TR3A Engine rebuild, open wallet surgery

[Adrian Fuller]

Hi all

 

I am moving onto the engine rebuild so this is probably the start of many posts/questions, thanks in advance for any suggestions. The engine was seized including the cam but the crankshaft looks ok and will be checked along with the block and cylinder head checks for cracks. I am currently planning on fitting 87mm piston and liners, Max Speed con rods, a Newman P1 cam and followers, rear oils seal conversion (is there a proffered make/supplier/type? , I have already purchased a Phoenix big bore exhaust and manifold. I am now looking at the cylinder head which is an early high port head. The valves and guides need replacing and I will convert to unleaded.  I now need to decide if the conversion to the 5/16 exhaust valves is worthwhile, is there much benefit and what is (if any) the downside of completing this, are there any significant additional changes/purchases that would be required.

I will also need to get the head skimmed and probably the block needs dressing or skimming. I have measured the cylinder head and do not believe it has had any previous work, my question is how much material is it acceptable to machine from block and head before there is any impact on liner fitment and then compression ratio.

 

Many thanks in advance

Adrian 

[Ian Vincent]

Hi Adrian, Pretty much all your queries have been addressed in previous discussions on this forum. A good place to start would be Bob LeBroq’s saga on his engine rebuild. 

With regard to valves, I stuck with the original sizes when I rebuilt my head, I wasn’t going racing and couldn’t see the need to spend extra. No doubt others will be along to advise differently. 

my strongest recommendation would be to find yourself a good machine shop that has handled TR engines before. It won’t be cheap but you don’t want to do it twice. I used Hamlins in Bridgewater and they were excellent. 

Rgds Ian

[Lebro]

Adrian.

If you are going to replace the valves & guides anyway, then there is no reason not to convert to 5/16"  it won't cost any more, you just need to buy the "conversion" guides.

https://www.moss-europe.co.uk/valve-guide-conversion-exhaust-136575.html?assoc=116018

Advantage is that you can delete the third valve spring, thus reducing wear on the cam & followers.

Links to a couple of threads I started which may be worth a read.

Any metal taken off the block surface will impact liner height unless exactly the same is machined from the liner seats.

Compression ratio not affected, but the pistons will need to be shortened to maintain the "deck" height.

any metal taken off the head surface will increase compression ratio, but that's not a bad thing. I took 60 thou off my head, which along with chamber mods gave me a CR of around 10:1

Bob.

 

Edited February 23, 2021 by Lebro

[Richardtr3a]

Ian is absolutely correct. I gave my engine to a well known engine repair company is Brighton. I supplied the new pistons and liners and a copy of the page from the manual illustrating the liner height requirements. I managed to get it running in time for the TR International in 1986, and won the TR3 concours. Standards were lower and only two entries. 

But the engine would overheat at any speed above 60 mph. After a couple of years Darryl Uprichard dismantled the engine and found the liner heights were wrong. He rebuilt it for me and it has been very reliable ever since.

I could not see which part of the country you are in, but it is worth using Racetorations, Revington,TR Enterprises, TR Bitz. and similar  and driving a few hundred miles is well worth it. There are other recommendations on this forum. If you use a company who do general engineering work make sure that they understand about the liner heights. It is a good idea to have the hardened valve seats as well.

Do not use any " Triumph " company associated with a very unreliable man Matthew L-Smith. See previous postings on the Forum.

Good luck Richard & B

[Ian Vincent]

Note. Hamlins in Bridgewater do all the machining work for Revington so they are completely familiar with TR engines. 

Rgds Ian

[ianc]

Get hold of Kas Kastner's Triumph Preparation Handbook" - I think it is available from the TR Register's on-line shop.

What Kastner doesn't know about TR (and other Triumphs) could probably be written on the back of a postage stamp.

Mick Richards and Bob LeBrocq [Lebro], both of whom post frequently, are among many who can provide sage advice based on many years of experience.

Ian Cornish

[Hamish]

Depending where you are the above named specialist obviously know the cars. Revington in the south west sponsor our club championship. 
TR Enterprises in the middle have a good reputation for reliable sporty engines to blank chq full race-

to me anyone who can do a good reliable race engine knows enough to build any spec.
 

if you are doing a Bob ( ie diy)

consider Peter burgess for the head work. Not used him myself but seems to be well respected.
 

[Motorsport Mickey]

Hi Adrian,

Just endorsing votes for Peter Burgess. He's been preparing TR cylinder heads for me since 1986 and cut 3 x Championship winning heads as well as many roadgoing cylinder heads for myself and others in the 4 cylinder. He's situated here in the East Midlands J28 off the M1 is about 2 miles away from his shop in Alfreton and he will accept heads by post and carriage them back to completed...what's not to like. I don't know how close he is to you because you've not put it in your profile (always handy to do that to save us suggesting things that you can't access in your area) but the post option will sort you out on that anyway.

Peter Burgess 01773 520021 Auto Performance Engineering.

Mick Richards

[John McCormack]

On 2/23/2021 at 7:29 PM, Lebro said:

Adrian.

If you are going to replace the valves & guides anyway, then there is no reason not to convert to 5/16"  it won't cost any more, you just need to buy the "conversion" guides.

https://www.moss-europe.co.uk/valve-guide-conversion-exhaust-136575.html?assoc=116018

Advantage is that you can delete the third valve spring, thus reducing wear on the cam & followers.

