well it's not the carb...

M

MPGmustang

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So i'm back to chasing ghosts in my car, I know it not the carb cause I just got it back after pony carbs fixed everything that was wrong on it, even tested it for me on a real engine in a real car.

issue - can't idle cold, floods easily, takes for ever to fire, won't even putter when cold, when cold the exhaust "pops" as if gas didn't burn in cyl and now in exhaust and I don't go anywhere when I hit the gas, RPM guage is beserk!, DUI is tightened and still can be move/adjusted, oil leaks at the distributor hole, and my car isn't on the road yet (cause it can't run right). GOT LESS THAN 8 MPG LAST NIGHT freeway only!!! revs just fine but the second load is applied it DIES only a few feet away!!!

First, what can I use to keep that distributor from moving?
Second, I will try moving the long choke tube and wrap it around the header itself and see if that fixes my choke not working. (pony carbs confirmed that they had the choke working in shop perfectly) as suggested by pony carbs (so that's my error, I'll see IF that affects anything)

I want the idle to be less than 900 rpm but I can't get more than 6-7 vacuum @ 800 rpm and it dies, or I get 14-15 vacuum @ 1400 rpm and it just doesn't seem like its supposed to idle there...

my next step is to go back to basics, I'm going to try my LOM distributor with the SCV and see where that puts "dependability" cold or not. I have already replace the DYNA MOD in the DUI because it wouldn't start/run, now it does (minus above problems). I know some performance is hindered but I need it to go/drive and it wasn't (still isn't) doing that.

If the problems are still there then I'm going to degree my camshaft myself and see if the engine build shop even did it right.

I'm really sick of not haveing everything working together, I know its far from stock but the basics in tuning a car don't even work I can tune the car all I want when warm, but after it cools off, It don't run the same even after it gets back to that temperature I initially set/tuned it at!! ARRGG! :deadhorse:
 
Howdy MPG:

Sorry for your frustration. I'll bet that when you figure it out,it will be something fairly basic.

On the distributor hold down, try another washer on the hold down clamp bolt. It's likely that the bolt is bottoming out in the hole before tightening.

Good luck on solving the delema.

Adios, David
 
David, I don't think it's the bolt, as the hold down is tight, just not against the distributor, it's like the distributor is a tad smaller than the LOM distributor. But I will check it and post my findings, I hope its something easy. I'd rather drive it everywhere I need to be at.
 
You're getting the same kind of numbers I do with that cam.
There was a thread here talking about an issue with the o-ring on those dizzies.
 
IIRC, there are two different dizzy hold down clamps. The spacer part of the clamp may be too thick causing the bolt to get tight before it clamps the dizzy tight.

Do I need to send a DSII setup to test with? I may be able to piece one together, or temporarily pull mine. It would require freight both ways.

Did they test it on an engine with the same cam? The cam will make less vac than a stock cam. It will pulse more than a stock cam. Compression will make a difference on vac also.
 
It really sounds like a Cam timing issue. Being extremely rough when cold, and a lot better, but not so great hot. Hate to say I know that's it because I'm not sure, but unless the lack of seal with the DUI is causing crankcase pressure to escape too quickly and reduce vacuum.
 
Answer this question: Can you make the idle mixture too lean and too rich?

You can smooth out a small cam with a rich mixture. The best example I can offer is a SBC with a Competition Cams 268H. When it's cold you can hear a nice lope. On a good hot day with the engine warmed up, you can't even tell if it has a cam. Take this engine and install a carb that won't quiet feed enough fuel at idle and it will run better when warm, but not at all when cold.

Now, if the idle mixture is lean, the off idle circuit will also be lean and it may bog. However, when warm, it will be better but still may not be good enough.

When an engine is cold, it acts lean. You will notice that a choke makes it smooth out when cold.
A cam lopes more when the engine is cold and smooths out some when warmed up. It acts lean.

It is possible that the idle circuit cant quiet feed enough for cold engine operation. Also, if the carb was tested and set on a stock engine, it may not be set properly for your engine.

