How a plastic Chain ramp can ruin your engine

[WMontald]

Hello everybody,

Want you to know that a plastic part that costs 6.5$ can severely damage your car.

When my engine one day runned on 3 cyl, I thought that my chain tensioner has failed as the timing of valves was completely wrong. At pelican Parts they told me that if the chain tensioner fails , you can hear it as the chain is not under tension.
In my case I did not hear anything, but had no compression on one side.

After dismantling the engine I discovered that the plastic chain ramp on one side was broken and that that piece blocked the sprocket, resulting the chain skipping a theet. Result Bend valves, rocker arms broken (so the design works) and the chain Cover damaged beyon Repair.

[tazzieman]

Bad luck mate , it's true some dirt cheap parts can fail and wreak havoc.
How many miles has that chain mechanism seen? Engine/year?

[tobluforu]

Happened to me, one broke and locked up the motor.

[Flat6pac]

That appears to be the early hard rubber of the 70s not the present plastic.
Bruce

[Grady Clay]

WMontald,
First, WELCOME to Pelican
You will find a lot of help here.

I’m sorry your first post is about a ‘disaster’.

You appear to have ‘hard rubber’ (not plastic) chain ramps.
These ramps were superseded in about 1975 because of this issue.
There was an update change with the 1978 models.
The replacement ramps are plastic.

The current accepted configuration is:
Five (black) ramps – 911.105.222.06.
One (brown) ramp – 911.105.222.05 in lower-right position.
These are available from our host.

Be sure and inspect everywhere for any ‘lost’ pieces of ramp.
It is common for a piece to be lodged between the sprocket and the large jack-shaft gear down inside the crankcase.

Inspect that jack-shaft sprocket (and the others) for damage to teeth.
The chain may have becme stretched (there are 'split-link' chains available).

When the piece of ramp went between your right cam sprocket and the chain (damaging the chain housing and jumping cam timing), it also completely collapsed the right chain tensioner.
This can have over-stressed the large steel pin supporting the tensioner and idler sprocket.
Confirm that the pin is still firmly pressed in the chain housing and the epoxy on the back-side is intact.

I can’t tell if you have the updated ‘Turbo’ tensioners and the 2-bearing idler support arm.
These are worthwhile updates.
At the least, I would rebuild both tensioners with the kits and inspect the right tensioner for damage.
A more comprehensive (and expensive) update are the ‘Carrera’ tensioners with external oiling. There is a bit of controversy about any increase in reliability.

What year and model is your 911?
Where are you located?

There may be more important updates that your 911 has missed.

Again, WELCOME.

Best,
Grady

[howard freeman]

That is one of the old rubber chain rails. That type rail should always be changed for the later plastic ones. Those things would fail when new 40 years ago.
Howard

[911pcars]

You got pretty good life out of the rubber ramps. They must be petrified by now. Mine lasted only about 10 years before I broke the rockers, bent valves, etc. on my orig. T engine.

Sherwood

[80-911SC]

I found t=one of the C clips that hold the ramps in at the bottom of my engine the first weekend I had it when doing an oil change .. grove me nuts .. and had little black curlies in the oil .. Thanks to this place .. pulled the cover .. got a new ramp and clips . put it in and no more noise and 3 years now still hangin in ther ... KNOCK 2x4

[911pcars]

Originally Posted by 80-911SC

I found t=one of the C clips that hold the ramps in at the bottom of my engine the first weekend I had it when doing an oil change .. grove me nuts .. and had little black curlies in the oil .. Thanks to this place .. pulled the cover .. got a new ramp and clips . put it in and no more noise and 3 years now still hangin in ther ... KNOCK 2x4

Clips? Ramp clips? To the best of my memory, there are nada clips for the chain ramps. Or maybe my engine is missing them. Uh-oh.

Sherwood

[john walker's workshop]

man, it's been eons since i've seen a rubber ramp. you could bend them into 3 pieces when they got old. no clips, they just popped on. from the looks of that extended tensioner, the chains are well worn (longer). no tensioner guards either. pure luck it lasted this long.

[howard freeman]

There have never been any clips for rubber ramps,however the old original aluminum ramps with bakolite did have some type of spring clip arrangement,now that was a long time ago.I will have to check,I still have some of those in the archive. You would only see those in the chill cast case engines pre 68.
Howard