Close



Page 1 of 4 123 ... LastLast
Results 1 to 25 of 79

Thread: Spark knock

  1. #1

    Default Spark knock

    Ok I am getting a spark knock ping etc with my engine. Comp cam xe274h afr165 1399, 10:2:1 compression
    I recurved the duraspark2 to 35deg max all in at 3000.
    Initial 14. Knocks with the vac advance plugged. Back off timing to 0 initial same thing. Can knock by revving at idle. New engine need to figire this out.. have one lighy one heavy on the distrub. Help!!!

  2. #2

    Default

    Can we have a bit more background please? Did you just build this engine from the ground up with all new parts and it's the first motor you ever put together? Or was it running perfect and nothing was changed at all and all of a sudden this issue appeared etc?
    I just did a little (emphasis on little) research and it seems that cam uses the non- HO firing order, is that correct or not?
    Last edited by homer302; 05-27-2018 at 06:47 PM.

  3. #3

    Default

    First time I drove the car. With the new engine. 10k spent in a shop over 1 years to build(hard to get parts in Canada)
    I put together lots of engines at age 41 mostly deisels up to 15l.
    A shop did the work up to the heads on and getting the pushrod length figured out. Scorpion rockers 1.6 I put in.
    Maybe I need to go 2 heavy springs in the distubutor?
    Ok... its a 302 forgot that part. Holley 600, air gap rpm, 4psi fuel pressure regulated.

  4. #4

    Default

    So you installed from the short block up and stabbed the distributor it sounds like. Is this a HO firing order cam or not?
    Last edited by homer302; 05-27-2018 at 07:11 PM.

  5. #5

    Default

    It is a flat tappet 302 cam standard firing order. Yes from the heads up. So rockers, breaking in cam, installing inner springs, setting rockers 1/2 preload one at a time. Recuving the ds2 cam to 20 mechanical and 14 inital and running one light and one heavy spring. I am thinking I need to run 2 heavy springs maybe. Would it ping at idle? 190deg t stat(should be a 180 but thats all they sell here unless special ordered)

  6. #6

    Default

    I had to move the plug wires all 1 over to get the distubutor in the correct position hace 13-14 inches of vacuum.

  7. #7

    Default

    I rebuilt the c4 myself with a 500hp kit. Maybe the new vac modulator leaks...I have been removing the vac mod to check vac and use its port.. but you would think it would have problems idling like that and idles fine. Anyone have to run a low total advance like less than 25 to get rid of knock with a 10:2:1 engine.

  8. #8

    Default

    When I say ping at idle it will do it with a rev to 3k . I never had it over 3200 yet. Has 2.64 7.5" gears going to 3.31 8.8"

  9. #9

    Default

    You should be able to run 16 or even 18 degrees initial with all that hardware and camshaft, though the carburetor's on the small side and will pull 1.5+"Hg up top (not sure why everybody goes ape $hit with the engine hardware and then chokes it off with not enough carburetor, losing hp and tq everywhere... there's no penalty for running some more carburetor that's tuned properly, only gains), BUT anyway, with modern fast burnin' chambered aftermarket cylinder heads, you don't need as much mechanical/centrifugal advance, and nobody needs the magazine-touted "all in by" somewhere in the mid range rpm either... ~ 32-34 degrees total advance is often best... so 16-18 initial plus ~16 crankshaft degrees mechanical/centrifugal (~ 8 distributor degrees), "all in" somewhere above 5000rpm (you're on the right track with the installing stiffer springs idea) should produce a 302 creating the most power it can with those heads as well as get rid of any pinging/knocking that's going on.
    Last edited by Walking-Tall; 05-27-2018 at 07:52 PM.
    Mike
    1986 Mustang convertible 3.8L ---> BUILD THREAD
    1983 Mercury Cougar 3.8L LS
    1986 Ford Thunderbird 5.0L ELAN
    1966 Ford Fairlane sedan 200-6
    1966 Ford Fairlane GT (390ci 4spd)
    1981 Mercury Marquis Brougham
    1980 Capri RS Turbo
    1971 Mustang Fastback
    1974 Pontiac Luxury LeMans