Just offering food for thought.
 
I'd agree with assessment. It just ain't gonna run worth a crap cold.
I have to continually pump the throttle when it's cold.
 
Okay, I think I figured it out!
First some questions I can answer...
The bolt doesn't bottom out, I actually have a washer on there now, and without the clamp I can tighten the bolt to the block, so it's not the bolt.
When I started I moved the distributor and it was LOOSE! I bet that was the main culprit.
Even with the distributor clamp on and the bolt as tight as I can get it, I can still (with great effort) move the distributor? I'm going to modify the clamp and see if I can help it more on the DUI.
I also traced my wires from the DUI all the way to the ignition switch, I didn't find any resistor, I now think it was pulled by previous owner to use pertronix, I decided to not use a fuse or relay or anything else in-between the ignition switch to the DUI, This might have caused some current feedback. So now it’s a straight connection - ignition switch to DUI, full 12v (tested). My rpm gauge seems to no longer jump everywhere, and is more accurate, that’s a huge bonus.
I wrapped my long hot air tube around exhaust tube from cyl 6 (should be the hottest) and adjusted my choke spring (when car was idling and at temp) to hold the choke up but still be "loose enough" for when cold. I'll double check when it cools down to see if it closes
For about 3 hours of fiddling with the carb and timing (no timing light as I'm going off vacuum) I got a steady 13 vac and a good rpm of 850-950 range. No sputtering on idle. I am using manifold vacuum for the DUI, always have... My goal is to reach 700rpm with the same vacuum; this is by far the closest I’ve got with that much vacuum.

She Idles way better, runs a lot smoother, and can accelerate! I don't get the big popping noise I'm used to hearing when unburned gas burns in my headers. I'm still tuning it, I have a 65 jet in there ATM which should be good for about 120hp?? (Wish I knew the calculations)
This morning was a starting test, It still took me 15 min’s to get it “ready” to drive (luckily without fiddling with anything), it started right up with my foot partially down, had to hold it for the first 5 mins, then tried to let it idle as I backed out the garage, but dies, so I let it idle with no foot for another 10 mins, and I was at temp, it’s a lot less than the 45 mins I used to wait and not to mention all that fiddling during that time.

I think the problem was/is the distributor hold down, it’s not able to hold it down tight enough. I’m going to try to modify it so it sits only on the block and distributor base. also I'm going to look into a seal to stop the oil sepage.

Jack - I read that thread too, I'm think I'm going to go look for one, I'll check my LOM and see if it has one I can snag form it, (I actually have 2 of them)
The cam I’m very leery on as one I don’t have much experience, but still trust the engine shop. It’s possible that they didn’t and just “lined up” the dots on the timing chain. But it’s a last resort. Not to mention with the LOM I was able to go anythwere dependably.
Stubby – Yes the idle mixture screw can make it lean or rich, very easily. I too thought this initially and set it, but as before it would change the next time I started it. (not the screw but the idle quality) You don't need to send a DSII setup, I'm good with a LOM spare to test running quality, I'm not even sure it's the DUI but just settings.
Jack – Yes I used to have to pump the pedal just to keep it from dying turns out my throttle shaft was loose/broken, Pony-Carbs replaced the entire setup on the carb, now I don’t, and they even redid the idle mixture circuit. Fixed a lot of initial problems.

In the end I need a turn key car, I enjoy the look of this car, just wish it was/is more dependable. I don't mind fiddling with it on my time, but when I have no time it's a really PITA

BTW thanks guys for the suggestions, I always appreciate them and they ususally always guide me in the right direction. looks like I won't need to swap the DUI anytime soon, really don't want to go back the LOM.

So, now what can I do to get the clamp to clamp more? is there another clamp that will work better? where to look, I'll just go to a store and pick up one, no junk yards as it's always a drive to get to one for me and spend the money in gas anyways.
 
When I started I moved the distributor and it was LOOSE! I bet that was the main culprit.
Click to expand...