Links to a couple of threads I started which may be worth a read.

Any metal taken off the block surface will impact liner height unless exactly the same is machined from the liner seats.

Compression ratio not affected, but the pistons will need to be shortened to maintain the "deck" height.

any metal taken off the head surface will increase compression ratio, but that's not a bad thing. I took 60 thou off my head, which along with chamber mods gave me a CR of around 10:1

Bob.

 

Interested in the valve spring issue.

When I rebuilt my low port head I didn't use the 3rd valve spring. It is a stock head on an engine with 87mm liners, mild cam and balanced.

The engine revs sweetly to 5000 which is more than I use. I have a self imposed 4500 limit (apart from a couple of test runs after the rebuild).

Am I inadvertently making a mistake by not using the 3rd spring?

[Ian Vincent]

3 minutes ago, John McCormack said:

Interested in the valve spring issue.

When I rebuilt my low port head I didn't use the 3rd valve spring. It is a stock head on an engine with 87mm liners, mild cam and balanced.

The engine revs sweetly to 5000 which is more than I use. I have a self imposed 4500 limit (apart from a couple of test runs after the rebuild).

Am I inadvertently making a mistake by not using the 3rd spring?

The third spring definitely increases the risk of coil binding with a high lift cam and from various conversations I have had with people who should know, is not necessary if you are not revving the engine above about 5000 rpm.   I used TR4a springs (with the appropriate valve caps) for my TR3a and am happy with them.

Rgds Ian

[John McCormack]

3 minutes ago, Ian Vincent said:

The third spring definitely increases the risk of coil binding with a high lift cam and from various conversations I have had with people who should know, is not necessary if you are not revving the engine above about 5000 rpm.   I used TR4a springs (with the appropriate valve caps) for my TR3a and am happy with them.

Rgds Ian

A mate and close neighbour had terrible problems with springs binding and breaking on his rebuilt TR2 low port head. He removed the 3rd spring and problem solved, which is why I didn't use them. 

On rev limits we have a member down under with an extraordinarily quick racing 3A. He had a special crank made for it at great expense (he's a doctor). I asked him what revs he used at the Winton track and he said over 7,000. Reckons it sounds wonderful. I'd be in panic mode.

[Adrian Fuller]

Thanks for the advice all. I am not sure what in am doing wrong but I really do struggle searching the site for specific subjects. I am only 8 miles from Hamlins and getting the machining completed there. I have another question about crank seals..as everything is in bits which is the best seal to go for, the one that requires a jig/alignment tool or the one that requires the crank machining?. The block is quite rough where the gasket sits! If it is not too bad and to avoid a load of machine work is there a quality sealer that could be used with a gasket?.

 

Thanks again for advice.

Adrian

[Motorsport Mickey]

Adrian,

When you say "The block is quite rough where the gasket sits " ! which gasket do you refer ? The gaskets on the block are the bottom for the oil sump to go on, and other than that ...there isn't any ! The crankshaft does not have a gasket...or even a rear oil seal. It has a a scroll oil scavenge system which skims oil from off the surface of the crankshaft which needs a mandrel ( a dummy machined short crank dummy to fit the oil scroll...I think you refer to it as a "jig " ?. The other seal is a lip seal which fits upon the crankshaft which has to be machined.

The best seal is the Christian Marx lip seal which fits BEHIND the existing crankshaft scroll seal, this gives the advantage of the original oil control system and an additional lip seal behind it. The crankshaft has a rough sort of thread machined into it which returns the oil back into the sump after it is scraped off by the alloy scroll fitment supplied by Christian Marx. This also needs a mandrel ( a dummy machined short crank dummy to fit the oil scroll ) also in the kit from Marx. Is this what you refer too ?

Mick Richards

[Ian Vincent]

I believe there are people who will lend or hire you the mandrel for the CM seal.   You don’t necessarily have to buy one  

Rgds Ian

[Ralph Whitaker]

12 hours ago, Adrian Fuller said:

 The block is quite rough where the gasket sits! If it is not too bad and to avoid a load of machine work is there a quality sealer that could be used with a gasket?.

 

Thanks again for advice.

Adrian

Adrian, if you are referring to the head gasket face, a skim is undoubtedly the best option, but as the main compression seal is the liner top, which will be new, and the rest of the block face only has to contain water at say a maximum of 10psi depending on what radiator cap you use there is a chance you could get away with a sealer on that part only. (standing by to get shot down !). However what are the seats like at the bottom of the liner where the FO8 rings fit ?. If they are badly corroded it would pay to get the head face and the FO8 seats re cut at the same time, after all you only want to do the job once don`t you.

Slightly off subject, I once had to re use a head gasket on a Hillman Imp, which was a definite no no (I couldn`t get another at the time), and smeared both faces with Green Hermetite which sets hard. I never had any trouble with it after.

Ralph

 

[Lebro]

RE the crank rear oil seal.

The same mandrel is required whether you re-fit the original Triumph scroll seal, or if you fit the Christian Marx viton seal. Note that the one of the dimensions given in the workshop manual for the mandrel in incorrect, the larger diameter should be 2.818" not 2.822".  You can buy the whole seal including new scroll parts, or you can modify the original scroll parts to accept the viton seal (lathe required). TR shop sell both options.

Bob.