Moparts
Cam timing vs distributor timing - New info
Posted By: kenz
Cam timing vs distributor timing - New info - 04/03/11 10:18 PM
Would a cam installed retarded cause the need for excessive initial distributor advance?
We recently fired the 318 in our Duster for the first time. We got it running pretty good and broke in the cam. Now we're getting down to setting everything up. Using the vaccuum method of setting distributor advance, we need to go to 30 degrees initial to get a smooth idle at 900rpm. Anything less and the car will die when put into gear. That seems like way too much initial to me, but maybe not?
We have a Mopar Performance distributor, Summit "small" cam and an Edelbrock 600 carb on an otherwise stock rebuilt 318.
Any thoughts and/or suggestions?
Thanks,
Ken
Posted By: NITROUSN
Re: Cam timing vs distributor timing - 04/03/11 10:44 PM
If you are sure your timing marks are right ten over advancing the base timing is just putting a bandaid on the problem. Sounds like a vacuum leak.
Posted By: RapidRobert
Re: Cam timing vs distributor timing - 04/03/11 11:06 PM
set the timing marks on ~30BTDC #1 compression and take off the cap and hand turn the crank w a breaker bar until the rotor is near/under #1 cap terminal (mark the outside of the dist for that place) and the reluctor blade is even w the magnet & JUST starts to move away from it & that's when it fires and see what the timing marks are at. Want ~10-15 initial. Also what Nitrousn said may b vac leak. We can pull the pass valve cover & check "rockover" on #6 & at that point the timing marks will b way off from TDC if it's off a tooth but the easy stuff 1st & not sure the best way to check for a vac leak. Holler back when you find something out
Posted By: kenz
Re: Cam timing vs distributor timing - 04/03/11 11:11 PM
Quote:
If you are sure your timing marks are right ten over advancing the base timing is just putting a bandaid on the problem. Sounds like a vacuum leak.
I'm pretty sure the timing marks are correct. We checked TDC when we degreed the cam. The cam was 2 degrees off so we installed a 2 degree offset key but now I'm wondering if we installed it backwards.
The vaccuum is steady at 19" at 30 degrees initial and 15" at 17 degrees initial, but it idles a bit rough at the lower setting and dies when put into gear.
I'll check for a leak just in case. Thanks for the suggestion.
ken
Posted By: RapidRobert
Re: Cam timing vs distributor timing - 04/03/11 11:14 PM
2 deg retarded would not skew it that much
Posted By: Sport440
Re: Cam timing vs distributor timing - 04/03/11 11:43 PM
The spark timing is referenced off the crank. The distibuter doesnt care where the cams at, 2/4/6/8* advanced or retarded.
A good example is pull the distributer out and spin its gear around anywhere you want and stick it back in. The only thing you will change is the position on the cap of the new # 1 cylinder.
Of course you will now need to fine tune the timing advance in reference to the crank.
Now, a cam being retarded will have a later IV close so it may want some more initial timing advance. But not 30* IMO
Its something else
thats requiring that much advance to run smoothly. Are you using a adjustible timing light? Wire order correct,? ETC
Posted By: kenz
Re: Cam timing vs distributor timing - 04/04/11 01:06 AM
Sport440,
Yes, we are using an adjustable timing light, two of them in fact. Both are within a degree of each other.
We double and triple checked and we're defintely on the #1 plug wire. :-)
Thanks,
Ken
Posted By: RapidRobert
Re: Cam timing vs distributor timing - 04/04/11 01:15 AM
(Do) holler when you find it!
Posted By: buildanother
Re: Cam timing vs distributor timing - 04/04/11 01:23 AM
Nitrousn is right about that possible vac leak, and maybe a 318 with a little cam that really isn't very little, may need a looser torque conv.
