: 425 timing help
hi, put a 425 in a 86 chev and its ben fighting me the whole time. the main problem now is i have to run the timing way advanced or else it has no difference past 1/4 petal. everything seams to work, vacuum adv, cintrif... but im realy not sure on how to fix it. Thanks for any help n take it easy on me, this is my first post ever
05-26-11, 07:29 PM
you could have the wrong timing marker, they made 5 or so different ones and you can not mix them.. bring number one up to top dead center through the spark plug hole and see where your marker is.. also check that your centrifical advance is not frozen
05-27-11, 06:56 PM
The 425 needs a lot of initial timing. I forget the figure but it is more than any other car i have owned. How much are you running?
i havent even realy used the timing marker. i was using a vac guage to set it then i had to advanec it till the bog wen away. it runs good now but wont start when hot. and i checked the advance and it moves freely but how are the springs suposed to feel? mine feel like they wouldnt realy hold the weights back at all.
That's your first mistake. You need to use a timing light to time the engine, not a vacuum gauge.
well ether way, the initial timins not the problem. its fine at idle and up to about 1/3 throttle. ats after that i have a problem. it just wont accelerate any faster past that and to solve that problem i gota run so much advance that this weekend my starter all but exploded from the stress of starting it when warm.
and a timing light only gets u close bc every motor is diff. a vacuum guage will alow you to find exactly where the motor is creating peak vavuum at idle indicating where the motor is running at its most eficient... usually. lol but being a cad motor and knowing that these are diff than others in their own way i figured id ask if anyone had any experence with this. sorry so long
06-04-11, 03:14 PM
I starting to think you have a problem with your timing gear... The cam gear they used was metal that is coated with plastic on the teeth of the gear.. This was to make then quiet ..On all these stock gears after 20 years the plastic chips and breaks off... This makes your cam timing late and jump all over.. If yours is still stock it needs to be changed. DO NOT use a cheap timing chain, gear set.. use a good set like a cloyes 9-3139 .... and if you are using a stock cam use the +4 key on the cam gear..
thats the kind of info im looking for. iv ben thinking bout changing it anyway bc of whats said on here. will that timing set come with the advance plate or do i have to buy that sep? and if i wanted to go top of the line, how much dose that usually run?
found the price, $135? is that the best out there?
n what bout the cam gear?
nevermind lol i was thinking the on for the dist...
06-11-11, 08:12 AM
It sounds like there is an issue with the mechanical advance if you say the springs seem too weak. Also the vacuum advance probably isn't working either. that's why you have to advance the initial timing so much to make it run right. Those weights and springs should work smoothly. You should be able to hear a difference in the engine when you unplug the vacuum advance. A timing light would verify all of this.
the vacuum adv is working just fine. i had someone check out the dist and they cuoldnt find anything wrong with it. and i used a timing light to check the vac advance and it worked how it should. i didnt check the cintrif but i will when i get my starter. had to special order one threw aur small parts store but the said it should b here today or tomorro. ill let uk what happens
06-13-11, 05:04 PM
You could try to check how much play you have in the timing chain and gears.. Take of the distubtor cap... now turn over the motor by hand until you see the timing mark..Now rotate the motor backwards while watching the rotor on the distrubtor and see how many degrees it moves backwards til the rotor moves...I would guess that a new chain set-up would have 2 or 3 degrees play.. a worn set would have maybe 6 or so degrees play..If you got much more than that it needs parts..
7651776516ya iv thought of that but the motor is real hard to turn by hand. i mean real hard. some of it is bc my power sterring pump belt is kinda rigged and not alota room between radiator and crank. its got alota custom parts including motor mounts bc i have built this truck with less than $1000 and thats including the truck and the 2 previous motors.
ok i finnaly got my truck back and i got about 10* or so of play in the chain. i also have other issues now but im thinking its the carb. someone vandilized my truck and broke the windows out so i figure they messed with my carb and other things. but i should b able to to get it