1290 SOHC Dellorto DHLA Jetting

[Abarthnorway - Remi L]

Hi Guy!


1) I am looking for jetting advice on the following engine as buildup time is nearing fast - time flies!!:
Engine specs:

128 1290cc engine
Compression 10:1
Cam steel billet 284`/ 10.5mm true lift / 3.5 mm TDC / 106` Lobe separation (similar to James Bowen)
4-2-1 exhaust manifold
32 mm exhaust valves
36.2 mm 30`back cut intake valves
Intake port taken to 32 mm at port face tapering down to 28.5 at port venturi. Material removed from port sides and roof only at venturi. SSR rounded off and valve "bowl" enlarged.
Exhaust port now 29mm from valve throat and out.
Valve seats internal diameter now taken to 32.5 on intake and 28.5 on exhaust.

2 * Dellorth DHLA 40:
No suffix/emissioncontrol
Currently running 32 chokes
Current emulsion tube 5

2) Oilway plugs in crank removed for cleaning (look pic below).... btw recommended as it was unbelievably much muck in there after 30+ years.
I have ordered som new aluminium plugs, as I am not keen on tapping the crank myself - don`t trust the quality of my tapping tools - do not want a broken tap in there....

Will it be ok to use std plugs for lets say a possible overrev to 9000rpm?

Please advice.


Thanks!

Best regards

Remi Lovhoiden

No pictures of finished engine parts yet as they are in for machining at the moment.

But some Do - It - Yourself pictures so far:




This is the debris from one hole only!!! a good spoonful there!




Bigend oilway before




Bigend oilway after




Another shot of oilway after




Tool




New oilpump and new higher spec oil valve spring to the left

[Acki]

Looks like a Uno SOHC oil pump?
Don't make too much oil pressure with the harder spring ;)

That's looking nice:


I thought about this but I don't know. Do "we" need this? Guy what's your opinion?

Why you don't made the back-cut on the exhaust valve? I think this make it easier for the engine to push the exhaust gas out of the engine and the engine don't need to use "the power" of the crankshaft for this. Like on turbo's with the exhaust gas pressure. :)

[Abarthnorway - Remi L]

Hi Acki!


For the sake of simplifying the engine specs I have left out some details.

Yes the exhaust valves are back cut too.
Shorter 42mm flowed race guides put in almost flush with port roof.

I will post more pictures as I get the parts back and build begins...

Btw have a nice weekend.


Best regards

Remi Lovhoiden

[Guy Croft]

Remi, hi

Re: Jetting Dellorth DHLA 40:
No suffix/emissioncontrol
Currently running 32 chokes
Current emulsion tube 5

Mains - 120
A/C - 190
Pump jets 40
Idle Jet - 40

Would be my starting point. Re-read James' post on how jetting is optimised too.

Don't run std plugs, use NGK B9EGV race, I am an agent for Race Div NGK, I do stock, though I am not recommending them simply because I'm an agent. Never use road plugs on a race engine.
As for your crank plugs, I don't see why you'd break a tap if you use No1,2,3 progressively with proper tapping oil, those cast-iron cranks are pretty soft compared with TC 2 liter.


GC

[Abarthnorway - Remi L]

Hi Guy!

Thanks!

Best regards

Remi Lovhoiden