Thread: 383 questions

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Hello all,

I'm new to this forum as you can probably tell,
anyway i am in the process of building a 383 stroker for my caprice coupe, the short block is a 4 bolt main, scat crank and rods and speed-pro flat tops, was told with 64cc heads the CR would be 10.2:1 and with 72cc it would be 9.1:1, i will be using a set of of edelbrock performer RPM heads that are 70cc, hoping that would make 9.5:1, can i run the 64cc heads and still use pump gas? i havent bought the heads yet so i can go either way, my next question is about a cam, i was told by comp to use the xe268 that has 224/230 dur@050 .477in .480ex, and the guy who owns the speed shop here says to go with the xe284 that has 240/246 @050 and lift is .507in .510ex, both have 110 lobe seperation, what cam do i go for? this car is not going to be a daily driver but will be driven almost always on the street (weekends, cruises, ect), the car does have PS/PB and A/C and i would like to keep them, would even consider running a vacum canister if need be, i just dont want to get it to the point where i have to work to drive it, but i also want as much power as possible (can i have both?) any sugguestions would be very helpful

Hey Machu10,

You should have no problem running pump gas with that compression ratio combo. You can stretch up to 11:1 with 92 octane. You may have to back off your timing a little, but with less than 10:1, you should be good.

Regarding the cam, you could contact one of the big cam mfg's and tell them what you want to do. They will ask a bunch of questions like RPM range, vehicle weight, tire size, etc... and they will be able to recommend the best lift/duration/lobe sep for your needs. Or, if you have a program like the desktop dyno, you could profile your engine and plug in the two specs to see which gives you what you're looking for (i.e.: Torque or HP at a particular RPM range).

A few points about the 383...maybe you already know this so ignore if I'm redundant:

1.) In a 383, you bring the stroke closer to other moving parts. Remember to clearance your rod ends and bolts to make sure they don't hit anything...like your cam!

2.) You may want to consider a reduced base circle cam to give additional clearance. If so, this will change your pushrod length and require to you to properly size them.

3.) Regarding the cam...the "general rule" about lift is stay below .500 for a street vehicle. Most factory springs can handle this lift. When you get taller, you run into things like coil bind, not enough pressure, etc... Regarding duration, that's what you really have to watch when it comes to clearances. Depending on what piston to valve clearance you have, longer durations run the risk of hitting the piston. If you don't flycut the pistons, you will need to watch that valve opening/closing to piston clearance very closely. Remember to mock up your cam install to check these clearances.

Good luck!

tj

Thanks tj,

I will make sure to check the piston to valve clearance, and all others for that matter, even though the shop building the short block says they do all that, a little extra checking can never hurt,

Edelbrock say the heads will handle up to .525 lift easily, so the lift of the XE284 shouldnt be a problem, i just wonder how rough the idle will be? comp cams tells me that the specs show the cam as having a rough idle and vacum will be marginal at best, but they also say that thats in a 350, my speed shop/engine builder tells me since the cam is going in a 383 that it will be smoother? I dunno? i sure would like to hear from somebody that has a xe284 or something simular in a 383 to get there opinion,

Thanks again for your help,

Mach

My main question would be "carbed, or injected?"

Im running a 383 with a CompCam 280 (I think they changed the number a couple of years ago and we built it in '98). I know it has over .500 lift and it sure sounds cool. The biggest issue I had was getting a chip burned so this rumptedy-rump stick would not load the tailpipes with too much fuel due to the duration being so long.

As for my suggestion, I would go for the 268 if you are going with efi and the 284 if you are going to carb it. The 268 still has enough sound to get attention but enough performance and vacumm to not be a pain if you go with the fuel injection. I know thats what I would do if I did it over again.

Thanks for the input troy,

I am gonna be using a carb on the engine, Right now i am thinking of going with a speed demon 750 and a performer rpm intake, i havent heard any bad things about the demons and they do look pretty cool too! lol


Mach

This probably explains why your engine guy is recommending the 284. Again, being carbed (and like the demons too, Bary Grant knows his stuff) I wouldnt see a problem with the larger cam. Just depends on what your after.

If you are looking for gas mileage, the 268 would be smart. But if your like the most of us horse power freaks, the 284 shouldnt be too big and will give you the head-turns when you crank it up.

