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Discussion Starter #41
oldbogie said:
The lowest power valve Holley makes opens at one inch of vacuum. The power valve can leak from a backfire even with a protection device in the carb. There's other sources of leaks, I'll get to that.

The powervalves front and back are new as of yesterday, no way are they leaking or bad just yet

We're assuming your wet plugs are fuel not oil or water, knowing this is most important. You can see, smell, and taste the plugs we can't. Black liquid out the exhaust doesn't tell us much. It could be raw fuel, a match ought to id that or not. It could be oil, in which case it will feel smooth and slick between you fingers and will probably not ignite with the match test. It might be dirty water. That and CO2 are the principle products of combustion so there's plenty of the stuff though it usually comes out the pipes in vapor form but it can condense and drip out. Plus it could be leaking coolant into a cylinder and pumping that out the exhaust.

It's funny you bring up water, cause the evac tubes fogged up while it was leaking the water so the temp outside might have been affecting the air in/out of the engine... I also ran the engine for about 15 minutes trying different stuff to make it idle right and so on... I started to notice that the base plate and spacers along with the manifold runners were starting to be COLD to the touch, not just cool.. COLD... Whats this a sign of?? I run 104 unleaded threw the motor also..

Certainly if the problem is oil or water then chasing the carb isn't the solution, so you gotta check this out and report back.

Im about 10% it's oil blowby, 80% it was water condensation and 20% it's fuel being rich...

The carb you have has 4 corner idle, that should be plenty to distribute the idle air and fuel requirement around to where none of the transition circuits are exposed. Nor should it be pulling any fuel out the boost venturis. If it's doing the latter the reasons are as follows:

It's not dripping fuel..

1) The power valve has failed and is leaking or the vacuum is so low it's turned on. All the carb's circuits feed from the main well. The well is fed by the main jets and the power valve. If the power valve is leaking (one can consider a bad gasket or a crack in the metering block or main body to also be a contributor to this) there will be so much fuel in the main well that changes in main jet size will prove to have no effect upon mixture ratio.

Powervalve isnt leaking unless the 4-6" is still to small for the 2.5" powervalve?

2) If the amount of fuel in the mainwell is excessive, the air correction jets will loose control of the emulsion process and can result in dripping boosters at idle. Same for way too high of a fuel level in the bowels.

I will try lowering the floats and get back with you on that.

3) If the secondary idle is not set properly the primary throttle plates can be too far open allowing the transition circuit to be exposed.

Whats the secondary idle?

a) In that case the idle and transition circuit will feed fuel making a rich mixture. The rich mixture causes you to open more throttle since the idle mixture screw is becoming ineffective.

I noticed that my 4 corner screws all the way in the motor seemed to run better? My old setup with a 750 it wanted to die when you run the screws in all the way??

b) The excessive amount of air flowing thru the primary side can cause the mains to turn on and drizzle fuel. What now happens to many tuners who find themselves faced with too much fuel, they close the idle mixture screws, or nearly so and open more throttle. You just get into this vicious cycle where you end up idling the engine too fast to try and burn too much fuel which is running out the boosters because of so much air going thru the venturis.

Any of this sound familiar?

You're running what for fuel, gasoline or alcohol? If alky, ethanol or methanol?

104 unleaded

Was this carb set up for alcohol and is now running gasoline? Talk about being rich!

No it's a gas carb to my knowlage? It has the small metering plates..

You've got nitrous, does that system leak fuel when it should be off? Is it jetted properly?

Doesnt leak cause it's not on, jetted right...

You sure that stack of spacers is really air tight? Holley's are pretty easy to bend on a stack like that such that the throttle plate is bowed in the middle and not making a seal.

Yes, the good old carb cleaner test proved no leak there... I can install the carb strait to the manifold to satisfy this question if need be?

Bogie


THANKS FOR THE REPLY! Please reply back
 

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Discussion Starter #42
coldknock said:
I'm not being antagonistic or trying to bust your chops but, you do not have enough compression for that camshaft unless that small block is near 500 cubic inches. No amount of tuning will likely result in the truck being any quicker than it already is.

It's a 406 sbc.... It runs 7.2's at 94 mph on motor

On top of that the heads are choking it up at about 5500-6000 rpm, the plenum volume is too large, and yes 70/71 jets may very well be too rich for your engine. There is no set-in-stone rule concerning jetting. The engine wants what it wants.

