Question for all the 5.0 guys out there!!!!

[alsil]

So, due to the events of yesterday ..........All I had time for was to swap the carbs and see if it made any difference. It made none. Hopefully thursday I'll have a bit more time. I'm going to do some jet/rod swapping and see what that does. And every other check I can think of. Who knows?

Terry - Do you think a stock 350 with ram horn headers would need more fuel than a 302 with a roller cam? I fugured from the size of the cam they put in the late 302's that it would be semi-close. What do you think? I know my 305 I had in my old truck ran leaner than my old 302 in my Mustang. Neither of them had big cams, although the Mustang had a medium cam with a Torker II intake and ported Hi-Po heads (2.1X1.25 I, 1.4x1.1 E). Any ideas?

 

Thanks

Al

 

I'm not a religious guy, but pray for the people we lost in NY

[Guest Anonymous]

Alsil, did you get it running?

 

jon

[alsil]

Working on it this morning. Trying some new stuff. Very baffled. I might have been on the wrong track. I think it may be running LEAN instead of rich. It is kind of doing all the symptoms - running hot, missing, surging, and backfiring. Also, there's never been smoke out the tailpipe, and if it was rich there probably would be. I'm going to find out right now.

 

Thanks!

AL

[alsil]

Nope.

Good try though.

 

!&@^#@!!!

 

Al

[Tim240z]

Alsil,

Is your fuel pump in good shape? As it gets hot, the pressure drops...had this problem with a used holley blue years ago. I found the problem by manually pouring fuel down the cab throats (with some old vacuum hose connected to a ketchup bottle like the kind you find in diners). As the motor began to miss I started squirting.....smoothed out. Changed the pump...100%

Tim

[alsil]

Good idea, but no, the pump is OK, I have good pressure, the bowls are full when it runs like crap. I have ruled out the carb- I jetted it 2 steps rich, 2 steps lean, no difference. I am at a loss. The engine is getting fuel and spark. I am going to thoroughly go through it and see what the hell is up. Pretty much I'm planning on a crate motor. if I can't diagnose it soon, it's gone. I want to drive my Z.

Thanks for everyone's help!

 

Al

[Guest Anonymous]

Hey guys,

 

I hope you found your problem by now,but I would check the distributor gear.

 

You are using a steel one,I hope.

 

The stock cast iron gear will shred and send metal shards into the oil system,as it's eaten away.

 

PS I like this board,I wonder what my next project is

[Kevin Shasteen]

I hate problems like this-they'll drive you crazy. Especially if/when you've spent this much time/money on the car.

 

These are my experiences w/idle or lack of idle problems.

 

1) Helped a friend w/260 Olds V8. Started the engine after rebuilding it...Engine wouldn't idle below 2500 rpm's; scared us silly. Turned out the parts shop gave us Olds 350 Intake manifold gaskets which caused a vacuum leak. Rpl the gaskets & the car idled down to 650 rpm's.

 

2) Myself & the same friend were hot rodding

a 73 Olds 455/V8. Again, rebuild engine: new cam, new 750 Holley, new dist...yada yada yada. The car would not start...AT ALL! We tried the dist in all positions-never made a difference. I took the timing chain cover off & confirmed the timing marks were correct...they were. We finally decided the "New Carb" was running extrememly rich. Exchanged the Carb & it fired up immediately.

 

3) Had a Intern'l Scout w/304 V8. It had been sitting for years. It wouldnt start so I put a used coil on it...engine fired up but as it warmed up the engine would stumble. Turned out one of the cyl.heads was cracked. When I'ld take it for a test drive it had no power the faster I tried to go as usual w/a cracked head, the temp gauge got hot/in the red but wouldnt "Overheat" till all the coolant was ran out the tail pipe.

 

4)This was kind of dangerous; but we were careful. Again-the same friend & I were rebuilding a SBC 350 in a P/Up. The engine was rebuilt & in the truck. We hadnt installed the carb nor attached the fuel lines to anything....the truck had to be moved (for whatever reason I dont remember) and we had no time to install the carb. My friend & I used an oil squirt can filled w/fuel: while he cranked the ignition key I squirted fuel in the intake-the engine started & as it would begin to run out of fuel and begin to die, I'ld give it another squirt. Took us a few tries before we got it down well enough to move the truck. But we moved it about 20ft w/out any prob's and let it run long enough to check for leaks as the engine warmed up...we ran out of fuel in the squirt can but it worked flawlessly.

 

***Side-Note***

If your life insurance policy is paid up & you're feeling brave-try removing the carb & squirting fuel in the intake after the ignition key is cranked. "Remember" I was a professional..please do not try this at home! I dont accept any mishaps (that's my disclaimer!).

 

5) On another car my friend & I bought where the previous owner claimed the car ran rough & would die at idle....we discovered the radiator cooler tubes were punctured allowing ATF in the coolant which overheated the engine...causing the owner to think he had a blown head gasket. (I wasnt sure if you had an automatic or standard trans-but mentioned this one anyway).

 

Just of the top of my head:

 

1) What is the history of your engine; specifically the cyl.heads?

2) When the cyl.heads were seperate from the engine were they magnafluxed?

3) Are the cyl.heads remanufactured? Valves replaced? Valve Seats replaced? New valves on Old Valve Seats?

4) If your rocker arms are not adjustable & the new valves/old valves are resting on old valve seats on cyl.heads that were improperly "Rebuild"...then as you tighten the rockers you think you've set them correctly(?) when actually you've put excessive pre-load on the valves causing the engine to lose its sealing capabilities (the same signature as a camshaft w/huge lift/duration-short LSA). In other words-your engine may not be sealing: during a cold start up your carb is running rich-so idle is mostly smooth. As the engine/carb choke warm up-the carb leans and your engine tries to die because it's:

 

a) getting to much fuel due to the cyl's losing their pressure & not sucking the fuel into the cyl's caused from the valves never closing due to the improper geometry from used valves or used valve seats(?)

getting to little fuel to the actual combustion chamber due to the cyl's losing their "pull" from not sealing due to bad geometry of your valves/valve seats(?) therefore the vaccum signal to the base of the carb is minimzed due to the cyl's not sealing.

 

When I rebuild my 350/V8 Olds for my Cutlass I purchased a tool made by Joe Mondello where you can check the Valve Stem Tip's height right at the point where the rocker arm touches. Turns out my valve stem's where slightly low. It took my machinest two days before he found new Int/Exh valves that were the proper length!

 

You've already ruled out an external vaccum leak-this means you have an internal leak...effecting your fuel delivery to the combustion chambers. That's my story & I'm sticking to it!

 

If you havent ran a comp.check or a leak down test-I'ld do that before giving up on your engine.

 

Whewww! That was a mouthful. Just brainstorming from the top of my head-hoped some of this was helpful!

 

Kevin,

(Yea,Still an Inliner)

[Guest Anonymous]

wouldent it be easyer to just swap intake headers and carb so you do away with almost all your vacume all together and see what hapends maby a friend will have these things and you can try it but as the guys have sead it sounds like vacume