CP 51000 HE engine advice needed please

[Besalu]

I have bought an early CP 1972 engine which i plan on fitting in my TR4a. The engine is currently with Classic and Modern in Bracknell awaiting stripping etc. I have a few questions for the TR Guru's but first a little bit of background on why i have decided to go down this route.

I bought the first car i saw and it had been for sale for a long time. Probably not a good idea and at the time i didn't know the difference between a distributor and a differential. I knew that the car was an original 65 UK market car and was imported in to Spain (where i live) in 1975 and converted to LHD. Long story but i was ripped off by a Spanish mechanic who took me to the cleaners. Later i found out that the car was on either a TR5 or early TR6 chassis (Stuart down in Cornwall had the car for a while and told me there was the bracket for the PI) and the car had quite a few TR6 elements. I now realise it was probably a write-off which the PO bought and brought over to Spain and bodged up. 

At first i was intent on getting the car back to original as much as i could but after four years i realise it probably won't happen. Just don't have the skills, time or funds to do that. I have never been really satisfied with the performance of the car and when i saw this CP engine for sale i decided to spend a bit more money and go down this path. All i want to do is get in, drive it, enjoy it and not have to worry if it is going to break down again (wishful thinking maybe). I am not that bothered about the bodywork or fine details, i just want to drive a nice nippy reliable car. Because it is on a PI chassis the engine should fit in well (famous last words).

So, on to my questions.

I have read a lot of good stuff about Classic and Modern and decided to take the engine to them. I have been reading about all kinds of "upgrades" i could do while it is being rebuilt. Fast road cams, head polished and gas flowed, flywheel lightened and many more. I am by no means a boy racer and i do not intend to race the car in any shape or form but if there are any cheap(ish) upgrades i could do which would give a few extra bhp then i would like to consider.

I have already ruled out a fast road cam after reading a few other threads on this theme. I will stick with the original cam. The head i am not so sure about. Is it worth spending a bit extra and having some work done on this? Having the flywheel lightened and balanced seems to be a good idea?

What about the exhaust manifold? I am happy to stick with original 6:2:1 and am not particularly keen on stainless steel (have read about overheating issues)

I will have twin SU carbs (flirted with the idea of triple SU's for a while but discarded that idea). Will probably fit electronic dizzy but haven't decided yet for sure.

Any suggestions, advice or ideas would be greatly appreciated.

Richard

[trchris]

Hi Richard if you have a 4 cylinder engine fitted you cannot just swop to a 6 cylinder engine without modifying the front of the chassis 

Chris

[RogerH]

Hi Richard

I have been following your chaos and I wish you well.

I have a 4A with a Newman PH1 cam -  next step up from standard - and it tours very well.

When you get whatever you are after you will end up with a silly grin on oyur face everytime you get in and drive it.

Good luck

Roger

[michaelfinnis]

The CP cam had an unusually long valve overlap, made possible by the injection system, which is where much of the power increase over the carb cars came from. I’m not sure how well it would work with carbs.

Also, the TR6 engine with twin SUs, ie American market cars, has about the same power output as the TR4 engine. I know UK cars had a different cam and higher compression ratio, but I wonder if twin SUs are the best option if you’re looking for more power.

I’m sure there are some tuning guru’s on here who can advise on what the best set up would be.

Mike.

[Besalu]

47 minutes ago, trchris said:

Hi Richard if you have a 4 cylinder engine fitted you cannot just swop to a 6 cylinder engine without modifying the front of the chassis 

Chris

chris, it is a early 6 chassis with the correct engine mounts i believe. It also has a 6 radiator. What else will need to be changed?

[Besalu]

32 minutes ago, RogerH said:

Hi Richard

I have been following your chaos and I wish you well.

I have a 4A with a Newman PH1 cam -  next step up from standard - and it tours very well.

When you get whatever you are after you will end up with a silly grin on oyur face everytime you get in and drive it.

Good luck

Roger

Thank you Roger. Chaos sums up the last four years pretty well

[Besalu]

27 minutes ago, michaelfinnis said:

The CP cam had an unusually long valve overlap, made possible by the injection system, which is where much of the power increase over the carb cars came from. I’m not sure how well it would work with carbs.

Also, the TR6 engine with twin SUs, ie American market cars, has about the same power output as the TR4 engine. I know UK cars had a different cam and higher compression ratio, but I wonder if twin SUs are the best option if you’re looking for more power.

I’m sure there are some tuning guru’s on here who can advise on what the best set up would be.

