Removing Performance? Need Cam Help...

[nico]

I have come to realize that I enjoy the stock 350 in my 88 Burban tons more than the 383 in my 84 C10. Is it really that bad to be thinking about doing away with nearly all of the performance parts it currently has... I will probably keep the headers, aluminum cooling system and MSD ignition components though.

I think I would enjoy it way more as just a driver that I can jump in and run to town, the junkyard or the dirt track without worrying about the current 7 MPG and questionable drivability...

1. Replace the Comp 280H (.480 lift, 230 duration at .050, 104 LSA) with a more streetable dual pattern cam that won't require my current stall converter. I still will need a small base circle cam to reuse my Trick Flow Pushrods.

2. Replace my Edelbrock Performer RPM and Demon 750 with a standard aluminum intake and 800 CFM Q-jet I already have.

3. Replace the TCI manual-valvebody Turbo 400 with a 700R4 and stock converter. I haven't decided to keep my Hurst shifter or go back to the factory column shift...

So far, everyone I have mentioned this to says I'm crazy... Any opinions or recommendations on a cam?

[vern350]

Nah, your not crazy. I've been thinking about the same thing, putting a stock/milder motor in my truck so I can drive it more without worrying. I currently have a 294S(.525 lift, 248 duration). Not sure on the cam question as I'm looking forward to replies as well.

[sdavid]

I would probably just install a milder cam and then if the carb was too much change that. That intake is good for stock type application. The 700R4 will be good for some better fuel mileage "if" it is in overdrive. If you are in town all the time, then it is not doing you much good.

A comp or voodoo 262 or 268 cam is a good compromise. You can get better or custom, just a how many dollars type of thing. Either of those should idle smoother and have good vacuum.

But you need to be aware of what your compression ratio is. If you are around 10 to 1 or less you should be OK. Above that, then you will need to consider higher duration cam to match.

[Kaysenmc]

Crazy! Just build your dream driver outta that white and blue 84 with the burb drivetrain. Then go wild in tan

[flamingbig10]

leave it as is

[grinch4om]

I'd take the demon carb off and try that 800 Q-jet, jetted right those carbs have tremendous drivability and 800 cfm is plenty on a 383. I'd bet on better MPG and you'd fall in love with the truck all over again

[mrbigshot]

i say leave it as is as well. a nasty cam is perfect for these c10's. theres plenty of mild ones running around.

[Pyrotechnic]

7 MPG.....

Something is WRONG. What you have sounds perfectly streetable. I run a wilder motor on the street than you do and get 14-15 MPG while doing it. Others here have reported similar results from their 383's.

If you are having questionable driveability and that bad of gas mileage, I'm going to wager that there is something causing the motor to run badly. The combination itself should be fairly tame and streetable.

Things as simple as retarded timing, timing curve in distributor too slow, vacuum advance set wrong, carb too rich, carb flooding, vacuum leak, etc will all cause this kind of behavior.

Can you give us a detailed parts break down ? What kind of timing are you running ? Have you jetted the carb or did you just bolt it on ?

[boatpuller]

yea,i agree with pyro.something doesn't sound right.you don't here of people wanting to remove performance very often.i'd be sure i wasn't removing some of the fun to drive factor.sometime's it's money well spent to take it to a good pro and spend the buck's to have it hooked up to a dignostic machine and have it checked out.

[flamingbig10]

I just have a little better than stock 350 and only get around 5 to 10 mpg, but my carburetor is junk and my harmonic balancer is out of wack

[nico]

The setup just does not have enough compression to run the cam and carb it has... Performance is okay and it can reach 12-13 mpg on longer trips, but just running around town, mileage is fairly poor. And it doesn't really make great power until 2500+ RPM's.

My thoughts were not to go back totally stock, just a more street friendly cam and converter package, an overdrive trans and maybe a quadrajet carb.

The current setup includes:

GMPP four bolt block (standard bore)
Scat 9000 3.75 crank
LT1 Rods (5.7")
Keith Black Hypereutectic Dished Pistons
Comp 280H small base circle cam (.480 lift, 231 duration at .050, 106 LSA)
Comp 1.6 ratio full roller rockers
GM 487X 75cc heads with mild cleanup, 2.02/1.6 stainless valves
Edelbrock Performer RPM intake
Speed Demon 750 vac. secondary choke, 1" aluminum spacer.
MSD billet distributor, 6AL box and Taylor wires.
Hedman long tube headers, 2.5" exhaust with H-pipe and Flowmaster 40's
TCI Turbo 400 transmission with full manual valvebody (forward pattern)
TCI 2500 RPM stall converter.
The rear end has 3.73 Richmond gears and a Detroit Locker.