Anoter helpful point, make sure "you" order the cam and springs together. I let my engine builder supply them and he didnt buy the matched kit like he promised. He built a kit with what he thought would work. After 3 different coil bind failures, I called CompCams and ordered the correct springs and had to pull the heads to machine them as the the springs for that cam are much larger in dia. Ive never had any issues since and it runs like a champ.

Mine dynoed at 402 with heavy rains (high humidity = low hp). So with the injection it was limited by the air intake design of the manifold. It should be good for an easy 10% more with a carb like your demon your talking about. Ive got ported and polished Brodix heads so you might have to add that in to estimate yours accurately, but you should have no problem getting 425-450 horses with the 383.

425 to 450hp souns good to me,

i was just checking into the AFR180 street head with compitition porting, a few of the mags have tested them, and even with small 180cc size they flow better than most 200cc heads, did a little playing them on desktop dyno, shows about 20 more hp and over 45ftlbs more torque over the edelbrock rpm heads, dunno how accurate dyno2003 is but its showing 440hp@5500 and 484tq@4000 with 10:1CR, but it dont show me an option for running roller rockers dont know how much of a diff they will make?

Mach

I would say that software guess is fairly accurate. Mine posted 481 ft/lbs torque at 5200 rpms. I am running the rollers and Im sure they help but dont know how much. Nevertheless, you shouldnt have a problem getting the horses and torque you are looking for with this combination.

I still think either cam will work for you. If you are making a daily driver, the 268 would be my pick. But if this is a weekend cruiser, the 284 should be a kick. I checked the CompCams website and the 284 is what they replaced mine with. And it rocks as long as you have the springs to match the cam.

the car is gonna be mostly for weekends, maybe a few short road trips of under 150 miles to shows, can i ask what kinda car you have your 383 in? and how heavy is the car? and if your running an auto tranny how much stall you got? sorry for all the questions but i am fairly new to building cars, and i was thought that the only stupid questions are the ones that dont get asked,


Mach

The 383 is a good stump pulling motor, you will be happy with it. Plenty of my friends run them and get some really good horspower out of them. I opted to try something different and went the other route, a destroked 400 using the 350 crank, I must admit the 383 is a much better street motor due to the torque.
10:1 isn't a problem with the 93 octane pump gas as mentioned earlier. I'm managing to run 11.5:1 on pump gas now, but your camshaft makes a difference on how much static compression you can run in a motor and still run pump gas, yours should be fine. Remember too that the more cam duration you have you really need more compression to make the motor work properly or you can loose bottom end torque. So I would say if you go with the larger grind go for the higher compression.

The 383 is in this 34 Ford Sedan pictured on the left. It has a ZF-6 speed and 34's weigh around 2800-3000 pounds depending on how much metal they have. I was lucky to inherit this one from my dad who bought it in 1965 so it weighs around 2900 lbs. It gets great gas mileage due to the 6 gears. With 4.11s and in 6th, it only turns 2300 rpms at 100 mph. 6th is a .49 gear so I dont even get down off the shelf unless Im cruising over 80 mph.

I use the car as much as I can (14,000-20,000 miles per year) so I would go for the bigger cam too. If your only going on short trips, you will smile the whole way knowing your running big lobes. I do and don't even blink at a 1,000 mile trip. In fact, I love 'em!

Like I heard a smart rodder say not too long ago, "If you don't drive 'em, you might as well just hang 'em on the wall for everyone to look at!"

nice ride troy!

i agree, a car should be built to be driven, I have a 39 cadillac lasalle and a couple other old caddys that my grandfather left me the 39 hasnt been started in over 20 years so the motor is locked but it is super solid as its been in georgia all its life, that car is gonna be next project, i might try to do a northstar in it? i just noticed that your in fort worth, i used to live in lewisville and i have a bunch of family in the DFW area, we just might run into eachother down there? i travel to TX often, and since my daughters are getting married july 7th and will be moving to houston, tx will kinda be my stomping ground as i plan on helping them as much as i can to get settled,

thanks!

That Northstar would work great in the LaSalle. Get'er runnin and we can meet up at the Nats.

I am never surprised how small the world is.

I run pretty fast with my job, but if I'm in town and you need help, just give me a shout.

Hi guys,
Sorry I'm of no help with the cam question but I have a question specially for troy:
You said you get good mileage out of your 383. What mileage would that be? I'm just curious because I have a 350 and I get quite bad mileage out of it. I run a stock cam, can I get better mileage out of a different cam? Which one? Would just like to know if you can help. thanks a lot!