Got the distributor in, going to be a tight fit on the back 2 plug wires but should work. The MSD is alittle taller then the procomp. Only issue I have hit is that the cap hold down screw hits the coil the way I have it now. Not sure how much adjustment I will have. May be able to get it to work. Can always fab up another coil mount elsewhere. Think I will just give it a shot the way it is and if I need to rotate the distributor more I can either move the plug wires one time or reset the distributor one place back. Then clean it up this winter. Should get her running again tomorrow or Friday. Hopefully.

 

Good luck with it. Let us know how it works out.

Also do you have the part number of the crane can?
Thanks

 

I went with Crane 99601.

 

Got it in and temporarily wired without the 6AL. Took alittle bit to find the sweet spot but with the help of my wife I got it fired. Didn't get to let it warm up and mess with it much, but got it running and set the total timing to 34. Was still pretty cold but would almost idle on its on, but still wouldn't.

Hopefully get some more time within the next week to get it out of the garage, warmed up, and can mess with it. Glad to finally have a distributor that is adjustable.

 

Not really much to update with. Got the truck out and drove it some the other day. Had to open the primaries a tad to get it to idle when warm, but at this point I dont care. Still going to work with it, but was nice to drive it and be able to come to a stoplight and have it idle on its own. With the time change and deer season I dont have a lot of time to piddle with it, but planning on working more on it in next week or two.

Plan right now is to verify the timing again and see how the vac advance is acting. I havent touched the adjustment on it since I installed it. Then go from there with the carb.

So.......we will see.

 

My brother and dad where down for the weekend, so today we played with the truck a little. Needed to get it cleaned up and put up for the winter anyways.

Well I drove it and got the truck warm. Sitting at 180, I had dad in the truck and my brother and myself up front. First thing I done was unhooked the vac advance and checked the timing. 24 degrees in and out of gear. Total 34 degrees by 3k.

In park at idle with idle at 1300 rpm with vac advance hooked up, sitting at 50 degrees advance. 18" vac. Unhook vac advance it dropped alittle rpm and ".

Now put it in gear is when the problem becomes very noticeable. With the vac advance hooked up, the motor will idle in gear. The rpm fluctuates. RPM will hang steady around 1k, then suddenly drop to 600. Then after a bit it will recover. Vac drops off greatly. Timing fluctuates greatly with the vac change. If the canister is unhooked, vac and rpm still fluctuates, but of course the timing doesn't change. RPM acts the same.

So we start looking for vac leak with some carb cleaner. Sprayed everywhere but finally found a small spike in rpm and vac around the brake booster line coming from the carb. Didn't have much time to fool with it, but that's the first place Im going to go back and try to ensure that there is no leak.

So, atleast I have something to work towards.

 

can you record a video of a vacuum gauge with the engine idling at 1000 rpm in park and holding at 2000 rpm in park?
Also can you take pics of all 8 spark plugs?

aside from that it could be a vacuum leak (maybe the underside of the manifold that you cant check. The spark plugs will tell you if that is an issue), miss timed camshaft, misadjusted rockers, missfiring or low compression cylinders.

 

I could never get mine to work right with the auto transmission using manifold vacuum, the RPM drops too low and dies as soon as I put it in drive no matter how it's adjusted, it works good with ported vacuum and I don't feel any difference in drivability

 

.

 

Therein lies the problem with tuning for full manifold vacuum.
Unless you precisely know the rate and settings of the vacuum canister, you may run into problems with the idle speed dropping when placed in gear, then the vacuum drops some, the timing drops out and the whole thing spirals to a stall. Remember that it only takes about 2" of vacuum range (set points are adjustable) for the can to be fully deployed so if you fall out of that sweet spot, then you're bound to have idle issues.
What worked for me was a hand held vacuum pump to actuate the vacuum can manually. I tie the advance weights so they can't open and I work with the vacuum pump and observe when and by how much the timing changes. Then you'll get a real sense of what's happening with the the timing when everything is connected. My exmple is: engine vacuum with 12 degrees initial (mechanical disabled) and no vacuum advance is 12". Adjust the can so that all of the vacuum advance is in by 10". In my case I had 20 degrees available in the can. That gives me 32 degrees at idle with 12" of vacuum and my idle speed set accordingly. Here's the important part, when I drop it in gear, it's important that the vacuum doesn't drop below 10". Otherwise I lose all that advance and the idle speed goes away. If it does, I re-adjust the starting point for the vacuum advance and start again.
I wouldn't discount the possibility of a vacuum leak but once you clear that up, you may find that full vacuum is very usable.
The difference is drivability is in the idle quality and to some degree the part throttle responsiveness. Full manifold or ported vacuum will behave much the same at cruising speeds where it has a real benefit.

