Well i'm researching 383 shortblocks, which means that i'll have a new base to add parts to. What i know for sure is that it will have 9.5 compression when it initially hits the road, with 76cc heads, but there is a possibility it will have smaller chambered heads resulting in higher compression. So i've been trying to find information on 383's with similar compression to see what carbs and cams they are running. I constantly see 383's coming in at 450-460hp with simple parts, but every cam used is different. The only problem i have now is that im running parts tailored with a 350, 600cfm carb, 1 5/8 headers, so i want the cam to be able to accomodate future upgrades, but also blow my current 350 out of the water.

I know the details are vague but any information you can give, combos that work, would be appreciated. Two requirements, it needs to be able to run good on the streets, this car is driven daily, and i dont want to go roller because frankly i cant afford to purchase a roller cam and lifters in addition to everything else.

Thanks

do you already have the pistons? If not, the compression doesnt necessarily need to by super high with smaller chamber heads. You can use dished pistons with the smaller chamber head, and depending on how much smaller the chamber is, that will dictate what size dish piston you need to make a compression that works. Anyways, if its an option youd be better off with some smaller chambered heads and a dish piston. My guess is that the 76cc heads you referred to are factory castings. One thing I would like to know is what heads you actually have, if anything good has been done to them, and would you consider an aftermarket head. I have some ideas for a camshaft, but what might work with one particular cylinder head can easily be a bit of a mis match for the stock heads. Another thing is what is your current drivetrain specs(tranny type, converter size if its an auto, and rear gearing). And, would you be willing to swap the drivetrain stuff if necessary? Finally do you have a budget? Id hate to reccomed a combo that completely smashes your budget and also doesnt run well with your drivetrain and whatever current engine parts(mainly heads) that you have now if you cant change those parts.

Well, the thing is that it's gonna be a slow around the bases upgrade path. I'm going to start with the 383 shortblock, and get her back on the road with the new foundation. My current budget is for the shortblock, and depending on what he has, maybe a longblock. I can't afford a set of aftermarket heads right now, i'm hoping he has a decent set of heads for a cheap price at the shop. If he doesn't ill have to stick with the stock 76's until i can upgrade. THe block is a "hecho en mexico" 350, not sure if ill be giving him the core yet, still have to work it all out.

I want to go with flattop pistons, that way even with these heads they will help make some power, and when it comes time for aftermarket heads ill go with a 68-72cc chamber to get a reasonable compression ratio.

The drivetrain sucks, but like i said, it wouldn't be upgraded until the budget replenishes itself.

TH350 tranny, not sure of hte convertor, depending on what the engine turns out to be i'll swap the convertor. The rear is your stock 2.76 10-bolt pegleg. Daily driver, so the gears aren't great for performance, but than again my current combo makes no low end torque so i really dont know what they are capable of.

We've talked before. I agree with Greg. I believe those heads are 75cc but that's not any difference. The valves are probably 1.94/1.5 and those did well in earlier cars. You should tell whomever you're buying the pistons from what combo you have and they should nail your CR needs pretty well. Flat tops with valve relief should get you in the 9.5 to 10.5 range.

If you're on a budget find some 400 rods and have them resized with new bolts. Buy an Eagle 383 cast crank int balance for 189 delivered to your door. Rebuild your 350 using 30 over hypereutectic pistons at 30 a pop. Use your heads just get new valve guides etc if you can. If not then just run them. Do get a new cam and lifters or use the cam and lifters you have making sure you number them and keep them straight. Otherwise you'll wear your cam down in no time. Don't mix new cams and old lifters and vice versa. You can find a 72-?86 lowrise alum manifold that will help for 50 or less. Pick up a 750 and get someone to help you tune it. That's the cheapest way I know how to do what you're trying to do.

When you're through with that project you'll be ready for a bigger one. Best.

I'm guessing a 274/276/284 is where i should be looking for a cam adv. duration, that seems to be it for most tech articles i see.

Also what should i look at for a convertor, im pretty sure thats an upgrade that i do need. Remember this is a daily driver, id like to match the convertor to the cam.s

Figure out what your freeway/highway cruise speed is, 70? 75? Then calculate the rpms at that speed with the tire diameter you run and axle ratio. Make sure you don't pick a converter above what your cruize rpm is or you'll heat up your tranny from all the slippin that'll be going on. JMO

I did some math for you assuming you have 26 inch tall tires. Assuming you have a tire that tall, and couple that with your 2.76 gears, it would take 2500 engine rpms to cruise at 65 miles per hour. Lets say you went for a 2800rpm converter to match whatever cam it is you use. Like baddbob was sayin, thats a recipe for problems. You are trying to cruise at an rpm that is below your stall speed(unless you cruise way higher than 65), and considering that the engine has to work fairly hard to maintain 65 miles per hour, it will stress your converter a good bit trying to maintain those high speeds. Thats what creates the heat and destroys a tranny pretty quickly.

