Hi guys.
I know this is an old question, but I feel every build is diffrent and what people are looking for in a motor is diffrent. So this is what i have so far.
79 Vette, restoration in progress.

4 bolt Block
Eagle Cast crank and rods. (To be balanced by local machine shop)
Speed pro -12cc dish pistons, advertised CR 9.9:1 / 64cc heads.
Edelbrock E-Tech 200cc heads with 64cc chambers. p/n 60989
Edelbrock RPM Air-Gap Vortec Intake, 1500-6500 RPM Range.
Edelbrock EPS 800 Carb. p/n 1413 (not the best choise, I've been told, but will do for now.
MSD Ignition Kit. p/n 121-85551K

I am going with a retro hydraulic roller cam, but the question is which one...

For Rockers I was hoping for 1.6 on the intake and 1.5 on the exhaust.

This motor will be mostly used for street driving with maybe a few runs at the local track. Low end torque winning out over hp.
I would like a fairly lumpy idle, keeping in mind I'm running power brakes, so vaccum is an issue. I'll be running a rebuilt 2004R and a stall which I hope you guys can also help me select. My rear end has also been rebuilt with hardened side yokes with 3.55's.

If someone with a DD wouldn't mind running some numbers.... I'd be really greatful.

Many Thanks
Clyde

 

-you could easily bump up the CR with those heads
-convertor stall is largely determined by cam specs
-what size headers and exhaust will you be using?
-total cam lift needs to be within valvetrain specs
-remember that more cubes tame cams...ie: a cam that is "big" in a 350 will be much tamer in a 383 or bigger

I am running a Comp XR-282 Hyd Roller cam in my 406 with 1.6 rockers on both valves, 230/236 duration and 510/520 lift (544/555 lift with 1.6 rockers) and although it is fairly lumpy, it still runs all my vacuum and is very streetable.

 

Thanks 7t2vette.
I'll be running hooker ss side pipes, not quite sure of the tube size right now.
Since I first read your reply,I have been trying to find the max lift for the valves on these heads, but as of yet, no luck.
I'll be getting the block decked when I get the rest of the machine work done, so my C/R may jump a couple of points.
Thanks for the input

Clyde

 

Find the specs for the valve springs so you know what the max cam lift you can use is. Also helps to know the flow numbers for the intake and exhaust ports of the cylinder heads to help decide what lift you want to use.......there is no sense in having a cam with 600 lift when the intake ports max flow is at 550 lift for example. Forgot to mention that I am using a 2500 stall in my TH400 with that cam.

BTW, there is a very active Canadian section here:

http://forums.corvetteforum.com/canadian-events-97/

 

If you have an efficient 9.5 inch lockup TC you can put in lots of stall.

I had a 750 DP on my 383 and I always thought about installing a 650 to make it instant on with my single planes.

I originally had a 3.55 gear with my 700R4. You just need to see how it would work for you.

For 9.9 and 383 a 230/238 Crane HR would be about the minimum cam to use

 

Clyde, your thinking here is pretty darn good

Max lift and other specs are at the link below; .575 for your heads.

http://www.edelbrock.com/automotive_...head_specs.pdf

For cam selection, we start with the flow the heads will sustain:

http://www.edelbrock.com/automotive_.../flow_data.pdf

We can see that there's not a lot left on the table for flow after about .500 lift - so we don't need to go nuts and that's a perfect lift for a mild street 383 IMHO, there's no reason to mix rocker ratios - the reverse of that was an old racer trick to compensate for single-pattern cams and headers. Cam design has come a long, LONG ways since then.

If you really must have a "lumpy" idle, consider one of the CompCams Thumpr cams - they have a profile that provides the overlap that gives the sound without having the rest of the racing profile that usually goes with it. We get a good street cam that sounds like a racing cam. IMHO, you're giving up power for sound...but it's worth thinking about if it's important to you.

The carb is way, WAY too big - and I think you'll be disappointed with low-RPM throttle response - but that's your call.

I made a DD Advanced run based on the CompCams XR276HR cam, which would be about as far as I would go.

 

Here's a list of parts for the 383 that I just built for my '81 project. I'm also using the 200r4 but with a 3.73 gear. The converter I went with is 2800 stall with lock-up. Not up and running yet as I'm still changing bushing/brakes/etc. Should be fairly lumpy and really strong.

383ci
Flat-top pistons with 4 valve reliefs
9.8:1 verified compression
487 chevy heads professionally ported with 2.05"/1.60" valves
Crane billet HR 234/242 @ .050" with .539"/.558' lift on 112 lsa
Edelbrock RPM intake
Speed Demon 750 carb
All MSD ignition & distributor
Headers, 2 1/2" duals and Flow 40s

 

Thanks 7t2 vette.
I appreciate the tip to the canadian section. I have been visiting this forum for 2 years and knew nothing about it.
I'll try to find the specs on the springs and I know popular hotrodding did an article on the intake, comparing it with others on the market and were pretty impressed with the numbers from a big cam and a small one.

I was looking at the specs for 3 of the recomended cams that Edelbrock for these heads and they all require stock rocker ratio.
I'll do a little more research on the flow rates today and get back to ya.
Thanks again
Clyde

 

Billa
Thank you so much, I really appreciate the time and your opinion. I purchased the top end kit with the misunderstanding that bigger was better. In the last few months i am learning that is not the case. What carb do you recommend. I would like to go with a Holley D/P. Which one and part number do you think best fits.
As far as the lumpy sound goes, the misses and the son love that throaty rumble, and i must admit I like it as well, but I wouldn't want to give up any HP/TQ. It's costing too much to get it.