Mike.

Mike, thanks. Were the US market cars on Strombergs? This is a 150bhp engine from a UK car. Anyway, i was thinking about triple webers as well but ruled them out for cost and also they seem difficult to balance. Not sure there's any Spanish mechanic in my neighbourhood who could help me with those!

[Rob Salisbury]

As Mike says if you run with a CP cam then you will be disappointed running carbs, get a fully refurbished Pi system, distributor etc and if it has a TR4A diff (3.7 to 1 ) the car will go like stink!! or put a 3.45 to 1 diff in for a slightly more relaxed drive. If you've got a 4A body then the right hand front inner wheel arch will have to be "adjusted" to accommodate the Pi plenum ( a large hammer and a big round dolly works here!!). Alternative way to go would be Webers but that's a whole different game and you'd have similar costs.

Don't forget to fit a fuel cutout switch if using a Pi pump

If you really have a 5 or 6 chassis then fitting the 6 pot will not present too many problems.

I wouldn't down the engine "upgrades" route (apart from hardened exhaust valve seats), fully refurbished the CP 6 pot will be great.

Cheers Rob

[Malbaby]

So you currently have a TR4A body fitted to a TR5-6 chassis with 4 cylinder engine mounts and still have the engine mount brackets for the 6 cyl engine on the chassis?...Presumeably your current R&P steering is mounted on brackets for TR5-6....If not the rack will have to be moved forward for the 6cyl engine....Do you currently have TR4 or TR6 brake syatem?

As others have mentioned, to fit the factory fuel injection system or webers, the inner wing would have to be modified.

Alternatives for fuel intake without wing mods...Twin/triple SU's or Strombergs...Mikuni's...Aftermarket EFI......In your shoes I would probably go with EFI, with the accompaning modifications of the fuel lines and pump.

The factory FI cam profile is very good.

Try to find the twin outlet factory TR exhaust manifold [semi extractor design], fit a collector and run a larger single system.

Edited April 30 by Malbaby

[Paul Hig]

10 hours ago, Rob Salisbury said:

As Mike says if you run with a CP cam then you will be disappointed running carbs, get a fully refurbished Pi system, distributor etc and if it has a TR4A diff (3.7 to 1 ) the car will go like stink!! or put a 3.45 to 1 diff in for a slightly more relaxed drive. If you've got a 4A body then the right hand front inner wheel arch will have to be "adjusted" to accommodate the Pi plenum ( a large hammer and a big round dolly works here!!). Alternative way to go would be Webers but that's a whole different game and you'd have similar costs.

Don't forget to fit a fuel cutout switch if using a Pi pump

If you really have a 5 or 6 chassis then fitting the 6 pot will not present too many problems.

I wouldn't down the engine "upgrades" route (apart from hardened exhaust valve seats), fully refurbished the CP 6 pot will be great.

Cheers Rob

Not sure you can fit hardened exhaust valve seats to early CP enginges due to the size of the exhaust valves (not enough meat in the head to cut in new seats) Just had my engine rebuilt and hardened seats were not possible, so continuing with lead replacement addative

[Rob Salisbury]

Chris Witor of the Triumph 2000/2500/2.5Pi Register probably knows just about all there is to know about Triumph 6 pot heads, so he's the guy to ask, but I used to have a '73 2.5Pi saloon (MG series engine number) and had no problem with the fitting of hardened exhaust seats, maybe your head had already had seats fitted and replacing those would be difficult or just unreliable. 

[jerrytr5]

Don't the valve seats only need doing on inlet or exhaust, not both? Can't remember which, or did I imagine that?

A bit of careful crank polishing just to remove casting flash & balancing is worth doing. You might want to do the same with con rods - something you can do with kitchen scales. You'll probably find quite a variation in weights.

Port match the head & manifolds & exhaust downpipe if using cast manifold.

Jerry

[michaeldavis39]

Hardened seats for exhaust only, had my early new old stock head done no problem. Some machine shops fear doing damage to the head but that doesn't mean it cannot be done if careful.

 

Edited May 1 by michaeldavis39

[DRD]

4 hours ago, michaeldavis39 said:

Hardened seats for exhaust only, had my early new old stock head done no problem. Some machine shops fear doing damage to the head but that doesn't mean it cannot be done if careful.

 

My CP head was fitted with hardened valve seats, no problem.

[Kevo_6]

9 hours ago, DRD said:

My CP head was fitted with hardened valve seats, no problem.

Same here, no problems.