79vetter

I have about 800 miles on my newly rebuilt '79 motor and in a nutshell, I'm disappointed. I just don't quite have the giddy up that I expected.

Here is what I got:

Rebuilt 350 engine : I re-used my L-82 Crank with Flat Top Hyper. Pistons. Bored over .020. Done by a reputable builder.

Comp Ratio - 9:6:1
New Vortec Heads - not modified
Gm Cam # 24502476 - Hydraulic Flat Tappet
New 476 cam is a bit smaller than Old L82 ... (new 212/222 .435/.460 112.5 lsa ... vs ... old 222/222 .450/.460 114 lsa)
New Performer Intake for Vortec
Q-Jet Carb rebuilt by Lars
I have rebuilt my distributor and have set it up for 32 degrees of total timing. I feel like it is tuned.
True Dual Exhaust-no Cats

I like acceleration and won't be driving high RPMs or top end. I also like a smooth idle.

I am not opposed to changing the cam. I heard that the BeeHive springs will allow more Cam.
Anyone have a recommendation on a Cam that would satisfy this need?

thanks

Scott Marzahl

You don't have enough compression to really start increasing cam durations, and as you do the power band shifts to the right. Are you sure of your compression ratio? What cc heads are the heads and the piston volume? Did you degree the cam when you installed it? Also what is the ICL on that cam? If its something like 109-108degrees I would just advance it 2-3 degrees and that will increase your bottom end. Beehives as far as I know only help with a few more RPMs before float. I would also take it to 36 degrees by 2,800RPMs too.

firefighter

My 2 cents....... Pull the heads mill them bump up the compression 10:1-10.5:1 gasket match all the ports. And get rid of the cam you should have at least gone to something comprable to the L-82 cam even bigger would've been more like it. Shoulda done a roller conversion. I built a 383ci for my old mans '65 C-10 that is putting out about 525hp and roughly 500ftlbs at the crank. I am at 11:1 compression (aluminum Edelbrock E-tec heads) with a HSR fuel injection set up (would never fit under the hood of a C3) and all roller Comp Cams valve train. All that being said I would bet with the right cam and those iron heads and that Performer intake (an RPM would be nicer) 400hp/400ftlbs is doable.

7T1vette

Is the throttle linkage and adjustment allowing your carb secondaries to open completely? You need to check the carb's opening capability by hand....and then with the 'foot' [someone in driver's seat pressing accel pedal full open while you check the butterflies].

larrywalk

Also, with a Q-jet carb, make sure that the choke mechanism is working properly. If the choke doesn't warm up enough, it will not release the secondary butterflies to operate. The lockout is on the right side of the carb and prevents the secondary opening until the engine is warmed up (choke is off).

BKbroiler

My engine, although it is a 383, is not too different than yours (see sig for specs) and it runs pretty well. My cam is 218/224, approx .465 lift. Other than that, you need 36 deg total advance, all in early. I have headers with full 2.5 inch duals.
My Vortec heads have the valve guide bosses cut to allow for extra cam lift,although I think that is required only over .470 lift.

Ironcross

You may try a few more degrees lead, but your down on compression and the ability to rev the engine much past 5500 effectively. At least a solid lifter cam of earlier years will get you past that limitation. Bee hive valve springs have been around for nearly 50 years or more and were not any good then. Build it like a 1970 LT1 if you want it to run like one...

firefighter

The 78/79 were that heavy? Holy ****. My Monte in HS weighed almost 400lbs less and it was a 79.

79vetter

To answer the previous questions, yes I have verified that the Secondaries are opening up. I think that Lars told me to run 32 deg. max for Vortec heads.
BTW- gears are 3.36 w/ original 4spd...

a1sensei

I can't believe no one is saying "more cam lift!" Good grief! I consider myself a conservative cam person, but I have less compression (9.1:1), higher gearing (2.87) and with a flat tappet cam with 462/469 lift, my car runs like a scalded dog!

YOU NEED MORE CAM!

Go with a Comp XE268H or if you really want to do it right, get a roller conversion.

http://store.summitracing.com/partde...8&autoview=sku

God bless, Sensei

firefighter

Uhmm I think I said that in my first post. But either way I agree.

Scott Marzahl

The stock Vortecs need some machining to run more lift, a XE268 is on the edge, a XE262 would be a more conversative pick as for lift and no machining. No mention of headers and with the 110LSAs that Comp grinds, headers would really help with the exhaust side of the Vortecs.

The Gm Cam # 24502476 was designed for the Vortecs with its longer exhaust duration than intake.

For a roller conversion, I'd buy different heads before spending the money on machining Vortecs.

fetorino

What does that mean. What is your intitial timing? What RPM are you all in at? You'd be surprised what a dog a poor ignition curve can make out of a motor. I also agree the cam choice may not be the best but start with the timing.

BKbroiler

If you don't want to listen to real experience, why are you asking? I have Vortec heads, a mild cam AND 36 degrees total timing, and my car idles fine and has run 12.80 in the quarter. I think you should go out on a limb and advance your timing. If it is detonating, you will hear it before any damage occurs.

Matt Gruber

yea
BK has a real hot car and his small cam proves your cam is NOT the problem. Where is the base timing? 16-17 should do it. CC did a build up with the 212 cam and made 348 hp w/ vortec 350.

79vetter

I appreciate all the advice from all. Initial timing is 17 and its all in by 2600 RPM.

Matt Gruber

what r u comparing it to? lots of new cars are quick.
u need some times on it.
what is the cranking compression?

QIK59

BK what is the cam you are you running ?

Thank you,
Jerry

bluedawg

If you were going to continue to run the vortecs I'd definately get them machined for more lift, or call comp and find out about the beehive springs. Bk's combo athough its a 383, sounds like it works great and doesnt have much more cam. What size stall and gears? It says you have duals, are you running headers.

Doug1

I'm kinda surprised you guys are comparing a 383 with a 350. I've had both, and there is world of difference in the power department, at least to me there is.
gm stock 882 on both also, only difference is 750 cfm carb on 383 and the 350 had a 600cfm carb, both rochester