high lift cam or vacuum leak?

[GearAddict]

OK...Manifold replaced...took longer than I thought, but I spent some time inspecting what was going on in the lifter valley.

In addition to what I posted above it appears that at least some minor gasket match porting was done to the heads and manifold. I still opted to use the new manifold but I will clean and inspect what was done to the old one (Offenhouser 360) later.

Bad news is, I just started the car up and I get the same 5Hg vacuum as before. Considering the Purple Cam, I'm thinking this might be normal.

I'm headed out to replace the plug wires and maybe the distributor if I have the energy.

 

[440beep]

Have you tried resetting the idle mixture screws and see if the vacuum changes? Perhaps the PO had them all f'd up.


I see I'm the second guy to mention the screws, have you done that yet?

 

[67Satty]

Yeah, if nothing else make sure the idle mixture screws are set 1 and 1/2 turns out from lightly seated as a baseline. That would just take a minute.

 

[GearAddict]

Yeah, if nothing else make sure the idle mixture screws are set 1 and 1/2 turns out from lightly seated as a baseline. That would just take a minute.

Sorry, I know the intake manifold was a little out of order in troubleshooting, but I was dying to see what condition the valvetrain and cam were in.

I set the timing for highest vacuum and was able to get 8Hg at 1,000RPM's ( I should have reduced the idle before moving to the carb I think, more on that later)
I then richened (is that a word?) the mixture 1/8 turn at a timek, both sides until I got to 11Hg of vaccum at which I stopped and dial back a little after it started to run a little rough. When I checked the RPM's were up to 1,200.

I dialed the idle screw down to 900 and the vacuum stayed at 9-10. The engine sounded good overall and reved well not under load (did sound smoothest at 1K idle or above).

I did not go back and check where the timing ended up at, but I think it is advanced too far because it now struggles to start.

Good news is that the vaccuum is up! now just need to get the timing right

 

[440beep]

Just remember, when you change the timing again, you will need to readjust the idle and the idle mixture screws for best vacuum. If my understanding's correct, all three interact together.

Sorry, I know the intake manifold was a little out of order in troubleshooting, but I was dying to see what condition the valvetrain and cam were in.

I set the timing for highest vacuum and was able to get 8Hg at 1,000RPM's ( I should have reduced the idle before moving to the carb I think, more on that later)
I then richened (is that a word?) the mixture 1/8 turn at a timek, both sides until I got to 11Hg of vaccum at which I stopped and dial back a little after it started to run a little rough. When I checked the RPM's were up to 1,200.

I dialed the idle screw down to 900 and the vacuum stayed at 9-10. The engine sounded good overall and reved well not under load (did sound smoothest at 1K idle or above).

I did not go back and check where the timing ended up at, but I think it is advanced too far because it now struggles to start.

Good news is that the vaccuum is up! now just need to get the timing right

 

[19polara64]

Kinda sounds like someone threw a .509 in there, about the right idle vacuum for that cam. I'd check the valve lift before you button it back up. You can pick up a dial indicator and base pretty cheap at Harbor Freight. Rene'

 

[charger360]

a couple of things i get from what i have read. if you have low enough vac in gear at idel and you don't have the right power valve you are going to be dumping fuel which will cause all kinds of issues! and if you have a decent purple shaft in there you are not running enough initial timing! just putting more initial in will get you more vacuum as well. i would think you will need 18 to 20 initial if it will take it at start up and about 35-36 total mechanical. if you run vac advance 50 degrees or so will work ok. you may have to recurve your distributer to get it where you need it. i run into this all the time guy's throw in a big cam and set the timming back to stock even with a stock cam i find that today's fuels need way more initial timming to run well. good luck man hope you can tune it out!

 

[GearAddict]

Kinda sounds like someone threw a .509 in there, about the right idle vacuum for that cam. I'd check the valve lift before you button it back up. You can pick up a dial indicator and base pretty cheap at Harbor Freight. Rene'

Thanks, I will pick one up.

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a couple of things i get from what i have read. if you have low enough vac in gear at idel and you don't have the right power valve you are going to be dumping fuel which will cause all kinds of issues! and if you have a decent purple shaft in there you are not running enough initial timing! just putting more initial in will get you more vacuum as well. i would think you will need 18 to 20 initial if it will take it at start up and about 35-36 total mechanical. if you run vac advance 50 degrees or so will work ok. you may have to recurve your distributer to get it where you need it. i run into this all the time guy's throw in a big cam and set the timming back to stock even with a stock cam i find that today's fuels need way more initial timming to run well. good luck man hope you can tune it out!

I have the initial advance up in the 19-20 range right now, but it went from starting up first time, every time to now I have to crank it for a minute before it will start. I did adjust the idle mixture when I set the timing, so that might have effected it as well I suppose. I will be dialing it back a little today to see if it will sustain vacuum and start easier.

