lilman0883

I'm building a 383 stroker for my 1983 trans am.
I bought a eagle rotating kit with dished hyp pistons 5.7 rods, balance assembly external.
Stock vortec heads and I have yet to pick a cam, I want something that I can still use the stock converter any ideas???

Orr89RocZ

iTrader: (20)

Stock converter will hold it back but you can get away with a mid sized cam with good tune.

What gears and what cam type is the block? Hyd roller or flat tappet or ?

Is it carbed?

lilman0883

flat tappet cam. i will be putting a carb on it and i think the gears are 3.23

Orr89RocZ

iTrader: (20)

Xe268 or similar grinds

brodysZ28

I've got that rotating assembly in my 83 Camaro. Are you aware of the issues with flat tappet cams and today's oil? I strongly advise to go to a roller block and cam for both the power increase along with reliability. That being said I have the XR288HR in my motor and the car runs very strong. I've got a stick in my car and I am no expert in how an auto affects cam choice, so a smaller cam may be better for you as Orr89RocZ recommended. I also have a pretty free-flowing exhaust system too. Not sure what you are running.

SpitotRs305

i would worry about the xe268 being too small...

i would pick the xe274h10 although the lift is pretty close to where the vortecs need work done to them... need to keep in mind your comp ratio here which was what i based the too small comment on.

and if you want to veto my pick because of the "dyno" numbers comp advertises... take a look at the compression ratios of those "engines" both list 9.25:1

due to the low CR the smaller duration camshaft will appear better... and possibly is better at any dynamic compression ratio... however i bet you would like to run pump gas and as i believe the xe268 would put you pretty close to detonation territory

we need more than displacement and heads to truly suggest anything... well anything that is going to make you and the engine happy.

piston dish cc?

accurate static comp ratio?

intake?

something?

Orr89RocZ

iTrader: (20)

With dish pistons it should be close to 9.8-10 to 1 which is getting high for iron heads. Xe268 should still handle pump gas. Being that he is on stock converter, i wouldnt go too much bigger. You can but then you will have a lazier off idle feel and it may suffer some driveability. Efi could likely tune it out, carb i am not sure.

If you stalled it up abit, 274 wouldnt be too bad

Screamin82 Z28

I have a XE268 in my 360 (350 - .060 over) with 3.73 gears, and vortec heads. It would be a bit to much cam for a stock converter in a 350 however in a stroker you should be able to get away with it. I don't think you can go any bigger successfully. I think it is a good choice however, I put down 275rwhp at the dyno last fall on a very tired/beat motor.

Make sure as mentioned previously you use appropriate oil. Comp cams now states that there break in additive must be used with every oil change in order to ensure longevity of there flat tappet cam shafts. As I learned the hard way in 2003 (before this was known) I wiped a flat tappet cam out in 15k miles. So USE IT!!

Orr89RocZ

iTrader: (20)

I have tuned a bigger cam in a 350 on stock converter and it drove fine. Soft bottom end but no issues. That was efi however, and a carb may not like it due to lack of fine tuning fuel curve and timing and transient throttle fueling. Xe 268 has always been a popular street cam for 350-383 motors and especially with vortec heads.

brodysZ28

I went to roller after having 2 flat tappet cams wiped. I'm not sure the cost of the additives but definately add it every oil change. I would think the cost of that would justify going to roller. But that is just my opinion. I also don't have actual dyno numbers to back it up, but a roller cam will make more power due to the more aggressive cam profiles.

SpitotRs305

as you say it may be safe. and the OP may be happy keeping his stock stall but the simple fact is that a stock 1800rpm stall is not the right choice for this engine, with either cam shaft.
that number comes from a stock 350 putting out much less Tq./HP while the vehicle weight has remained the same... basically why i ignored what stall is presently installed.

with the greatly increase TQ that stall will act like a much lower rpm stall in either case you will need to purchase a higher stall...

http://www.hardtail.com/techtips/sel...converter.html

other than that the difference between the cam orr89rocz picked and the one i did... increased exhaust duration was also something to look for with those heads... well it wont matter much which one you pick if you keep the stock stall. it will be soggy.

lilman0883

alright well this car might be a daily driver so i was trying to keep it simple but thinking about a 270 magnum comp cam but i dont know what torque converter will be best

SpitotRs305

what are you changing your gears to? 3.73? 4.XX?

the magnum 270 i would say is a trade off between the two cams that have been mentioned... but gives up the benifits of both cams. loss of lift over both cams less duration and softer ramp rates than either of the XE cams which means less power... and for about the same cost... oh and you would still need a stall cant get away from adding an extra 33 ci.

Screamin82 Z28

For a daily driver I would lean to the XE268. I have run both the xe274 and 268 in my car with a T-10 and 3.73s and I decided that the extra 15hp at the top wasn't worth loosing it at the bottom. Now only you can make that choice, but for a daily driver I would likely go a size down if you are looking between cams, as 10-15hp at the top isn't necessarily something you will feel seat of the pants. It only shows up on the dyno/track, but bottom end is something you will feel.

As for how the 350 and 383 act differently it is not so much the cubic inches gained that has an effect on the cam so much as the stroke. With the longer stroke it in essence lowers duration. A good rule of thumb is if you were looking at 224/230 @ .05 for a 350, you would look for a 230/236 for a stroker and expect them to act the same.

Also in your case I would go with a longer exhaust duration (not the magnum cam). If you have high flowing heads (ports flow closely intake and exhaust, like afr) and a good exhaust (long tubes, high flow cat, dual or single 3.5") the best pattern is an even lobe set. However if you are running lower end heads (vortecs), shorties, and 3" custom exhaust to flows, (<---me) the longer exhaust duration is a good thing. Lets face it, how the exhaust is run on these cars is not ideal.

