Continued 383 headaches

BangkokDean

BangkokDean

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So now with help from Lars I can get the motor to idle at 800 rpm and 950 with the A/C on. But when giving the gas it wants to bog unless I get the revs up to 1200-1500, then while driving I am unable to get into 3rd or 4th gear around town. When the traffic is moving 40 or more it runs ok in 4th. But in slow traffic I can only use 1 and 2nd keeping the revs above 1500.

I have not changed the Trans or rear gears from the 350 but the 350 ran great in show traffic and idled 750 and with A/C 800.

Also I am getting a strong UN burnt gas smell out of the side pipes that in traffic I am unable to put the windows down as it chokes. :sos:
 
How big of a cam are you running? If you have a bit of a cam, you're going to have to keep the rpm up - nothing abnormal with that. I run a moderate cam, and never run the rpm under 2500 unless the car is idling. If you have a modest cam yet get a hesitation or bog when pressing the gas, you need to richen up the carb if you're running close to the stock jetting: Verify proper accel pump action, richen up the accel circuit, then richen the main metering circuit if it's still exhibiting a lean tip-in.
 
Did you post the specs somewhere ? Cam/compression/carb ?

My 383 with a Comp 230-236 (CS XR282HR-10) runs ok between 1600 and 1800 even in 5th gear, however full throttle at 1500 is not a good idea, it is a little rough until it gets closer to 2000rpm.

The LSx with fuel injection runs great even at 1200 rpm ;)
 
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here are the motor & cam specs
ENGINE HAS THE FOLLOWING:
• Premium Seasoned 4-Bolt main block.
• GM 350/3.750 con rods with NEW HP rod bolts and nuts.
• NEW Eagle 383 Steel Crankshaft.
• NEW Hyperutectic Flat-Top Pistons 10:1 comp ratio.
• NEW Plasma Moly Piston Rings.
• NEW Cam and Lifters, Hydraulic Flat Tappet, Advertised Duration 308/318, Lift .488/.510, Lobe Separation (degrees): 112 (Edelbrock 7102)
• NEW Performance Gasket set.
• NEW High Volume Oil Pump.
• NEW HD Tri-Metal 780 "IROC" Series Rod,Main & Cam Bearings.
• NEW Flex-Plate. GM Harmonic Balancer.
• NEW HP Double "True Roller" Timing Set.
• NEW Brass Freeze Plugs.
• NEW 64CC Aluminum Cylinder Heads, 190CC intake ports with NEW Stainless Steel Swirl Polished 2.02/1.60 valves, Comp Series Springs .530 Lift, Bronze Valve Guides, Hardened Locks & Viton Seals.
• NEW Head Bolts.
• NEW True Roller Rockers
MACHINE WORK
• Bore and hone block with torque Plate with moly finish.
• Deck cylinder block parallel to main line with CBN.
• Re-size connecting rods with new bolts & nuts.
• Hang and align pistons onto connecting rods.
• Line hone main line.
• Fully balance engine assembly.
 
MYBAD79 said:
I would not expect this cam to run smooth at 1200- 1500, that's even "hotter" than my cam.
Click to expand...

OK it is advertised as "recommended for high-performance street and strip" cam? It idles a little high and I can live with that but it does not like being lower than 1,500 rpm in gear causing me to have to drive around in 2nd or 3rd gear. Now I am thinking that putting a lower gear in the rear like 3.72 it will help in city driving or at least getting into 4th once in a while.

If I were to change the cam what would be a good option to keep performance and give it better manners? That is using the existing motor?

Thanks Lars I do have some new jets and metering rods for the Ebelbrock 750 carb but do you have any idea as to why I am getting the excess fuel fumes smell out the side pipes? Especial on the drivers side.
 
You can't run a cam like that under 2000 rpm when driving - lugging the car around at 1500 simply won't work - you have to keep the rpm up. No amount of tuning will allow you to run in 4th gear at 40mph, and there's no way you can get rid of a hesitation when nailing it at 1500 rpm. You need to downshift, get the rpm up over 3500, and then you can go. That cam will run "dirty" at any rpm under 2000-2500, and you will have exhaust fumes at idle - no getting around that.

Lars
 
lars said:
You can't run a cam like that under 2000 rpm when driving - lugging the car around at 1500 simply won't work - you have to keep the rpm up. No amount of tuning will allow you to run in 4th gear at 40mph, and there's no way you can get rid of a hesitation when nailing it at 1500 rpm. You need to downshift, get the rpm up over 3500, and then you can go. That cam will run "dirty" at any rpm under 2000-2500, and you will have exhaust fumes at idle - no getting around that.

Lars
Click to expand...

I agree. I had that cam in my 383, (M21 with 3.55 rear) and it was a pig until it hit 3500, then it was lots of fun.
 
My cam is a roller, but it is 222-236 duration and .518-.539 lift @ .50 woth 112 degree seperation, also a 383. It definitely does not like to run @ less than 1800-2000 rpm. After that it wakes up. I have a 700R-4 with 3.70 rears and I have to run in 3rd in town and up to about 45 mph.
 
I have this GM cam in a 350. Runs great-- above 3000 RPM. Idles like crap and stays rough and nasty until you hit 3k. If you let it idle below 1000 RPM it'll eat spark plugs like candy. Solid lifter and way before anyone was running roller anything except for the big buck race guys.

