[cutsupreme]

Hey guys

1987 Chevy caprice, 305 carbed

I posted a thread a while back about having an issue with the timing mark bouncing. I figured out that to time the vehicle I had to unplug the four wire plug on the distributor first. So I did that then timed the motor to 0 degrees which is factory specs. Car runs a lot better with the timing set correctly. Although I think I am experiencing some detonation.

It runs OK at idle and part throttle, but when I get heavy on the throttle the engine will start rattling and making some bad noises. I tried messing around with the timing a bit to see if i could get better results. I put it on 4 degrees but that only seemed to make the rattling worse. The more I retard the timing the more the rattling fades away. But It seems like the more I retard it the less power the engine has.

Right now I have the timing set back on 0 degrees. Do you guys think its just time for a new timing chain or could it be something else. The distributor is brand new. Timing chain is probably original to the car as far as I know, and it has 160K. Is it possible it could be anything else like the camshaft.

Thanks for the help

[oldbogie]

Lots of reasons why old engines rattle ranging from loosing their ability to cool inside at specific spots around the combustion chamber; to creeping increased compression due to carbon build up, to failed EGR not diluting the fresh charge, valves that are damaged or don't seat properly, oil getting past the rings which kills the octane rating of the fuel, cam running retarded because of wear in the gears and chain, and more.

The list is long and distinguished. At 160K it's time to think of rebuild or replacement, doing a fix at this age just emphasis problems somewhere else. An engine overhaul/replacement will lead to the automatic croaking so figure its rebuild/replacement in the price as well.

Bogie

[cutsupreme]

yeah, doin a rebuild or getting a new motor is something I would definitely like to do at some point. But this is my daily driver and I don't really have enough time to spend with it not being drivable. Its more an issue of time than it is an issue of money, however I don't think a crate motor is in my budget right now either.

Thanks for the input

[cutsupreme]

Any one have any more ideas

Thanks

[Big Mouse]

You said the distributor is new. Tell us about it.

Is it an aftermarket one or stock rebuild? I'm wondering if the advance curve (springs & weights) are too aggresive for the condition of your engine.

Perhaps you could swap the advance springs for STIFFER ones and see if it doesn't help.

Regardless, at 160k that engine owes you nothing.

[HalfOunce]

i would stick a scanner on it and drive it to see if the ecm is seeing the knock aka ping.
it could be as simple as a knock sensor

[A355CAMARO]

if you are experiencing detonation, you could have carbon buil up on your valves or anywhere in the combustion chamber. Try running premium gasoline. 93 octane has a higher resistance to detonation. The definition of octane is gasolines resistance to detonation. If your detonation goes away with higher octane, than you are either over heating, timing is too far advanced, or you have carbon build up.

[cutsupreme]

Distributor is just a stock replacement, not a high performance part.

I had detonation with the old distributor as well

[Slimpikins]

You wouldnt happen to know your engine specs would you. What is the compresson ratio?

[novajohnb]

Get the engine up to normal operating temp. Remove air filter and slowly dribble about 1/2 pint of water into the carb. Work the throttle to keep the engine from stalling. This will clean out the carbon from pistons/ valves. GM sells a top-end cleaner for this purpose too.

[jankinnu]

It is worth checking the old harmonic balancer (damper). The outer part of it can twist if it is broken and the timing marks are not correct anymore.

[cutsupreme]

I don't know the engine specs but it is all stock

[docvette]

Doc here,

IIRC, 305 timing chains were Notoriously Weak..might be worth a replacement at 160 K...If your planning on keeping it around..

Detonation is only going to tear up more parts, so you really need to address the issue.

You might (since you replaced the Dizzy) Check your static timing..

Pull #1 plug, Compression, TDC, Both Valves DEAD closed, Timing marks lined up..

IF you have that, your mechanical timing is OK, (close enough) Chain, Gears and damper are where they are supposed to be. IF the timing mark does not line up, But you have all the rest, look for a slipped damper..

If that is good, Check the dizzy, pull the cap, before you do..mark on the base with a laundry pen, the center of the #1 Tower..then pull the cap, see if the Rotor is lined up, If not , advance/ retard it until it is..AND if not enough swing on the base, pull and reset the Dizzy so that both the rotor AND advance / Retard swing are both center of the #1 plug tower.

Then time it with a lamp..See if that does not cure the problem..

Add some Octane boost to the tank (double the amount.) that will tell you if it's fuel or bad timing..Having to run expensively Cheap gas is a real problem now a days..

Doc

[cutsupreme]

When I put in the dizzy I made sure I had the #1 plug at tdc.

I think I might just retard the timing a little bit for now to see if I can get the detonation to go away. Then put on a new chain the next time I get a chance.

My friend told me that to put on a new chain I would have to drop the oil pan to get the cover off. I didn't think that was necessary for a sbc. Can someone verify this.

Thanks

[cutsupreme]

I just went to the local autozone and picked of a timing set and all the seals and gaskets. All together was only around $47.

I've never done a timing chain before so I wanted to know if anyone has any good tips.

I'm assuming I do have to drop the oil pan since one of the seals that came with the kit looks like its made to fit at the front of the oil pan. Will I have to take the whole pan off or just loosen the front bolts?
If I do have to remove the whole pan will I probably need a new gasket?

Thanks