Late into this thread but here is a UK perspective.
Just about to finish my second twin spark conversion. I wouldn't fit anything else.
garagiste- would you mind fleshing out your build detail a bit ? More specifically :
Which TS cyl. head and what block- Alfa 75, 164, or...? ?
What compression ratio ? What intake manifold, throttle body make and size ?
"usual valve performance stuff" ?
Did you do the final tuning with the aid of the auto tuning feature of the Omex and/or rolling road sessions ?
Generally, how much of the project did you manage by yourself ?
I know it is presumptuous of me to ask for so much detail but your build sounds manageable as described and as we all know the Devil is in the details. I have done one such conversion several years ago but retained the stock e.f.i. and ignition. Made for a nice performance improvement and a much more linear power delivery as well as excellent drivability in my 74 GTV. That car is gone but I think there is one more Alfa twinspark project left in me. I have the drivetrain out of a 77 Spider and another complete Alfa 75 TS sitting on a pallet collecting dust. I'm currently casting about here in the States for a suitable Giulia Super project/recipient and your recipe may help me along. TIA...
I know there are a lot of folk out there with more knowledge than me and this has been done before so this is just my take having done a couple.
My general MO is do do as much of the time consuming tedious and straight forward stuff myself. So strip, clean the long grind of basic porting and gathering together all required bits. Then hand it over to a good engine builder with Alfa experience. This keeps my cost to a minimum, gives me a level of involvement but lets someone with the knowledge and kit do stuff like grind the cam caps correctly, balance it up nicely and zip it up correctly, a good engine builder is more than a nut and bolt tightener.
Happy to go over the parts recipe if you wish but I won't get long winded unless you want.
I use the head and block from a 75 twin spark and sump from the Nord.
Inlet manifold is a Twin Webber conversion, a couple of places sell them over here.
Throttle bodies are Jenvey, these match the Webber bolt pattern.
The valve springs are Kent race with new valves and guides. I kept standard valve sizes.
Piston compression ratio 11:1 (but depends a bit on if your head has been skimmed). Seems a lot but with a high overlap cam it retains the cylinder pressure (getting into physics I'm a bit iffy on here).
Standard rods on the first but am fitting Carrillo on the next.
As you need two 4 cylinder coil packs and a lot of 4 cylinder ECU's won't drive them you need get them to make one with no internal amplifier and use two external amplifiers in parrallel (more info if you need it).
I have always used a good rolling road for set up, so much better but now I have my first map and one supplied by the ECU supplier to choose from for running in.
I've used a lot of different suppliers in the past but have pretty much settled with Alfaholics for most of my Alfa stuff, they can be pricy but there stuff is proven and good quality, they are also a font of expert knowledge.
So I guess its a case of knowing my limitations and cherry picking between my cheap time and the experts expensive time.
I seem to be rambling so will stop, any specific bits I can help with let me know.
PS Power curve attached
Drivability good pulling smooth from the bottom, the beauty of efi and mapped ignition.
Used the standard Twin Spark trigger wheel. Body size 45mm.
A couple of pics attached. As can be seen I didn't do much about the valve recesses on this one, my next has a lot more flaring out there, I ground an old valve down to sit low into the valve seat to protect the seat insert before attacking with the Dremmel.
You sure folk interested in the complete recipe, happy to list if you think worth it.
View attachment 1666771 View attachment 1666772
Looks like a complex mix but that's good power, even with big valves not sure I would get that. Clever stuff, well done.different engine setup here: 155 2 liter block (the one with piston cooling in the oil system), 90 mm crank, 85 bore, JE pistons matched to long old nord rods (K1 used) . 10.5 CR 75 TS head with tilted intake ports , short 48mm Jenvey ITB with DTA computer. custom made exhaust and airbox, last dyno 213 hp @ 7200 (over 200 from 6500-8000) and 225 nm torque (peak at 5500 but allready 200 at about 3500). Is my race engine but will hapily crawl up a tilted trailer without burning the clutch.
Hi BjarneHi Martin and Walter
It's nice to see there's a good talk about TS conversion and experience. I might well miss a more telling thread than this one. After spending some winters getting the body back in place, and having started assembling that car after painting, the turn has come for the engine. The engine is a 75 tsp that I have cut together with parts from, Poul Spuell, Alfa Holic, Ferrea, Cat cams and more. I have two questions that I could use help with.
1. according to the picture there is a small hole in the middle bearing fit, it is for lubrication of the valve lifters, I was in doubt as I have not come across it before.
2. I bought an Omex 710 box, as I had a plan to go for full sequential injection, I am missing like everyone else a 720 ° signal, therefore know one of you someone who has used AW-delta´s distributor that could be use both as a engine position, but also for a distribution of the ignition, if I use the old ignition coil system. is there any of you there now if this Is a suitable way to go?
I add a couple of pictures of the engine.