5 GT Turbo Fast road engine build - help and info needed

[Gt Tony]

Hi everyone, this is my first time posting on a forum of any kind.

I’m carrying out a rebuild on my 5 and am struggling to find any reliable info. I’ve currently got the engine out and stripped, the bottom end is shot, crank and bearings are knackered so was going to replace it with a nitrided one from CGB as it costs about the same as a regrind. I’ve just had the turbo rebuilt. Going to pick it up later today, it’s a standard t2 but it’s been hybrid with bigger compressor wheel and turbine and the housings machined out. Have no idea of what boost it will run safely.

One of the things I need to know is what sort of height is the cylinder head from new and what the minimum height allowed is, as no doubt it’s been skimmed in the past. Also do you guys think a 270 cam would suit an uprated t2 turbo.

Here’s some pics of the engine so far.

Thanks for reading





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[Duncan Grier]

Sure 73.5mm is a standard non skimmed head.

270 would be fine but do a comparison of the 285 also. Plenty on here that know the c1j far better than me

 

[Duncan Grier]

Just had a quick look in the old haynes manual which states:

Max permitted warp 0.05mm
Max permitted refacing cut (aka skim) 0.5mm

Of course thicker head gasket may help

Congratulations on 1st ever post

 

[Gt Tony]

Thanks for that Duncan, I’ll have a measure tomorrow and see if I can get away with a thicker gasket. Have you or any of the other members ever used a hybrid t2. Picked it up earlier today so my pockets a lot lighter but hopefully will be a good turbo.


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[Duncan Grier]

I think between most of the longer serving members on here every configuration of turbo will have been tried

A hybrid t2 a very common upgrade, do you know the spec of build? What is the goal from the engine power wise?

 

[Duncan Grier]

I have used a few different t2 hybrid turbos and vnt but some years back. On my c1j build using a t2 hybrid (cant remember spec) was spec'd as upto 200bhp but only running 160-180bhp for reliability with supporting mods.

 

[Gt Tony]

Over 200bhp would be good, I was going to go for as much power as possible but the cost to do it properly would just be to much. The company that built the turbo say it would probably be able to run about 26psi. I’ll just get as much power as the turbo will give and rods will take I guess.


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[Gt Tony]

I had a 200bhp r5 back in the day but it was like driving a diesel and ran out of puff at about 5k rpm. It had a t2 stage 1 I think running 16psi. Then I got this one and it blew the socks off the old one. Unfortunately I was on a driving ban at the time and sold it after a week of owning. I managed by pure luck to find the car 10 years later on eBay and went and bought it back home (rattling its arse off the whole 200 mile trip) but now I’ve striped the engine down everything is standard so god knows what happens to the heavily tunned engine, probably blown to bits.


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[Mark Davis]

If memory serves anything below 73.4mm isn’t ideal.

I’ve proven standard rods are good for about 235lb ft.

I’ve ran both 270 and 285 cam to good effect albeit with much bigger turbo and revving to 7500rpm.

The key as I’m sure you know is making sure your fuelling is safe. I’ve spent the last few years tuning the C1J so should be able to help if you have any queries.

 

[Gt Tony]

Hi mark, thanks for the reply. Fuel and tuning was going to be another question once the build is done.

I picked up my turbo yesterday and it looks good, I’m waiting for the spec it’s been built to to be emailed to me. All I can see is cut back blades on the exhaust side and a nice looking compressor wheel.

I’m probably going to stick with the standard pistons and rods but fit strengthened liners and the strongest head gasket I can find.

Would 235lb be around 250bhp? Not sure what to expect from this little t2 but will be interesting as it has the most modern internals possible.


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[Gt Tony]

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[Mark Davis]

Hi mark, thanks for the reply. Fuel and tuning was going to be another question once the build is done.

I picked up my turbo yesterday and it looks good, I’m waiting for the spec it’s been built to to be emailed to me. All I can see is cut back blades on the exhaust side and a nice looking compressor wheel.

I’m probably going to stick with the standard pistons and rods but fit strengthened liners and the strongest head gasket I can find.

Would 235lb be around 250bhp? Not sure what to expect from this little t2 but will be interesting as it has the most modern internals possible.

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Yes it was 255hp, you’ll struggle to get to that with your turbo and set up without a lot of supporting mods and in my case full EFI, anything past 220-230hp and the carb becomes a bit more troublesome fuelling wise.

I wouldn’t worry about upgrading internals at all unless you are going to push past 250hp odd. If set up right they are strong little engines.

The Corteco blue head gasket is the one you want to use, about £50 from memory. I used an Athena MLS but overkill for your needs. Source some high tensile head bolts too.

 

[Gt Tony]

Do you think a 270 cam would suit this set up or is it a bit to much, not sure about whether an adjustable vernier pulley is worth buying either.

I’m with you on the internals, the only things that will be uprated will be a nitrided crank as it’s only £50 more then a standard one and I may as well use stronger liners.

Your 255bhp car must have been awesome. Efi must change the character of the engine completely.


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[Raj]

Correct me if I'm wrong,
Regarding over skimmed heads (to a certain degree).
I'm sure mecaparts do various head gaskets, with there max thickness being 2.2mm or 2.3mm i think.

 

[Mark Davis]

Do you think a 270 cam would suit this set up or is it a bit to much, not sure about whether an adjustable vernier pulley is worth buying either.

I’m with you on the internals, the only things that will be uprated will be a nitrided crank as it’s only £50 more then a standard one and I may as well use stronger liners.

Your 255bhp car must have been awesome. Efi must change the character of the engine completely.


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270 will be good for your needs for sure.

Worth vernier pulley so you can time cam to your required needs/rev range. Your last 5 felt dead on its ass by 5k for that very reason I imagine.

There is a massive thread on here somewhere on my EFI fun and games.

 

[Mark Davis]

Here you go if you get bored lol

EFI - GT Turbo