[Genevieve!]

So, Gen's been reading this forum for a while now, and i thought you guys might have some insight towards my problem here. Okay, so i have a fresh new engine, here's what it is, and what it's doing.

its a '96 351w roller block, freshly machined with a new 408 stroker crank, forged pistons at about 10.25:1 compression, edelbrock aluminum heads with 2.02/1.60 valves and 185cc runners, crane powermax roller cam 224/232 @0.50 114 LSA and 542/562 lift. edelbrock 750cfm carb, mallory distributor.

here's the problem.

it ran fine while braking it in for about 600 miles, then i started to open it up a bit to see how it did, and it ran.. bad... so i adjusted the timing using a vacuum gauge, and ran it.. then backed the timing off just a tad until it didn't ping. it still ran really bad, after about 1/2 throttle, it falls on its face and runs kind of ragged, at higher rpm's it's even worse. so i took it to have it dyno tuned. the dyno showed about 180 rwhp and 250ft/lb torque, and that it was running very lean, so i put in the biggest jets, and the smallest metering rods i could get and that helped it a little but it was still showing up lean. that got it up to about 200hp/260tq. but it was still running really bad.. and on the street it seems worse. i have tried both ported vacuum, and manifold vacuum for the vac advance, too. plug wires are double checked and are in the right order for the cam. there is plenty of fuel pressure and volume, the dyno tech was at a loss for ideas, as well as myself. anybody have any? all the parts are brand new. could this be an ignition problem? or do signs point to a faulty carburetor? what's next? and what do you guys think is a realistic amount of HP/torque that a build like this should produce?

[r.barn]

What was your a/f ratio while making dyno pulls ?

Have you put a vac gauge on vac system to check for vacume leaks ?

Have you done a compression test ?

Have you done a leak down test ?

Have you pulled the plugs and check color or fouling ?

How did you "break it in" ....... engine need to be driven hard top seat rings
not "baby'd" for first few hundred miles.

Any smoke out tail pipes ?



Leak down test and plug inspection is first thing I would do.
Make sure engine is sealing good to begin with.

[jasons_98gt]

driving a new engine hard to "break it in" is the worst thing you can do just drive it like you normally would with no sudden accleration or braking

[69fastback]

Did the lean problem ever go away on the dyno?

[Genevieve!]

No the lean problem never went away on the Dyno, It started with the A/F Ratio around 15, re-jetted re-metered the carb to run as rich as possible and got it down to about 13 gaining approx 20HP, tested the compression and its fine, there is no smoke from the exhaust, or blow by. I took all the plugs out (all looked normal) and re-gapped them to 32 most of them were 38 and a couple were over 40. It runs better now, but still not perfect. It runs fine at idle, there is a lot of vacuum and I don't hear any vacuum leaks

[TheUNZippee!]

Gene, I seriously do my best to try and avoid post whoring in the legitimate technical forums.

But hearing you talk lake that gives Zippy a happy.

Sorry.



Resume mature posting:


Is it missing? You say you have double checked the basics such as the firing order, but also check for a cracked distributor cap?

Double check the plugs, and the plug gaps. While you're at that, let us know how the plugs look.

Is that Edelbrock a single or dual feed?

If all that's good, you're down to the carb not being set properly or having a malfunctioning part in it. I've never wrenched on an edlebrock, so I have no clue as to what to check on those. I know on a Holley, you want to look for things like a stuck float, a cracked power valve, etc.

Or the timing is not set correctly.

[JakeM]

Ok...

Spark plugs are OK.
Vaccum is good at idle.
You have the Carb maxed out fuel wise.
Your running dangerously lean.


Heres my questions. You changed the spark plug gap and that helped? While on the dyno was the wideband reading taken with the shops wideband or do you have one installed?

I wideband oxygen sensor is made to read oxygen right? So if you don't burn the oxygen in the cylinder its going to show lean. Even if there was a lot of fuel in the mixture still because a O2 sensor doesn't know how to read fuel. Are you spewing a lot of grey smoke ? Can you smell a lot of fuel with it jetted up like that?

I'm wondering if you don't have a spark problem and you have been chasing a fuel problem. The reason I say this, is because when you changed the spark plug gap, you said it got noticably better.

So. If I were you, I'd double check (triple check if you already have) the electrical system. Make sure you getting enough spark and at the right time. IMHO, this is going to either be spark energy or spark timing. The only thing that doesn't fit, is the plugs not showing anything. If I were you I'd take them back out and take a look again.

[MustangOne]

This may be way to simple,

Have you tryed changing over the Carb to say a Holley 750 and see how it is

Edel seem to run lean as a rule. and Holleys seem to run fat.