 

The problem isn't the vacuum can hooked up to full vacuum. He says it still fluctuates when idling in gear without the can hooked up. The vacuum reading should not fluctuate like that. This is usually the case with cylinders that aren't firing properly. When hooking up the can it is however causing a timing fluctuation issue described by skinny, but this is not the root problem. Just an after effect.
Please record a video of the vacuum gauge like I asked for earlier. Also do you have a temp gun? If so check each header pipe about an inch from them head. they should all be around the same temp. if not that's a bad running cylinder. Or you can also try a cylinder balance test.

 

Weather looks good for this week. Will get you a video by atleast friday.

Dont have a temp gun, although I may look into getting a cheapo for stuff like this.

What is a cylinder balance test?

 

like this

except you are going to have to actually poke the boot with the test light. They all should drop around the same rpm and sound the same when shorted out. If one has no difference it is not firing and if one hes less rpm drop or sounds different than the others then it is not fully firing.

 

Ah. Ive done that before on a 3400, just didnt know what it was called.

Doesnt feel like an underpowered cylinder, but then again, I dont really know.

 

50* its way to much idle advance for an automatic, the engine has to make some power at idle to overcome the load of the torque converter not like a manual transmission, ive been fighting with mine for 4 years, had it every way possible and no way it runs right with manifold vacuum unless I have less than 8* static, even with 18" of vacuum at idle, but then I won't be no where near the optimal at cruise.
Try this: set the max advance to 36* and let the idle advance be, you don't need 50* at ide not even 30, plug the vacuum advance to the ported vacuum, set idle at +-1000 and afr to around 12-13 and report back. I could be wrong but what you are experiencing sounds like what I've been fighting with
Mine idles at 14* and 16" of vacuum 13:1 AFR, when I shift to drive it only drops 200rpm and 2" of vacuum afr goes to 14:1 , with the vacuum on manifold for 36* and 18" vacuum ( after readjusting idle) when I shift to drive it drops 600rpm vacuum drops 6"and afr to 15-16, if its not full warmed up it wont stay idling

 

Do you know the specs of your vacuum can? How many inches of vacuum are needed to start the advance and when is it all in by specifically. What is the total available? Do you have any means of adjustment?

 

I don't know the specs but its adjustable and i can even limit the amount of advance max is 22 i have it set to 17, i checked the advance in drive with manifold vacuum and it doesn't change, it just doesn't like all that advance period

 

I fired the truck up and pulled it outside and let it warm up to about 170 and took some videos with the vac can hooked up. One thing I did notice is how erratic the AFR monitor is at times. Exhaust smells rich. Only thing that I thought about after the fact was that Im not sure where the transition slot is right now since Ive messed with it to get it atleast driveable. Probably 1/4 to 1/2 turn open past square. But im not certain on that. But at a steady state I don't see how that could cause what Im experiencing. While driving at cruise the AFR monitor is about 13-14. If you punch it there is a slight hesitation but then pulls very well.

Videos are being uploaded. Durn slow connection. Give me a bit.

 

Another thing I want to add that confuses me is this.

Like I mentioned before, Ive drove the truck for years with the carb being way off from what it should be. Meaning that the main idle screw was opened way too much. Well past having the transition slot square. It was probably a full turn or more past square. But the truck would idle in and out of gear. It also wouldn't drop in rpm as much when I put it into gear. Probably idled around 1000 in park 800 in gear and never acted like it would die.

Fast forward and the only real changes that have been made is that the main idle screw has been screwed in to where the transition slot is closer to being square, while opening the secondary screw. Now the idle is higher and the rpm drop going into gear is much greater. Is there anything that could be out of whack in the secondaries that could be the matter? Just seems like it runs better the more the mains are opened and the secondaries are closed.

Just trying to make sure I mention anything and everything. Maybe I just need to pull the carb and start over. Resquare the slots, turn the secondary screw around so I can adjust it without pulling the carb, etc. In ways Im glad winter is coming, I wont have to worry about wanting to drive it!

Videos are still uploading.

 

Okay, here is one at idle. Truck sitting at about 170.


Here is one in gear at idle.

http://www.youtube.com/watch?v=cwQpw...ature=youtu.be

This one is at 2k in park.

http://www.youtube.com/watch?v=MGI6z...ature=youtu.be

Here is a second one holding at 2k in park.

http://www.youtube.com/watch?v=XpclN...ature=youtu.be

And here is one taking a short little drive in 1st.

http://www.youtube.com/watch?v=kgR0Q...ature=youtu.be

 

Couple of questions that you may have answered but I'd like to ask.
What are your cam specs?
Have you had a timing light on it while it's idling and the rpm is changing?
What is the carb and it's history?
What was the timing at during the video? Initial. Vacuum advance source. Mechanical curve (starts at, all in by, how much total)?
Fuel pressure?

