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Old 08-21-2012, 08:59 PM
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70 El Camino aka FRANKENSTEIN
 
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running rich and smokes at start up

Ok so I have been working on this issue for sometime now. I have tried many different things to help with the issue but i still havnt fully figured it out yet.

Here is the whole set up:

71 C20
700r4
4.11 rear gears 30" tires
GM goodwrench 350 (16"hg of vacuum at idle)
MSD pro billet dist (timming is 18* initial and I dont remember the total Ill have to check if anyone wants that)
MSD street fire ign box
Summit full lentgh headers
K&N air filter
Edelbrock fuel pump (running 5psi)
Edelbrock 500cfm carb manual choke (choke is wide open and not in use)
Edelbrock performer intake

Here is a little history on my issues...

It had a th350 that burned up on me and instead of rebuilding the th350 I slapped in a 700r4 that I had laying in the garage. Once that was fitted and the truck driving again the weather started to get very hot (102* and up). The truck developed fuel boil in the carb. I cured that by insulating the hood and fuel line and I also installed a 1" phelonic 4 hole spacer. Hot start issue and fuel boil is now completly gone.

The truck has always smoked on start up its partly oil burning I know that. I smell very strong fuel odor every start up. I have tried all kinds of combos on the carb to lean it out or richen it up and the leaner I go the better it gets. But Im unsure of going to lean because Im already very lean...

Currently set at...
0.083 primary jets
0.086 secondary jets
065x052 rods
blue springs 3"hg
floats are set at 7/16 (upside down) and 1" hanging (right side up)

Its currently running at 12% lean primaries and 12% lean secondaries softest step up springs with the smallest plunger squirt. I have no lean spots or lean surges in the throttle at any point. I even stole my sisters 600cfm eddy carb and the truck was VERY rich.

With the th350 I was getting 9mpg city and 10-11highway. Now with the 700r4 Im getting 12mpg city and 10mpg highway!

I should be getting far better milage right now and I cant figure out why.
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Old 08-21-2012, 11:37 PM
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What is the fuel pressure?
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Old 08-22-2012, 12:38 AM
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It's an edelbrock street fuel pump and it's running at 5psi at idle.
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Old 08-22-2012, 04:41 AM
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The jets are not the problem.

Rich smelly exhaust at idle:

its the idle circuit and or a ignition fault.
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Old 08-22-2012, 07:21 AM
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running rich and smokes at start up

Is this the GM 290 hp Crate motor? If so one problem is the compression is too low (8.0-8.5) for the cam installed. If you go on line and pull up the specs on that motor the cam was ran in an early model 350 ci with 11.0 compression. Another thing the head ports are small and the engine don't breath all that good. Good luck!
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Old 08-22-2012, 11:41 AM
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I was messing with the mixture screws just the other day but got side tracked and never finished I'll check that and tune with my vac gauge.

No its not the 290hp engine it's the 195hp this engine...
GM Performance 10067353 - Chevrolet Performance 350 C.I.D. Base 195 HP Engine Assemblies - Mobile SummitRacing.com

It was in the truck when I bought it. I pulled it apart to check it all out and it was incredibly clean. A friend of mine and I believe there's under 20,000miles on the engine. All I did was regasket and paint it I didn't change anything.
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Old 08-22-2012, 11:58 AM
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Look for a vacuum leak.
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Old 08-22-2012, 02:30 PM
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Ok so I messed with the mixture screws and it's running better and the smoking seems to have gone down a bit but time will tell. I was able to get much higher vacuum at idle went from 16"hg to 22"hg. Needles to say that was very much needed.

I noticed that when I hit the throttle gas doesn't just come out of the booster nozzle but around it where it's pressed into the booster so I'm thinking I need new boosters.

I've read that lowering the floats from 7/16ths to 3/8ths or even a hair lower can help out with the fuel consumption.

I did not find any vacuum leaks either.
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Old 08-22-2012, 03:17 PM
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Replace your spark plugs with new.

Smokey exhaust:
Check the PCV valve and PCV hose for oil migration into the motor.
Most aftermarket valve covers have no or very crappy oil control baffles in the valve covers
and oil gets sucked into the intake manifold thru the PCV.
This is a common issue with aftermarket valve covers.
You can fix that by adding a oil baffle in the valve cover.
The opposing valve cover should have a breather.