Here is it's "plain tan wrapper..."

[grinch4om]

you need 32+ degrees total timing in by 2800 rpm. try the Q-jet with a fresh rebuild and drive it! by the way...cool truck!

[grinch4om]

I'll tell you what, I have had good luck with this method.. hold the throttle at 2000 rpm, advance the timing till the engine misses, back it off till it doesn't , go drive and listen for ping, try to start hot, retard 2 degrees at a time till any or both of those things go away. put a light on it so you know where the timing now is, drive the wheels off. for those of you running a chevy distributor, take one spring out from under the rotor and do this method, the throttle response will be heavenly.

[swb85]

Great looking truck BTW.

Mismatched combo, plain & simple. You're probably running around 8.7-9:1 compression (depending on some unknown specifics). While that's not horrible, it's pretty low. Dunno what your budget is, but if you're willing to do all the work you're talking about then why not just fix what's wrong with your combo and bump the compression (head swap) to where it should be for the cam you have? With more compression you'll keep your top end power and gain a bunch of low/mid torque and drivability. Just my $.02.

Just some food for thought: I'm running 10.4:1 compression and a 232/238 cam in my 383. Makes a ton of power, averages 15-17mpg and runs all day on 91 pump gas. LOVE it and drive it every single day.

[SS79chevy]

have to agree its a mismatched combo the cam you are runing is a pretty mild cam already id stick with it but it needs about a 9.1 to 9.5:1 compression ratio and your runing around 8.5:1 depending on the dish of your piston that could be more or less and your over carbed demon 750s thend to flow like holley 850s that setup really only needs 650-700cfm i would go with a dubble pumper over the vacum secondary as well as for the timing iv found that sbc's like it in the 36-38 degree range total

if it where mine id bump the compression to around 10.1 and probly run a 700-to 750 holley

[Pyrotechnic]

I agree, you should swap heads to some that flow better and have smaller combustion chambers.

Also as a note with the MSD Pro Billet distributors, they comes with the heaviest springs from the factory to give the slowest timing curve so those with detonation prone combo's don't destroy stuff. If you haven't already, you need to use the lighter springs that come with the kit to get a proper advance curve. One blue and one silver spring is what I used on mine.

[Slik69]

I am doing the same thing. You get tired of the noise.. and when you're not in a good mood it drives you even more crazy. Not to mention the gas.. that no one but you is paying for. I live in a fairly conservative neighborhood and I see a lot of classics pass by almost daily. A lot of trucks too and they sound/run good and strong without all the noise 383's make. Good choice Nico. Just get the right parts together for a nice street daily driver with some balls if you need it.

[454HO]

Sorry to say this nico, but your truck is completely a lost cause. An absolute total basket case. Nothing you can do will fix it. You might as well just give it to me and I will drive the snot out of it just like it is.

Seriously, that is a beautiful truck. A stock 350 would just not do it justice. I think a milder cam would be the way I would go too if I just wanted to tame it down a bit. Good luck with whatever you decide.

[nico]

The more and more I think about it, I will either go with a COMP 268 and dial in my carb more closely (really need to hook up my wideband-O2 sensors) or go with a set of stock-ish vortecs and an IMCA intake that a buddy has laying around...

I agree with the noise... At times, I'd love it to be a stock 350 that you can jump in and drive around town, at other times thought, it is fun to have a lumpy idle and enough steam to boil the tires.

Thanks to all that have suggested parts, given advice and handed out compliments...

[sdavid]

Do the vortecs and the Comp XE-268 and you will probably not be able to wipe the smile off of your face. Gain power with the vortecs and calm it down with the 268 all at the same time. It would put your power back down in the 2000 to 5500 rpm range. I feel certain it would still boil the tires anytime you wanted to.

[Slik69]

what's the lift limit on the vortecs.

[sdavid]

Lift limit depends on if you leave them stock or not. You can machine them to take a higher lift cam, but stock I think they have about a .480 limit. Some year model vortecs are less if I remember correctly, so do some research before buying a pair. Or buy a new set already machined and dressed for a high lift cam and bolt 'em on.

[Slik69]

I asked b/c I am seeing varying number from 450 to 470, now 480. When they machinist called me yesterday I asked him.. ahd he said what lift cam am I trying to run and I just threw out .500 and he said it would handle it. Maybe he doesn't have a lot of experience with vortecs. I have the 906 heads.

[sdavid]

Here is a link to an article that will help you answer some of the questions you have. Quick reference are the pics with captions on the left side. Scroll to the bottom and check it out.

http://www.customclassictrucks.com/t...evy/index.html