 

Cam is a solid flat tappet Lunati grind: 244/249 @.050 .530/.565 108 LSA

Yes on the timing light. Timing remains stable in park. In gear it remains stable then you can watch it drop then pick back up. Basically follows along with rpm and vac.

Carb is a 4150 650DP. History is unknown. That's one reason Ive wondered if this is simply a screwed up carb or if previous owner done something that I don't know.

24 initial. Vac advance hooked to manifold which brings in 16 deg. 10 mechanical coming in about 1500 and all in by 3200.

Fuel pressure 5psi.

 

Your timing specs look spot on. That's 8 initial plus 16 vacuum for total of 24 at idle, correct?
I had thought that perhaps your mechanical advance was hanging up or on the verge of deploying at your idle speed in gear. That would cause some of the symptoms. I've had a situation where m y advanc ewas set to come in about 1000 rpm. As time went buy, and the springs lost some of their stension, the advance start moved closer to idle speed. Caused all kinds of grief. Doesn't look like it in your case though.
This is all with the manifold advance disconnected too isn't it?
It's difficult to see on the gauge in the video. What's the idle vacuum in the picture in your next to last post. The needle is in the green.
And yes, it could easily be the carb. Does your Holley have 4 corner idle?

 

No. That's 24 initial + 10 mechanical = 34 total with 50 max with vac advance

High initial, but if you read back through, I done on purpose to make sure that it wasn't a timing issue causing the problem. That and with the way it is running right now, I don't think it would idle in gear any lower.

The mechanical advance is working.

Those videos are with manifold vac advance hooked up.

That is showing 20". When holding at 2k, its at 25". But in the video when it is in gear it starts out around 9, then jumps to 15, then bounces between 11 and 13.

When Im driving it, it runs good, but when I approach a stop sign, as I slow down everything acts like it should. Vac is good, idle is good. But as soon as I come to a stop, the vac drops below 10, the idle drops near 600 and the truck is barely running. But I can shift into park at that point and the rpm jumps to 1200-1300!

 

When the vac advance is unhooked, the rpm and vac still jumps around like that.

So I understand why the park idle is high (to an extent) because there is enough vac adding to the timing (while connected to manifold), then in gear the motor isn't making enough vac to add the vac advance.

But something is causing the fluctuations and I don't think it is related to timing.

 

That perfectly describes how full manifold vacuum advance behaves when the set point doesn't match the idle vacuum level. I know that's been mentioned but I think it was determined that's not an issue.
Regarding the carb, and I think we've touched upon this before, you mentioned how it liked the primaries opened and the secondaries closed despite the mis-set transfer slot. Opening up the secondaries (as you have) to help idle quality was a new one to me as my old carbs never had a 4 corner idle circuit and it didn't make any sense to crack the secondaries a little to compensate for a larger cam. We always drilled the primary butterfly to enhance air flow at idle. Sounds like your engine might like the same treatment even though I think the trick is outdated now.

 

Well that right there flew up a red flag to me. Ive read and read about cracking the secondaries, but I don't have 4 corner idle adjustment.

Is that mandatory?

Because Ive never read anything about that, but it makes sense. Seems like right now the way it is, the motor would be relying purely on the secondary booster signal to supply fuel.

 

No, I don't believe it's mandatory. It seems to be an accepted means of adding a bit more air, not necessarily fuel, into the intake. The idle circuit isn't needed. I've never done it that but can understand how it work. Too much and I'm sure there would be trouble. It's a different story with four corner idle in that there 2 sets of transfer slots to set so messing with the secondary idle stop screw gets you into the same trouble it does with the primary.

 

Id skip drilling holes in the butterflies and drill your idle air bleeds/tap them and play with those it will idle right and run off that circuit alone like its supposed to
ran into the same thing on a 750DP idle circuit was lean with the cam always burned eyes. Wound up with an AED built to spec idles down as low as I want.
IAB jets takea a minute to change

 

doesn't look like you have a funny cylinder from the vids.
I am beginning to think there may be some issues with the idle circuit. Maybe clogged or something.
try this. Hook the vac can up to ported for now. resquare the transfer slots and turn the secondary stop screw upside down. Reset the a/f screws and idle speed in gear. Forget what the a/f gauge is showing. just set the screws for max idle speed and or vacuum. Then turn them out another 1/8 of a turn. Set it for like 800 to 1000 in gear. whichever I likes. Forget about rpm in park for now and see how it is. Its basically a pretty big circle track cam and is going to need to be idling high in gear for it to be stable.
O and don't drill holes in the primary plates. opening the secondaries is doing the same thing.
As far as the hesitation off idle. It probably just needs a blue pump cam, but don't worry about that until the idle is set right.

 

Thanks guys. I really appreciate it.

