Pontiac 400 timing chain

[zaleonardz]

Hi All,

First post here (2nd after the intro) and I would like to start straight off the bat with a technical question.

I have a pontiac trans am 400 with T-tops and she has been standing for a year, and this has got to stop.

I got her in bad shape and have been slowly fixing up bits, with the last being a full service. While the car was idling nicely and I was replacing the shaker scoop, I had turned to go and fetch something, and I heard a "clang"

Top and bottom are not turning together, this can only mean timing chain is gone, and since it was at idle, I doubt there is any damage.

Can anybody detail the procedure for replacing the timing chain on a original 400, I have the Fisher body/mechanical guides but they do not discuss the procedure.

I have stripped off the nose and the radiator, so I have plenty of access.

Is it a simple case of stripping off the water pump and just replacing the chain ?

 

[melsg5]

you got it, remove the pump, the front damper, and the timing cover. make sure you get new gears and a heavy duty chain.

 

[R_T_71]

They mostly come as a kit. and as long as u put them dot to dot, should be fine

 

[melsg5]

correct they come as a kit, but if you can go for the extra bucks get a double roller timing chain, here is a link to some choices
http://www.summitracing.com/search/...-Type/Timing-Chain-and-Gear-Sets/?Ns=Rank|Asc

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[zaleonardz]

Thanks gents.

Stripped her down today, strangely enough, the chain did not snap, but the crank gear burst/shattered into 2 + many pieces, and the top cam gear is stripped to high heaven.

This makes me believe that there is mechanical lock somewhere, even the crank pulley has sheared/broken off.

Its not in the bottom end, as the starter still turned.

Will post some pics by next week when I get in there with a camera, but this is no doubt a rebuild, and as it is the original motor still, its worthwhile.

There is a lot of metal filings in the sump due to the gears exploding, and the water channels through the block has some yellowish gunk in it, so there is no choice but to rebuild, I am however really impressed with the price of spares, this is not going to cost me nearly as much as I though, and price comparisons are about a quarter to a half in comparison to my BMW's v8, which is a plesant surprise.

I will do a rebuild thread just so that I can pick on your knowledge, as I dont know the old school muscle motors at all

 

[R_T_71]

Thats one thing i have always like about older GM vehicles in general, as long as drive train is good, usualy only costs about 30 bux to fix everything else!! lol

 

[zaleonardz]

Here is a quick update on the bird with some pics.

Firstly, here is the damage.

This is the crank gear

This is what the crank pulley looks like

WHat I am very pleased about is that I did not damage the crank from what I can see, the guide pin that fits onto the crank gear is just fine, if that was damaged, I would have been screwed.

I do not have a decent photo of the cam gear, here you can see it from the top, and all the crap that fell into the sump, this means sump off, which I cannot do without pulling the motor, as there is a crossmember in the way, but its all good, my engine stand is coming this week.

Here is a pic with the carb removed, I dont quite get this "carb" thing, fuel injection no problem... carb not so much... got a bit to learn here I see.

How siff is this powersteering bottle, I will need to replace this

Here is a photo of the intake off as well as the valley pan removed. I am pretty chuffed that the cam lobes are still clean and there is no muck in the motor. I also could not see any visible burn/scortch marks. Engineering will tell for sure, but looks good.

So ya, lots of gunk, lots of cleaning to do

How siff is this intake.

I dig working on this car, check all the space in the engine bay... dont have that on my E34

Heads will come off tomorrow night, they are already loose, I just need to drop the exhaust.

 

[zaleonardz]

Hi All,

Here is a quick update on the bird with some pics.

Firstly, here is the damage.

This is the crank gear

This is what the crank pulley looks like

WHat I am very pleased about is that I did not damage the crank from what I can see, the guide pin that fits onto the crank gear is just fine, if that was damaged, I would have been screwed.

I do not have a decent photo of the cam gear, here you can see it from the top, and all the crap that fell into the sump, this means sump off, which I cannot do without pulling the motor, as there is a crossmember in the way, but its all good, my engine stand is coming this week.

Here is a pic with the carb removed, I dont quite get this "carb" thing, fuel injection no problem... carb not so much... got a bit to learn here I see.

How siff is this powersteering bottle, I will need to replace this

Here is a photo of the intake off as well as the valley pan removed. I am pretty chuffed that the cam lobes are still clean and there is no muck in the motor. I also could not see any visible burn/scortch marks. Engineering will tell for sure, but looks good.

