Wet Liner Engines & Valve Interference

[TR4nut]

Hopefully this is a simple question:

Is the TR3/4 an interference engine?

Just got back from our monthly club meeting, where I mentioned to two club members that I needed to get my timing chain replaced as I can hear it rattle pretty heavily on warmup. Told them I wasn't too concerned running around like that, at worst it would be a tow back home. At that point they looked at me aghast and told me I was in danger of bending a valve. Got me a little worried, but I was certain that valves don't interfere with the pistons, right? Or do I need to be worried?

Thanks,
Randy

 

[TR3driver]

AFAIK it's non-interference, tho I can't say I've ever specifically checked.

However, I'd wager your chain is fine. If it is the chain you are hearing, then likely you have a broken tensioner. However, unlike some of the later Triumphs (TR7, Stag, etc), the TR2/4 tensioner does not work on oil pressure; so there is no reason for timing chain noise to change.

 

[HerronScott]

I'm pretty sure it's a non-interference as well. Not too long after I restored my TR4A, I had an issue where the timing chain "broke" and I had no problems other than needing to replace the timing chain tensioner stud which had sheared off and the timing chain cover which had a hole in it.

Scott

 

[TR4nut]

Thanks, that makes me breathe a little easier.

Whatever the reason, my engine is pretty quiet when first started. After I get to full operating temp, though, I get a very mechanical 'rattley' noise on idle - definitely not rocker arm related. Over time I've gone from a generator to an alternator, changed the metal fan to plastic, changed out the water pump, and I still notice the noise. So I think it may be time to pull the timing cover and see if something obvious is staring at me.

Randy

 

[MadMarx]

depending on the cam and head thickness you use.
A high lift cam in combination with a thin head can interfere the intake valve with the sleeves. To avoid this you can champfer the sleeve edge at the intake.

See the Kastner books for details.

Cheers
Chris

 

[MadMarx]

Rattle noise at idle:

Piston slap!

 

[TR4nut]

Rattle noise at idle:

Piston slap!

Well, that's a cheery thought! Not sure how to diagnose, but my compression last time I checked was good on all cylinders, oil pressure 50 psi at 2500 rpm fully hot (and today in Houston it was hot), and it seems to run fine.

The offending noise is at the front, sounds like it is coming from the timing or belt area - and it sounds "chainlike" so I'm still thinking timing chain related. At least I hope so.

Randy

 

[MadMarx]

piston slap don't effect compression. But this is the only noise that occurs at very low revs.

Maybe you might think about a worn cam lobe too. If the tappet is juping over a worn lobe that makes a bright noise too. Simmilar as tooo much valve clearance.

Also a piston hitting the head can make valve like noise. Depending which head gasket you use the pistons might getting too close.

Now the last idea:

If it comes from the belt area, check for a crack in the belt.

Cheers
Chris

 

[DNK]

Chris, How's the racin this year?

 

[Bob_Muzio]

I seem to recall that the TR4 timing chain cover should have a sound deadening goop on it to tone things down and many times in restoring an engine this might be cleaned off. Lack of this amplify noises in that area.
Might be worth looking at.
Bob

 

[Don Elliott]

If you are driving under power and the rattle is not there - but then you let up off the pedal and you start to hear the "clatter", then it's the timing chain tensioner. They last about 35,000 miles. Think about it. Under acceleration the timing chain is tight one way, so there is no clatter. Then when you let off the gas, the timing chain "flutters" till you get into serous deceleration still under engine compression when the timing chain is tight again, but the other way.

 

[TR4nut]

Thanks, Don- that is what I think it is also - but I will probably change out the timing chain as well since it is the first time I'll be in there as its latest caretaker. Noise definitely occurs after backing off at idle. Don't know why it is louder after warmup, but perhaps there is enough viscous oil in the area when it first starts to quiet things down.

Randy

 

[TR3driver]

If you are driving under power and the rattle is not there - but then you let up off the pedal and you start to hear the "clatter", then it's the timing chain tensioner. They last about 35,000 miles. Think about it.

Doesn't make sense to me. The camshaft has no idea whether the engine is making power or not, only what speed it is turning. The camshaft has very little inertia compared to the forces required to open a valve, so the power transmission through the chain is always somewhat 'jerky'. And when you let off the pedal, the speed doesn't change much so the conditions at the chain remain basically the same.

In well over 200,000 miles, I've broken a tensioner once.

 

[TR4nut]

Not sure it is power related, but it could be rpm related if the tensioner is bad perhaps? I notice it at idle, 600-800 rpm.

 

[TR3driver]

Not sure it is power related, but it could be rpm related if the tensioner is bad perhaps? I notice it at idle, 600-800 rpm.

Sure, that makes sense to me. At low rpm, the jerks are farther apart and can whip the chain around. At higher rpm they are much closer together and the weight of the chain will average them out more.

When the 3A chain broke, the noise was only noticeable at idle ... but part of that was because at higher rpm the other noises covered it up. My exhaust might have been just bit loud ... at the time I had the stock setup but all the fiberglass was long gone.

 

[MadMarx]

I tell you next week when I had my this years first appearance at Hockenheim.
I did paint my car (by my self) and colored the plastic panels.
Today I worked on the doors.
Tomorrow assembling Friday - practice.

Cheers
Chris

 

[billspit]

Rattle noise at idle:

Piston slap!

Mine sounded almost like bells. Been 30 years but I remember it well.

 

[DNK]

Video is nice Chris!

 

[MadMarx]

Video is nice Chris!

Maybe this might be interesting for you.
It is a little boring because there is very calm movment in the scene. I'm not reliable for people who fall asleep and receiving any harm from hitting things hard during falling down.

https://www.youtube.com/watch?v=68JyWluuaOU


Cheers
Chris