Have you compared the measurement of the DUI dist. body lenght to the old LOD? Maybe needs more or less shims between drive gear on the DUI dist. body.

I am using manifold vacuum for the DUI, always have...
Click to expand...

I would try a ported (carb base) vacuum source you are probably advancing too much at idle (will also keep you from being able to idle it down to a lower RPM) it’s easy to see with a timing light if you can barrow one.
 
bubba22349":1xah2ae4 said:
Have you compared the measurement of the DUI dist. body lenght to the old LOD? Maybe needs more or less shims between drive gear on the DUI dist. body.
Click to expand...
No I havn't that would require me to pull the DUI, would like to avoid unnessasary labor, but I will measure the diameter of the 2 dist.'s

bubba22349":1xah2ae4 said:
I would try a ported (carb base) vacuum source you are probably advancing too much at idle (will also keep you from being able to idle it down to a lower RPM) it’s easy to see with a timing light if you can barrow one.
Click to expand...
I wish I could try a ported vacuum source, I am using the pony autolite 1100 with the SCV blocked off, is there a way to convert it over?
 
Check the thickness of the flange on both dizzys. There may be a difference. I know there are two different hold down clamps.

You use vac for timing and idle quality so you know that when the timing changes, the mixture setting will be different. Glad you are headed in the right direction.
 
Stubby, I'll have to get back you on that when I find a finner measuring tool, mine is non-digital and reads the same size.. lol

I was pingging on the freeway yesterday so I pulled off and changed my timing, I'm now idling @ 700-900 with roughly 10-12 vacuum at temp, I don't ping anymore unless I'm on it in high gear going uphill, I drop a gear and the ping goes away, I'll have to continue to fin tune it until it no longer pings anywhere. but for now I'm hunting for a distruibutor clamp that I can swap, or to figure out some way to modify mine to work better.

I'm having the most frusterating time not flooring my pedal, right now it sits perfect hieght, but the floor is too far away and when floored the little stick between the pedal lever and the carb fly's off every time, I'm looking for a block to mount to the pedal arm but can't find the right size.

while It was up on blocks I got 16mpg, and last night I got 14mpg, Hopefully I can get the timeing stationary soon and the MPG will stop moving as much as the timing.
 
Just a quick note on fuel. I cannot run regular from Exxon. I can run regular from just about anywhere but Exxon.
 
TYVM guys, almost there

still figuring out how to get it to idle better cold, it's alot more dependable.

to keep my DUI from moving I took my angle grinder to my clamp and grinded about 1/4inch away on the bottom from the edge where it rests on the DUI. now it's snug and doesn't even move, I did check for an O-ring, I have one and it's in good condition, I bet I was leaking due to it not being as tight as possible I'm very happy with it so far, I'll degrease that area and watch it for future reference.

I'm running 91 octain, seems to like it more and I can run more timing, 18+ MPG agian ;) in the city, and 21 on the road.

Steering I figured out, suspension is complete, and my disk brakes are on thier way.

Now to kinda change topics to oil seepage...
I'm getting alot of seepage at my head gasket, when I received the engine from the build shop they said it was ready and I asked them if I needed to tighten anything down after a few heat cycles, they said no it won't leak... I'm thinking of just tightening it, can't hurt...
But what about the oil pan, I have gone through those and they are all snug/tight, the rear seems to have seepage too, but it's not sealing up, should i try some oil adative to try to seal it up, I got 12k on the new engine and it's been doing this since day 1
 
I'm wondering if the oil pan bolts have been over-tightened.
If so, the pan edge could be deformed, it's very soft. They are not supposed to be tight.
9-12ft/lbs IIRC, which is practically finger tight.
Also the bottom edge of the block may not be true.
Did they use a gasket, or just some Permatex?
 
Jack,
it looks like they used just a gasket, no permatex anywhere, so I'm thinking of pulling it, and adding some, or drop it without disconnecting anything and appling some with my finger then re-snug it, yes I know the pan is very soft metal and the bolts are little more than hand tight, not too tight though IMO...
 
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