I know the heads are a weak part of the setup... Cam Motion says the cam isnt TOO big but it's right there.. They made the cam for my setup... I have the jets I can keep going down if need be... On the highway when I pull into the garage the plugs look GREAT and tan... So I know at WOT or part throttle the motor runs GREAT... It's just idle...

Now with that said, you probably don't have nearly enough cylinder pressure at any rpm, or enough timing, to have a complete burn cycle and the rich mixture is slowing the combustion process even further.

36* locked out on the timing

If your plugs are black after a full throttle pass, it is rich. Whatever the reason may be, it is rich. Period.

No, my plugs are bad at idle...

Verify that you're not burning oil and fouling the plugs first, then try smaller jets. With those old heads I doubt that the engine is drawing enough air through the venturis to warrant jets that would be considered normal, based on my experience. Try 68s' front and rear.

I can try anything man, I have nothing but time.... I will try the smaller jets! I know the 71 rears on the highway pulling into the garage and killing it the plugs are a pretty tan... So the WOT is fine, just the idle....

Good luck to you my man. I hope you get it sorted out and have some fun with it.

Im having fun now, lol... This is part of the fun making it go even faster!



Larry

THANKS FOR THE REPLY! Reply back!
 

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Joshua Lee said:
THANKS FOR THE REPLY! Please reply back
Hey Josh not to leave you hanging, I just read your responses. I've got get out of here, will write you on Sat or Sun when I get back on line. Good data thanks.

Bogie
 

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Ok now we're getting somewhere.

Driving on the highway doesn't tell the whole story, it's certainly not wide open throttle running, or I hope it isn't. :D

If you have good color from part throttle cruising, idling at stoplights and meandering about town then it definately not fouling the plugs up from a rich idle/low speed mixture.

The only time the plugs get dirty is at the track under w.o.t. passes right?

If that's the case then your high speed air bleeds could probably use a larger sized "jet". Be careful here and only go up one size at a time. This is where your fuel mixture gets air for emulsification in the main well at upper rpm. Too lean and you could burn a valve or a piston if it's really bad.

Go up one size, make a pass, look at the plugs. Do this until they look just about like they do after a sprint on the highway. Don't go too lean, it will hurt your performance and possibly your engine.

Be careful and keep it slightly rich on the upper end and your engine will be happy.

One more thing, while I'm thinking about it, make sure that the passages for the air bleeds aren't stopped up before you make any changes.


Larry
 

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Discussion Starter #45
Well guys... good and bad news

Good news...
I put more jet in the front after my first pass seemed to bog and take off (maybe lean at the hit)

Bad news....
Truck ran great, great throttle response ect.... After the next pass the engine seemed "off" so I go for the next pass and I hit full throttle and "IT" happened.... bent two valves....

I did get some info for you and I will post it up tomorrow... IE: what I changed and what I learned after I tore the top end off..... Yes, I trailored it home and tore it down and it's 4:15 and Im about to go o bed, lol... Hardcore? :thumbup:
 

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Discussion Starter #47
All the combustion chambers looked like this:




Plugs were the same color :boxing: why this color??

The bottom of the carb, top of the spacer, inside of the nitrous plate and the intake runners were this color:






Ideas? :thumbup:
 

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Joshua Lee said:
All the combustion chambers looked like this:




Plugs were the same color :boxing: why this color??

The bottom of the carb, top of the spacer, inside of the nitrous plate and the intake runners were this color:






Ideas? :thumbup:
Reversion! You're see back pumping of the intake charge and its lightly coking the exposed surfaces, or an intake is/was leaking a little and the combustion gases are blowing back up the intake.

Bent valves are almost always a problem of the springs loosing control (surging) which could also be part of the reversion problem seen with the intake. This problem can be very complicated involving push rod bending, rocker studs weaving around, rockers bending or not tracking straight, as well the the expected issue of the spring loosing control for a host of reasons.

