okay.. I got my new intake today for my truck.. replaced it.. (took a little under two hours, would have been quicker but i spent 15 minutes looking for a pipe thread plug)
cranked it.. the extender tube for the oil sender broke at some point in the process.. replaced it.. cranked it up.. couldnt find my trusty vaccum gauge to retime it
grabbed my timing light just to get it close.. set it to 15 deg advance, then drove over to my friends house to pick up the vac gauge i loaned him. ran like a gutless wonder the whole way.. and got very hot.
hooked up the vac gauge.. got 12 lbs... this thing has a stock cam so i knew this wasnt right... timed it to peak.. 19 lbs.. and now it runs like a scalded dog.
put the light on it just for fun.. it says im running 30 deg initial time..
POS needs to be recalibrated and its only about two years old. I hate timing lights. This is why I NEVER use them to time a car if I am able to use a vac gauge.
even if your vac gauge shows the wrong figure.. doesnt matter as long as you can find a peak..
btw.. just went back down to retune again.. decided to recheck idle mix with new intake..
got the vac up to 19.5 from about 18.75 at idle.. so it made a difference..
Ben, when were kids we use to set our timing by ear to the highest RPM.When you use a vacuum gauge do you hook it direct on the intake or a port on the carb?. Your talking vacuum at idle.I'm gonna try it and compare it to a timing light,and see which way runs better.
Dave
yeah i used to time by ear also.. just that I usually got it too high..
i use direct manifold vacuum.. and if im feeling espeically anal retentive that day ill unhook and plug all other vacuum accessories.
i always remove vac advance line and plug it. then turn timing to peak vacuum.. it will turn quite bit without change at the peak.. i turn it back down until it drops again.. then back up just enough to hit peak again..
this works very well for me.
if you do this and find that you get a little detonation under load.. (i did this evening) then replace your distributor advance springs. i did this.. no more detonation.. i dont think the springs had ever been replaced in my truck.. they were very weak. unless youve replaced them recently i would try this before turning timing down a little.
the higher the manifold vacuum.. the "hungrier" the engine is..
Ben, What did you use on the botl threads? I have used Permatex #2 in the past but the last time I put the intake on I used the paste that ARP recommends and most of them are leaking now. I plan to go back to Permatex.
Brian - NCM Lifetime Member
73 coupe L48, Flat-top pistons, Performer RPM Heads, Crane Cam and roller rockers, Holley 650 vac sec. Performer intake,
3.55 gear BTO 200-4R trans,
Leather seats, Seatbelt Plus 3point seatbelts, Pioneer CD player
Magnaflow Exhuast System
Ben, What did you use on the botl threads? I have used Permatex #2 in the past but the last time I put the intake on I used the paste that ARP recommends and most of them are leaking now. I plan to go back to Permatex.
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do you mean the pipe threaded plugs for unused manifold ports ? i used high temp plumbers thread tape
Brian - NCM Lifetime Member
73 coupe L48, Flat-top pistons, Performer RPM Heads, Crane Cam and roller rockers, Holley 650 vac sec. Performer intake,
3.55 gear BTO 200-4R trans,
Leather seats, Seatbelt Plus 3point seatbelts, Pioneer CD player
Magnaflow Exhuast System
Brian - NCM Lifetime Member
73 coupe L48, Flat-top pistons, Performer RPM Heads, Crane Cam and roller rockers, Holley 650 vac sec. Performer intake,
3.55 gear BTO 200-4R trans,
Leather seats, Seatbelt Plus 3point seatbelts, Pioneer CD player
Magnaflow Exhuast System
you're welcome tom..
my grandfather taught me that method.. he was "old school"
for curiousity what does your light say..
cthulhu
Hooked up the vac guage to the line running between the carb and the distributor. Turned distributor to peak vacume (went from 10 to 17). Car idled higher so I turned it back down to 800 rpm with idle screw. Car did not run well when I accelerated - rough. What did I do wrong? I read your comment about replacing distributor springs. Do I even have those in a transistorized ignition (71 LT1)?
Thanks for any suggestions
Rgds Neil
You don't want the vacuum line from to the distributor. You want a manifold vacuum.
And yes, the car does have the springs. You will find them under the distributor rotor.
Thanks Ken
Now for the question I'm sure you knew was coming. Where do I find "manifold vacume". Sorry for being such a DA but I have never done anything with vacume and don't know much about it. Thought it might be an easier way than using a timing light. Just bought the guage yesterday. Can I get distributor advance springs from Autozone etc?
Thanks again
Neil
Any vacuum souce connected directly to the intake manifold.
Examples: Vacuum line to the transmission. To the brake booster if you have power brakes. PCV valve. If you have a Q-Jet, the top passenger side corner of the carb where the line connects to go to any air filter connector. Any line connected directly to the intake, and not the carb.
AutoZone does not have the advance springs. NAPA might. Summit, Jegs etc. will. At one time these were common, but it getting more limited due to drop in demand for the cars that use them, and are still being driven.
Thanks Ken
I'll try the power brake booster vacume line tommorow.
Rgds Neil
cthulhu
Hooked up the vac guage to the line running between the carb and the distributor. Turned distributor to peak vacume (went from 10 to 17). Car idled higher so I turned it back down to 800 rpm with idle screw. Car did not run well when I accelerated - rough. What did I do wrong? I read your comment about replacing distributor springs. Do I even have those in a transistorized ignition (71 LT1)?
Thanks for any suggestions
Rgds Neil
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did you recheck for peak AFTER you turned the idle back down.. you have to have manifold vacuum peaked at IDLE speed..
it sounds like you peaked it.. then dropped idle.. and didnt re-peak
cthulhu
OK I peaked vacume (turned distributor counterclockwise) then reset idle then repeaked. Still runs rough after about 2000 rpm. Found a vacume advance spring kit at a local speed shop and will try new springs later today as I am pretty sure mine are original. If that does'nt work for me I can always set it back like it was (distributor about an inch clockwise from where it is now). I will let you know how it works.
Neil
cthulhu
I put new springs in. Got an MSD kit. Started with light ones and then went to medium. I could NOT get it to run right at peak vacume. Went back to the timing light and set 12 degrees initial and 36 total all in at 3500 rpm. Car seems to run fine even at high rpm (5-6000 rpm). This leads me to conclude that I must still be doing the vacume procedure wrong so I'm just going to leave it until someone can show me how to do it right. I did learn alot more about how to use a timing light today and also how to change the distributor advance springs so that was fun.
Thanks again
Neil
My 82 CE has a stock crossfire system, does this method of timing by using vacuum also work on motors that are electronically controlled?
Thanks,
Tom
My 82 CE has a stock crossfire system, does this method of timing by using vacuum also work on motors that are electronically controlled?
Thanks,
Tom
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nope... only for non electronic cars