kip
thanks for the advice

Re: the cap / rotor mismatch i have fiddled with a couple of different combinations but will re examine this again.

Re: air in the oil pressure guage line i attempted to bleed the line by watching the oil move thru the line and then intalling it on the guage so i dont think this is a problem but at this point i will try anything. When i disconnected the line from the block oil pumped out on the floor of the garage pretty hard but i still have zero pressure on the both guages i tried.

Re: arcing plug wires i examined this carefully in the dark and could see no arcing. Additionally i have had two sets of plugs and plug wires on the motor so i doubt if this is causing my problem

The miss seems to worsen as the engine warms up. Doc advised me to loosen the valves on the aftermarket comp cam which seemed to help some. Right now the truck is back at the machine shop. they are replacing the leaking head gasket for the second time and i also asked them to consider my oil pressure situation. I am beginning to think i gotta a crappy rebuild but i have always had good service from them in the past.

Thanks again for the advice and i will keep you posted.

Dean

PS Kip I see that youre in Akron. I am located about 15 miles up the Ohio River from Marietta. If youre ever down this way drop me a pm as i would love to see your truck and shoot the breeze with such a devoted slanter.

Dean,
Been thinking about something else - if the assembler neglected to use sealant on the oil pickup tube, that might draw a little air and make for a low oil pressure reading. It would still flow, and it would probably make good pressure at higher rpm, but it would be low at low rpm. It's a thought.

I'm trying to think of a situation where a blown head gasket would screw up the mixture, but the miss as you describe it sounds more like an ignition issue than a fuel issue. I guess a blow head gasket could allow one cylinder to put exhaust or fuel/air into an adjacent cylinder, but if that were happening the engine would barely be running. Just a guess.

I don't go down toward Marietta that much, but if I do I'll look you up. Marietta - lovely town.

Kip

_________________
1965 Valiant wagon Turbo slant (work in progress)
2000 Chevy 155" cargo van - The Abductor
1970 Newport convertible
1996 Buick Roadmaster Wagon
1966 CruiseAire motor home
1990 Toyota 1 ton box truck TURBO slant (scraped)

sounds good Kip
i look forward to your visit. Every once in a while i fly out of Akron so maybe i could look you up sometime as well.

The head gasket is leaking lots of oil. this is the second time i will have it replaced. The compression is spot on 120 # for all cylinders except 4 and 6 where i cant seem to thread my tester in the plug opening. I cant hear or feel any gas whizzing past the plugs on those cylinders. i kinda think the compression is probably ok.

The miss sure does 'feel' electrical but i dont know. Is worse when after full warm up. Loosening the valves seemed to help along with disconnecting and plugging the vacuum advance. I also wonder if the aftermarket cam is somehow involved in messing up the distributor advance. I might change it back to stock or attempt a dizzy recurve. i've read lots and lots about it on the board but have never attempted one. Always a first time for everything but its colder than heck around here now.

But i cant live with it until spring so break out the wrenches. (sometimes i feel like this has become my secon job)
stay in touch
Dean

i took the motor to the machine shop. they couldnt get the pressure up and ended up pulling the motor and disassembling it. turns out a cam bearing was not installed properly. it had already slightly damaged a couple of the bearings so they reinstalled new bearings. the cam they said was ok. oil pressure now great.

they also of course replaced the head gasket and decked the block about .002 they said it was out only .003 so i am hoping the dang thing will no longer leak around the head gasket

it still has a very slight miss at cruising speed and at coast down. most
non slanters probably wouldnt even notice it but i am a perfectionist as most of us are on this forum.

here is my situation. i have an aftermarket comp cam 264s-10. the motor is out of a 75 duster that i have installed in my 87 dodge 150, with super six. based on doug's great advice and never expecting the manufacturer had such bogus lash specs i have loosened the valves considerably. that has really helped. the motor now idles perfectly with rock solid 19'' of vacuum. the machine shop has them currently set at intake .018 / exhaust .028 cold. the motor sounds great with that old familiar solid lifter rumble we all know and love (and without clatter).

after reading all of the dizzy recurve posts on the site i am now thinking the miss MUST be in the advance.

