New cam installed, no start
03-14-2009, 10:41 PM
#1
Staging Lane
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New cam installed, no start I have just installed a 268h comp cam into a 350 sbc, and as the title states... no start.
The cam was installed straight up, also lifters and new springs were installed.
The OEM HEI distributor was replaced with a HEI jegs brand distributor... this is in a 1983 C-10 pick-up, and the old distributor had a 3 prong hook-up in the back of the distributor that the new distributor did not include. Does anyone know what this is for?
The distributor was installed with the rotor toward the #1 plug wire on the cap, and the #1 cylinder at TDC on the compression stroke.
I believe it is getting fuel and spark because it was backfiring through the carb.
I'm assuming my timing is off, but am look for suggestions.
The cam was installed straight up, also lifters and new springs were installed.
The OEM HEI distributor was replaced with a HEI jegs brand distributor... this is in a 1983 C-10 pick-up, and the old distributor had a 3 prong hook-up in the back of the distributor that the new distributor did not include. Does anyone know what this is for?
The distributor was installed with the rotor toward the #1 plug wire on the cap, and the #1 cylinder at TDC on the compression stroke.
I believe it is getting fuel and spark because it was backfiring through the carb.
I'm assuming my timing is off, but am look for suggestions.
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03-16-2009, 09:47 PM
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TECH Apprentice
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ive used that cam before and i know NA it like 36-37 all in by 3000. we put squeeze on it and cranked 10 degrees out for it. and it was still a tad high. what compression are you running, aluminum heads or iron?. that will dictate it even further.
03-16-2009, 10:19 PM
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Staging Lane
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its the 260hp crate, so i think its like 8.7:1 CR, on iron heads, how do i set total timing, i only know how to set initial using the timing tab, were you at 10*BTDC... to advance timing i assume i go towards 0, and away from zero to pull timing...?
03-17-2009, 09:09 AM
#12
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it runs now jmd, just trying to tune it the best i can, but i waited till the lifters were at the bottom of the cam circle took up 0 lash and then 3 quarters of a turn after that, then rotated the crank till i had done that on all of em... seems to run well.
03-17-2009, 10:04 AM
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The type of HEI Jegs used will determine how much advance you get. There are three catagories of timing:
1)Initial - set at idle with the vacuum advance disconnected and reading your timing tab
2)Mechanical advance - controlled by the distributor. This can only be adjusted by modifying the HEI. The weights and springs control how fast this advance comes on.
3)Vacuum Advance - controlled by the vacuum canister. It adds to the two mentioned above and is a big help for gas mileage and around-town driving.
If you are reading 10* on the timing tab and your HEI allows for 25 more, your total will be 35 (disregarding vacuum). You can check your total by reving the engine and using a timing light with a dial.
1)Initial - set at idle with the vacuum advance disconnected and reading your timing tab
2)Mechanical advance - controlled by the distributor. This can only be adjusted by modifying the HEI. The weights and springs control how fast this advance comes on.
3)Vacuum Advance - controlled by the vacuum canister. It adds to the two mentioned above and is a big help for gas mileage and around-town driving.
If you are reading 10* on the timing tab and your HEI allows for 25 more, your total will be 35 (disregarding vacuum). You can check your total by reving the engine and using a timing light with a dial.
03-17-2009, 12:25 PM
#14
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thanks pancherj, to the rescue again always helping me out!
Remember a few months ago pancherj, i couldnt diagnose why i could rev above 4k rpms... well it turns out... the TDC mark on the balancer was in the wrong position... the motor was never timed correctly.
so if i am reading 8* on the timing tab and i want to advance the timing, and i move it from 8* BTDC to 4*BTDC... did i advance it?
Remember a few months ago pancherj, i couldnt diagnose why i could rev above 4k rpms... well it turns out... the TDC mark on the balancer was in the wrong position... the motor was never timed correctly.
so if i am reading 8* on the timing tab and i want to advance the timing, and i move it from 8* BTDC to 4*BTDC... did i advance it?
03-17-2009, 02:09 PM
#15
Launching!
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Ahh...I do remember that. When you "advance" the timing, you are causing the spark to happen sooner (before the piston reaches top dead center). If you are at 8* and you want to advance it 4* you should then be reading 12* at the balancer. It is confusing because of the terminology (advance, retard, etc), but if you think about it, it will make sense. The flame takes a while to spread out from the sprak plug. In a perfect world, the spark would happen right at TDC and completely burn the mixture in a few degrees after TDC giving you your highest cylinder pressure with your greatest moment arm between the crank and rod.