A leak on the underside of the intake manifold gasket is another source of oil contamination
and a pesky oily exhaust and short spark plug life.
Snug up the intake manifold bolts a bit. By hand) Hand wrench tight is good enough.
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Old 08-22-2012, 03:23 PM
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You will find that when using the Edelbrock Performer intake manifold that getting the manifold plenum temp just right is critical. This intake manifold tends to get too hot if the heat riser passages (intake gasket) are open.

Runs best with either both sides blocked or one blocked and one with a 1/4" to 3/8" hole.
This gets the manifold and carb body temp just about right.
The wood carb spacer is a good deal too. COmbine the two and you'll be good to go.

From this you can probabuly go back to the default out of the box car jetting
and adjust again.

The booster clusters in that carb are removeable. There is a gasket. The gasket may be torn.
This can really upset the carb. Something to look at.
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Old 08-22-2012, 03:31 PM
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Once these areas are corrected I would go to
.086" primary jet .098" sec jet
.065x .052" pri rod and the 7" spring.
And tune again from there.
You'll need to go to the drag strip to find the best power jetting.

A AFR gauge and a manifold vacuum gauge really helps for dialing in the gas mileage.

be prepared to fine tune the vacuum advance system (amount and rate) too. For mileage.

Once you get the intake manifold and carb body temp optimized it will come around for you.

Last edited by F-BIRD'88; 08-22-2012 at 03:39 PM.
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Old 08-22-2012, 03:46 PM
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TRUCK power and fuel mileage:

These engines have a very low compression ratio
and really crappy heads.

You can improve the gas mileage and power, torque and efficientcy by upgrading the cylinder heads for
a bit more compression and better port and combustion chamber efficiently.

L-31 vortec heads really shine in your application.

Lots of ways to skin this cat.
This is another example of the kind of motor that can really benefit from my low buck home ported 305 HO head swap. Can you dig up some #4416 305 heads?

Are you allergic to running something a bit better than 87 octane gas?

max imum mechanical advance should be in the 34 to 36deg zone.
Correcting the balancer timing tab TDC mark location, using a piston stop is a big plus to getting
it all dialed in. They are always out of wack a bit. Sometimes a lot.

Last edited by F-BIRD'88; 08-22-2012 at 03:56 PM.
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Old 08-22-2012, 04:09 PM
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Doing these combined improvments will alow you to step up the cam a bit
for more truck power and torque.
Lets the headers work.
Something torky like the good old Comp High energy 252H-10 cam and 1.6 rockers.

It will be a whole different truck.
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Old 08-22-2012, 05:14 PM
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Quote:
Originally Posted by elcaminodragster View Post
I noticed that when I hit the throttle gas doesn't just come out of the booster nozzle but around it where it's pressed into the booster so I'm thinking I need new boosters.
Check to see if the cluster screws only need tightening. If they're already tight or it still leaks after retightening, replace the gasket under the cluster.

Click on image for details:

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Old 08-22-2012, 05:57 PM
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Well the valve covers do have the crapy baffling but i have semi improved on that I have a breather on the valve cover then rubber hose to the in line pcv then to the carb. Really cuts back on the oil in the line. Yes there is a breaher on the other side

I left the heat crossover wide open but I might pull the intake to completely block it off. That would help with the heat quite a bit.

I really rather not spend money to improve the engine any further unless it's my only option to cure this issue. As for a cam swap Im sure it would run far better but again I rather not spend money like that if I don't have to. Plus the time I have to work wih and this being the only truck. It would mean I take time off to do the work.

I'm sure I can get those heads I know many ppl with engines laying around and there's a bunch of junk yards around me. Swapping heads wouldn't take long at all.

I have no issue with running 91 if needed. Tho the prices these days staying at 87 would be nice.



I removed the carb tore it apart checked everything and all is well. There was a bit of dirt in the carb. I changed the fuel filters. I have 2 filters in line. The first is a paper filter right of the sending unit the next is a screen filter right before the pump.
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