Car stumbling and dying

[DRJDVM's '69]

Hey Guys
I just put a new small block 434 in my car with a Pro-systems carb built specifically for my application. I've got just over 450 miles on the motor so far, but am having issues with the idle.

The car takes awhile for it to "warm up" until it will idle on its own, then seems to run fine for ahile where it will come to stop and idle but then after I drive it for awhile, when I come to a stop it wants to die unless I feather the throttle to keep it running...

For example....yesterday i drove it to work. When I first leave my house I need to keep tapping the throttle to keep it idling. The I get a couple of blocks, it idles fine. Get on the freeway for about 15 minutes, then off and through town... a couple of stop lights through town it wont idle when I come to a stop....it wants to stumble and die unless I feather the throttle.....

I havent pulled the plugs yet, but that was next.

I plan on getting it dyno tuned to really get it set up right, but want to put some more miles on the new motor and clutch etc before I really beat on it. For now I just want to get it to idle around town...

So any suggestions on what to try first ??

[camcojb]

sounds lean. I'd check the carb adjustments first, starting with the mixture screws. Sounds like they're in too far. Float level, etc. should also be checked.

Jody

[68protouring454]

call patrick even on a weekend, he has some of the best tech support out there.
also i am with jody, try idle mixture screws, try 1/2 turn out and take for ride, also verify float level

[DRJDVM's '69]

Float level is good... thats what I checked first......

Its just wierd that it runs fine and then after awhile it starts trying to die at a stop.

So mixture screws all the way in and then back out 1/2 turn ??

[68protouring454]

no go out 1/2 turn from where it is now, however screw them in so you know where they are now and can reset it if it does not help any

[camcojb]

Float level is good... thats what I checked first......

Its just wierd that it runs fine and then after awhile it starts trying to die at a stop.

So mixture screws all the way in and then back out 1/2 turn ??

Ned, screw them in slowly watching vacuum or rpms; the vacuum will drop and the rpms will drop as it leans out. Start screwing them out until you get the best vacuum and/or highest rpms at idle. If you go too far out the rpms and vacuum will drop again. Find the happy medium, highest vacuum or rpm. You'll probably end up 1.5-2 turns out, sometimes a bit more.

Do both sides a couple times. If they're way off the idle speed may go up enough that you need to drop it back with the idle speed screw, that's fine. Also, if that carb has four corner idle circuits (idle mixture screws on the secondaries also) then do the same with them.

Jody

[68protouring454]

the pro systems hp1000 i got for the 496 in vins car, the mixture screws are only 3/4 a turn out from seat, i messed with it but it just messed carb up, put them back and have never had a problem.
you should really call pro systems(patricks) tech line

[camcojb]

the pro systems hp1000 i got for the 496 in vins car, the mixture screws are only 3/4 a turn out from seat, i messed with it but it just messed carb up, put them back and have never had a problem.
you should really call pro systems(patricks) tech line

that's true Jake, with a modded carb like that the correct setting could be anywhere. Give it what it wants, try adjusting it but don't get hung up on exactly how many turns that ends up being.

Jody

[68protouring454]

that's true Jake, with a modded carb like that the correct setting could be anywhere. Give it what it wants, try adjusting it but don't get hung up on exactly how many turns that ends up being.

Jody
exactly jody, if i were ned and did not want to get to into it to deep with tools,
i would turn the idle mixture screws all(4) out 1/2 turn, go for ride, if it got better but not perfect go 1/4 turn more out.

just before doing that turn them into seat so you can return it back to how it was originally.
on vins car when we turned them out, it made it pig fat, on just off throttle and idling.
so it may help yours, try it, but call patrick also

[Vegas69]

Idle speed is very important as well. Carbuerators are notorious for variation in idle speed. Depending on your camshaft shoot for 800-1000 minimum. That is where you want to start adjusting your idle mixture. After your mixture adjustments then re dial in your idle speed. A little to fast is better than slow. It gives your carb some room to wonder with varying conditions. All the adjustments should be made at operating temp.

[DRJDVM's '69]

Big problems now....****..

Did the vaccum guage and it peaked around 1-1.5 turns out.... car seems to run better too..... did it a couple of times and messed with the idle.

Took the car out for a ride and it seemed to run better. Went on the freeway, got on it alittle to pass someone, then started to cruise at about 70 MPH and 2000 RPMs in 5th gear....went about 3/4 mile just cruising and ....bamm, some black smoke.... car just started to die and I had to pull over on the side of the freeway.... car cranks but no oil pressure....WTF....

called AAA and the car is home....

