Close



Results 1 to 10 of 10
  1. #1

    Default How do you time a slightly modified motor

    From reading these threads, it seems like our cars (from factory) like 10 BTDC initial timing and 32 BTDC total timing?

    I just installed a new dizzy and today will fire it up.

    Is there a way to find the correct initial/total numbers ideal for a modified engine if you're not exactly sure the cam specs, etc.? My motor was rebuilt by someone many years ago and all I know is it has a more aggressive cam, high rise intake and 4 barrel carb.

    Do I still likely just want to set to 10 BTDC initial? If not, how might I find the ideal advance for my setup?

    Also, can anyone clarify how you set total timing? From what I understand, you set initial at say 10, then you rev engine to (correct me if I'm wrong on RPM) about 2000 to 2500 RPM and note wherever timing stops advancing on the balancer. I then turn the dizzy whichever way so that advancement on the balancer now stops on 32? Obviously my initial could be very different from the 10 after this adjustment, but that's ok since total timing is my final parameter before locking down?

    Thanks for tolerating my newbie questions. Appreciate any advice!

  2. #2
    Moderator wraithracing's Avatar
    Join Date
    Jun 2010
    Location
    Grand Junction, CO/RR TX
    Posts
    13,753

    Default

    Initial timing generally is going to be the most important for a Daily Driver. Total timing is a function of the distributor and the advance curve that is built into the distributor. Depending on the distributor, the advance curve and total timing can be altered, but I won't get into all that right now.

    You don't state, but I assume this is your 82 GT with a 5.0/4 spd. If that is the case, then you will need to disconnect the vacuum line from the ported vacuum nipple on the carburetor. You might also verify at this time that the vacuum port only has vacuum when the engine speed is higher than idle. There should be no vacuum on the distributor at idle.

    Now, start the engine and allow it to settle into an even idle (generally you want the engine at operating temperature, so may need to run or drive it for a bit before beginning). Using the timing light on the # cylinder spark plug wire, check the timing on the balancer. 10 degrees BTDC is often a starting point. Many 5.0's will benefit from a slight increase in initial timing, but the amount will vary and ultimately not affecting the starting will often determine how much initial your engine can tolerate. Other other point is that more efficient cylinder heads and specifically aluminum performance heads many times do not need a lot of initial timing for peak performance. In my experience usually 12-14 degrees is a sweet spot for many 5.0's in regards to initial timing. As you add more it can cause hard starting issues, especially in heat soak situations, so I caution against that.

    If you distributor is OEM then there really isn't much you want to do in regards to total advance. Once you set your initial and reconnect the vacuum line, you can rev the engine up and verify total advance, but that's about it. If you have an aftermarket distributor or you really feel the need the play with the total advance or advance curve then depending on the distributor, you can change weights, springs, etc. to alter both the curve and total advance. Generally I wouldn't recommend messing with it unless you are going to do back to back testing to verify that what you are changing and the direction of changes are actually improving performance and drive-ability and not making it worse. If for some reason you don't have full advance, then you might want to check your vacuum signal, for vacuum leaks, the distributor, etc. to verify why that is the case.

    Also unless you are specifically racing your vehicle and need a set total advance at a specific RPM or something like that you would never set (lock down) the distributor using the total advance number. You set initial timing and verify total advance. If the total isn't what or where you need it, then generally altering that inside the distributor is how you make those changes. Initial timing set too high will cause hard starts and can also cause knocking(detonation) if the initial timing is too much.

    The quick and dirty way to test initial timing changes is to time the car on an open secluded road or drag strip. Increase the timing by 2 degrees each run. If your time continues to get quicker and your speed at the end of the test run increases, the engine likes the additional timing. As soon as it slows down, then go back to the previous setting and call it good. This also assumes that the initial setting doesn't cause hard starting issues either. Hope that helps somewhat. I am sure others will post even more information, tips, and tricks.
    ​Trey

    "I Don't build it hoping for your approval! I built it because it meets mine!"

    "I've spent most of my money on Mustangs, racing, and women... the rest I just wasted."

    Mustangs Past: Too many to remember!
    Current Mustangs:
    1969 Mach 1
    1979 Pace Car now 5.0/5 speed
    1982 GT Ongoing RestoModification
    1984 SVO Awaiting Restoration
    1986 GT Wrecked by PO, but still want to save!

    Current Capris:
    1981 Capri Roller
    1981 Capri Black Magic Roller Basket Case
    1982 Capri RS 5.0/4spd T-top Full Restoration Underway
    1984 Capri RS T-top Roller
    1983-84 Gloy Racing Trans Am/IMSA Body Parts

  3. #3

    Default

    Thank you for such a detailed/helpful response!

    To answer a couple Qs, yes, this is for my 82 GT. The distributor I just placed was meant to be a direct replacement of stock.

    So what I’m hearing is that the track is probably the only way to find best initial for a custom setup...and maybe 10-12 is what I should set for now based on the mods I describe and since I won’t have access to a track for a while.

    Another question, when you disconnect the vacuum line from the dizzy, they say to plug it. Do you also need to cap the nipple on the dizzy while timing?

    As you said, I just want to verify total is in the right ballpark, was I correct in saying our cars are about 32?

    Finally, I noticed the rotor distance to the points was adjustable with a screw. Are those usually set from the factory? I couldn’t even see how you would measure gaps since the distributor would have to be on to measure/and is thus unattainable.

    thanks again for the awesome response!

