TTSSZ

iTrader: (8)

It started out having a bobble off idle. Tried a few different things, then I changed the little plastic ramp on the carb for the front squirter.

That seemed to do the trick. It was crisp off idle, I thought I had it. Drove around fine till I did a 1st to 2nd holeshot, at the top of second it felt like the power was dropping so I got out of it. After that the thing started stumbling again. When I hit the gas it would go dead for a second then pick up, then it was ok. I hit the hiway, at 70 I hit it a bit and it dropped completely, The only time it was getting gas was when I would manually pump the squirters. I limped it home pumping the peddle. I then check the fuel filter, its filthy, so I change it, start the car, it seems fine again, I go around the block, nail it a few times, its fine, come to a stop, do another 1st to second smoker, no power brake, just drop the peddle, starts screaming, again I feel the power drop half way through second so I let off. Again it starts stumbling of idle, not half as bad as after the hiway romp but still bad. It's drivable but you have to get it off idle easy then it seems to be ok but seems to miss a bit here and there. Took it home, changed the fuel regulator, set it at 6 lbs and tested it. Still no improvement.

Not sure what the f it could be know. Seems like a fuel issue, I'm going to re-time it again. This car sits allot, I don't drive it much. The carb is brand new, I went from a 850 down to a 600cfm. (The guy at my local speed shop said he found by dyno testing a bunch of big blocks that I only need 600 for the power I am making. Only 350hp 390tk at the wheels) I was having all the same problems with the 850, thats why I changed it in the first place. Today I'm going to check the fuel pump connections and re time it. Also extend my fuel pressure guage off the carb so I can see it when driving.

Specs - basically stock 1970 427 - 30over - iron heads 11-1 comp, been running 100octain, msd - 69 vette intake - 1" spacer. new holly 600 with the jets that came with it.

W.T.F. any ideas I can try.

89L98T56

iTrader: (8)

My best friend was having the same problem with his 396 in his 84 Z28. It would fall on its face right away and then pick up again after a second or two. It also wouldnt Idle smooth and we could tell it was losing alot of power. We tried adjusting everything and couldnt figure out what it was! So we took a can of starter fluid and sprayed along his intake manifold where it meets up to the heads, and the idle would jump up when we sprayed the drivers side. So we pulled the intake and replaced the gaskets. After we let it dry overnight we started it up and holy **** that thing ran like a raped ape!! Smooth, crisp throttle response and so much power!! Unfortunatly we forgot to drain the radiator fluid when we pulled the intake so alot of water got into the oil and we didnt change it. So after about an hour of driving, the oil pressure dropped and we lost a rod bearing. He is in the process of rebuilding now lol. So if thats your problem be sure to drain your coolant before pulling your intake!!! lol

ulakovic22

iTrader: (12)

Esp on old school carb motors, check your vacuum.

TTSSZ

iTrader: (8)

Thanks for the info.
I will check for vacuum leeks.
I am at a loss for ideas, the other day it was doing the same thing, I played with the carb a bit, just opening and closing the throttle. I went for a ride and the problem seemed to go away in till I hit a huge bump then it was magically back. So I was thinking it might be an electrical gremlin somehow. Or maybe something in my carb is sticking, was freed up when I was playing with it and then got stuck again when I hit the bump?
I think I'm going to bite the bullit and bring it to the local speed shop, let them figure it then dyno it.

TTSSZ

iTrader: (8)

With the cam Im running the vacuum is very low at idle.

Drumer919

iTrader: (2)

How is the fuel system set up? Where is the FP gauge? Somewhere you can read it while driving?

TTSSZ

iTrader: (8)

I have the gauge on the hard line where it splits and goes into the carb.
I was planning on extending it to the back of the l-88 hood so I can see it when driving. I also just bought a better fuel gauge, liquid filled, to get a better reading then the 12 year old holley one I have.

It’s a holley blue pump, 3/8 line, 600carb 6# fuel pressure.
Carb is brand new, regulator is brand new too.