WTF did I do ??? How could I have broken something cruising at 70 MPH..... I did get on it alittle before but it seemed fine and nothing went wrong for almost a mile..... the motor is all forged, Dart block etc etc, so....

Could I have leaned it out too much and got into detonation ??

Not good....

[camcojb]

Big problems now....****..

Did the vaccum guage and it peaked around 1-1.5 turns out.... car seems to run better too..... did it a couple of times and messed with the idle.

Took the car out for a ride and it seemed to run better. Went on the freeway, got on it alittle to pass someone, then started to cruise at about 70 MPH and 2000 RPMs in 5th gear....went about 3/4 mile just cruising and ....bamm, some black smoke.... car just started to die and I had to pull over on the side of the freeway.... car cranks but no oil pressure....WTF....

called AAA and the car is home....

WTF did I do ??? How could I have broken something cruising at 70 MPH..... I did get on it alittle before but it seemed fine and nothing went wrong for almost a mile..... the motor is all forged, Dart block etc etc, so....

Could I have leaned it out too much and got into detonation ??

Not good....


I doubt it, at least as far as doing damage. You'd have plenty of warning; pinging sound, etc. and even then you'd have to do a lot of it before breaking a ring or piston. You'd still have oil pressure.

Black smoke is usually super rich a/f, like a float stuck, dirt in the needle and seat, etc. I'd pull the air cleaner off and first check if gas is pouring down the carb when you turn the pump on (if electric; if manual you'd have to crank the engine over). Also, what is your fuel pressure? If it's too high, or right at the limit it will cause numerous flooding issues, erratic idle, etc. Also, do you have access to another oil pressure gauge? Is this one electric or manual? If electric, make sure the wire is still connected, didn't burn on the headers, etc. I always start on oil pressure issues with trying another gauge, and the vast majority of the time the gauge or sender is bad, and there is no real oil pressure issue.

Jody

[DRJDVM's '69]

Pulled the valve covers.... things look okay, no milkshake or obvious spring broken etc...

Pull the spark plugs... they all look decent with a light coat of black soot....

Pulled the distributor cap off... nothing there......

Turn it over by hand..... distributor turns, and the valves move.....

So my biggest troubleshoot.... no oil pressure when cranking......

My friend that built the motor is coming over to troubleshoot but any suggestions would be welcome.....

[Vegas69]

How long are you turning it over? It takes quite a while to register pressure while cranking. Does it have an oil safety switch? If so maybe your sender went out and cut your fuel pump or spark. I agree with Jody...always check an oil pressure problem with another gauge if possible.

[DRJDVM's '69]

Well we found the problem... the distributor gear went bye-bye.......

Its was pretty trashed and broken apart on one side....... I'll try and post pix later......

When I turned the motor over by hand more the rotor turned but got to a point that it seemed like it lagged some. The timing marks were pretty close, so at first we didnt think it was that. But I couldnt come up with a different scenario to have the car die and have the oil pressure disappear ( I can understand the guage thing, but it would have to be one hella of a coincidence to have the car die like that and have the guage/sender die too..)

Its and MSD distributor and Comp Cam said we didnt need to run a bronze gear with this cam, so we left the stock gear.....

So I think the safest thing to do is pull the motor and check it all out.... I have too much $$ into this to risk it.....

We drained the oil and cut the filter and there is some fine metal in the filter.... the motor was set up with no oil bypass so 100% of the oil goes through the filter and I was using a K&N, so hopefully there isnt much metal floating anywhere....

PITA but the safest thing......

[ohcbird]

So what's the verdict on why the cam gear went? Are you using an 8620 cam? If your using an iron hydro cam w/ stock gear, I'd look further into why that gear busted.

The black smoke was probably from when the gear went & it went fat, real quick (434Ci is alot of unburnt fuel).

Good luck on the refresh- sounds like a nice combo.

[camcojb]

if this is a roller cam with iron gear compatible dist gear on it, get the melonized gear from GM and have it honed to fit the MSD distributor. You won't have another issue. I get my gears honed to fit from Mike at http://www.lewisracingengines.com/

Jody

[68protouring454]

i will second the quality of mike's work....

[DRJDVM's '69]

The cam is a "standard" (i.e not billet etc) Comp Cam and the distributor gear was the stock MSD piece....