It would be best to swap gears as well with the converter swap so the converter isnt worked as hard, but if that cant be done right now, than you have to work with what you got. Id go with about a 2400rpm converter at most cause thats a large enough stall speed to perform well and support a descent size cam, without being total overkill for those gears. Either way, even if you did swap gears right now still get a good tranny cooler. For a cam, look for something of about 222-224 degrees duration at .050 at most(roughly 268-274 degress advertised duration at most) in your 383 with roughly 9.5:1 compression. A cam like that will allow you to run a more mild stall converter(like a 2200-2400), and it will work ok(not good) but ok with your current gears.

This is still assuming that you will eventually swap gears though, cause although it can work out, thats not the best camshaft with a 2.76 gear. It would take a 3.55 gear to make it be real nice, and you could go for a 3.73 if you wanted a little more. Another thing with a cam like that is its a good size to run with a descent factory cylinder head. If you go too much bigger than that, you will either need to start with a good factory casting and port them pretty extensively in order to help a cam larger than that perform to its potential, or you will need some heads from the aftermarket.

Anyways, assuming you go with a cam about that size(Id say the comp XE 268 is a safe bet) and 9.5:1 compression, a high rise dual plane aluminum intake, a 650-750 carb(your 600 carb will work for now if thats all you got), and at least ported stock heads, you can muster over 350 horsepower with torque approaching 400ft/lbs. The power numbers could end up being higher than that depending on the quality of the cylinder head. Once again, a 2400 converter and a 3.55-3.73 gear is what you should eventually go with and you have a combo thats easily capable of mid 13's. It could definitely run about a 13 flat, maybe high 12 with a good tuneup and the right heads. As far as all these motors making huge horsepower with seemingly simple combos, I will beleive it when I see it. I wouldnt take the magazines word for it, cause I think either their editors, or the dyno is a little optimistic cause 450 horsepower isnt quite as easy as they sometimes make it sound.

Explain to me this 'cruising below the stall speed' thing. I've got a Vega 4-cylinder thet stalls the converter at 1500 rpm so I can cruise safely at 2000 rpm without the converter getting hot. If I swap out to a LS1 that stalls the same converter at 2500 rpm I can't cruise at 2000 rpm anymore? How does the converter know what the stall speed is?

ChirpO8,
Consider this Solid cam. from UD Harold/Lunati.
P/N 40199
Grind #01-TF80-TF72-1
Specs are:
ADV duration 267/275
.050 239/247
Lift w/1.5 RR .510/.530

I installed this one in my brothers 10-1 383
in '72 Chevelle with TH350, 3.55's and 26" tires
In full street trim has gone 12.54@ 108mph

If you're cruising at 2200 rpm at highway speed you don't want a 3000 stall converter or even a 2500 one.

Running a big cam is not going to help without changine the drive train or getting into a lot more CI.

A PG would help. A 3.73 rear end would help more with what you have.

There is no easy way around this without changing some things and spending some money.

If you can't afford to do things all at once then buy a 350 4 bolt. Then machine it. Then start adding what you want part by part as you can afford them.

Or look for a ragged out body with a decent engine, tranny and RE. Put the good stuff in your car.

That's the fun of doing this stuff.

Can you explain to me why some guys are running 274, and 284 adv. duration cams in engines like mine, except with heads? Your saying no matter what i do a 268 is the most i can run, even with gears, a convertor, and heads?

Is the converter something i should do? Your kinda telling me more bad things about it than good, what advantage will it actually give me with these gears?

It's not a matter of spending hte money, its a matter of i actually do not have that much money in the bank, if i had the money by all means id have a 12-bolt posi in there by now ;)

I tried to find any info on that cam you recomended chvl, but that part number brings up nothing on the lunati website, and nothing comes up in google. What advantage does a solid have over a hydraulic flat tappet in my situation? All i know is they need more compression.

I think i narrowed down the cams to either hte Voodoo 268, or hte lunati 401A1.

The cam is a custom recommended By Harold for my brothers combo, Which sounds very similar to yours.
The solid offers more duration @.050 and .200
for the same seat timing.

Maybe UDHarold could better answer your cam questions. Possibly steer you in the right direction.
All I can say is this cam in his 383 performs quite well with a tight(2500) converter and 3.55 gears. Slight lope at idle at 750. Works power brakes. Runs 12.5's @108
Would the voodoo 268 do that? it might...
Thanks,
Dave M

No, thats not entirely what I am saying. Its not that I think a 268 cam is the best cam for a 383 hands donw, but it seems to be in you situation. If you do end up getting good cylinder heads and the right gears and converter, you have the option to run the cam you want(as long as all those parts work well with the cam).