So ya, lots of gunk, lots of cleaning to do

How siff is this intake.

I dig working on this car, check all the space in the engine bay... dont have that on my E34

Heads will come off tomorrow night, they are already loose, I just need to drop the exhaust.

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[R_T_71]

Good pics, but looking at that engine and the corrosion in the water jackets, i would just rebuild that motor.

 

[zaleonardz]

R T 71, we are going to do just that.

Purchased a new engine stand this weekend at Adendorff, was R500 and stand can support up to 450kg. its pretty basic, but it does its job quite nicely, I would suggest this for the local enthusiast.

Right, so friday evening me and dad decide motor out.

I converted an old manual forklift into an engine hoist not too long ago.

Block on the ground

Onto the engine stand

Filthy as hell

That is one dirty daddy

Look how decent those pistons and sleeves are looking though

Valves are fine

So now for the shocker.

What happened is at some point the previous owner opened the motor, and the oil dipstick holder was supposed to be mounted with two bolts onto one of the crank bearing caps, and it wasnt.

The dipstick holder was chewed up by the spinning crank, and actually hit a hole through the sump. The idiotic previous owner just brazed the sump, and must have sold the car to me.

Look at the crap in the oil pump pickup. we actually cleaned some of it out.

Now what we suspect is that the part that broke off actually jammed into the timing gear, and that shattered the gear, we are exceptionally lucky that it happened this way, because the engine is fine, it just needs to be cleaned.

This happened at idle right after we changed oil, which makes sense, cause we think the part that broke off jammed in the sump, and when we drained and refilled the oil, it dislodged. Had this happened at 4500 RPM, it would of been a writeoff.

Spot the clean block

Also the previous owner did not believe in coolant, spot the corrosion on all of the parts,

So here is what is going to cost us.

Bearings - R450+450
Rings R400
Oil Pump 450
Oil filter R75
Gasket set (complete for heads+all water+valve stems+intake+exhaust) R800

How cheap are these spares, its insane. We are going to come away with less then 5k

We are sending everything into engineering to check and reassemble to spec, but ya... she will ride again within the next few weeks

Not a bad way to spend a weekend

 

[melsg5]

how about a new camshaft and lifters and of course new timing chain and gears and throw in a new water pump

 

[R_T_71]

Heck no i love spending time in my garage when i can

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[zaleonardz]

We will see what engineering says if I need new lifters, and if the cam is in spec. Whatever needs to be done will be.

I toyed with the idea of a slightly wilder cam, but figureed I am going to keep it stock as much as possible.

The only thing that I am going to mod is dropping the viscus fan for an electric, and I will be retrofitting a new aircon system, simply because mine is stuffed, and I hate the amount of space that the OEM system takes up in the engine bay.

Block should go into engineering as soon as I borrow a delivery vehicle from the office, I spoke to the engineers today, and they said that there is a slight chance that with the force of the crank timing gear snapping, that I may have bent the crank, but we shall see once they mic everything up.

Will keep updating until she is firing.

Also I dropped off the flywheel and clutch/pressure place today at my local clutch shop and the guy looked at me funny, he said he is going to try and source, if not I will have to import, but I am not rebonding the clutch, I refuse...

 

[melsg5]

I just noticed you are in South Africa! On the clutch and other parts you can try www.summitracing.com. Do you know the engine code? It's a 2 or 3 letter code on the block right in front of the passenger side cylinder head. Crane makes some reproduction camshafts that you might want to check out, in particular the one that the original Pontiac number ends in 068. Not too wild but was rated as high as 366 HP gross when installed in the 1969 Ram Air III 400 CID engine.

 

[zaleonardz]

Thanks for the heads up man, I have the number somewhere, but not with me.

As for summit racing, I can only dr00l at the awesome stuff that they have there, and while import is possible, it becomes really expensive in terms of shipment (unless you do it sea freight and then you wait months), there is also the very good possibility that the goods go missing en route, which is most annoying.

I shall first see what my local guys can source, and there are a few specialist US spares shopes here, let them take the risk.

My spares guy has given me a 3 week lead time, but he has quite a bit of the spares that I require in stock.

Its all good, I am also waiting for a complete suspension rubber kit, I want to replace everything while the block is out of the car, it makes it a great deal easier.

The previous owner annoys me, if you want to own a classic, you need to do maintanance on them, parts wear out, they need to be replaced, if you are not prepared to spend a bit of money, you should not own it.

Oh well, thanks again for the heads up, will look into the cam