Posted By: kenz
Re: Cam timing vs distributor timing - 04/04/11 01:41 AM
Quote:
set the timing marks on ~30BTDC #1 compression and take off the cap and hand turn the crank w a breaker bar until the rotor is near/under #1 cap terminal (mark the outside of the dist for that place) and the reluctor blade is even w the magnet & JUST starts to move away from it & that's when it fires and see what the timing marks are at. Want ~10-15 initial. Also what Nitrousn said may b vac leak. We can pull the pass valve cover & check "rockover" on #6 & at that point the timing marks will b way off from TDC if it's off a tooth but the easy stuff 1st & not sure the best way to check for a vac leak. Holler back when you find something out
RapidRobert,
I think we did this right. We set the initial at 30 degree while the car was running. The we shut it off and turned the crank by hand until the timing mark was at 10 degrees. We popped the cap and the rotor is pointing about a quarter of the way past #1 toward #8 (see pic. black line indicates where #1 terminal is) and the tab on the reluctor blade is quite a bit past the magnet tip.
Posted By: kenz
Re: Cam timing vs distributor timing - 04/04/11 01:45 AM
And here's a pic of the reluctor.
Thanks again for all the help.
Ken
Posted By: RapidRobert
Re: Cam timing vs distributor timing - 04/04/11 03:54 AM
Good pics, I wish I could get my $150 camera to do that good. From what I see you could rotate the housing clockwise a bit till the black mark is under/near under the rotor blade which'll move the magnet closer to the reluctor tooth & w it dead even & just starting to move away it will fire at that point which is 10BTDC that the dampener marks are at so the dist phasing is OK but it will not run timed at 10 b 4
. That only leaves carb/vac leak or WAY retarded on the cam. How about this, take out the plugs & do a compression test on the most convenient hole (just 1) & see if you get anywhere normal psi & take off the pass valve cover and (keep plugs out for easier turning) turn it till both rocker arms on #6 are open the same amt and when a helper moves the crank back & forth a hair w a breaker bar both rockers move.
this exact point of same height/moving is "rockover" on #6 and #1 is firing on TDC compression and at that exact point the dampener slit must b within a degree or 2 of TDC & if not the cam is off & if good there then What Nitrousn said: carb/vac leak. And if you get rockover and at that point the marks are retarded (after TDC) then yes the cam is retarded because (in effect) the crank has moved forward but the cam has stayed still
Posted By: 1_WILD_RT
Re: Cam timing vs distributor timing - 04/04/11 04:04 AM
Is that an MP distributor? Put a timing light on the car & watch the timing marks as someone puts the car into gear..... There should be no timing advance in at idle so when dropping the car into gear causes a slight reduction of idle RPM the timing shouldn't move... Often with the MP distributors the springs are so light at idle 10+ degrees are brought in.. When the car is dropped in gear the rpm's drop so timing falls out.. When the timing falls out the idle rpm's will drop further... When that happens naturally the timing falls out even further, probably back to true base timing but at that point the rpm's have fallen so much there's a good chance the engine is gonna die..
Posted By: kenz
Re: Cam timing vs distributor timing - 04/04/11 03:55 PM
RapidRobert,
It's my daughter's camera and I think she paid several hundred for it. It does take great pics.
1 Wild RT,
Yes, it is a new MP distributor. We bought it from Summit about 3 months ago.
Thank you both for the suggestions. We'll try them both tonight and report back.
Thanks again,
Ken
Posted By: kenz
Re: Cam timing vs distributor timing - 04/04/11 07:53 PM
Quote:
Nitrousn is right about that possible vac leak, and maybe a 318 with a little cam that really isn't very little, may need a looser torque conv.
The only vaccuum line hooked up goes to the hand held gauge. We sprayed carb cleaner all around the carb and intake and it caused no change in idle. Any better way to check?
The cam's spec are pretty mild, 204 int./214 exh. duration and 0.420 int./0.442 exh lift. Lobe separation is 112.
Thanks,
ken
Posted By: kenz
Re: Cam timing vs distributor timing - 04/05/11 03:04 PM
Quote:
Is that an MP distributor? Put a timing light on the car & watch the timing marks as someone puts the car into gear..... There should be no timing advance in at idle so when dropping the car into gear causes a slight reduction of idle RPM the timing shouldn't move... Often with the MP distributors the springs are so light at idle 10+ degrees are brought in.. When the car is dropped in gear the rpm's drop so timing falls out.. When the timing falls out the idle rpm's will drop further... When that happens naturally the timing falls out even further, probably back to true base timing but at that point the rpm's have fallen so much there's a good chance the engine is gonna die..
Got a chance to check this last night. Timing mark stays in place both in and out of gear. Idle decreases about 100 rpm when put into gear.