Right now though, you arent sure of the heads you will end up with, so we cant be sure if you will end up with good ones or not. Larger camshafts allow for better higher rpm peformance, but they hurt lower rpm performance(a large camshaft basically shifts the powerband). So whereas a stock camshaft would make power off idle to like 4500rpm, something like a 284 cam will make best power from about 3000-6200rpm. If you stick with stock gears and a stock converter, you will have a very hard time accellerating good cause of the lack of low end torque below 3000rpm or so. And, if you end up with heads that dont flow good, you wont be able to make very much high rpm power as well cause the heads might really limit the power potential over 5000rpm, yet that cam wants to rev over 6000rpm. Basically if it happens like that, you lose across the board.

Now, if you get the right gears and converter and heads, you have the option to run a larger cam and get very good results.

In your situiation lets say you got the 284 cam. The right converter for a 284 camshaft would be at least 2500rpm, and you could go with something that stalls at about 3000-3200 rpm to get the best results at the drag strip while still being able to drive it a lot. But, if you dont get gears right now to match that large converter, your tranny might not last long enough til you can afford the right gears. This is because a gear like yours will normally put the cruise rpm below 2500rpm, and if your converter stalls much higher than that, there is surely potential for excess heat and that kills a tranny.

Or if you get the camshaft, but decide to wait to get both the gears and the converter so you dont hurt anything(which aint a bad idea), you will have to deal with some sloppy low end performance until you can afford to make the gear and converter changes.

When you posted, you said you are getting the cam, and a set of heads but you arent sure which heads, and you can probably get a converter, but not gears right now. With that in mind, something like a 268 is a happy medium in my opinion cause it will work well enough for you that you wont be totally dissapointed with a marginal cylinder head, your gears, and a mild torque converter. If you went way too big on the cam and didnt do everything at once, something will suffer until you can afford to finish it all. If you go with a big cam like an XE 284, and it takes you say another year to get all the money together to get a new rear set up with posi and gears and also heads that flow well enough to support that cam, than you basically will have less than good results for a year. Im tryin to help you not overshoot things. There are a lot of cars on the road that sound radical, but they dont run like they sound. This is because many people usually over cam and over carb their motor, but they dont put all the rest of the pieces into the puzzle. That voodo cam is probably a real good option. It wont need a huge converter so thats ok, and it will run ok with your current gears til you can get better ones. So, it wont be terrible until you can afford the better stuff.

As far as the vega converter, Ive got a bud who builds trannies for a living. When he isnt working, he is racing. He also builds most of the trannies for the local guys in the area that race and they all get good results so I tend to agree with what he says about a tranny or converter. He too has tried the vega converters over the years as a cheap alternative, and he just dont do it any more cause of bad results. I also have a vega and considered running the 4 cylinder converter behind a small block. He said, if I go that route, and especially if it will be street driven, run two good tranny coolers for sure. He said the only time he really got em to last for a while is if if he was only bracket racing and the car was trailored to and from the track. during regular street driving, they arent an efficient converter by any means and they are being worked much harder than they are meant to and its hard to keep the tranny alive. Without an overkill tranny cooler system he said they never got em to last long enough on the street to be happy with. With two coolers and a deep pan and of course a good tranny to start with, he said it can be made to last for a little while, but still not forever. Now, the tranny coolers of today are probably higher quality than back when he was tryin this stuff out, so it might not be necessary to go with two nowadays. Either way, I wouldnt expect it to last real long still. I mean, a smaller diameter, more efficient aftermarket converter will still create heat and wont last if you dont keep it cool. So something thats about 30 years old thats really not that efficient, nor is it meant to be behind a small block, would be even harder to keep in check.

My example didn't use an old Vega converter but a $500 furnace brazed modern converter. If I put it in my poorly tuned 4-cyl Vega it stalls at 1500 rpm, so I cruise at 2000 rpm. How much heat does this converter produce?

I swap my 4-cylinder for a modern aluminum V-8 and retain the same drivetrain and converter. This new engine will stall this same brand new furnace brazed converter at 2500 rpm. I continue to cruise the car at 2000 rpm. How much more heat does the converter generate and why? How does the converter know what the stall speed is? Is there something magic that happens at the stall speed?