[r.barn]

Originally Posted by jasons_98gt driving a new engine hard to "break it in" is the worst thing you can do just drive it like you normally would with no sudden accleration or braking

No its not. You just gave worse advice possible, other than letting it
sit and idle for a few hours on first start up.


You ARE supposed to drive a new engine HARD to properly score cylinder walls
and seat rings. Key is proper warm up.

Break In Secrets--How To Break In New Motorcycle and Car Engines For More Power

[Onemanzu]

okay, this might sound like i have no idea whats going on, which is true, but what is your fuel pressure right before the carb? are you running an electric pump?

don't count fuel delivery out of this problem. getting the gas from the tank to the engine is a big part of making a car work.

[SWEET2KSTANG]

Originally Posted by jasons_98gt driving a new engine hard to "break it in" is the worst thing you can do just drive it like you normally would with no sudden accleration or braking

wrong

Originally Posted by MustangOne Edel seem to run lean as a rule. and Holleys seem to run fat.

i have seen this as well, but not all the time. a lot of it is what the edelbrock is put on and which edelbrock is bought.

Originally Posted by r.barn No its not. You just gave worse advice possible, other than letting it sit and idle for a few hours on first start up.

+1 on that. every builder has their way of breaking in a motor, i have my way i like to break mine in.



GenevieveD, sending pm.

[JakeM]

Originally Posted by MustangOne This may be way to simple, Have you tryed changing over the Carb to say a Holley 750 and see how it is Edel seem to run lean as a rule. and Holleys seem to run fat.

Even with the largest jet setting possible? As you know a 750 isn't a small carb. How could it be running THAT lean with max jets? Unless its some other mechanical issue with the carb?

I'm not being a dick, I'm seriously curious.

[03_StangGuy]

Originally Posted by jasons_98gt driving a new engine hard to "break it in" is the worst thing you can do just drive it like you normally would with no sudden accleration or braking

Originally Posted by r.barn No its not. You just gave worse advice possible, other than letting it sit and idle for a few hours on first start up. You ARE supposed to drive a new engine HARD to properly score cylinder walls and seat rings. Key is proper warm up. Break In Secrets--How To Break In New Motorcycle and Car Engines For More Power

Driving hard can mean so many different things. Beating on a new motor is obviously bad. You do need to drive it hard enough to get enough cylinder pressure so the new rings can be filed down from the hone to fit the cylinder properly. While taking it easy wont hurt the engine it can reduce the compression and performance. Just drive the car like you would on a normal trip anywhere. Rev it up to 3k or so give it moderate throttle and you shoudl be just fine.

Ive said it before and ill say it again, the ONLY metal to metal contact in a motor once its running is the piston rings to cylinder walls.

[SWEET2KSTANG]

Originally Posted by 03_StangGuy Driving hard can mean so many different things. Beating on a new motor is obviously bad. You do need to drive it hard enough to get enough cylinder pressure so the new rings can be filed down from the hone to fit the cylinder properly. While taking it easy wont hurt the engine it can reduce the compression and performance. Just drive the car like you would on a normal trip anywhere. Rev it up to 3k or so give it moderate throttle and you shoudl be just fine. Ive said it before and ill say it again, the ONLY metal to metal contact in a motor once its running is the piston rings to cylinder walls.

wrong again. like i stated before, each person has their own way of breaking in a motor. there are a ton of builders that will go ahead and jump in and run the living shit out the motor after initial start up and checked over.

[MustangOne]

Originally Posted by Towelly Even with the largest jet setting possible? As you know a 750 isn't a small carb. How could it be running THAT lean with max jets? Unless its some other mechanical issue with the carb? I'm not being a dick, I'm seriously curious.

If we keep it simple, witch most problems should be.

The car uses a carb. It is running really lean. we have the bigest jets.
Still lean. We have No Vacuum Leaks. and we have good fuel flow.

My vote is a no brainer, I have to go with Carb Problem.

[Genevieve!]

The problem turned out to be the fuel pump , I guess it had fine pressure at idle and at normal RPMs but at full throttle it had little to no pressure at all, it was kind of sperattic, so we ordered a new one and are in waiting. Hopefully that was the problem, as I am sure it is but, you never know.



I am not sure if I mentioned that this engine is in a 1982 Ford Bronco, offroad rig. for those who are wondering.

[G.T. Rags]

Originally Posted by Onemanzu okay, this might sound like i have no idea whats going on, which is true, but what is your fuel pressure right before the carb? are you running an electric pump? don't count fuel delivery out of this problem. getting the gas from the tank to the engine is a big part of making a car work.

omz fucking new it all along