|08-13-2012 04:10 PM|
|08-12-2012 08:12 PM|
|alsadler||found the cam was in wrong.|
|08-12-2012 12:51 AM|
|the california kid||
a piston stop is for keeping the
#1 piston from going all the way to top
WITH HEADS OFF.
ok, maybe there's one that fits through spark plug hole.
it's for marking TRUE top dead center #1 ON THE DAMPENER.
yes, good chance dampeners can be different.
yes, timing to an off TDC mark can cause problems.
have a nice day!
|08-12-2012 12:16 AM|
|08-11-2012 09:43 PM|
|alsadler||what is a piston stop? Is there a diference between the timing marks on a 1964 283 balancer and the 1985 305 balancer on it? could this be causing my issues?|
|08-11-2012 07:33 PM|
|alsadler||Still screwing with the distributor position. Seems to have low manifold vacuum. Carb screw crancked in all the way for idle, still not idling.|
|08-11-2012 01:31 AM|
|the california kid||
to clear off whether valves are hitting piston top.
what pistons are you using?
what's the cams lift?
you're rotating camshaft with heads on
and valve spring pressure?
i've never done that.
sounds kind of hard.
i know 283 but not 305 heads.
let me see, smaller chamber equals
valve closer to head or not?
is this a fresh engine or problem just start?
have a nice day!
|08-11-2012 01:11 AM|
|08-10-2012 05:00 PM|
|bullheimer||brilliant replies logged and noted. and from my read, either way you drop in the distributor, aint gonna make valves hit or not hit. u got other issues. good luck on that, an pls report back w/ what u found. Rotating the motor by hand after the install is really the only way to go any more in my world, where i build like one motor a decade. cheap insurance.|
|08-10-2012 02:51 PM|
Great reply Boogie and very good point. Logic oftern has little to do with it.
|08-10-2012 02:28 PM|
If infact the pip marks when facing each other actually has number 1 ready to fire then it will be on the power stroke and 6 will be intaking.
If none of this is happening then the cam and crank are not coordinated and you've got other problems.
These days with so much stuff coming from parts unknown it is not uncommon anymore to find gears, cams, and cranks that are not indexed correctly so be prepared for totally off the wall results, it does happen.
|08-10-2012 01:59 PM|
|alsadler||I know there is no way when the dots are together no 1 is not at top dead center because |I can feel the valves touching the top when |I try to line up the marks. It might just be that I am 180 degrees out. Have to try again.|
|08-10-2012 12:05 PM|
Setting up the SBC when the marks are facing each other then both number 1 and 6 are at TDC but 1 is finishing exhaust and 6 is ready to fire. If you know this you just drop the distributor in with the rotor aligned to fire number 6. This doesn't change where the vacuum advance can is aimed. The crankshaft and camshaft will be aligned so there should be no problem with the valves hitting pistons unless you've got so much lift at the valve that they can't miss the pistons but this is a different issue.
If the engine is left in the position with the timing gear pip marks facing each other if the distributor is installed with the rotor aligned to number 1 the timing is 180 degrees out of phase. It may well start from here but will be weak, wanting to stall, will take revving to keep it going and will probably backfire with some significant force through the carb.
If you're timed to number one it may still prove problematic to get running especially with a larger cam I really can't say a whole lot about this, it just takes fiddling with the thing to finally get it settled in.
As a side note there have been miss marked gears over the years, itís always a good idea to at least rotate the engine a couple times to be sure the valve events and piston position and distributor/rotor positions occur where they should. Setting up with a degree wheel is the best way, but is probably overkill for engines that are not going racing, still it's darn definitive in locating where and when things are happening.
|08-10-2012 11:52 AM|
However, always read the instructions with an aftermarket timing set, while I haven't seen one where the marks pointing at each other (like a SBFord) is number 1 firing, there's always the possibility that some one struck out on their own ideas about this.
If you think this is fun try a Harley twin cam where the pip marks on the cam to cam gears are on the inside and can't be seen without a mirror or pulling the outer cam bearing plate with cams out of the engine. You ask who thinks this stuff up? Beats me, but they have a perverse sense of humor. Remember the old International V8 that times off number 3? Plus I previously mentioned the Y-Block Ford with 12 chain link pins between the gear marks with the marks parallel to the ground and facing the drivers side (American). If anyone is looking for logical and simple this ain't the place to find it.
|08-10-2012 11:22 AM|
I did read. Actually even.
I'm not disputing what the directions say or what is the correct way to do it is. My point is that it seems odd.
I just don't follow why GM didn't just have the marks line up at the closest point and THAT be #1 TDC.
However, I know why they do things like that sometimes. For example the Chrysler V6 that was a 318 with two less cyclinders employed something like that. When the teeth were lined up it was not at #1 TDC. I understand why that happened because they took an existing design, modifyed it and all the same design specs, just a shorter block, crank, heads etc. Great for reducing design costs, bad for things being done as they normally are.
Did GM make a change that brought about this or had that application always been that way?
|This thread has more than 15 replies. Click here to review the whole thread.|