SpitotRs305

perhaps you could elaborate on the theory behind this statement? always looking to learn.

Screamin82 Z28

The theory here is "leverage". Think of it like this. Picture your crank being like a wrench. If you are trying to loosen a bolt and you have a short wrench, it's going to be pretty hard to break it loose because you don't have enough leverage, but once it is loose, you can turn that short wrench pretty fast and remove that bolt quickly. Now, if you get a longer wrench, you'll be able to break that bolt loose pretty easily but once it's loose, it's pretty hard to turn that long wrench very fast. So it's kind of a catch 22 situation. Cranks work exactly like that. A longer stroke makes for greater leverage which equals more torque. A long stroke acts like long wrenches, making it easier for the engine to pull a heavy load but in return, it can't spin very fast because of the reciprocating mass. A short stroke makes an engine rev fast because of less reciprocating mass but it's like that short wrench, it's makes it tough to pull heavy loads or make much torque being that there's less leverage.

So long story short, more high reving hp from a standard stroke. To make up for this lack of top end people typically put in bigger cams, a higher flowing head with bigger ports, etc.

SpitotRs305

Sorry that doesn't explain how stroke length alone decreases effect of camshaft duration...

Clearly the information I was looking for... Not the basic principle behind stroker engines

Screamin82 Z28

What I was trying to say is with the same cam and a longer stroke because of the leverage and greater mass of the 400 crank the operable RPM range drops somewhere around 500. So if a cam were rated for a 350 with an ideal operable range of 2500-5800, with a stroker and the same cam that range would be 2000-5300 power band. It doesn't actually decrease duration physically, it does however lower the operating range the cam has on the motor. More on bottom/less on top (acting like less duration), which is almost exactly what caming down does. I'm not sure how else to explain it.

A good example would be my friends 1996 TA LT1. He stroked it keeping the same cam utilized with his first build. His peak HP on the 350 was at 5800 and after stroking it dropped down to around 5350 with the peak torque coming much earlier than that. He thought he had too much cam for the 350 and with the 383 (with the same cam) it was far more he felt it to be a good match and very streetable. Due to the increased torque and bottom end power.

Orr89RocZ

iTrader: (20)

Stroke and overbore increases cubes. More cubes = more cylinder volume. More volume to fill with air means one of 2 things, or usually both: 1) need to hold valve open longer to fill the new cylinder volume for a given valve lift. This means more duration. 2) increase lift to allow more air to pass thru for given duration. This can work but increases stress on valvetrain due to fast opening ramp rates requiring more spring pressure.

So most tend to do both, increase duration and lift.

Mass of rotator has nothing to do with it. Piston speed does sorta but you can have lighter stroker cranks than stock cranks

SpitotRs305

So by the logic of stroke not CID... Then any cam will act the same in a 305 as it will in a 350... I think not.

Orr89RocZ

iTrader: (20)

Exactly, its more based on volume/displacement. Stroke and rod length however do change things when comparing different motors of same displacement. Rod length can change how piston moves during stroke, basically the dwell time at tdc and bdc. Small changes in dwell time can require slightly different valve events on cam.

4" bore 4" stroke 400" motor should require different valve events compared to a typical 4.125" bore 3.75" stroke 400" motor

Screamin82 Z28

I'm not trying to start a fight here. Everything comes into play when choosing a cam. CID, stroke, heads, CR, exhaust, etc. If you don't agree with me, then please explain yourself. How does 33 CID, add so much low end torque, and steal from the top end of a motor if stroke has nothing to do with it.

I believe my explanation of why a stroked motor (about 5-6 posts up) shows exactly why a larger crank (connecting rod journal farther from the centerline) adds low end torque while stealing power from the top.

All I am trying to say is CID and Stroke both have an effect on where the power is in a motor. Not once did I say CID has nothing to do with it.

TTOP350

iTrader: (8)

I don't think it "steals" power from up top.
Everything comes into play when building a motor. Take my 400 EFI stroker, it makes a buttload of power everywhere and spins up to 8k rpm.
Cam, heads, exhaust an intake really wake up any size motor.

Screamin82 Z28

Agreed, by steal I am referring to a 350 and a 383 with identical cams and where the power band would lay out. Not kick *** ones that rev to 8 grand! Got a dyno chart for that motor, I'd love to see it.

firefighter736

I will never put another flat tappet cam in anything I own. Definitely costs more but the time/frustration saved is worth it.

lilman0883

So with those cam choices what torque converter should i get. Also what about my stock heads, with stock valve springs? Because these cams come with kits with springs, so do they fit my heads? Should i not go with the kit?

lilman0883

So with those cam choices what torque converter should i get. Also what about my stock heads, with stock valve springs? Because these cams come with kits with springs, so do they fit my heads? Should i not go with the kit?

DeltaElite121

holy thread necro... by the OP no less.

lilman0883

What is OP?

DeltaElite121

OP = original poster (you).

2 years is a LONG time to not have started a build, lol.

apie2546

Some of us take time to have enough money lol

Probably would have been better to start a topic with what you know now

lilman0883

Ya its been a while i bought a house and had a honeymoon to pay for haha. So im starting where i left off, im about to start clearencing the block lm Still unsure which cam to use, but i want to make a big order and try to get a lot of the parts i need. So thats why i asked about springs, and torque converter

DeltaElite121

PM me what you need and I'll see what I can do to save you a few bucks.