Will try RapidRobert's suggestion next.
Thanks again to all for the help.
Ken
Posted By: kenz
Re: Cam timing vs distributor timing - 04/10/11 08:25 PM
Okay, we finally got a chance to check some things.
First, compression. All cylinders measure between 145 and 155 PSI.
Second, checking the "roll over" point on # 6. We hand turned the crank (clockwise when looking from the front) until the intake on #6 started to open. Using a pointer as a reference, we marked this sopt on the crank pulley. Then we continued turning the crank until the exhaust valve closed and marked this spot. Turning the crank to the middle of these two marks showed the TDC mark on the dampener to be at 4* BTDC.
Would that cause the timing issues we're seeing?
Or do we have a vacuum leak or other problem?
Thanks,
Ken
Posted By: RapidRobert
Re: Cam timing vs distributor timing - 04/10/11 11:07 PM
"Rockover" is diff from what you did. Might re read that/check it & time the dist at 10 BTDC #1 & holler back
Posted By: kenz
Re: Cam timing vs distributor timing - 04/15/11 10:28 PM
Okay, we decided to tear into the engine. We double checked that TDC was marked correctly and that the cam was installed per the cam card. Both were correct.
However, when taking the intake off we found that we never put any sealer on the gaskets between the intake and the heads. Not sure how we missed that. Could that have caused the vaccum leak that NITROUSN mentioned.
Not sure what else to check, if anything.
Thanks again for all the help.
Ken
Posted By: RapidRobert
Re: Cam timing vs distributor timing - 04/15/11 11:07 PM
Been wondering what you found. Alright, cam is degreed/TDC mark correct. Were they tin or composite gaskets? I'd button it up w new gaskets w sealer/mockup the dist at 10/start it/time it & see what develops
Posted By: kenz
Re: Cam timing vs distributor timing - 04/15/11 11:39 PM
Robert,
Yeah, having to work for a living instead of playing with cars is a real bummer. LOL!!
They were Fel-Pro 1243 gaskets which block off the heat cross over. Plenty of heat here in AZ. I guess you'd call them composite as they aren't metal.
I've spent the past 30 minutes or so looking at cam specs. The reason is that the Summit specs seem stange to me. The intake opens at 5 ATDC (@.050) and closes at 29 ABDC. That seems late compared to other cams. Would that cause some of the problem?
Since we have it opened up, and I have to order new gaskets anyway, maybe I should order a new cam. What's a nice cam for an otherwise stock 318? It has a Performer (not RPM) intake and Edelbrock 600 carb. I was looking at the MP 340 replacement cam or the Comp 250 Xtreme Energy cam. The specs are real close but the MP has a little more duration. Don't want anything crazy, it's my daughter's car.
Thanks again for all the help. I think we're getting somewhere.
:-)
Ken
Posted By: RapidRobert
Re: Cam timing vs distributor timing - 04/15/11 11:55 PM
Quote:
Yeah, having to work for a living instead of playing with cars is a real bummer. LOL!!
What's a nice cam for an otherwise stock 318? It has a Performer (not RPM) intake and Edelbrock 600 carb. Don't want anything crazy, it's my daughter's car. Thanks again for all the help. I think we're getting somewhere.
Yeah I know I've been (gainfully) part time employed for about 7 months now after having been on disability for 40 yrs. I'm not a cam guy but I would avoid the MP cams and get one of the real mild comp cams but iirc been a few reported probs w their lifters & I've been following threads on them & w the near stock (in effect) intake/carb plus it being her daily driver I'd want a very near dead stock idle w maybe a bit more lift/area under the curve to build some psi for more mileage/driveability. I'm still wondering if a vac leak required that much timing to get it to run or if the dist/inter gear was off. I sure hope we're getting close(er) 
EDIT Comp or Voodoo
Posted By: kenz
Re: Cam timing vs distributor timing - 04/16/11 02:28 AM
Thanks Robert.
I decided to go with the smallest Comp Xtreme cam. It's specs are:
250/260
206/212 @ .050
.432/.444 @ .050
110 lobe separation
I ordered it and the gaskets I need from Summit, so I'll have everything next week to put it back together next weekend.
Say a prayer, keep your fingers crossed, and all that.
Thanks again,
Ken