Some solutions can be 3/8s push rods even composite designs if you can afford it. The use of 7/16 studs with a girdle. Stainless roller rockers for additional stiffness and better tracking. Raised end guide plates to control the push rod higher up to the rocker so there are less angularity problems between the rocker and push rod. Additional spring pressure, though make sure you have adequate damping of the spring first before adding stffness, reduced weight of the retainer and lock assembly. Proper alignment of the push rod thru the rocker to the valve stem; the pushrod working at the slightest of angles is a reason for it to bend; in bending it acts like a spring becoming longer or shorter at a frequency that probably has nothing to do with the timing of the opening and closing cycle of the cam. Bronze guides or an alloy thereof are very helpful to insure that the stem and guide run tight without binding, cast iron against the stem often results in a loose clearance that lets the valve "orbit" and encourages grabbing the stem in the guide; always use a good hard chrome stem valve.

Anyway this can go on for a long time.

Bogie
 

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Less cam. Hell, I run similar numbers in a 454 with 10-1 comp and a 800cfm Q- Bog duel plain manifold with 124cc chambers. And it's a monster 500ftlbs tq
Yes it pissed me off, but while scoring some quality time in a dino cell a guy (smart) was running impressive numbers (mouse 700 hp naturaly aspirated). He took the carb off for a swap and wouldn’t you know it he had filled half of his plenum with epoxy!!! :smash: He broke it down for me with one word VELOICTY!!!
Lift and lose
 

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If it's reversion why do the intake runners look clean, at least in the picture they do apprea quite clean?

That whole head surface and all the combustion chambers basically look kind of like a mess. With nitrous being way too rich can be as bad, or worse as being too lean.

I would most certainly inspect all the pistons looking for crushed skirts and ring lands. I'd also measure the bores. I'd suspect your rings are shot as well. Just a guess.

When you have the heads rebuilt you really need to clay the tops of the pistons to check PV clearance.
 

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Discussion Starter #53
It's all motor.... No nitrous being used at all yet.. Pistons are fine and rings all are within 10psi

Would driving down the track after that valve bent cause the black in the carb & spacer?? Since it was the intake valve the exhaust would be going up inside the intake correct?

The P-V clearance is great... With the bent valve it still didnt hit, lol..

Ok ANYBODY have a guess at why the combustion chambers and plugs are light tan/yellow??? It's 104 unleaded fuel if that helps!

I APPRECIATE THE HELP GUYS! :thumbup:
 

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Joshua Lee said:
It's all motor.... No nitrous being used at all yet.. Pistons are fine and rings all are within 10psi

Would driving down the track after that valve bent cause the black in the carb & spacer?? Since it was the intake valve the exhaust would be going up inside the intake correct?

The P-V clearance is great... With the bent valve it still didnt hit, lol..

Ok ANYBODY have a guess at why the combustion chambers and plugs are light tan/yellow??? It's 104 unleaded fuel if that helps!

I APPRECIATE THE HELP GUYS! :thumbup:
Yes

Bogie
 

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Discussion Starter #56
Yes, before I bent the valve and there is no way to tell now unless I pull the short block and that isnt happening...

The piston had a VERY small scuff and after I cleaned the carbon I could BARELY see where it hit... :thumbup:
I know what a broken piston looks like... Mine are ok unless your going somewhere with this and then I will post up a pic to satisfy you.. :pimp:
 

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Discussion Starter #57
oldbogie said:
Yes

Bogie
:thumbup: then Im not worried about the black... I drove (idle) all the way down the 1/8th without the valve hitting the piston, lol.. I have a lot of room w/ 9:1 pistons and 68cc heads... trust me

What about the color of the plugs bogie? any idea? looks to ME like burnt water? :sweat:
 

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What were you running for fuel?? That color in the chamber is not all that unusual for some race gases, especially if it's leaded fuel. Might be a bit rich but that's all.

Reversion is not at all uncommon, and will happen in a perfectly functioning motor. It's a combination of things, intake and exhaust timing, pulse waves bouncing back through the cylinder from the exhaust, which will end up in the intake if the pulse arrives in the cylinder during overlap.

You definitely have a valvetrain issue to solve(weak springs), but the reversion probably has little to do with it.
 

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i thought the same about the water but if you had alot of carbon on the piston i would rule that out,also it would have to of been burning in all cylinders from the way it looks to me.
 

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Discussion Starter #60
I run 104 unleaded Sunoco fuel

So the yellowish color is from the race gas? If so then Im not worried but the plugs are usually brown/black and now they are white/yellow? :sweat:
 
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