speaking of cams and timming i have a question?

[max]

i ran into this awhile back and i can't explain it so maybe someone else can.

i put a 340 togeather last spring, everything was new. the cam i first installed was the MP .484/284 and i degreed it in according to the cam card and got the engine running and i went to time it in and the timming marks on the damper were like 90* off and weren't even near the timming scale.

so i'm thinking that the damper has slipped so no biggy just remark it and go about my way. so the engine is up and running and i have about 1 hour on this cam and decided it was just not right for the combo.

i pull the cam out and replace it with a stock 340 cam and i degreed it in as well. i reused the timming chain, gears and damper so now i'm thinking since i have the front of this engine off go ahead and remark the damper.

so i put my TDC tool in the #1 cylinder and run it around both ways and divide it by half and the TDC mark is right where it should be on the damper

i get the engine running and time it in and the timming marks are right on the scale which with the previous cam it was off by 90*.

this is not the first time i have heard of this so what gives. is the cam changing the timming of the engine or is it possible to get the oil pump gear off just a bit to change the timming marks? 

[Chryco Psycho]

I have no explanation , the piston is at TDC realtive to the crank position & there is no way the crank can be in a different position relative to TDC

[firefighter3931]

  i was thinking about this yesterday and couldn't come up with a reasonable explanation. Did you degree the cam in Max ?

Ron

[max]

i was thinking about this yesterday and couldn't come up with a reasonable explanation. Did you degree the cam in Max ?

Ron

Ron, yes i degreed in both cams and i used the cam keys for this engine. when i built my 426 i had to use an offset crank woodruff key on it so i knew it would move the damper and it did so i had to remark that damper.

but this is the first time i have ever ran into this problem when degreeing just the cam. the weird part is i had read on another board of a fellow that ran into the same problem.

i would think it would have to be in the distributor timming, since the damper would be in the same location as what it would be from the factory.

i'm sorta lost on this one.

[Ghoste]

Could a cam ground incorrectly cause this?

[max]

Could a cam ground incorrectly cause this?

humm, i need to think about that one for alittle while.

if i didn't know as much as what i do about engines this might have never bother me, i guess it's just the principal of knowing what it did and me not being able to figure it out.

the cam was the only thing that was changed and both were degreed on the cam side, the same timming chain cover was used, the same distributor. but yet the timming marks were 90* different.

[Ghoste]

And I'm sure no expert but if that is the only thing different between the two, could it be possible that the blank was indexed wrong when it was put into the grinder?

[firefighter3931]

Max, i'm a BB guy so i'm only slightly familiar with smallblocks. I did help a buddy with his 408 build and remember he had 2 different timing covers with the tab on opposite sides of the cover. Each cover obviously required to correct balancer to be matched up so that tdc was properly indexed on the dampner....i'm assuming the incorrect dampner matched to the wrong cover could account for a 90* offset on the timing mark. I know you said that it was the same dampner and cover being used for both cams....but that's all i can think of.

How did it run with the 484 cam ? Did you ever fire the motor ? Talk about a brain twister  

Ron

[max]

Max, i'm a BB guy so i'm only slightly familiar with smallblocks. I did help a buddy with his 408 build and remember he had 2 different timing covers with the tab on opposite sides of the cover. Each cover obviously required to correct balancer to be matched up so that tdc was properly indexed on the dampner....i'm assuming the incorrect dampner matched to the wrong cover could account for a 90* offset on the timing mark. I know you said that it was the same dampner and cover being used for both cams....but that's all i can think of.

How did it run with the 484 cam ? Did you ever fire the motor ? Talk about a brain twister  

Ron

yeah, i know of both types of timming covers (well actually 3 the 1967-1968 style also) but this is the first time i had ever ran into this. i did see the same question posted on moparts awhile back but it was on a big block so it isn't the first time i have ever heard of it, coarse no one over there could answer it either.

now this cam is an oval track cam for 3/8 mile. i didn't catch or figure out till after i went for a ride, but the power range on an oval cam should be all power in by 3000-6000 with out much to the bottom end but that still doesn't explain why the timming marks would be that far off unless it is in the grind of the cam.

i never checked the lobes side by side to another cam to see if they were cut differant as to the centerline of the cam.

the engine is a .030 over 340 with 10.1 pistons and everything was balanced. the cam which of coarse is a .484 lift and 284 advertised duration it has a LSA of 108*.

i put the cam in and installed it at 104* centerline, it sounded like pop corn popping at the tail pipe and the throttle response was great. the car unfortanatly has an MP 145k convertor (or stock convertor) and the gears are 3.73.

intake is a performer with a 750 cfm holley vac sec and electronic ignition, all sitting in a 1967 dart.

i backed it out on the road and brought it against the brake and it layed down a wonderful 4 footer but as soon as the rpm came up (guessing 2k no tach) it was like you side stepped a clutch at 4k on a big block. the car actually kicked side ways and both rear tires (70 series) broke loose and i wasn't ready for it and i almost lost it.

i decided right then and there it was time to go back with the stock 340 cam for street mannors and for bottom end power which it has now.

maybe since the .484/284 cam is a race only piece it is designed/ground totally different then the street cams.

i was just thinking maybe i put it in wrong or missed something to get that odd timming problem on the damper

[Chryco Psycho]

Even with  the dist being off the timing has to be within a few degrees with either cam so I can`t see the dist having an effect either
this is just wierd

[max]

oh well i guess it's just one of the mysteries that aren't ment to be solved

thanks guys for reading it over and for giving me your imput on it

[Rolling_Thunder]

HOLY SHIT!   I HAVE THIS PROBLEM -- no kidding i was trying to time the 484 cam and i could not...   the mark was around 90* off and it would die before it got to TDC....    I just got done swapping in a different cam --- hopefully this will solve the problem....      this was a BB bit still - the exact same problem,