Interesting point about the power valve.. I will have to look into that

 

[charger360]

make sure you don't have too much total timing now that you have a fair amount of initial if it has a stock curve in the distributer it will have to be recurved. to know what power valve you will need you will have to check the vacuum in gear. also if you that high up on idle it will be hard to set the carb screws right as you may be past the transfer slots on the carb because the primary throttle plates are open too far try to keep the idle down low to set the air screws. you can bump it up later to get it where you want it. the rule of thumb is always timing first then carb and keep setting your idle speed so it does not get too high or you will get lost on your settings.

 

[GearAddict]

make sure you don't have too much total timing now that you have a fair amount of initial if it has a stock curve in the distributer it will have to be recurved. to know what power valve you will need you will have to check the vacuum in gear. also if you that high up on idle it will be hard to set the carb screws right as you may be past the transfer slots on the carb because the primary throttle plates are open too far try to keep the idle down low to set the air screws. you can bump it up later to get it where you want it. the rule of thumb is always timing first then carb and keep setting your idle speed so it does not get too high or you will get lost on your settings.

Thanks Charger, I'll be going back through this today.

 

[GearAddict]

a couple of things i get from what i have read. if you have low enough vac in gear at idel and you don't have the right power valve you are going to be dumping fuel which will cause all kinds of issues! and if you have a decent purple shaft in there you are not running enough initial timing! just putting more initial in will get you more vacuum as well. i would think you will need 18 to 20 initial if it will take it at start up and about 35-36 total mechanical. if you run vac advance 50 degrees or so will work ok. you may have to recurve your distributer to get it where you need it. i run into this all the time guy's throw in a big cam and set the timming back to stock even with a stock cam i find that today's fuels need way more initial timming to run well. good luck man hope you can tune it out!

Ok..so I had walked away from the timing issue for a little bit, because my passenger side drum had locked up on me when I took it out for a spin...disc brake kit and front end rebuild kit coming....back to the timing.

I started her up this morning... adjusted the idle down to 850-900 (really doesn't like to be below that), loosened the dist and started to turn to get strongest vac... best was 7hg and the needle dithers between 6-8. Seemed like I twisted pretty far from where it started...then when I checked the timing with the light I was at almost 30 Deg initial timing! It did seem to like this at idle though...is that much advance plausible? I'm scratching my head a little... should I back it down to 20 degrees and then figure out where to go from there?

Any help is highly appreciated

 

[charger360]

30 is too much 20 is ok if you have a lot of cam but 15- 18 should be ok. are you sure you timing marks are good?the balancer slips somtimes and they are getting pretty old! do a tdc test and check your marks. if they are good i would set it at about 18 btdc then tune the carb from there. how much total do you have this is important if the curve in the distributer is stock you wioll have too much. but that is ok for tunnibg you carb you won't be under load. also you do disconect you vac advance when doing you timing right?

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just for fun how far out do you have the air fuel ratio screw turned out? sorry to keep asking questions but it is hard to get a handle on whats going on over the computer! ha!

 

[GearAddict]

30 is too much 20 is ok if you have a lot of cam but 15- 18 should be ok. are you sure you timing marks are good?the balancer slips somtimes and they are getting pretty old! do a tdc test and check your marks. if they are good i would set it at about 18 btdc then tune the carb from there. how much total do you have this is important if the curve in the distributer is stock you wioll have too much. but that is ok for tunnibg you carb you won't be under load. also you do disconect you vac advance when doing you timing right?

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just for fun how far out do you have the air fuel ratio screw turned out? sorry to keep asking questions but it is hard to get a handle on whats going on over the computer! ha!

Charger360, no problem on the amount of questions, I just appreciate all the help.

I am worried the the balancer slipped, but when I checked it a year ago against TDC it was good. I will check it and move to 15-20 deg as you suggested and then take it from there. I am timing with Vac Adv disconnected and pluged at the carb. Dist is hooked to ported vac when hooked up.

As for the Advance curve... I have a new MSD Ready to Run distributor ready to drop in. I might as well set the advance on it now while it is out of the vehicle. I was going to switch ofver to it this weekend (although I think the current mopar unit is working ok). I realize I will have to spend some time dialing it in, but can you suggest a starting point for the advance curve?

On the Idle mixture screws, I have them 3/4 of a turn out from baseline (1-1/8), this seemed to be about the most improvement to vaccum.

Other item I know I need to do is replace the power valve with a 3.5. But if I understand how this PV functions, I assume it is not effecting the tuning at idle.

For a manual trans with high lift cam, what kind of idle speed should I be targeting? The engine smooths out above 950 but will idle as low as 700-750 without stalling.

so, this weekend I will..

1. Check TDC to verify timing marks still good.
2. Set initial timing to 18 deg
3. reset idle mix to stock setting and tune from there.
4. reset Idle, re-check timing
5. Check Vacuum
6. Report findings to all the helpfull people on FBBO

Let me know if I got anything wrong....I will leave out the distributor swap until the timing is more settled.