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5.2 ltr engine


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Yes, you start with a 3.9 and stroke it via a crankshaft from a 4.4lv8, very big job! Lots of machining of conrods (chevy), pistons tops (new ones), main bearing area and some grinding of the bottom of the crankcase, lots of torque but they dont like to rev beyond about 7000 more than once so HP isnt as good as one might think. Torque makes wet weather driving very very exciting and the dry with yokohama 225 50 A032R wasnt much better.

 

Standard box lasts around a two years of track abuse on a 10 12 events per year basis (mine tends to break 5th gear).

I imagine the T5 would be stronger.

 

Diff gearing is critical to get the best setup for each track, this can become a real pain in the proverbial, i ran 3.77 for tyre shredding acceleration in hillclimbs, sprints and 3.08 for circuit stuff.

 

I currently run a 4.4 which is a 3.5 stroked with the same crank as above and much more flexibility with revs and reliability and predictability with cornering etc, times are about the same as before.

 

If you do go down the 5litre route fit a rev limiter and set it around 6000RPM if you want it to last.

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It really depends upon what class you will be running in and how serious you are about winning. You will probably find that the other people with big engines have done more development than you will have so you will be in catch up mode for a long time.

 

Also you must have a limited slip differential, bigger tyres (which means flaring the guards) some big brakes and a well sorted suspension you just wont get the best out of the engine with 200lb all round spring set and spax shocks.

 

If you want monster torque and arent that worried about all of the extra costs i would go for a 5ltr or bigger.

 

In ten years of track work in my TR8 and TR7v8 i have found the following as the best way of improving lap times (from biggest to smallest improvements), really sticky tyres Yoko A048R's or Toyo proxies or similar, uprated brakes (i have rear discs which make very late and very hard braking possible), suspension, then the engine, then bigger rims and bigger tyres and so on.

 

Its funny how everyone starts at the wrong end IMHO modifying the engine first!

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  • 2 weeks later...
Are there any tr7v8 s on the register running a 5.2ltr engine? I have seen one such car in a magazine. I know there are a few 4.6 but has anyone gone further?

What gearboxes have people tried D suffix Lt77, R380, Borg and warner T5 from TVR?

 

I run a 4.6 with some mods; Edelbrock manifold, 4 barrel Holley, road race cam,power steering etc. Not sure on the gearbox, looks like a standard 5 speed with shortened lever. I bet the 5.2 goes like s##t off a shovel; personally I have enough power to cope with "340 bhp if you believe the rolling road at the international"but I think a 5.2 would be "exciting".

 

good luck if you go for it.

 

Jo.

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