  10. #10

    Default

    I will change springs to the two heavier factory ones and see what happens..
    The carb was one I had on a fresh 289 with 3 miles on it 20 years ago.
    I use the formula for carb sizing cubic inches and rpm 6-6200.
    I find the mistake everyone always makes is over carbbing decreasing velocity and losing power and also usually dropping in too high gear ratio like 4.11s on a light high hp car like the fox.
    I thought high performance more compression was supposed to be less total timing and faster. But maybe I am wrong as it is less total and stock curve rate.

  11. #11

    Default

    The worst I have going on is the factory air clean I did the math it would lose 35 hp at 6k. How to run a stock hood.. maybe a ram air system someday.. 2 headlight system..(but then again would be kicked off 4eyed pride..)
    I need to have it running for fathers day car shows. I am going to make people throw up with my ugly to most people futura.(well I like it)

  12. #12

    Default

    Factory-wise since the '60's, efficient-er SBF combustion chambers have never needed as much advance as soon as SBC chambers... which is where much of the snowballed magazine hoopla of "all in by 2500-3000rpm" still annoyingly lives on today... and so you add faster burning efficient chambers, you don't need as much ignition advance and since it's still a SBF under the heads, it's not needed as soon as some bring it on.......... regarding snowballed hoopla = ditto with all the drama of carburetor sizing and malady myths over the years...
    Last edited by Walking-Tall; 05-27-2018 at 09:08 PM.
    Mike
    1986 Mustang convertible 3.8L ---> BUILD THREAD
    1983 Mercury Cougar 3.8L LS
    1986 Ford Thunderbird 5.0L ELAN
    1966 Ford Fairlane sedan 200-6
    1966 Ford Fairlane GT (390ci 4spd)
    1981 Mercury Marquis Brougham
    1980 Capri RS Turbo
    1971 Mustang Fastback
    1974 Pontiac Luxury LeMans

  13. #13

    Default

    Each engine likes a different timing. Everything is centred around gm. I used the phrase all in by and ran all this number crap cause I find on forums people think they know everything and anyone asking questions is a newbie.
    My brother has a built dodge 383 he didnt set his timing curve right and may have screwed his engine after 200 miles as can not hear knock at high rpm.(he has lots of blowby)
    I am trying not to f#$kup my engine as well..
    The directions for the crane cams tell me to plug the vac advance then if pings back off 2 deg initial still pings change springs. Then after set the vac advance by driving and adjusting the vac pod.
    Btw thanks for the advice.
    Last edited by 78futura; 05-27-2018 at 10:06 PM.

  14. #14
    FEP Senior Member qikgts's Avatar
    Join Date
    Jan 2010
    Location
    Rockledge, FL
    Posts
    934

    Default

    Just a few silly thoughts... Are you using the right timing pointer location and have the timing marks on the balancer been checked? Are you using a new/known good balancer that the ring is sure to not have slipped/moved on the hub?
    '85 GT

    The other one... 2016 F-150 XLT Supercab Ecoboosted with 3.73's...

  15. #15

    Default

    Quote Originally Posted by qikgts View Post
    Just a few silly thoughts... Are you using the right timing pointer location and have the timing marks on the balancer been checked? Are you using a new/known good balancer that the ring is sure to not have slipped/moved on the hub?
    Its a new balancer, crank bolt, blue loc tite and torqued to spec.
    The timing stays consistent and can see it advance with rpm.
    Timing pointer is on the passenger side with the two bolt holes. Should be right.
    Last edited by 78futura; 05-28-2018 at 07:05 AM.

