Ok i have a 88 iroc that came with a 383 stroker. I didnt build it and dont know who really did, But I have had problems from day one with this motor, so i decided to build another one. I have a 350 block in my garage So my question is, do i want a 355 or a 383.

Im not looking for a drag race car. Or a daily driver.
I want a car that i can take out crusing, thats as awesome low end torque and acceleration and throttle response. I want a stop light to stop light car. Were it gets up and goes off the line. And will put on a good smoke show. I really want torquq, and i want alot of bottom end for the stop light and get up and go. But can still turn a low 12's. The highest octane fuel i can get around here at gas stations is 91.

I just want to start over and make the car what i want. It has a 700R and limited slip 3:73's.

Heres my questions.


355. or 383
5.7 or 6 inch rod
cylinder heads ( are there any cast iron factory heads off anything that can be ported and polished and flow good?)
Intake
Carb
compression ratio
cam choice

Whats a good combo for the low end torqe motor, that can still do awesome at the strip. but have good acceleration for quick cornering, and stop light races. Thanks For all the help. If theres anyone who has a combo like this I would really like chattin with them about this. thanks

 

The stock 350 (depending on year) will do most of that already. With 240/350 hp/torque, and 9.3:1 compression, there isn't a lot that you would have to do. But i'm not a tech...

 

383. The crank is the same price with either one, might as have more cubes, that helps with your low end torque.

Forget 6" rods, for your powerband and useage, it's a non-issue. Use the 5.7" rods IMHO.

low 12's is pretty big power. keep that in mind.

any 10:1 vortec headed, 650CFM double pumper, performer RPM, w/ xe274 383 would do the job damn well.

 

hey 70gmc
well i am in the same place you are,but i have gone with a combo i think you might think about, 357 its a long rod 355 6'' rods 3.50 stroke its light rotating mass, and the motor spins up fast it has more torq then a 355, and 383
what i have found if your car is heavy or you want real low end torq go with a 383 , but keep in mind you need big runners to make it work, head with 200cc
or 215 or bigger for big power. your torq is great off idle to about 4600rpm
this is great for light to light and smoking tires.LOL

The cheapest way is a 355 with the wright cam and set up you can make a nice street car.

ill post the dyno number on the 357 when i run it.

what intake are u running and think about most of how u will drive it.
i think the 355 works great for the price, for more torq & more power the 357 is great, and will go high in the power band. and its not much more money.

i hope it helped, i just choice to try this combo, i post the numers of you guys.

rick

 

Thanks for the help the 357 doesnt sound to bad, Any opinions on that, goods and bads?

Ill mostly be driving this car on the weekend nights riding cruising with freinds, the occasional drag strip, and honestly proably runnin the **** out of it. I want something fun and fast, I love working on cars so if i break somethign ill fix it bur i enjoy runnin them hard.

Sonic: you said 12's is alot of power and i understand that. So in your opinions is it possible to get all that and a 12 second car. still streetable and lots of low end for quick acceleration? What would your recommend?

Thanks for the help

 

sounds like your after exactly what I want.. I'll tag onto this thread and keep reading

 

 

if you're buying everything new, and not re-using your stock crank - there is NO REASON to get another 350 crank. More cubes = more power. The price of the 383 crank vs 350 crank is $10 max. Usually $0. Easy 20HP minimum. Probably more like 35HP.
Look over in the organized racing board, at the people with 383, which rev over 5000RPM. The stroke (longer) doesn't make it a "diesel" or TPI motor. (ie, only low RPM). Usually the valvetrain limits RPM, until about 7000RPM, then you need to pay attention to the bottom end more. (I mean shorter stroke that is, either way a balanced rotating assy is a good idea, etc...)

More cubes make more power, period. Also, the powerband of a larger motor is not only bigger, but it comes on earlier. Ever drive a honda? Yea, it sucks. Revving it to 3000 to take off from a light to keep up with a farm truck. It's shameful. That's small cubes for ya. The bigger cubes of a 383 just bump that torque down a bit lower. That's what sinks you back in your seat when you punch the fun pedal.

I'd look at the organizing racing boards, those guys go to the dragstrip more often then everyone else, so they'll have timeslips in sig, along with their engine combo. That's the best advice right there. 200cc or 215cc heads will make the 383 a higher RPM motor, more power yes, but it'll come on later. I don't think for 12's you need high RPM's in a 383 motor. You can get away with a more streetable RPM range, and still go scary fast. Shoot for a 2200-5600RPM powerband. xe274 is good for that. There's plenty of other cams that'd work great, I just know comp's cam's best.
Vortecs would work great, you'll be buying a new intake manifold either way right? Those are only 170cc intake runners IIRC, and I KNOW people have gone 12's on a 383 with it before. Trust me, it's not virgin territory there.

Or you could go to an aftermarket head style, lots of choices there. 190cc would work great, you'd still have low end torque, you wouldn't need to rev it over 6000RPM (RPMS kill, keeping it lower helps it last longer, etc.)

 

Here is a question. What parts do you have already?

What kind of heads do you have?
If its a 383, what kind of crank/pistons/rods?

What kind of problems are you having?

This will help in advising you on the right route.

Oh yeah, With traction/tunning/cool air, I should be in the low 12's with my combo.

 

I dont know exactly what i have in the 383 now i bought it that way, and was told some untrue stuff this far so i dont know if i can trust what he said. I dot have a 74 350 block and a 400 crank in my garage that i can use to built this new motor, rod and piston wise i have not idea im gonna order some but should i order 5.7 or 6, 5.7 seems to the more popular opinion but whats the ups and downs?

In cylinder head choice, What runner size is best for low end torqu? is the the smaller the better. Are the vortec heads worth redoin, are they a good performace head?

