Strada Abarth 130 TC potential on modified standard parts.

[Abarthnorway - Remi L]

Hi Guy!

Sorry to bother You with questions You have probably answered several times before - its a lot of info on Your site - can`t find it all....

I have finally found a reason to realise my dream project of getting the best out of the wonderful Strada Abarth engine. A new racing series for italian cars older than 20 years is starting this year in Norway. I will use a Strada Abarth 130 TC car/engine for this series - and want to see how far I can take the engine using original parts. Nice to have a set frame to work within.....

I am allowed to modify the engine using the excisting parts.
Stock carbs Solex 40 ADDHE- changing choke venturies/ram pipes OK
Air filtration - free
Stock cams - timing/valve clearance free
Stock pistons - Free block reface, modifying pistons ok
Head/manifold - Mods allowed
Valve guides - free
Stock Valves - Mods allowed
Stock valve seat dimensions - free to modify
Oil/cooling system - free
Std rods/crank/flywheel - lightening OK
Stock tubular manifold - free system from manifold and back.

The tracks is all Tarmac and some twists and turns, so I am looking for increased high middle/top range.

Carbs are flowed at aux venturi/throttle shaft/throttle plate and 36 mm chokes ordered. I am planning on keeping the std airbox with K&N insert filter.
I was thinking to deck the block approx 1.5 mm to increase compression from 9.45 to 10.5:1 (after valve seat, combustion chamber and piston pocket work)
Exhaust will be straight pipe from manifold and back with one silencer.
Flowed head/valves/seats

The questions I need to know more about are as follows:

1) Valve timing - can any gains in top end be gained here?
2) Valve clearances. How close can/should you go?
3) Intake Port diameters - will there be any gain in encreasing the intake port diameter from 35 to lets say 36,5 mm with stock cams? (removal from port sides/roof)
4) Valve guides - Seems from the thread at viewtopic.php?t=305&highlight=idf+manifold (Idf inlet manifold test data) that the guides rob quite some flow (-7,5 cfm with bare head). Good idea to shave off after seat work?
5) Exhaust: Manifold exit has 2" ID. Will I see gains of increasing tubing to 2,5" or 3" from here and back?
6) Any other good realistic ideas?

Thanks again for clear answers.

I will keep You updated on my progress - planning to attend in the 2008 season - lots of work waiting!!


Best regards

Remi Lovhoiden

[Guy Croft]

Remi, hi

1) Valve timing - can any gains in top end be gained here?
If someone said to me - play with cam timing - I'd do what software has been indicating over the last couple of years - narrow lobe centreline angle gives an engine that holds its top end power better and has more area under the torque curve = superior driveability. I'd go to 102 deg inlet and ex full lift, modify VRs accordingly.

2) Valve clearances. How close can/should you go?
I would not go tighter than 16 thou inlet 18 thou exhaust - the performance gain from going tighter will be modest and you might damage the cam lobes.

3) Intake Port diameters - will there be any gain in encreasing the intake port diameter from 35 to lets say 36,5 mm with stock cams? (removal from port sides/roof)
Don't go any bigger on inlets - just straighten out the port rood with guides removed and smooth the casting to an oiled 80 grit finish. On the ex ports remove 1mm or so adjacent to the guide boss on sides and roof and reshape the short side radius.

4) Valve guides - Seems from the thread at viewtopic.php?t=305&highlight=idf+manifold (Idf inlet manifold test data) that the guides rob quite some flow (-7,5 cfm with bare head). Good idea to shave off after seat work?
From memory I think that's an early head with 15mm guides which, yes, are very intrusive, yours are 14mm and nowhere near as bad, I don't shave race guides anymore really, makes seat overhaul pretty-well impossible, best to put the guides in a drill or lathe and reshape them till they have nice bullet-nose aerodynamic shape. Slim down an old cast guide and practice with that so you get the reshaped region where you need it.

5) Exhaust: Manifold exit has 2" ID. Will I see gains of increasing tubing to 2,5" or 3" from here and back?
No, you won't more likely power loss 2"- 2.25" is plenty big enough.

6) Any other good realistic ideas?
Just for now - It's well worth spending plenty of time to get oil temp to 85 deg C and engine temp to 75 deg under all max load conditions. Cold air ram ducting to filter an absolute must too. If you can afford it get a 4kg steel flywheel made up for 7.25" race clutch. Get one of those fantastic George Polley NHRA race mufflers too. You're allowed to lighten the crank I think, so I'd be for knife-edging the webs on that.

GC