  4. #4
    FEP Power Member richpet's Avatar
    Join Date
    Mar 2003
    Location
    Lowell, Oregon
    Posts
    1,734

    Default

    The tube should be plugged, even though there isn't supposed to be vacuum at idle. There might be some and you can suck crud right in to the motor.
    The nipple does not need plugging. It just goes into the dizzy.

    Sent from my Pixel 3 XL using Tapatalk
    83 5.0 GT. Quicker than it looks! 10:1 (or just over) 306, Motorsport a332 cam, 140A alt, t5 conv, 8.8 w/ 3.27's, Edel rpm, alum rad, very worked e7's, Holley SA carb, etc... SOLD IT!!!!

    Now an 1981 Granada! Building a 9.5:1 .040 over 302, Edel E-street heads, 268 cam, T5, 8.8 with 3.55, plus all the stiffening goodies, all control arms, lowered, alum shaft, x-pipe with Outlaws...

    "Never underestimate the power of stupid people in large groups"

  5. #5
    Moderator wraithracing's Avatar
    Join Date
    Jun 2010
    Location
    Grand Junction, CO/RR TX
    Posts
    13,753

    Default

    32-36 total advance is pretty normal for the 5.0. So as long as you are in the ballpark, you should be fine at least as a starting point.

    Yes, it is good practice to plug the vacuum hose if you disconnect from the distributor or cap the nipple on the carburetor if you disconnect the hose from there. I would also suggest checking for vacuum at the port. If you have vacuum that can be because your idle it set too high and should be adjusted down if possible. It can also indicate that you are connected to the incorrect port on the carburetor. Having vacuum at idle will advance your timing from your initial setting which is generally not what you want nor need.

    If the distributor you installed has points that is not a Duraspark OEM setup. Obviously points gap needs to be checked and adjusted as needed. As for the other adjustment. I honestly have never made that type of adjustment, so I can't comment and truthfully I haven't set points in probably 30 years or more. Everything I have owned has been electronic ignition other than my Dad's 1964 F100 292 3 speed on the tree and that was a constant work in progress just to keep it going. Love that truck, but don't miss the headaches.
    ​Trey

    "I Don't build it hoping for your approval! I built it because it meets mine!"

    "I've spent most of my money on Mustangs, racing, and women... the rest I just wasted."

    Mustangs Past: Too many to remember!
    Current Mustangs:
    1969 Mach 1
    1979 Pace Car now 5.0/5 speed
    1982 GT Ongoing RestoModification
    1984 SVO Awaiting Restoration
    1986 GT Wrecked by PO, but still want to save!

    Current Capris:
    1981 Capri Roller
    1981 Capri Black Magic Roller Basket Case
    1982 Capri RS 5.0/4spd T-top Full Restoration Underway
    1984 Capri RS T-top Roller
    1983-84 Gloy Racing Trans Am/IMSA Body Parts

  6. #6

    Default A huge thank you!

    Thanks a ton for all the help! I love this community and wish I could buy a beer for everyone who's helped so much.

    I got it started up, washed and waxed for the first time in 22 years this weekend.

    Name:  IMG_0946_sm.jpg
Views: 79
Size:  867.7 KB

  7. #7
    Moderator wraithracing's Avatar
    Join Date
    Jun 2010
    Location
    Grand Junction, CO/RR TX
    Posts
    13,753

    Default

    Congrats! Looks GREAT! I am actually a HUGE fan of Purple!

    My 82 should hopefully look similar with Cervini Saleen side skirts and rear valance, although mine with be black with Lime Green accents.
    ​Trey

    "I Don't build it hoping for your approval! I built it because it meets mine!"

    "I've spent most of my money on Mustangs, racing, and women... the rest I just wasted."

    Mustangs Past: Too many to remember!
    Current Mustangs:
    1969 Mach 1
    1979 Pace Car now 5.0/5 speed
    1982 GT Ongoing RestoModification
    1984 SVO Awaiting Restoration
    1986 GT Wrecked by PO, but still want to save!

    Current Capris:
    1981 Capri Roller
    1981 Capri Black Magic Roller Basket Case
    1982 Capri RS 5.0/4spd T-top Full Restoration Underway
    1984 Capri RS T-top Roller
    1983-84 Gloy Racing Trans Am/IMSA Body Parts

  8. #8

    Default

    Quote Originally Posted by wraithracing View Post
    Congrats! Looks GREAT! I am actually a HUGE fan of Purple!

    My 82 should hopefully look similar with Cervini Saleen side skirts and rear valance, although mine with be black with Lime Green accents.
    Thanks and definitely post pics of yours when you get it finished! Sounds pretty.

  9. #9
    FEP Power Member
    Join Date
    Nov 2007
    Location
    San Mateo, CA
    Posts
    2,015

    Default

    Old school method of adjusting the timing is to advance it until it pins, then back off. Pinging is not ideal so that's right at the limit..
    Fox Body/3rd Gen MCA Gold Card Judge
    84 SVO 24K miles, 85 Mclaren Capri Vert. 84 GT Turbo Vert.
    88 Mclaren Mustang Vert 20K miles, 89 Mustang LX Sport Vert,
    03 Mach 1 7900 miles, 74 Mustang II, 69 Mustang, 67 Mustang, 14 Mustang CS/GT,
    15 F150 FTX Tuscany, 16 F250 Crewcab, 67 Tbird 47K miles

  10. #10

    Default

    Equally old school is hooking up a vacuum gauge and advancing the timing until it reads max vacuum, then back it off a bit from there, usually about an inch or so of in/hg is good enough to prevent it from pinging. Good a place to start as any.

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •