Converting Tu3M Spi To Tu3S Twin Carb Spec

[A1AXX 26 2 Cars]

Hi,

 

Has anyone on here tried converting any SPI model 205's to the twin Solex from an XS or AX GT?

 

My main questions I couldn't find many answers for....

 

Reducing the fuel pressure? The SPI in tank pump is over the PSI of any fuel pressure regs, I was thinking of running a solid state facet pump to sytec pressure reg to run 3.5 PSI.

 

The ignition is ECU controlled, so can this be kept for running the ignition on the carb setup? The SPI doesn't have a crank position sensor, but is told to spark by the ignition amp / module bolted to the side of the rotar arm housing on the cylinder head.

 

Other than that im good, I know the cam is different on an M head and an S head, so I will get a different camshaft to ensure valve lift and duration is right.

 

Cheers

[RossD 43]

If you change the cam to a TU3S spec one you'll also require a TU3S distributor - changing the cam changes the ignition advance requirements of the engine.

[allye 530 3 Cars]

I used a SPI engine to replace the buggered original engine in my Rallye. I can't help on the ignition side of things, I just bolted on the carb and used all the original Rallye wiring and mechanical fuel pump.

[batespeed 0]

i did exactly this on a gtx 2 years ago,it was a tu3m iron block single point injection that i couldent get to run right

you need the complete cylinderhead of a tu3s (205xs or axgt) with everything attached, ie inletmanifold and twinchoke solex, mechanical fuel pump , distibutor , coil and the wee plastic fuel return pot thats bolted to the inlet manifold.

 

lift up the back seat and remove the wiring plug from the high pressure pump in the top of the tank, then eveything else just bolts on, you can use your old exhaust manifold and down pipe, you will need a new cylinder head gasket (make sure its the right one for iron or alloy block , whichever you have) my one had a distributor anyway, so the ecu was only for the injection so this was removed, and the rest is just as straightforward as a cylinderhead gasket change.

 

ive done 15k miles in mine since this and it flies , the extra hp is realy noticeable and it revs to 7000rpm, so basicaly its an iron block tu3s.

 

i also put a straight through front pipe (no silencer or cat) and a gti back box on, along with a k&n air filter.but the standard ones would do. its a bit loud, but sounds great at 7000 rpm !

Edited January 10, 2012 by batespeed

[welshpug 1,629]

sounds much easier to fit the complete engine, a friends has one for sale but he's not in ireland.

[batespeed 0]

no its a piece of piss ,( as long as you have all the bits)

 

from memory , once i gave up on the injection , it took 2 hours to get it running on the carb, and that included removing the cylinderhead from the doner car !

it realy is as simple as a head gasket swap.........

Edited January 10, 2012 by batespeed

[welshpug 1,629]

I wasnt saying it would be difficult, just the number of parts required makes much more sense just buying a complete running lump and swapping them over (mate only wants £50)

[batespeed 0]

yes ,i would buy the whole engine, but if the existing engine has a good bottom end i would just use the bits ive listed and keep the alloy block as a spare.

 

your still going to have to unplug the pump and do the other stuff even if you fit the whole engine,

it just seems like a lot of extra work for nothing, its a lot easier to do a headgasket than to swap an engine. plus you know its got a new gasket.............................

Edited January 10, 2012 by batespeed

[johnnyboy666 195 1 Cars]

*cough* Ive got an xs TU3s engine for sale *cough*

[welshpug 1,629]

I must have the same cold, COUGH....

[batespeed 0]

where were you lot when i was looking for bits ? i paid £50 for a twin choke solex and manifold of ebay last year

[johnnyboy666 195 1 Cars]

yeah they were going for crazy prices last year for some reason! I had about 3 spares so boshed them all on ebay and made about £140. tidy

[A1AXX 26 2 Cars]

I bought the carb today guys! Payed £50 on eBay! I've actually got the head an all off today as I'm doing the head gasket!

 

I found that a TU3m head and a TU3S head have the same part number. Just the different cam and distributor housing to take the lift pump.

 

Is anybody willing to break their engines they are selling?

[309jazzpanda 39]

just out of interest, how much for the tu3s engine jonnyboy? my gtx could do with a new engine