36 vs. 40 Dellorto's

For those who couldn't care less how their 356 left the factory!
Post Reply
Message
Author
Mike N
356 Fan
Posts: 54
Joined: Tue Mar 25, 2008 10:26 pm

36 vs. 40 Dellorto's

#1 Post by Mike N »

Hi,
I'd like to change out my carburetors from the current Solex 40PIIs to a set of Dellortos. What are the pros and cons between the 36mm and 40mm Dells? For example, if I go with the 36mm carbs, do I lose the top end?

Here are some of the specs of my motor:

1720cc Shasta pistons/cylinders
SC case, heads
Delong 6810 cam

The engine has been dyno'd for right around 100HP, if I remember correctly.

Thanks,
Mike

User avatar
Greg Banfill
356 Fan
Posts: 159
Joined: Sun Nov 30, 2008 4:32 am
Tag: I build my cars for me to enjoy, not you
Location: Nor Cal
Contact:

Re: 36 vs. 40 Dellorto's

#2 Post by Greg Banfill »

Either one will work just fine.
Your venturi size is what really makes the difference.
Registry Member #30711
54 Outlaw
VW / Porsche - Vintage Warehouse 
Parting 55 Coupe

Kevin Wills
356 Fan
Posts: 501
Joined: Wed Jan 27, 2010 9:04 am
Location: Northern Virginia

Re: 36 vs. 40 Dellorto's

#3 Post by Kevin Wills »

+1 to what Greg said about vent size. Also remember that Dells are basically one size up from Webers. A DRLA 36 is like a 40 IDF. A DRLA 40 is like a 44 IDF. FWIW, I run DRLA 40s on my 356 which has a similar build to yours. I did notice that on the top end, it pulled stronger than with the Solexes, but I am not convinced that I couldn't make the Solexes pull just as hard and smooth with one size larger vents. I would also not be opposed to running the 36s. If set up correctly, I believe it would have enough A/F for your motor.

Mike N
356 Fan
Posts: 54
Joined: Tue Mar 25, 2008 10:26 pm

Re: 36 vs. 40 Dellorto's

#4 Post by Mike N »

Thanks for the replies. How about the bottom end, idling, every day driveability? Is there any big difference between the two?

Mike

User avatar
Greg Banfill
356 Fan
Posts: 159
Joined: Sun Nov 30, 2008 4:32 am
Tag: I build my cars for me to enjoy, not you
Location: Nor Cal
Contact:

Re: 36 vs. 40 Dellorto's

#5 Post by Greg Banfill »

No difference.
Registry Member #30711
54 Outlaw
VW / Porsche - Vintage Warehouse 
Parting 55 Coupe

Kevin Wills
356 Fan
Posts: 501
Joined: Wed Jan 27, 2010 9:04 am
Location: Northern Virginia

Re: 36 vs. 40 Dellorto's

#6 Post by Kevin Wills »

Either will work OK for your motor. If you are in the ballpark, it is all about the build. Adjustments in jetting and vent size will make either work well. Just don't expect that you can bolt on the stock settings of either and have it be perfect.

Alan Klingen
356 Fan
Posts: 209
Joined: Thu Oct 21, 2010 9:57 pm

Re: 36 vs. 40 Dellorto's

#7 Post by Alan Klingen »

The Dellortos are famous for their ability to have good low end performance. This allows you to have a mo0re radical motor and still work well at slow speeds. As far as the size are concerned is your motor is like a 356C or milder then the 36's will do well. If you have a SC or 912 style of motor then the 40's are for you. I do a lot of Dellorto work so when you get the cars you want give me the engine specs and I can give you some jetting advice. Dellorto's tend to use larger jet sizes than a Weber or Solex but this is just the nature of the design they don't use any more fuel. You also need to make sure the ignition is working well these carbs like plenty of ignition advance.

Alan

User avatar
Steve Proctor
356 Fan
Posts: 1318
Joined: Fri Mar 28, 2008 12:15 am
Location: Spring Hill, TN

Re: 36 vs. 40 Dellorto's

#8 Post by Steve Proctor »

I ran 36mm on my 1720cc 912 with Elgin 280 degree 7008 cam and chopped flywheel. Revved up and down like a sprint car!! Got 40mm with update kits on the 1720 912 engine in the Speedster with Elgin 268 degree 6708 cam and is not quite as dynamic. 40MMs come stock with 34mm venturis and according to Spenser's chart, 32mm would be better to 6K RPM, I think it is...still has very clean low end and smooth to the top...
STP
Steve Proctor
Member Since 1977
VIN 84757

Post Reply