I dont know what the cam gear looks like but I assume its trashed too....... I kinda want a diff cam anyway since this one didnt lope or sound as mean as I was hoping.... the 434 ate it up and it sounded too mellow to me anyway....

I did an internet search and found out alot about the melonized gears....seems to be a common choice...... but not everyone agrees.... seems like a billet cam with pressed on cast gear with the meolinized dist gear seems to work for alot of guys..

I went onto the MSD site and there were quite a few posts about gear failure....mostly Fords..... some "possible causes" were excessive endplay, high volume oil pumps and some other crap....no real specific casues... the scary thing is that there were posts with mulitple failures.... I really dont want to keep doing this.....

One of the theories is about high volume or high pressure oil pumps.... my engine builder put in a custom built oil pump that he swears by.... he runs on in his car and so does my friend with no problems......the oil pressure is around 20 at idle and often in the 70's at highway.... I've never had oil pressure that high....

I just dont want to do this again .....

[camcojb]

The cam is a "standard" (i.e not billet etc) Comp Cam and the distributor gear was the stock MSD piece....

I dont know what the cam gear looks like but I assume its trashed too....... I kinda want a diff cam anyway since this one didnt lope or sound as mean as I was hoping.... the 434 ate it up and it sounded too mellow to me anyway....

I did an internet search and found out alot about the melonized gears....seems to be a common choice...... but not everyone agrees.... seems like a billet cam with pressed on cast gear with the meolinized dist gear seems to work for alot of guys..

I went onto the MSD site and there were quite a few posts about gear failure....mostly Fords..... some "possible causes" were excessive endplay, high volume oil pumps and some other crap....no real specific casues... the scary thing is that there were posts with mulitple failures.... I really dont want to keep doing this.....

One of the theories is about high volume or high pressure oil pumps.... my engine builder put in a custom built oil pump that he swears by.... he runs on in his car and so does my friend with no problems......the oil pressure is around 20 at idle and often in the 70's at highway.... I've never had oil pressure that high....

I just dont want to do this again .....


trust me Ned. If the cam has the iron gear for a standard dist gear, use Mikes melonized gear. The MSD has had many problems with failures on Chevy's too, been through it myself.

The cam gear is likely okay, but now's the time to change if you want to. I prefer the billet cams with the iron gear pressed on, especially if you're running a higher rpm and more spring pressure. The standard hydraulic roller blanks are soft in my opinion, seen several that the roller lifter actually dents the lobes.

Jody

[Blown353]

Be very careful Ned; don't just throw a new distributor gear on and go.

A few years ago I ate my distributor gear (MSD gear and Comp standard cast core hydraulic roller.)

It took 2200 miles on my car to completely destroy the gear, and the gear on the cam wasn't so hot afterwards either. Not bad, but not great.

I didn't have my oil filter bypass plugged and the debris scored all the bearings in the motor and trashed the oil pump.

What I'm saying is this... while everything is probably OK because you were running a good filter and the bypass is plugged, if it were my engine I would pull and check all the bearings.

Anyways, as said the fix is to run a genuine GM Melonized gear. It will live a long and happy life against a Comp -8 cast roller core.

The MSD gear / comp cast core cam incompatibility has been well known for several years now and unfortunately you found out about it the hard way as did I.

Also as Jody said, the -8 roller cast cores can start "tracking" the lobes; after about 400# open spring pressure or so you are playing with a ticking bomb. It may eat the lobes, it may not. The cast cores really aren't even stout enough to withstand the springs necessary to properly control the valvetrain. If you call comp and ask for spring recommendations for 2 identical cams, one on a cast core and one on a billet core they always recommend more spring pressure for the billet core cam even though both cams have the exact same lobes!

The best bet is to get the cam custom ground on a -9 billet core and then have an iron distributor gear pressed onto the cam core; comp can do this even on hydraulic roller and "street" solid roller cams. The press-on iron gear lets you run a GM melonized gear on the distributor for a very long life. That's how I do all my hydraulic roller motors now; I have 4 or 5 I've put together now on -9 cores / press on gears with GM Melonized gears and they're all running great, some have 25K+ miles on them now and the distributor gears & cam gears still look brand new.

If it was my engine, my game plan would be to pull the motor and inspect the bearings, then have the same cam reground on a -9 billet core with the press on iron gear. Put it back together and put a genuine GM Melonized gear on the distributor and it should last many, many miles.

[DRJDVM's '69]

Hey Troy
I was hoping you would drop in here. I remember talking to you about your distributor gear issues.