 

6" rods are *usually* more cash. The diff in performance is so miniscule it's not worth even thinking about. 5.7" rods are more plentiful, and you get more choices.

I'd suggest looking at ohio crankshaft. Get some of their 5.7" rods, and some "383" pistons. They have a different piston pin location so they can be used with a 383 crank, with "normal" 5.7" rods.
You'd have to get your 400crank turned down to 350 mains. If the machine work needed for that crank is high, you might as well get a new one. Looking at like $200 for one anyway.
You can get pistons/rods/crank all from one company, then you can get it as a balanced assembly. Ohio crankshaft can do that, summit maybe, and a schwack of others.

You've got it right on the intake port size.

 

What kind of problems are you having with the motor??

Have you tore it down yet or is it still together?

If we can figure out what you have, you might be able to reuse some of the parts.

What are the casting numbers on the heads?

 

The 383 stroker is what you want because longer stroke = more torque
But you already have all this so stuff in the engine u have so why not rebuild it.You may end up being lucky and only have to freshen it, put a different cam in, maybe new heads( with the money u are saving not starting from scratch)
What are the problems u are having?
My first thought is that is your car is fuel injected The cam needs to be for a fuel injected car and often the computer needs to be reprogramed to work properly with the new setup, B4 you start all over for nothing let us know what ur problems are, there are alot of knowledgable people on these boards
you may end up being able to just fix the problem and save some $$$$

 

The problems i have been having are quite a few actually. I have them posted on some other boards here, but i must say this one is getting alot more attention and i appreciate all the help on this one here. Heres what i know about the motor.

79 350 4 bolt block
stock 400 crank turned
gm 5.7 rods ARP bolts
dont know about pistons
The heads are a off brand of aluminum... 2.02 and 1.60 valves
The cam is brand new about 200 miles ago mine went flat. its a 488/ 510 lift
intake is a torqer ( Just what i had layin around, i want a air gap)
carb 750 holley
and a hei distributor

I know the intake is not matched to that cam, but if i simply swapped it to a air gap would i notice a difference? How much if so?

I have two big problems in my opinion.

1) As posted on another board on thirgen.org is low oil pressure, at idle i have about 5 to 10 psi. But goin down the road its fine. After a little help i believe its a spun bearing or whoever put it together didnt gap them right.

2) Very sluggish. I hear alot of you guys with 383s run mid 12's I have a 383 in my 70gmc pickup that runs a 13.6 and thats with a mild built tranny and one tire 2.83 gears. And i know this camaro has a better tranny and rearend in it. So something is def. wrong. When I mash the pedal it takes a few seconds and then finally goes, but even then not what i would be excpecting.

Unless the oil pressure problem could be somethign else, then the motor will have to be pulled. And i think the intake swap would help, but how much? The guy i bought it from said it was runnin a 9.67 compression ratio i would like to get it up to about 11.1 for better performace. The only reason i was just gonna build what i have in the garage is so i KNOW whats in it. Alos I have heard some good things about vortec heads and there power output. With the aluminum heads on there now there just a no name brand and i dont know any particulars as runner sizes or combustion chamber size. Anything at all that would help i would appreciate. thanks

 

bump, any other opinions?

 

Find Traxion's old posts and just copy what he did. What exact problems are you having where you would blame the motor itself?

 

Ah, see what I get just answering the first post?

What heads do you have on it? You have to determine that, then timing comes into question along with your comp ratio. The intake may be a tad small depending on everything else. Have a spacer on there yet?

 

I used to have a 2gen(sold)with a 383 Eagle stroker kit with just the XE274 cam,junk iron heads(185s),3.73 gears 3000stall BM TH350 and 28" ET streets it did 13.02/163km/h on the strip,402m/quarter mile with a 100 shot it was in the low 12s.
With a set of good aftermarket heads you are definitely in the low 12s with a similar setup i think also i must say a very good street engine hardly noticeable idle and very strong from the bottom and very good response.
Oooh did almost forgot Xcellerator single plane and a 750AD Holley mechanical carb was also in there.

rgds Mats

 

If you're replacing the crank, why not use the same amount of money and buy a stroker? Sheesh, you can get one from eagle for $180. The extra cubes are going to make your goals a lot more easily attainable. It's going to make gobs of torque down low which is what you want for the street. Low 12's in a 3500 lb car will be much easier with a 383 than with a 355. And you will be able to do it with a smaller cam that will be more streetable. Look at my VBgarage page and you'll see my 383 setup. 100% streetable. I drive it to the track and to work a couple times a week. I would drive it more if I had overdrive .

 

I'm going to try to address these one at a time

The oil pressure is not the result of a spun bearing. If that was the case you would have no oil pressure and a bad knock or a rod hanging out the side of the block. 10 psi at idle isn't super, but it wont kill anything either. Chances are that the clearances are a little loose.

As for it being sluggish I can see a few problems. First is that intake. It's very restrictive. Old design and it's not very conducive to making power. Second could be the heads. Find out what they are. If they've got an excessively large runner then they're going to kill the torque especially with that cam and intake. Third would be the tune. That is a mild motor for a 750 carb. Are you sure it's jetted correctly? Also timing is an issue. Find out what it's set at and experiment with advancing it a little. Converter and gears too. What do you have in the car? It's going to be a terd with anything less than a 2800 stall converter and 3.42's.

I think most of your problems are from a poor combination. I would tear down that motor since it's already got a stroker crank in it and the block has been clearanced. Put in a good set of rods/pistons. Blueprint the assembly. Find out what the heads are and if they're junk with big runners/chambers and heavy valves then sell them. Vortecs make good power on motors like this. I put one together last year that made 465hp at the flywheel on a 6" rod 383 with a 650 DP, Air Gap intake and AFR 195 heads. I would put on a good dual plane intake and a 650 carb.