3927140 Mechanical - 257/269 - .493/.512 - 112 - Off Road
 
lars said:
You can't run a cam like that under 2000 rpm when driving - lugging the car around at 1500 simply won't work - you have to keep the rpm up. No amount of tuning will allow you to run in 4th gear at 40mph, and there's no way you can get rid of a hesitation when nailing it at 1500 rpm. You need to downshift, get the rpm up over 3500, and then you can go. That cam will run "dirty" at any rpm under 2000-2500, and you will have exhaust fumes at idle - no getting around that.

Lars
Click to expand...
Thanks all

I looked at the cam mybad79 linked and it says it is for a 87 up motor. I like the idea of a roller cam but with 530lift heads also with Lift .503/.510, it is not much different than the cam I have now (lift.488/.510)
Beginning Year 1987
Ending Year 1998
Engine Family Chevy small block Gen I
Cam, Lifters, Valve train, Hydraulic Roller Tappet, Advertised Duration 276/281, Lift .503/.510, Chevy, 305/350
Camshaft Usage Street/Strip
Application Notes Will not fit LT1 or LT4 engines.

I don't know which cam to go with to keep some good performance and better street manners.

Also if I go with a Hydraulic roller tappet cam like the one in the link below, do I need different push rods and timing chain, plus will my MSD distributor work? what else will be needed?

http://store.summitracing.com/partdetail.asp?part=CCA-CL08-503-8&view=1&N=700+150+
 
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Dean, the cam you linked to shows an RPM range of 1800 to 5800. that will improve street manners a bunch. Get that lower number down and you get things like a decent idle, good vacuum. But remember, it's going to be all done about 5800. Not a real problem unless you're doing something off road.

At worst, you'll need to change the drive gear on your distributor and either a timing chain set that's clearanced for a thrust bearing and button, or a touch of machine work on your current set. Pushrods might need to be shorter, but Comp will have all that info. You can check them yourself and figure out the length, then get some the correct length for your engine.
 
What do you folks think of this cam?
Camshaft, Hydraulic Flat Tappet, Advertised Duration 295/313, Lift .500/.486, Chevy, Small Block,

I Need decent idle and can run in city driving with my 5 speed? If I run this cam I can use my new (less than 100 mile) timing chain set, lifters and push rods.

http://store.summitracing.com/partdetail.asp?part=CCA-12-602-4&autoview=sku
 
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MYBAD79 said:
That would pretty much make the car impossible to drive in traffic.

This cam should work - if you're looking for a cheap and easy swap:
http://store.summitracing.com/partdetail.asp?part=CCA-CL12-242-2&autoview=sku

I chose Comp just as an example, pretty any cam with a 220-230 duration is better suited for your driving than the cam you have now.
Click to expand...

That cam looks OK but will it give good performance and a little lumpy idle? When I see it is good for towing I think of my old truck cam.:confused:

What about the cam in your 383? i know it is a roller cam but how is its manners?
 
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BangkokDean said:
That cam looks OK but will it give good performance and a little lumpy idle? When I see it is good for towing I think of my old truck cam.:confused:

What about the cam in your 383? i know it is a roller cam but how is its manners?
Click to expand...

I'm happy with it, it runs ok at 1600-1800 but it is not designed for full throttle at 1200rpm. It's happy at 2000 and above.
 
MYBAD79 said:
BangkokDean said:
That cam looks OK but will it give good performance and a little lumpy idle? When I see it is good for towing I think of my old truck cam.:confused:
Click to expand...

I'm happy with it, it runs ok at 1600-1800 but it is not designed for full throttle at 1200rpm. It's happy at 2000 and above.
Click to expand...

Sound like what I have now. The problem with cams is there are so many on the market it is difficult to get what you want out of the box. I don't want too mild a cam, but one that is better mannered than the one I currently have.
I have had the "truck cam" and the radical ones now some where in the middle,................. maybe a thumper????

Anyone else with options please chime in.
 
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The Thumper cams are great IMO... you can have the rough idle sound and still drive the car under 2500rpm.....

The cam I linked to (224-230) is one "size" smaller than mine, it's the cam that my engine builder recommended. With the 5spd and 3.55 gears the 230-236 cam works for me, the smaller one is the better choice for low rpm cruising.

You have to look at more than just the duration, you also have to look at when the intake and exhaust valve are closed. The RPM cam that you have has a pretty bad reputation across the internet, I personally have not found many who like it in either a 350 or a 383.

I installed the small Performer cam (194-208??) in my old 350, it also had the RPM heads and flat tops... it was a fun engine that pulled right off idle.... it died at 5000 (guessing, no tach at the time) but it was a nice engine with very good manners...
 
MYBAD79 said:
The Thumper cams are great IMO... you can have the rough idle sound and still drive the car under 2500rpm.....
Click to expand...

Please take a look at these and let me know which one you think will work for me???I am ready to order one now but need to know it will do the job.

http://store.summitracing.com/partdetail.asp?part=CCA-12-600-4&autoview=sku

http://store.summitracing.com/partdetail.asp?part=CCA-12-602-4&autoview=sku

http://store.summitracing.com/partdetail.asp?part=CCA-12-601-4&autoview=sku
 
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