I specifically asked about gears before we built the motor and Comp said "no problem". I didnt know about the melonized gears..... I thought the only alternative was bronze... I knew about the billet option, but not the gear.

Yes my plan is to pull the motor and pull some bearings and basically check it top to bottom...... I dont trust the cam gear either, so there is no way I would just drop in another distributor. Not worth risking the motor.....

So can I get the gear straight from Lewis Racing ? Or do I get it from GM and ship it to him ?? Or get it honed locally ?? Troy...where do you get your gears done ???

[camcojb]

I bought my last few direct from Mike, and I know Troy has in the past also. Maybe he has someone else he uses now, not sure.


Jody

[Vegas69]

Is this something we all should worry about, or only in specific applications? Or only a cast core?

[DRJDVM's '69]

This is so fun... what started out as a "tweaking the carb idle" day became a "pull the whole motor and replace the cam and dist gear" week... :D

I'll call Mike today and see what he has....

The one thing that still worries me.... the no oil pressure..... if the dist gear is trashed but the rotor still turns and the timing marks werent off, shouldnt I still be getting some oil pressure ???

That bugs me.....

What are your guys thoughts on the "high volume/high oil pressure" as being the cause ??

Like I said, my car has like 70 psi of oil pressure alot of the time.....

[Blown353]

Is this something we all should worry about, or only in specific applications? Or only a cast core?

This is a specific brand & material incompatibility issue; combining a Comp cast core roller (-8 core, the standard core Comp grinds their hydraulic rollers and "Street Series" solid rollers on) with MSD's melonized distributor gear (their standard provided gear) is a nearly guaranteed failure regardless of oil pressure or other outside influences.

The solution is to get a GM Melonized gear and have it honed out to fit on the larger .500 MSD distributor shaft; the GM gear and the Comp -8 core will "play nice" together, but that doesn't fix the potential problem of the soft -8 core eating the lobes up with higher spring pressures.

Ned, Mike Lewis usually keeps a dozen or so honed GM gears in stock and can ship it out same day. The other solution is to buy the GM gear locally and have a machine shop hone it out from the GM stock ID (.491" I believe) to .500" to be a nice slip fit on the larger OD MSD distributor shaft. Any local machine shop can do it, I know Walt (Performance Machine) could for sure. All he has to do is put it on the Sunnen hone and open up the ID.

The one thing that still worries me.... the no oil pressure..... if the dist gear is trashed but the rotor still turns and the timing marks werent off, shouldnt I still be getting some oil pressure ???

That bugs me.....

What are your guys thoughts on the "high volume/high oil pressure" as being the cause ??

Like I said, my car has like 70 psi of oil pressure alot of the time.....

If the distributor gear is trashed, then the distributor isn't turning and thus the oil pump isn't spinning, so no oil pressure.

As far as the HV/HP pump... a new engine that has been built with proper bearing clearances has no need for an HV pump and it's just taking extra HP to bypass the unneeded oil. I do like the high pressure Z-28 pump spring though for any performance build. The HV pump does increase the load on the distributor gear and probably expedited the demise of your gear. The gear failure is a material incompatibility, but excessive load on the gear certainly speeds up the failure.

The only time I would think about using an HV pump is if the bearing clearances are really loose or if the block has piston squirters or valve spring squirters installed, and even then I would consult with those with more experience to see what their recommendation would be.

[DRJDVM's '69]

If the distributor gear is trashed, then the distributor isn't turning and thus the oil pump isn't spinning, so no oil pressure

Thats the thing that bothers me....... when we turned it by hand the rotor still pointed to the #1 spark plug and the balancer mark lined up, so its not very out of synch...... when I turn the motor by hand the rotor moves, so the gears still do mesh at least some and enough that it stayed in synch with the rotor and timing mark...

Its gotta just be the gear, unless the sender took a dump at the same time.

I;ll call Mike right now.....

[DRJDVM's '69]

Talked to Mike....nice guy....not suprised the gear went south......

Also recommeded the billet cam with steel gear and the melonized dist gear..... so thats what I will be doing.....

The gear shipped to my door is $60......on its way...

[Vegas69]

There is alot of load on the geat while running from the oil pump vs. turning it by hand. That is the only way to have no oil pressure unless the pump shaft broke. Even with bad bearing you have oil pressure.

[class67]

Ned, if you need another pair of hands to pull the motor or whatever, let me know. I can help you out any time the next couple of weeks.