Reading Ted's advice i decided to check: Initial advance is at 25 (i set initial advance to maximize vacuum). Mechanical advance is 17.5 at 2500 rpm. Total is 42.5 which exceeds Ted's recommended 32 but if i reduce the initial to 10 as he recommends it runs like a constipated pig. 'No power at all. Very slight pinging when stressed but nothing i would consider abnormal or in any way alarming.

Now here is my dilema: when i hook up the vacuum advance at 2500rpm i get no additional advance at 2500 but the engine miss is much worse than it is if i leave the VA pod completely disconnected. Hooking it up causes the engine to shudder like it did before i loosened the valves. The VA port on the carb shows no vacuum at idle and begins to come alive at about 1300.

i am pretty much a virgin as it relates to recurving a distributor. Based on all this i am hoping some of you might have a thought about where to start. Perhaps try another VA pod and see if that kicks in some advance and retard it little on the initial advance? Does the mechanical advance seem ok? i would really hate to mess with the springs and governor but would if necessary. i think it must be tough to find a decent distributor these days. I try to by good stuff usually from NAP but cant seem to find one with an adjustable VA pod.

I have come this far and want the dang thing to be right.

Thanks for all the help. you all have been extremely helpful over the years.

Dean

Dean,
I agree with you that your advance is too much which will cause it to feel flat at cruise and misfire. You shouldn't be going over 16 degrees initial. 25 degrees is way too much! Most folks are happy with 10 to 12 degrees when the cam is installed (degreed) correctly. It sounds like they did not degree your cam when they reinstalled it. They should have advanced it at least 4 degrees for the low end torque your trying to emulate/get with the high initial timing.

Do you know what governor you have? or what pod your running? look on the arm and you will see something stamped on it like 8.5R, 11R, etc.
You need to map your distributor every 100 rpms to see what is going on. Start at 600 and work your way up to 2500 and check at 3000.
Once you know what the distributor is doing and what parts it has, we can help you get it dialed in.

Plugging in the pod must be putting you well over 60 degrees which causes the shuddering. Been there done that....

Take your time and one step at a time. Document everything, rpm vacuum and timing. Do your baseline measurements with out the pod plugged in. That way it will be clear how much mechanical advance the distributor is providing. To make it simple set the initial at 10 degrees.

_________________
Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

Thanks Ted

One item re the VA pod is that at 2500 rpm i dont see it adding any advance at all????

I will plot it out as you recommend: set initial timing at 10 degrees and work my up from 600 to 3000 rpms in 100 rpm increments, recording vacuum, and timing with and without the VA pod and report back

i will also try to determine what governor and pod i have but am a little leary of disassembling the dizzy. When i have looked at this in the past i dont remember any markings on the VA pod arm...but maybe i just missed it. Is there an easy way to see what governor i have?

i really appreciate the help and am anxious to jump on this as soon as i can do it with out getting frostbit...It got really cold and snowed last night



dean

Dean,
You can see what is stamped on the arm with out taking the pod out. Just pull the cap and read what is stamped on the arm. The governor is under the plate so it is much easier to just make a plot with out the vacuum advance. Later on when you take it apart to change springs you can see what is stamped on the governor.

_________________
Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

Hi mopardean. I shall not distract you from fine-tuning your ignition, but you mentioned that your miss seem to worsen when the engine is warm - i.e. the mix is leaner because it is off the choke. Are you certain that your carb is tuned for your new cam? The difference in the vacuum 'signal' the carb receives with a hotter cam may be enough to make problems. What intake/carb setup do you have?

Also, have you measured the ported vacuum at the revs you expect the dizzy pod should be activated? I presume the pod is not leaking?

Olaf.

_________________
Aspenized

I don't have much to add here other than on my carb, 1945 Economaster, the timed port is claimed to be for the charcoal cansister. I found that it did some weird things as far as when it opens and how much vac it generates. I should have/will do what Ted suggests which is mapping the whole thing out, but for now I had much better luck with using a regular full-time vac port.

