Building a 200hp Twin Spark
A quick history first . I put my Twin Spark into my spider with a Jim Steck distributor and Weber 45's . Over the last two winter I have gone to aftermarket fuel injection /ignition using motorcycle throttle bodies and GM coil packs all run by a DTA Fast computer. This and an Alfaholics stainless exhaust system. You can find more on that here. Twinspark running on Motorcycle Throttle Bodies
Now that the control side of things is all sorted I have been looking at getting a Twin Spark head from Alfaholics . They can supply a 198 hp or a 215 hp. Both of these heads come at what I think is good value for money but I think I can do a lot of the work myself. I am under no illusion that I can do as good a job as Max and the boys but I think I will end up with a great motor .
I am hoping to make 200 hp and to be able to spin up to 7000 rpm . I am going to follow the plan set out in Jim Kartalamakis book The Alfa Romeo DOCH Engine High-Performance Manual .
From what I have read the biggest problem with the TS heads are the Inlet Valve seats. They are recessed into the head.
To fix this problem I will replace the seats and the valves with ones 2mm larger than stock.
The next step to make more power is a camshaft change . I have yet to decide on the "right " cam for the job.
With the change to bigger intake valves and a higher lift cam comes the need for bigger cutouts in the pistons.
There are a few different sets available Alfaholics, AH Motorstorts ect . The ones I like like the best right now are from JE Pistons . This is because of cost and that there are no problem to have them modified. For a few hundred bucks I am going to upgrade to lighter wrist pins and Total seal rings.
The final compression is still to be decided on . I am thinking 11:1 or a bit higher . I want to run on pump gas. We can get 94 around here. But if I have problems I can use the 2nd map function of the DTA to retard the timing .
Since I will have to open up the bottom end I am going to get a set of Carrillo I beam rods. They are 56g lighter and good up to 200 hp and 7500 rpm. I have to find out if will be using standard bearing set.
Then there are the other items like reshaped valve guides , performance valve springs, valve shims and a gasket set.
So all that and the machining / porting should keep me out of trouble over the winter.
Also when the motor is out I am going to replace the four gear box studs on the back of the block with bolts.
I know a lot of people say it is easier to take the motor and gear box out together but this is not true with a Twin Spark in a spider. This kit should make the job even smoother.
Here is the parts so far from Paul Spruell
1 - Set of Pistons 11:1 Alfaholics
4 - 47mm Intake Valves Alfaholics
4 - Reshaped bronze Intake Guides
4 - Reshaped bronze Exhaust Guides
1 - Set performance Valve Springs
1 - Set Carrillo Rods I beam type
8 - Valve Shims / Lash Pads
1 - Main Bearing set
1 - Block rear Stud Kit
1- 13mm Intake Cam 1-12.9 Exhaust Cam Alfaholics
Remove head and strip
Replace Intake Valve Seats
Remove Valve Guides
Port intake and exhaust ports
CC of Combustion Chambers
Surface head if required
Install new Valve Guides
Install new Valves, Cams , Springs , shims
Remove rods Pistons Liners
Fit rods to Crank
Install new pistons
Find and fix oil leek (rear main seal?)
Change Gear Box studs to bolts
Well that is the plan for now . Did I miss anything ? Input on Cams and Compression welcomed .
Is it worth having the pistons coated? I am wondering about Crown and skirt coatings how much
difference do they make ?