what happened???

Just a quick up date. I havent had much time to mess with the jeep, but I did take off the valve covers and look at the springs. They looked fine, I went over everyone of them, I did find out they are double springed which I didnt know. The carb is still off, but I will be home for the next week so I should be able to get on it. I have a vac gauge now, if the throttle plates were open too far and off the idle circuit, could that cause the no vacuum at the manifold vac port, and explain the vacuum at the timed port at idle? At this point I am going to blow the carb out and reinstall it and see what happens. I will keep you posted. thanks

 

As you open the throttle, your port and manifold vacuum increases. You won't lose port vacuum until you go back to idle. The manifold vacuum will rise until beyond half throttle then drop off as you go towards wide open. I think I go along with A Mandery (thread #25) on blown head gasket. If the gasket is blown at the small portion between two cylinders (just a little) it will not be in the water jacket area. If the blow is small enough it will still allow both cylinders to pull enough fuel to fire but will cause pressure (compression) from the firing cylinder to blow over to the next cylinder as it is on open intake valve. This causes the intake manifold to be pressurized, granted not much but enough to screw things up. I highly recommend a compression test.

 

I got to spend some time yesterday on the jeep. This is what I have found out so far. The timed vac port on the side of the carb is pulling 5" of vac at idle, the full manifold port in front of the carb on the carb base plate is 0,(the needle bounces around on 0) and you can feel puffs of air coming out of it. I found a plug in the manifold itself between the carb and dist, I took the plug out and put a fitting in and hooked up the vac gauge directely to the manifold to check vac, it is pulling between 14-16" of vac. So, I just hooked the advance to the spark timed port on the side of the carb and drove it to my friends for a few hours. I seemed to run decent, the only gripe I had about it was below "say" 1800rpms there was a slight stumble when applying the gas then it would go. It was like the gas was either on or off, no smooth transitions. Above 1800rpms it was fine. So, my question is do you still think it is a head gaskete? It seems to me that it is in the timing or carb. I am using a B1 vac advance can, not sure if thats the right one or not. What do you think about doing this, I was thinking today I would hook the vac advance hose directly to the fitting I put on the manifold and see if that helps it any??
with the manifold pulling 14-16" of vac but im getting nothing from the carb manifold port, do you think that indicates my carb is toast? Oh, I do plan to do a compression test just to check as soon as my friend finds his gauge. Thanks and MERRY CHRISTMAS TO ALL OF YOU.

 

Is that a 4160 or 4150 Holley 650 DP?
According to Holleys site that one should have one timed port (for vacuum advance) one port that is full vacuum and one that is for PCV (which I would have thought would be full vac, but may not be)

You may be using the wrong ports, while trying to do this?

 

http://www.holley.com/data/products/pictures/large0-82651.jpg

This one maybe? With two metering blocks with mixture screws at both ends?

 

that looks close to it but not it. The model number is 4777-2 650 holley Dp 4150. My carb only has the screw on the front metering block. I have the (PCV or brakebooster) port on the back of the carb caped off. The port on the side of metering block is ported and the one in the front of carb on the base plate is manifold vac I believe. The one on the back is full vac also, I havnt hooked the hose up to that one and will see if it pulls vac. Getting ready to go mess with it now.

Ok, it now a few hrs later and this is what I did. I hooked the vac advance hose to the fitting I installed directly into the manifold and caped the "timed port" that the hose was attached to, and istantly noticed a improvement in idle quality, and my timing went from 12* to about 18* maybe even 20 my timing tag only gos to 16*. It still pretty much has the same problem, if you try to cruise or slowly aply the gas it will stumble for a few seconds then go just fine. It happens at any rpm range below 1500, over that it seems just fine. Im thinking it could be carb out of adjustment, to much inital timing, advance curve wrong(wrong vac can), and im not dismissing the above mention of head gaskete, just waiting on my friend to find his compresion gauge and trying everything else in the mean time. once its going it seems to run just fine. its when you try and cruise at say 30-40 mph and slowly applying the gas. don't do it above 1500 rpms. Oh, I did check the big port on the back of carb for the brake booster and pcv valve and it is pulling 14-16" of vac.

 

Hey guys, I played with the jeep some today. I have thought my problems seemed like a carb or timing issue, so I made a home made timing tape and didnt like what I found out. With the vac advance hose pulled and pluged, initial is 14*, I reved it to around 3000 rpm's and only seen 24-28*, I pluged the vac hose in and reved it to around 3000rpms and it went to around the low to mid 50's. I stoped marking my timing tape at 44* so I dont know the exact number. Not sure where to go with it from here. Im thinking I need to limit the total so that it is around 36* and change the springs in the dist to bring it in faster??? I have never messed with recurving a dist before. I have the B1, (PN1465,I think) vac advance can on it now, should that be changed as well?? Thanks for any help.