how slack should a timing chain be ? - Third Generation F-Body Message Boards

zs&tas · 08-03-2009, 10:23 AM

hey guys, firebirds been off the road for a while, was guna swap engine but getting married so need to rebuild for wedding car :-)
just went to take the timing chain off but before i did i had a good look, it 'looks' ok but i could push the two sides of the chain towards each other untill both sides (easily) touch the guide in the middle. this seems way slack to me, but its the first time ive looked at a 2.8 chain so have no reference.

2_point8_boy · 08-03-2009, 01:28 PM

My rule is: if in doubt...change it. You're already there and it's cheap insurance that it's not going to break on you.

New chains are fairly tight, but slack up a little very quickly. It's not uncommon for them to be able to touch the guides. How far worn are the guides? The true test of how badly it's worn is to remove the guide and see how much slack you have. Or count the degrees of crankshaft rotation from one side to the other before all the slack is taken out and the cam moves. You shouldn't have any more than 5* of crank rotation before moving the cam.

If I were you, I wouldn't think twice about replacing it since you already have it apart. Remember to replace the chain/gears as a set along with the guide.

zs&tas · 08-03-2009, 03:14 PM

hi, thanks, i am down there to change it anyways, was just wondering what gains im guna get looks like alot, the engine was reluctant above 4.5k so this will prob help if the guides werent there the chains would prob be a third towards each other !
i was wondering as on the condition of it ( not looking at the slack) it looks good and the motors been rebuilt at some time - theres markings everywhere so they knew what went where ive noticed - poss cheap parts ?

2_point8_boy · 08-03-2009, 05:28 PM

If the cain has a good bit of slack, then it will cause sluggish high end performance because every 2 degrees of crank rotation slack equals one degree of cam retard and timing retard. So, if the chain is fairly badly work with 10 degrees of slack, then the cam and timing will be retarded 5 degrees. This will have the effect of better low/worse high end because of the retarded cam timing, and even worse high end because your timing is retarded.

Now, the other thing that you have to remember is that these engines run out of breath at the 4k mark anyway, it doesn't matter how good your chain is.

Bottom line is don't expect great gains, just the fact that you are doing a very often overlooked form of maintnence should be good.

zs&tas · 08-03-2009, 05:34 PM

thanks, you explained that well.

i am in the middle of making a custom intake, i did start a thread a while back but i havnt had time, and i have some 3.4 injectors sitting here. should be good when all is said and done.
thanks again

firstfirebird · 08-03-2009, 07:20 PM

Quote:

Originally Posted by 2_point8_boy

If the cain has a good bit of slack, then it will cause sluggish high end performance because every 2 degrees of crank rotation slack equals one degree of cam retard and timing retard. So, if the chain is fairly badly work with 10 degrees of slack, then the cam and timing will be retarded 5 degrees. This will have the effect of better low/worse high end because of the retarded cam timing, and even worse high end because your timing is retarded.

Now, the other thing that you have to remember is that these engines run out of breath at the 4k mark anyway, it doesn't matter how good your chain is.

Bottom line is don't expect great gains, just the fact that you are doing a very often overlooked form of maintnence should be good.

VVT in a bad way haha.

Nice new timing chain should be difficult to slide the cam sprocket on the cam

zs&tas · 08-04-2009, 01:36 AM

vvt HaHa never thought of that !

ahh this one fell off :-)

2_point8_boy · 08-04-2009, 01:43 AM

well...not really VVT, more like unwanted adjustability.