned this before, but my small journal, forged crank 327, with twist flow heads , 270H Comp cam, and Pro-Flow EFI, made 435hp, and 493 tq, on a engine dyno! Those are big block numbers! Can't wait to get this puppy on the road!

[Guest Anonymous]

quote:

---

Originally posted by DavyZ:

Hrm, maybe you and I should catch a race sometime, eh Lone? I

think

they have dirt races at Altamont, but I'm not sure and I'll have to think about that. What tracks are in Sac?

 

David

---

 

My favorite track I could have hit with a rock from where I live, but its long since been closed. They do run asphalt in Roseville, but to me thats boring.

There is Placerville speedway (about 50 miles east of Sacto.) and I've yet to go there. I was just on they're webpage and they run like sprint 410's (410 cu in, 700 hp on dirt at like I donno, 1300-1400 lbs maybe a tad more?) And some other type of modifieds I've yet to see. I'll look into it, I've yet to go up there, but would like to see it again and see what the new school sprinters can do. Would be cool to do sometime.

 

Regards,

 

Lone

[DavyZ]

I'm game if you are!

 

David

[Z-Dreamer]

There's a sprint car dirt track in Chico. About two hours north of Sacramento. Lots of action at that track. I love watching the OutLaw Series cars 410ci SBC's on alcohol making over 800hp!

 

Mark

 

[ June 08, 2001: Message edited by: Z-Dreamer ]