drnick

im not the first person asking this question and i know others have achieved this and i am not as knowlegable as others on this subject. my only substantial experience of rebuilding an engine was with an old triumph spitfire, cast iron everything and pushrods. at that time the machine shop sourced the oversize parts, i didnt check the bearing clearances on re-assembly but relied on their measurements entirely.

in reading through other posts on and around this topic my take on the situation is this: the most straightforward method is to use a 5.0 block and 951 pistons, these are the only factory parts that will fit without extra machine work or coatings - is this the case?

i also have a few burning questions concerning the above: how do you match pistons rings and bore size, assuming the bore is as from the factory, and why cant the 951 connecting rods be used? are there no custom pistons that will work with our block? what is the best bore size for a custom piston and who makes the best pistons?

if its not so obvious then the reason i am asking this is as a prelude to re-powering my car with the intention of applying boost (the little triumph engine ran very well afterwards, too)!

blau928

HI Nick,

If you are building the motor for boost, then you may want to call Chris at Powerhaus. www.powerhaus.com He builds turbo 951's and 968's that get 400+RWHP on 91-93 octane.

He uses MAHLE pistons designed for the Reynolds 390 Block material. When I am ready to rebuild my motor to a 6 Liter, I will go this way as well. Not cheap, but he has lots of data and has done lots of testing with MAHLE, who made the OE Porsche piston.

JE pistons are good from what I have heard, but I will go the MAHLE route.. Now, if you boost this thing, your wing will really be handy...!

Cheers,

Ben Allison

The 944/951 pistons need a bigger small end width than our rods provide. You would have the big end width reduced on a 951 rod or else have a custom rod set made (Pauter can make a set for ~1500) with the 928 big end width and the 944 small end width. The center-to-center length is the same.

I've never done this, but there are people who have. You'd want to get verification before spending the money, obviously =)

I'd be curious to know what you found out (either about mahle pistons or using the 951 pistons with custom rods). I've been contemplating a similar setup, but for an N.A. monster instead of a boost one =)

drnick

richard,

i dont think i can achieve my goal of gaining an extra 100 or so bhp any other way, for the same cost. is it only my immagination or is there a disproprtionaly large amount of work needed to achieve say 400 crank hp naturaly aspirated? would this kind of engine be driveable on the street?

John..

Don't discount the Nikasil bore, then run whatever you want method. It is an effective way to have a lot of freedom with your setup.

drnick

john,

i am exploring all options here before outlaying cash. i am in touch with a company based in the uk called 'perfect bore' who do nikasil and act as agents for JE and carrillo.

i know youve done this yourself and i was wondering, would i need a completely custom piston in 97mm and is this straightforward to obtain?

Tony

http://www.marcus3.com/engine1/engine1.html

Here ya go Nick. You can Email Marcus as well im sure and he will lend some pointers?
HTH

blau928

Nick,

400 Crank hp is extremely possible from a 5L 32V engine. Some head work, a set of headers, and you are good to go. If you want 400 at the wheels, then you need to either bore/stroke/boost..

DEVEK has a nice header setup for the 32v cars, I just bought a set from them that is being ceramic coated. I will then use a custom X-pipe, Random Cats, Spin Tech mufflers, and 3 inch stainless tubes mandrelly bent all the way back. I figured that since I was changing the exhaust system, I may as well built it to handle the 6 Liter + boost when I redo the motor.

I think if you port&polish the heads, and use 968 valves with the DEVEK Headers and a revised exhaust, you should have the 400 hp at the crank. You will also need bigger injectors, and a rising rate fuel pressure regulator.

This way, you can keep the internals stock, and have a bit more reliable power...

Then, really watch out for the gatso's...

Cheers,

drnick

richard i will almost certainly keep my SE naturaly aspirated and probably undertake a program of modifications along the lines you are suggesting, when the time comes.

for now im focused on making the orange car into something special, i like its colour, the suspension setup and brakes are all good, it just needs to go faster. i plan on reducing the weight somewhat - removing the sunroof and mechanism and rear wiper, light weight door inside panels and recaro fixed-back seats - rear seats are allready removed. this will help but not enough. whilst im tempted to simply upgrade to a GT engine, maybe with headers and then save for a carbonfibre intake, the prospect of a breathed on monster with 400rwhp is even more enticing, kinda like 'well, while im at it..'