I started looking for corroded wire connections, the car sits all winter.
I was thinking I might have a bad ground or something. I found a few sloppy connections and cleaned them off yesterday but it didn't do anything.
Today I'm going to try looking for vacuum leeks.

LS1 Coupe

Being you checked the fuel filter and was full of crap, did you recheck it again to make sure it was still clean?

Drumer919

iTrader: (2)

Is the filter before or after the pump? How does the gas come from the tank, is it sumped or is there a pick-up tube, if so could the sock be dirty? Is it the original tank or a new stainless replacement / cell?

Try unhooking the line at the carb and running the pump to test for volume, check that against the mfg. specs on your pump.

TTSSZ

iTrader: (8)

Filter is after the pump and is still clean. The tank is the origional one.
I ran the fuel ga. up under the l-88 hood. Just for kicks i put a new liquid filled one because the one I had on there is 8 years old.
The new one reads 3# where the old one was reading 6. hmmm.
pushed it up to 6.5#, took it for a ride, was 95% better, now I think I just need to tune it in. I only took it around the block because it was to dirty to drive anywhere.
The whole car needs to be re-wired. Its a mess under the dash.
Thanks again for the tips.

XpEdItIoUs

iTrader: (44)

Off Topic, Thats a sexy car you have

TTSSZ

iTrader: (8)

I bought it out of the bargen trader - dec. 1995 on new years day.
Add read -

71 rs-Z28 427ci, Sq. port heads, fully restored.
black cherry paint... (and the price)

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V

$5500 obo.

{Still have the add}

XpEdItIoUs

iTrader: (44)

WHAT!, $5,500 obo? Is that a typo.

slvr98camaro

iTrader: (1)

wow, thats crazy, thats how much we paid for the 69' camaro unrestored.. around 96'

TTSSZ

iTrader: (8)

I'll have to dig up the add, Its in the back of pic. of my first rs.
I'll scan it in and post it.

creetz

what rpm does this motor spin to? At 6000 rpm you would need around 741 cfm's to be efficient? I think the 600 is way to small based off some calculations. 6-7 psi should be fine as your base fuel pressure.

MrOverkill

iTrader: (1)

Carb is WAAAAAY TOOOOO SMALL #1 the guy at that shop knows dick! Spend a few bucks and buy an HP Holley or Speed Demon. Even the 750 street version will work a TON better for you, the sell for $399 from Jegs or Summit.

Here is a test, take a straw and draw in a DEEP breath trough it, it works but it cant flow enough volume and it starves you for air. The same applies to your engine, and you should always look at it as a big air compressor. The faster, smoother and more effiecient you move air through it the more power it will make. Hence the term "theres no replaement for displacement" words to live by.....

Go to Holley.com and use the carb calculator if your unsure, but a 750 is the smallest carb I would even consider for your application..............

TTSSZ

iTrader: (8)

Yes I went to the Holly carb calculator and got the same #..... 750.

I had an 850 on there for a long time, I was having this same problem and that’s when I decided to try the 600.

So here is the latest. I think my battery or alternator is bad.
My voltage is varying and that’s why my fuel pressure is going up and down. When the voltage drop’s on the fuel pump I get about 3 1/2 psi and it runs like ****. When I'm getting full pressure it seems to run fine. That’s why every once and a while it would run good. I have an old battery and an even older alternator. The battery reads 12v when car is off, when I start the car up I'm only getting 11v. It should go up to 14v when it's running right?
I will try and replace them and chase all the grounds down and make sure there all good and see what happens.

I found the for sale add, I'll scan it in and post it up asap.

MrOverkill

iTrader: (1)

Also add a relay for the pump just to keep the voltage steady, triple check the grounds and PLEASE put the other carb back on it before the engine goes away on you......

Its lean already and at 3 1/2 psi is STARVING for air and fuel.....

slow95z

iTrader: (33)

sounds like the alt. is crapping out. do you have it converted to an internal regulated alt or external? double that for going back to the 850.