Converters basically react off torque. If you put it in the 4 cylinder, it wont generate a ton of heat cause it will never be pushed hard enough to stall at its maximum(or even close to it with the 4 cylinder). However, the V8 is gonna make much more torque, and it will push the converter higher. Its not a guarantee, but it is much easier for it to create excess heat. I mean, say you are cruising at 2000rpm and you try to pass someone, or you hit a descent sized hill or something like that. Really, reguardless of the cruise rpm(even if its above the stall speed) higher stall converters still make more heat than tighter converters do. If you cruise well below the stall speed, the converter can be loose enough that slight changes in load make the converter slip even more than it would if you were above the stall speed. that can make even more heat than they already do, so it can be harder to control the heat. Many things like gearing, engine displacement, vehicle weight, and all that other stuff effect it as well, so its not always a terrible situation, nor does it always work out though. Thats why its best to keep the cruise rpm and your converters stall speed close. If its over by a little bit, I wouldnt be too concerned but if you exceed it too much it can be a problem. Ive seen it happen on many occasions. I helped my buddy build a 400 pontiac for his lemans. At the time he put in a 2.73 geared 10 bolt just to get it on the road, and strapped some 28 inch tall tires on there. The tranny was a built up turbo 350 that he had been running for about a year with the other motor with no problems at all, and he bought a 2500-2800 converter for the new motor. I warned him, dont drive it too much with those big gears and tires with the converter until you get gears. Or keep it in second unless you are on the highway. Anyways, he figured it would be ok and it wasnt. It only took about a month before the tranny burnt up from too much heat.

I'm still confused a little. What happens at the stall speed that magically reduces the heat generated?

Well, i cant find the axle code yet, but it turns out its a 12-bolt rear, so now i dont know what gear ratio it is, its your standard GM CORPORATE 12-BOLT, but i cant find the axle code for my life, so the gear ratio is still in question.

Originally posted by onovakind67:
I'm still confused a little. What happens at the stall speed that magically reduces the heat generated? there is nothing magic about it, a converter will slip until it reaches its stall speed. if you are cruising below the stall speed of the convertor there will be excessive slippage which causes extra heat.

the number one enemy of an automatic trans is heat, and the extra heat caused by convertor slippage is transferred directly to the fluid, which will cook the fluid and the trans.

a converter will slip until it reaches its stall speed.

Would you be implying that the converter stops slipping at the stall speed? Does is lock up suddenly or something? How does the converter know when to lock up?

Its gradual, there isnt a definite point where its nothing, and then snaps to everything and puts all the power at once through the tranny. Actually, unless its a lock up converter, it never really locks up all the way. There is always some degree of slippage with any non lockup converter.

Lets say youve got a motor making 400ft/lbs of torque, and the torque converter company of your choice specs you a new converter that actually flashes 3000rpm of stall behind your motor. You can say that your converters flash stall speed is 3000. Meaning that when you nail it from a dead stop, it will push all the way to 3000rpm before it really puts the power to the tires. Under light throttle, it wont slip as much, so you might start rolling at 2000rpm, it wont take all the way to 3000rpm to really roll depending on how you are driving it. But, since you know that the converter is CAPABLE of stalling as much as 3000rpm, that tells you that if you are cruising below that rpm, there is potential for it to slip at lower rpms than 3000. It might not be slipping, but it definitely can be slipping if you know its capable of 3000rpm and you are only at 2000rpm. So, you dont want to put yourself in a sutiation where you are curising well below 3000rpm(in this example), cause depending on a few variables, it may slip enough that it does in fact create too much heat. Its not a definite yes or no, cause some converters will be more gradual than others, some cars weight more than others, gear ratios can be different and everything else, so you cant say for sure how the converter will act in your car. Since you cant be sure, its best to take the precuation and try to keep your curise rpm and your stall converter speed pretty close. To best do that, talk to the converter maker. Cause even if they tell you in the catalog its a 3000rpm stall converter, that too can vary depending on the whole setup so they can tell you best how the particular converter in question would stall behind your motor in your car, and Im sure they will have a good estimate of what is a pretty safe cruise rpm for their converter.

Originally posted by onovakind67:
a converter will slip until it reaches its stall speed.

Would you be implying that the converter stops slipping at the stall speed? Does is lock up suddenly or something? How does the converter know when to lock up? i should have said it will slip excessively until it reaches its stall speed. like greg said a non lockup convertor will have some acceptable slippage at or above the stall speed.

I'm still not sure how you figured out how a converter will slip more behind my 4-cylinder cruising along as opposed to my V-8 in the same car. What makes it slip more? Does it take more torque to cruise in a V-8?
I also have only seen one torque converter manufacturer make any reference to cruising 'part throttle rpm range' and for a 3500 stall converter they cruise at 2500 rpm. My Vigilante flashes to 3600 yet will cruise all day at 2400 rpm with no overheating.
This is not to say that you should just slap a little converter in and you'll be okay. Smaller converters have less fluid in them and produce more heat than stockers, so you will be well served with a good cooling system. You also get what you pay for in a converter, so a cheap Summit one isn't going to be as efficient as a custom made one.
I towed a trailer from San Francisco to San Diego and back with my 3600 stall converter and we had no problems at all.