TR6 engine into 2500S

[bergxu]

Hello gents,

Have a ‘77 2500S Estate which dropped a valve on #3 and destroyed the bore and, sadly I think, the combustion chamber of the head. Was wondering if a late US spec TR6 lump (CF prefix) can be used as a replacement (I know the front and back plates need to come off of the 2500S block, due to angle of the engine, and likely the sump pan needs to be re-used too for crossmember clearance) but was wondering if the UK intake with the SUs will mate up to the US head properly. Reason I’m asking about using a US lump is that I’ve got one available to me and thus far, seems to be the most reasonable solution. Anything else I need to take into consideration? The plan is to refresh the TR6 engine before dropping it in so want to make sure all of the effort and spend won’t be in vain. 

[jr2]

2 hours ago, bergxu said:

but was wondering if the UK intake with the SUs will mate up to the US head properly.

If your UK intake will mount to an PI head, then, yes the US head/engine will work.  All CF (1973-1976) engines have PI port spacing.

As a side note 1974 1/2 -> 1976 engine will have an EGR port that will need to be at least plugged up.

[jr2]

One more thing to consider.  The US engines use very low compression - 7.5:1

You will have to cut the head considerably.  Here is a reference:

TR6 Compression Ratio | Good Parts

[Richard71]

Check on the Chris Witor Triumph Web site. He has a technical section that will tell you all you need to know.

Richard.

[BlueTR3A-5EKT]

Dipstick needs to be changed.  2500s will be different markings to TR6. Due to Engine angle as you stated.     2500s with pas so different front pulley too.  
Agree head will need shaving to bring up cr.   

Have seen this swap done many times the other way round.  The front engine plate having its legs cut off rather than being swapped to TR type.

Peter W

[BlueTR3A-5EKT]

Just now, BlueTR3A-5EKT said:

Dipstick needs to be changed.  2500s will be different markings to TR6. Due to Engine angle as you stated.     2500s with pas so different front pulley too.  
Agree head will need shaving to bring up cr.   

Have seen this swap done many times the other way round.  The front engine plate having its legs cut off rather than being swapped to TR type.

Peter W

 

[astontr6]

8 hours ago, bergxu said:

Hello gents,

Have a ‘77 2500S Estate which dropped a valve on #3 and destroyed the bore and, sadly I think, the combustion chamber of the head. Was wondering if a late US spec TR6 lump (CF prefix) can be used as a replacement (I know the front and back plates need to come off of the 2500S block, due to angle of the engine, and likely the sump pan needs to be re-used too for crossmember clearance) but was wondering if the UK intake with the SUs will mate up to the US head properly. Reason I’m asking about using a US lump is that I’ve got one available to me and thus far, seems to be the most reasonable solution. Anything else I need to take into consideration? The plan is to refresh the TR6 engine before dropping it in so want to make sure all of the effort and spend won’t be in vain. 

Although that bore looks a bit of a mess? I would not write it off until a Car machine shop had inspected it with a view to sleeving that bore. Your problem also happen to one of our group members and this is how he reclaimed his block.

Bruce.

[bergxu]

Thanks for the replies all, is there a suggested vendor for the sleeves? I was thinking that someone ought to be able to add material into those gouges then machine back and then press at least one sleeve in. I reckon if all of the other bores look halfway decent I should only need to sleeve #3..

[astontr6]

31 minutes ago, bergxu said:

Thanks for the replies all, is there a suggested vendor for the sleeves? I was thinking that someone ought to be able to add material into those gouges then machine back and then press at least one sleeve in. I reckon if all of the other bores look halfway decent I should only need to sleeve #3..

Where are you in the UK or are you off shore? Also have you checked No3 Crank Shaft Journal? I would not worry about the gouges as most of that would be taken out in the boring out for sleeving.

There is a M/C shop near where I live called : HT Howard, Unit 15, The Business Village. Wexham Road, Slough, SL2 5HF. Tel,01753 525549. Chis Whitor used his services a lot when he lived in the Slough area and still does!

Bruce.

[DaveN]

Blimey I didn’t know Howard’s were still in business. They haven’t moved far from there original premises!

[astontr6]

6 hours ago, DaveN said:

Blimey I didn’t know Howard’s were still in business. They haven’t moved far from there original premises!

They are bigger now than when they were in their old premises!

Bruce.

[Rob Salisbury]

158942 is the part no. for the cylinder liner most of the usual suppliers have this part for around £30, however getting it fitted requires a machine shop that knows what it's doing, ... old school stuff, ... bored to the correct dimensions for interference fit, good old English tallow smeared on the cylinder and block and a substantial press with enough throw to push the cylinder home in one continuous movement, I saw it done many years ago at a machine shop in Kingston on Thames (now retired)  and it's quite exciting!!  

Cheers Rob

[bergxu]

I’m not in the UK hence my query on using a US TR6 block. Good news however, I took the head to a very well respected local machinist today and he said he can fix the damage on the head (first of course, he will disassemble it and pressure test it) and then if it passes muster, will go ahead with repairs. I showed him pics of the block and he said that also wouldn’t be a problem to sort with a sleeve. This particular shop has done a fair amount of Triumph engine work over the years so I have faith. 

[Dave McDonald]

On 12/18/2020 at 3:20 AM, bergxu said:

Hello gents,

Have a ‘77 2500S Estate which dropped a valve on #3 and destroyed the bore and, sadly I think, the combustion chamber of the head. Was wondering if a late US spec TR6 lump (CF prefix) can be used as a replacement (I know the front and back plates need to come off of the 2500S block, due to angle of the engine, and likely the sump pan needs to be re-used too for crossmember clearance) but was wondering if the UK intake with the SUs will mate up to the US head properly. Reason I’m asking about using a US lump is that I’ve got one available to me and thus far, seems to be the most reasonable solution. Anything else I need to take into consideration? The plan is to refresh the TR6 engine before dropping it in so want to make sure all of the effort and spend won’t be in vain. 

The inlet manifold from the UK 2500S (part No 219016 I think) will have wide inlet port spacings. The USA CF engine built for Strombergs will have a manifold with narrow inlet port spacings.

Measure the head between the inlet ports - UK 22mm; USA 17mm. The manifolds will physically fit either engine with all the fixings lining up but the inlet tracts will be misaligned with a moon crescent out of line.

Dave McD

[bergxu]

Thanks Dave. Helpful to know! So I’d need to re-use my head if I end up needing to use the US TR6 block. 

[stuart]

7 hours ago, bergxu said:

Thanks Dave. Helpful to know! So I’d need to re-use my head if I end up needing to use the US TR6 block. 

Blocks are the same throughout until CR/CF series., its the head port spacing thats different on early US engines.

Stuart.