I have checked out those thumprs, but didn't know what I would be giving up on HP/TQ

Great time to do a little experiment....

"***** THUMPR" 12-601-8 Grind # 291THR7
Advertized Duration: Intake...291 Exhaust....311
Duration @ .050: Intake...235 Exhaust...249
Valve lift @ 1.5:1 Intake.... .522 Exhaust.... .509
Lobe seperation: 107*

If you get a chance, run it with the same senero as you did on the last one. Check to see the power loss.
Many thanks
Clyde

 

Clyde, follow this link and download the free Comp Cams Camquest program. It's like Desktop Dyno, and it is already loaded with all Comp's Cam profiles:

http://compcams.com/Camquest/CamQues...dInstaller.exe

You can read about the program here:

http://compcams.com/camquest/default.asp

I really like this free program. All you need to do is plug in all the specific specs for your build and it will generate an estimated HP/TQ graph for you.



I just checked Edelbrocks specs for those heads by following the links provided above, and it looks like with the springs that the heads come with have a max cam lift of 575, but the intake ports max flow is at 700 lift! Weird! I wonder what's up with that?!?!

 

IMHO, the CamQuest program (an old version of DD) is WILDLY optimistic. Just one guy's opinion.

 

Is there a big difference between the two? I used to have DD a long time ago, don't know why it's not on my computer anymore or what even happened to it!! I'll have to get my hands on a copy of it again, I'd like to do some comparisons between the two programs out of curiosity.

 

The "accuracy" of DD is completely based on the accuracy of the head flow models and camshaft profile models. I've built a couple of hundred of each.

CamQuest uses "standard" models for heads, etc. and IMHO the cam modeling is incomplete at best. In my experience, as noted, the diffferences can be huge - I've run a DD Advanced and seen modeled 360HP, and seen the same "model" show 500+ in CamQuest. Based on experience you can tell which one is more reality

 

Actually, in CamQuest you can enter all the flow data for your cylinder heads or choose from a standard list. You just click on the "Port Flow" button in the "Cylinder Head" section and enter all your specific data. You can also use the same .DFW and .FLW files that you use in DD. You can choose from a number of different .FLW files for several dozen sets of cylinder head data that come with CamQuest if you click the "open" button after clicking the "Port Flow" button.

Maybe you were using an older version of CamQuest when you tried it out. I am using the latest version 6.0.040508.

Sorry for getting a little off topic here Clyde! Everyone has their opinion, and I feel CamQuest is a decent program when used correctly. As with DD, the estimated output is only as accurate as the data that you input. You have to take the estimations with a grain of salt, because it is an estimation after all. For what it is worth, I entered all the data for my old 406, and the estimated output was within 5% of the actual real-world engine dyno results.

 

Guys thanks for the input. No doubt that both simulations are off by a certain degree, and that any HP/TQ values you get are only that, a simulation. I do think though, that if you use the same motor specs and all you change is the cam chacteristics, then you should be able to see the power gain or loss from one cam to another. I played with the camquest program a little, my heads wern't listed so I used the port flow button and inserted the flow numbers from the link above, 0.100 lift to 0.700 lift, valve size, etc. I was supprised to see that there wasn't a block to enter the combustion chamber size and piston type. Anyway, my intake wasn't listed either, so I just picked a duel plane with high flow.
The most power and torque was with the :
12-450-8[10] 286HR Hydraulic Roller Lifter 2500 to 6000 RPM Using a 2500 + stall.
HP 501.3 @ 6000
TQ 485 @ 4500
Comments: Rough Idle, limited Vacuum.

The 12-432-8[10] XR282 RPM 2200 - 5800
HP 492.5 @ 6000
TQ 484.7 @ 4500
2100 t0 3100 stall.
Comments: Needs intake, heads, 2000 stall and gears.

The 12-423-8[10] XR276 RPM Range 1900 - 5600
HP 490.7 @ 6000
TQ 491.0 @ 4000
2100 to 3100 stall
Comments: Performance gears, choppy idle, street machine, 2000+ stall

The 12-422-8[10] XR270 RPM Range 1600-5400
HP 479.3 @ 6000
TQ 498.9 @ 4000
Factory stall
Comments: Performance application with stock converter. Noticeable idle.

The 12-430-8[10] 280HR RPM Range 2000-5500
HP 490.6 @ 6000
TQ 490.0 @ 4500
2100 to 3100 stall
Comments: High Performance street, aftermarket intake, headers and stall. 3.40 t0 4.10 gears. Mild rough Idle.

There are no hydraulic roller thumpr cams listed in there matches so I can't do a comparison.

I know these numbers are high, but it gives me an idea of what each cam does, but still leaves a lot to be desifered...

Thanks for all the info that 7t2vette and billa has given me. I'll keep checking to see if anyone else has any input.
Thanks again.
Clyde

 

Ya, it doesn't calculate your CR for you, but if you know your deck height, gasket thickness, piston cc, and combustion chamber size, you can use one of several online CR calculators to find it and then just enter the CR in the spot provided in CamQuest.....at least thats what I do anyways.

I was surprised that the Thumper line of cams wasn't included in the profiles, I even checked to see if I had the latest version, and I do. Then I changed the usage to #6 - Auto - Series Street, Some Strip, Mild-Rough To Rough Idle and they appeared in the profiles.

You'll drive yourself nuts if you play with these simulators too long!

 

I've calculated my C/R with the calculator and with .040 x 4.125 head gasket and 0 deck, it's about 10.2:1.
You're not kidding about the being driven nuts part,
These all describe me today. Well I'm going off shift now, I'll play with it some more tomorrow. I'll check out that # 6 section tomorrow.
Thanks again
Later
Clyde