 

wow, all this time, and someone just now thought that something on a used carb may be clogged ... if i were you, i would strip that carb, soak it in cleaner (make sure no rubber is left in it anywhere) blow air through every hole in it with a compressor, and go from there (if you have not already done that, it should have been the first thing done, imo) also, if you have ever had a backfire through the carb, and you do not have power valve saver(s) you have most likely blown the power valve(s) and it will never tune right at an idle, but will run good when wot ... it will also make it so that when you open the primaries a bit more, it will idle better ... so if i were you, i would get her cleaned and replace the power valve(s) and put in some savers

 

If the main transition slots are squared and the carb is actually idling on the idle circuit the power valve has no effect on afr. You could remove it and the most difference it would make is maybe .1 afr.

Do you have a friend you can borrow a carb from to test?

 

that is only true if you cap it after you take it out ... you cant just take it out and leave the opened hole ... and if it has blown, it is an open hole
and so far, it has shown not to idle with the slots squared off, but with the butterflies opened more ... that has been the problem (to a point) he had it running and driving when the slots were not squared off

 

If you are idling on the idle circuit you can remove the powervalve or have a blown one and it doesn't make a difference. I also use 10.5 valves in cars with less than 10 inches of vacuum at idle which is also the same thing. obviously you cant take it out and drive like that. I was making a point that it has no effect on idle.
Please research this as you are incorrect.
Here is something I remember reading a few years ago.
http://speedtalk.com/forum/viewtopic.php?t=14523

 

a lot of other people seem to think you are wrong if you read here

http://forums.corvetteforum.com/c1-a...-symptoms.html

 

idk, just going by what i have done in the past, and what i have read before i posted in this thread ... not trying to give any bad advice, but i did read in more than 1 spot before i posted, and i have seen it happen to my own car ... one reason i stopped using the holley and went to edelbrock (i didnt know about the savers back then)

 

That thread has no actual information on how a pv works.
If the pv is effecting your idle then you are not idling on the idle circuit. It is really that simple. The problem is a very large percentage of people are not idling on the idle circuit because their main idle screw is turned in to far. that is where the whole pv effects idle thing comes from. this is due to many reasons, but the 2 most common are not enough timing at idle for the cam size and using the main idle screw to raise the idle instead of the secondary one. Dominators and high end carbs actually have a secondary idle screw instead of a little stop screw to fix this issue.

 

so, at idle, if you had the pv out and left it open, no gas would get into the carb from the pv hole?

 

no, fuel would go into the pv restrictor holes. It just wouldn't make it's way into the engine until the carb is into the main circuit. The pvr's don't flow fuel into the idle circuit.

 

well, i just called holley to see who was right (Technical Service department at 270 781-9741) and they said yes, without a doubt even on idle circuit a blown pv will make it run rich and not hold a proper idle

 

Dude, they are 100% wrong!!!!!!! And this is nothing new, their tech department doesn't know their *** from their elbow. and even the guys at holley who do know will still tell you that because they don't want to have to teach you how to properly set up the idle circuit and transfer slots on a big cammed car. Its just easier for them to have you idle on the mains and have a pv half idle vacuum.
Who do you believe some moron tech at holley or the people who actually tune and build carbs for a living like in the thread I provided.
So I will say this again in big capital letters for all to hear.
THE POWERVALVE HS NO EFFECT ON THE IDLE CIRCUIT. EVER PERIOD.

 

hahaha ... i dont think you know more than they do ... he was able to tell me how and why it will effect the idle ... but you keep telling people you know more than the tech guys at holley ... feel free to prove me wrong by sending me an uncut video of your car running at idle, then taking out the pv and leaving the hole open, then start it back up and show me it idling fine ... all uncut ... then i will say they are wrong, i am wrong, and you are right ... but until then i will stick to what i have seen with my own eyes, and heard from holley ... i am done here now

 

ok I stand corrected on the removing the pv thing. I forgot the well behind it has vacuum and will let fuel in through there. Its actually the main jets you can remove and have no effect on idle. So a broken valve can cause a over rich issue.
But if the valve itself is open at idle it will have no effect on afr. So if you have a 10.5 valve in an engine that makes 8" vacuum it will not flow any extra fuel in the engine.

 

I installed a new pV earlier to make sure that it wasn't the issue. Also installed the lowest possible 2.5 to further prove that it wasn't the problem.

The carb has been took apart and air has been blown through every orifice.

Now that was earlier, if it has a small leak that developed IDK. I have had them blow before on our Chevelle (600 4160) and I know the pain they are when they blow at idle. This doesn't act that way. But of course, I am not ruling out anything. When I pull the carb back off again, I will install another one just for good measure.

Closest other carb I can swap on at some point would be a 600 4160. I may try that sometime.

 

yea try the other carb if you can just to see if you still have the same issues or not. I doubt it is a blown pv. if would be dumping so much fuel it would be almost untunable.