Hello!

My -78 L82 is toast. I can use block, crank and rods but rest need to be replaced. Car has a 5 speed and 3.55 or so axle ratio. Usage is street with occasional track day on road race track.

I have two possibilities: stay 350 or punch it to 383. In either case the engine would need to be a stump puller with max rpms around 5500. I would like to use an Edelbrock Performer RPM Air gap manifold, 600...650 carb, Hooker Super Competition headers and compression ratio around 9.5:1.

My questions at this point are as follows:

1. Should I get AFR Eliminators 180 or 195 with CNC option for the 350 and 383 respectively?

2. Which camshaft would you suggest for either displacement/head combo - I would prefer to use a hydraulic roller cam?

Your advise would be highly appreciated.

 

Do yourself a favor and go ahead with the 383. I just installed a rebuilt, slightly modded 355 in my '75, and wish I had gone the extra mile and done the 383 instead.

 

The 383 is a real good chioce if built correctly. You just have to pay attention to detail!!

Here are some links on some 383's we built.
http://www.chevelles.com/forums/show...highlight=DYNO

http://www.chevelles.com/forums/showthread.php?t=236517

 

Thank you for advise. So it would be 383 with AFR 195 Eliminators with CNC option. I take it the AFR 180s are too small for a 383?

What about camshaft? As I mentioned the engine would need to be a stump puller ie. I want the power peak around max. 5500 and as much torque as possible as low as possible. How would Comp Cams XR270HR or XR276HR suit my wishes? Or would they cause a mismatch? Suggestions would be very welcome.

 

AFR's 195cc heads (cnc) are a good choice. i've also heard things about the 210cc option. comp cam's is also a good choice, i love 383's!

 

Any comments/suggestions on camshaft?

 

You are getting great advise! Just stay away from big numbers! The 270 cam is great and I would go with 180 heads. I you go to big low end will sufferBeen their done that it sucks in a street car.

 

I think the 276 or the 282 would be a good match for a 383. You want the 195s on a 383, they are not too big as you will need the flow to feed the 383. Whether or not you spend the extra cash on the full comp porting is your decision. A 600-650 carb isn't big enough, you'll want a 750-850.

 

If he was revving over 5500rpm I would agree

 

One can't have too much carb, but they can have too little.

 

If you have to machine or replace the crank on overhaul there's no reason not to go 383 - especially given your goal of torque vs. HP.

Your budget is always a good place to start - your heavy right foot tells you what you WANT, your budget tells you what you can HAVE

Given that you're after a hydraulic roller (great choice) and are replacing your entire rotating ***'y you may want to consider building from a factory roller cam block - these are readily available and you can almost certainly reuse all of the factory roller cam parts (retainer, spider, lifters). Compare this to the price of a retrofit roller kit - and factor in that these blocks typically show little or no bore wear.

The cam and head decision need to be made together, but overall you're in the right zone with hydraulic roller for your RPM range, and I agree that 180-195cc heads are the right choice unless you plan to go VERY BIG on the cam and then a 210cc or larger head is needed. Cam is driven by usage and configuration - so make a pick there and match the head. Too-large ports makes for a dog at lower RPM - counter to your target. What transmission and gears are you running?

The Performer RPM is counter to your goals as it shows no gains until > 5500 RPM...and you're planning to make power below that. Consider either the Performer or Performer EPS.

Carb selection is always a spirited discussion. You can definitely over-carb an engine, losing mixture velocity and driveability. For a racing engine, different deal - we only care about 0-WOT response, but for a street engine a 650 vacuum secondary is fine for the 195cc heads, moving to a 750 if you're going big on the cam and matching heads.

Design is an interative process - take a first pass at matching up the pieces and see what you come out with I'd be happy to run some DD Advanced sims for you if you're interested - just PM The thing to avoid here is building something so mondo that it's just no fun to drive.

 

the 180's would be more than enough! especially if he is not going to spin higher than 5500. if you go bigger you will loose a some low end, and never pick it up because you are not winding the moter high enough. if you are going roller teh motor will never spin higher than 6500 no matter what cam you put in it. 750 carb is more than enough as well. for 383...you could run the 650 on the 350 too. I run a comp cams extreme energy 282 in my 383, edelbrock e-tec 200 heads, 750 demon, 2400 stall converter, 3.55 rear gear. the car runs like a raped ape, i have not had it on the dyno. but i think i would have made a little more low power with the 170's. my car def needs the stall converter.

 

Since you will be replacing so many parts, you might as well upgrade to HR cam. I have the 270 HR in my 355 w/TFS heads and Air Gap. It is a little soft just off idle then is has monster mid range. The top end is weak due to stk Rams Horns and beat up exhaust. 280 rwhp/315 rwtq
I'm thinking the the 180s Comp ported will flow about as much as 190s w/o porting. That should be more than enough cfm. I can't see you needing more than 650. Don't leave anything on the table, get you carb built by some pros. JMHO

 

FWIW, I did a quick DD Advanced run tonight for a 383 w/5.7" rods, 10:1 CR, AFR 195 Street heads and the CompCams 12-423-8 (XR270HR) w/650CFM carb, high-flow dual-plane manifold and small-tube headers with mufflers.

Results were 438HP@6000 RPM and 455TQ@4000 RPM. TQ was above 400 from 2500-5500 RPM. The curve is a little outside of your desired powerband.

A 750CFM carb made no difference.

Advancing the cam 4 degrees reduced power somewhat to 429HP, but moved the peak down to 5500 RPM. There was a very slight gain in TQ with a 458TQ peak at 4000, and the curve was above 400TQ from 2000-5500 RPM. Generally you're best to look for cams with the desired advance ground in, and I'm confident CompCams has one off-the-shelf but I didn't look much further.

Moving to the 12-243-8 (XR282HR) cam produced 446HP@6000RPM and 449TQ@4000. The curve was significantly more "peaky", not moving above 400TQ until 3000 RPM. This is all pretty consistent with expectations. The heads increase in flow right up to .600 lift, but I think with a cam that would really take advantage of the heads you'd have a dog on the street.

I tried a set of AFR 210 Eliminator Competitions since I had the flow files and didn't see any difference until above 5500 RPM. The drop-off in power below 4000 RPM was pretty dramatic.

The "accuracy" of these types of simulators is always suspect, but I've worked hard to build good flow and cam models and had an opportunity to do some engine/chassis dyno verification of a few of my builds and been right in there. Take it for what it's worth

 

Billa: I forgot to mention that I have 1.6RRs. The cooler temps alone were worth it for me. What would they add?

Ricisan

 

Well, there are two aspects: every .1 increase in rocker ratio increases duration by about 2 degrees, and the lift increases by x 1.067. I can run another DD, but frankly the net increase will be trivial.

Cooler temps from a 1.6RR would be a benefit I haven't heard of before...?

 

Billa: When I went to 1.6s, I got a smoother engine, the sweet spot went up 200 rpm and the overtaxed cooling system w/AC on, was able to handle fwy w/o running on the edge on a hot summer day!
I can't say how much hp I gained.
I would think AFRs could use the extra .030+ lift? I could see a weak flowing head unable to use the extra lift, but the AFRs use .600
and those cams are short of that. I would think they would be worth 25-30 hp?
I can't wait to see what I gain w/headers and new exhaust.


Ricisan

 

Thank you people for comments and PMs. Special thanks billla for the simulation. Now I have more information to consider.

BTW, is it normal that the figures between Dyno2003 and CamQuest differ so much from each other?

 

The only thing I have heard of is that roller rockers will supposedly cool the oil temps down a little.

 

In my experience CamQuest is WILDLY optimistic.