I bought the right sized timing tape from Summit, and it lasted about 2 days before it blew off. Anybody got any advice for that? I've got a dial-back timing light, but feels like a 60 degree timing tab would be more accurate.
Kip On Truckin'

_________________
1965 Valiant wagon Turbo slant (work in progress)
2000 Chevy 155" cargo van - The Abductor
1970 Newport convertible
1996 Buick Roadmaster Wagon
1966 CruiseAire motor home
1990 Toyota 1 ton box truck TURBO slant (scraped)

Again many thanks for everyone's advice and assistance. I am really anxious to jump on this again when it warms up. I am sure Kip can relate being from Akron and all but it was 10 degrees this morning. Back in my college days it didnt seem so bad working on stuff in this weather but now i guess i have devolved into some sort of wuss ..


As for the specific comments:
Ted re: markings on pod and governor: understood and thanks again

olafa (a.) miss worse when warm: since i have loosend the valves the miss is consistent when warm or cold.
(b.)I am running a brand new (bought from Dan a while back) stock holley 2280 on a stock super six intake. Other than mess with the idle setting i havent attempted any changes to the carb at all.
(c.)i have not measured the ported vacuum at the revs i expect the dizzy pod should activate as i dont know when it really should activate. The VA port on the carb starts to measure vacuum at 1300 rpm but even at 2500 rpm i cant see where the VA adds any advance YET i know it runs worse when i connect the VA pod to the carb.
(d.) i really dont know if the pod is leaking. the dizzy is new of course but that doesnt mean much these days. i am not sure how to tell if the pod is leaking

kip re: using full time carb port: i tried that on the egr port and it runs far worse. no doubt adding way too much advance. right now it runs the best without the VA connected. i am also using a dial back timing light. Never had any luck with the tape either.

Looking forward to warmer weather

Dean

Dean,

You need to run ported vacuum line on the vacuum advance pod or it will kick in in all the way at idle running the advance up even further on top of your initial advance........when the vacuum drops (pushing on the gas pedal to start out or going up a hill) so would the timing when hooked up that way. You should hear quite a difference unplugging the line and plugging it back in. Unplugged the idle will drop, plugging it back in the timing and idle go way up! Not good.........you need to fix that as soon as you can.

On most of the modern vacuum advance pods you can dial in where they start to engage with a 3/32 allen down the snout. Review the 4 pages Doc scanned in on how to Recurve a distributor and set up the vacuum advance pod. It's under Engine FAQ, Recurve Section.

That will give you something to do while it's cold out.......
Once you get the timing advance corrected your engine should run very good.
While it was being rebuilt, did you increase the compression? If so, how much?

_________________
Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

Ted,

Sorry for the miscommunication. running ported vacuum from the carb to the pod is exactly what i have been doing. I was just responding to kip's suggestion that his motor runs better with full time vacuum. When i tried this my motor runs far far worse. Disconnecting the VA and plugging the carb port makes mine run better particularly at higher rpm which seems to further confirm your suggestion that i have too much initial advance and / or a misconfigured dizzy.

Today when i called the machine shop they confirmed your suspicions and said they didnt degree the cam as they didnt have an offset woodrift key. The cam instructions say the cam doesnt really need degreed for street applications since they have alreay factored in about 4 degrees advance anyway. Keeping in mind my intention was to build a nice streetable work truck (but one that doesnt miss) do you think i need the offset ?

There was no significant increase in compression when the engine was rebuilt, just cleaning up the head and deck surfaces.

I will reread Doc's recurve instructions and plot the dizzy's performance first chance.

Thanks again for your interest in helping me.

Dean

From Ted:
You need to run ported vacuum line on the vacuum advance pod or it will kick in in all the way at idle running the advance up even further on top of your initial advance........when the vacuum drops (pushing on the gas pedal to start out or going up a hill) so would the timing when hooked up that way. You should hear quite a difference unplugging the line and plugging it back in. Unplugged the idle will drop, plugging it back in the timing and idle go way up! Not good.........you need to fix that as soon as you can.

