Engine Mods would they be worth it

[Chris Hubball]

Learned Gentlemen

 

I am planning the removal of my TR 4 engine to cure the oil leak from the rear crank seal by fitting one of the Lip type seals. The engine has done approx 35000 mile since its last rebuild and still has a good oil pressure and compression figures. The current state of tune is Stage 3 Head, Triumph Tune Road Cam, 87mm pistons, extractor manifold, and is fully balanced. While the engine is out I am considering the following two mods.

 

1) Fitting 89mm pistons and liners, will they be worth the cost and work involved as this is a road car ?

 

2) While the Flywheel is away being drilled to take a Diaphragm Clutch, having it lightened to approx 22 lbs I am aware of the advantages of doing this but are their any disadvantages ?

 

Your comments and advice would be appreciated.

 

Cheers Chris

[peejay4A]

Chris,

When mine comes out next I'm going from 87mm to 89mm. Not sure about the flywheel.

[Fireman049]

Hi Chris ~

 

When I rebuilt my 3A engine (2.2 L) I fitted the Mad Marx rear crank oil seal.

This gives me the advantage of having two oil seals and not having to machine the crank.

It is extremely easy to fit. If you would like some photo's please PM me your eMail address.

I also fitted the Moss lightweight steel flywheel.

 

Tom.

[Peter Cobbold]

Heavier pistons - won't the crank assembly need rebalancing? ...a complete engine strip down?

[TriumphV8]

Peter, some cranks need rebalancing when weight of pistons

or rods does change due to H-Beam Rods or forged pistons.

Especially the V8 crank like mine needs that.

On the bigends special weights have to be bolted on

and than the whole thing is balanced.

I built a machine for that and do that due to very large differences

when swapped to the Small Block Chevy rods and pistons I am using.

 

The TR6 and TR4 is balanced without those weights.

As the weight of pistons is not taken into account it can be changed later

and the only challenge is to bring that stuftf all like pistons, piston rings

and gudgeon pin and circlips on the same weight.

 

When doing that to a Healey we found two of the pistons

fully out of the range and had trouble to grind off everywhere

to bring them into limits.

 

From that day I check every piston before fitting.

 

A little scale for jewelry can be bought on Ebay and can be

used both for pistons and rods.

Rods must be balanced separated to rotating and reciprocing weight.

That seems to be a thing Triumph did not do ex works!

[Andy Moltu]

The 4 cylinder flywheel is a heavy lump and some theorise it is a contributor to 4 cylinder crank failures.

Larger pistons and liners probably a good idea.

 

While you have it out get the bottom end balanced.

[Peter Cobbold]

Interesting they use an unusually heavy flywheel. The tickover spark timing is also retarded quite a lot from what would be expected for a 9:1 compression bath tub head. And that too will smoothe tickover. Were the factory under pressure to smoothe out the tickover lumpiness ?

[TriumphV8]

Engine tends to pink around 2000rpm.

Maybe they wanted to be on the safe side with the timing

and with centrifugal advance only easy curves can be established

that also stay away from perfect timing in other areas.

 

Heavy flywheels are designed from the philosophy of the engineer.

Engine will not starv and pull from idle like the old father Ferguson.....

Some OPEL 1600cc and some Alfa Romeo although being sporty

engines had really heavy flywheels.