  16. #16

    Default

    Maybe it is the wrong balancer? As soon as you go aftermarket and the engine builder is a chevy guy does not ford make an 10 11 and 2 o clock balancer for the 302. But it is an 28oz one... hmmm i think the 78 gets the 10 o clock..
    The toque convertor and flex plate episode were the same have to order twice get the wrong stuff . I still have a b and m torque convertor for a small bellhousing collecting dust..lol.
    Here is another thought the balancer is right. It runs better as I approach 14 initial. Actually idles up a touch. And when retarded to 10 or less you can hear it in the pipes louder and makes more of a boat motor sound. I must be getting 28 degrees at 2100 and probably want 16-17.
    Last edited by 78futura; 05-28-2018 at 07:26 AM.

  17. #17

    Default

    Knock on wood, I mean no harm, honestly... what's the oil pressure like? ... and did this build involve new pistons and pins, pressed into connecting rods, or "full floating" pins?... in other words: might the knocking be mechanical?...

    As for balancer mark wonderment... I'd be verifying it's marks and the pointer myself with the engine physically set at #1 TDC of the compression stroke.
    Mike
    1986 Mustang convertible 3.8L ---> BUILD THREAD
    1983 Mercury Cougar 3.8L LS
    1986 Ford Thunderbird 5.0L ELAN
    1966 Ford Fairlane sedan 200-6
    1966 Ford Fairlane GT (390ci 4spd)
    1981 Mercury Marquis Brougham
    1980 Capri RS Turbo
    1971 Mustang Fastback
    1974 Pontiac Luxury LeMans

  18. #18

    Default

    Quote Originally Posted by Walking-Tall View Post
    Knock on wood, I mean no harm, honestly... what's the oil pressure like? ... and did this build involve new pistons and pins, pressed into connecting rods, or "full floating" pins?... in other words: might the knocking be mechanical?...

    As for balancer mark wonderment... I'd be verifying it's marks and the pointer myself with the engine physically set at #1 TDC of the compression stroke.
    Yeah I set it that way tdc on compression.
    Has 30psi at 1000 hot. 60 at idle 1000 cold.

  19. #19

    Default

    Was all assembled and balanced. Arp bolts. Clearanced for drag race. It was a one man owner shop that did it that is kmown for quality work.

  20. #20

    Default

    pull all the plugs and tell what the compression is, and when number one is at the top is that what the timing shows? ( trying to rule out the balancer slipping/ wrong balancer/ wrong pointer) .

  21. #21

    Default

    Yeah, that's an interesting idea unless the balancer is brand new. If it's older and has a rubber core it is possible that the balancer has slipped. That is a real thing for sure.

  22. #22

    Default

    Quote Originally Posted by bob85gt View Post
    pull all the plugs and tell what the compression is, and when number one is at the top is that what the timing shows? ( trying to rule out the balancer slipping/ wrong balancer/ wrong pointer) .
    I set it up like that. Pointer is original. I will start with the springs and pay attention to rpm when it knocks. It is a spark ping for sure. I know that sound from when I turned up my timing on my 79 mustang 23 years ago.

  23. #23

    Default

    I will do some changes and update you guys..thanks for the tips. Should be able to work on it after work sometime this week...

  24. #24

    Default

    still would like to know what the compression reading of the engine. what type of gas are you using? and are your plug wires separated about 1/2 inch from each other. 7+8 cylinders are easy to induce a false fire if wires are close to each other.

  25. #25

    Default

    Quote Originally Posted by bob85gt View Post
    still would like to know what the compression reading of the engine. what type of gas are you using? and are your plug wires separated about 1/2 inch from each other. 7+8 cylinders are easy to induce a false fire if wires are close to each other.
    I thought about cross fire so I replaced the plug wires, cap and rotor tonight. 2,4 7 and 8 can crossfire if not seperated. I made sure they were on oppsite ends of the wire holders.
    I drove it and the same thing. I am going to go with the springs and bend the tabs. It for sure is a timing issue.
    I dont have a compression gauge to test. It is running 91 octane with a 4 point octance boost bottle.
    Supposed to be built with 10.2:1
    Supposed the kid put 91 in and the guys actually had 91 in the tanks at the station. At $1.40 a litre he better.. also at 87 the boost should have bumped it enough to be enough octane to run...

Page 1 of 4 123 ... LastLast

Posting Permissions

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