Been wondering about this, but was kind of embarrased to ask because I'm sure the answer is Engine 101. But why is this a bad thing? If the engine is idling, it's not under load so it should tolerate quite a bit of advance. As soon as you step on it, the vac drops to near nothing so the vac advance is out of the picture anyway. Assuming that you can get it to idle at a low enough RPM , why don't I want VA to kick in? Particularly on a stick car?
Kip

_________________
1965 Valiant wagon Turbo slant (work in progress)
2000 Chevy 155" cargo van - The Abductor
1970 Newport convertible
1996 Buick Roadmaster Wagon
1966 CruiseAire motor home
1990 Toyota 1 ton box truck TURBO slant (scraped)

kipamore, you should never be embarrassed about the content of a question!

Ported vacuum reads zero at idle, manifold vacuum reads in the region 18 to 23 at idle, depending on the engine; cam choice and valve adjustment is a big factor.
Ported vacuum is at it's highest when cruising at highway speed under light throttle, and the vacuum pod on the distributor will improve mileage by using the vacuum to advance the timing.
You should normally (depends on engine setup) have in the region 8°-14° static (initial) timing, that is without any advance from the weights in the governor, and without any advance from the vacuum pod.
The engine should be very driveable with the vacuum line to the pod blocked at the carb.
When starting the engine you have the initial timing, as soon as you start driving with more rpm, the governor kicks in giving more advance, how much depends on the number on the governor, the point where it starts is totally adjustable via the springs that regulate the movement of the governor weights.
The vacuum pod for the dizzy moves the entire plate where the points or electronic pickup is mounted, and many are adjustable in the way that they are able to move the point of it's advance start by demanding more or less vacuum to move the membrane within the pod. The amount of movement is decided by the number on the pod.

The best way to actually see what your engine does, is to have two separate vacuum meters attached to the ports of manifold and ported vaccum, and also a rev counter, and observe them and make notes while having your buddy driving. Then you can adjust the vacuum pod advance kick-in point to the correct vacuum with a vacuum testing tool afterwards.
I have used my mityvac for more than 25 years.

Olaf

_________________
Aspenized

kipamore, your question was not really addressed.
You cannot have too much initial advance, because first of all, you will have great difficulties starting your engine. There is also a problem with the fuel mixture: while running on choke the mixture is richer than normal, but as soon as the choke is off, the mixture lean out. There is a combination of: air to fuel ratio = fuel density, temperature and pressure, that let your engine start if the spark strength and duration is sufficient. With a very good spark, you can ignite a very rich mixture quite early (within the laws of physics), but the same engine will probably be imposssible to start with a warm engine off choke, or keep running off choke with a normal air/fuel mixture.
You can easy experience it by turning the dizzy to advance the ignition at idle, you shall not give too much advance before the engine start to misfire.
In the other end of the scale you have pinging, or pre-ignition as is the right term, as a major problem. It is caused by the intake mixture igniting very early in the compression stroke - caused by too early ignition or maybe a hot-spot in the form of glowing piece of carbon - and it creates a detonation rather than a controlled flame front as you have with a normal ignition. The result is very high internal pressure in the cylinder, further enhanced by the piston being too far down in the cylinder, still on it's way up. The early buildup of pressure due to turbo- or supercharching, will for the same reasons demand a much later ignition point to avoid detonation.
Having too much initial advance + a heavy dose of mechanical advance + too much vacuum advance on top of that, bring you engine right into the ping zone: in my '77 Aspen the pinging begins by sounding like the cooling lines from the auto are banging together. They're not.
Severe pinging will cause major damage to pistons and bearings, and it may ruin the crankshaft and other components. Correct timing is essential to keep the engine running without causing stresses that can damage it or shorten it's life.

Olaf.

jeez, I have to start writing long novels or books, I've lost my 'stop' button...

_________________
Aspenized