1776 twin 40 dellorto trouble

Post Reply
elliot101
SSVC Member
SSVC Member
Posts: 410
Joined: Tue Mar 07, 2006 12:54 am
Location: Near Santa pod Northants!!

1776 twin 40 dellorto trouble

Post by elliot101 »

brought a 1776 engine off ebay 8O
as41 case
bolt up rockers
full flowed
009
minor head porting
standard points ignition
and standard mechanical fuel pump
with twin 40 dellorto carb's
owner brought a project with it in and couldnt get it to run right so sold it
looks like it hasnt been built long
fired it up today on my bench tester and it started up first time with no knocks grinding etc
but it was popping and back firing lowdly from both sides of the exhaust and throwing flames out
this happened at idle but more when accelerating
set the timing to 28 deg at 3000rpm and made no difference
also was idling very fast
any ideas , odvious things to check for ?
havent checked jet sizes yet
64 RHD 21 window devon



ImageImage

flatbeat
SSVC Member
SSVC Member
Posts: 1894
Joined: Thu Oct 04, 2007 4:06 pm
Location: Gloucester

Post by flatbeat »

It's a good idea to use a fuel pressure regulator if you're running a mechanical pump.
Packed a few belongings and headed out to Pirates Cove. In my buddy’s old grey Kombi we rolled until the gas got low.....

1965 11 Window aka 'Rustina'.
1961 Beetle.

lambretta
SSVC Member
SSVC Member
Posts: 1104
Joined: Sun Feb 06, 2005 9:21 am
Location: Up North (Near Newcastle Upon Tyne)
Contact:

Post by lambretta »

flatbeat wrote:It's a good idea to use a fuel pressure regulator if you're running a mechanical pump.
Yeah this is what Paul from T2D told me recently, I have twin 40 dells and apparently they struggle if the pressure is too high, unlike Webbers which can cope much better.

Having said that, I dont have one on and mine runs fine - I did have the carbs setup by a specialist on a rolling road though as I had exactly the same issues when I first fitted mine. Even though we set the timing properly and balanced them they still didn't run properly. Fantastic now though.

Where are you based? I'm sure someone will be able to recommend a decent place to set them up for you nearby.

elliot101
SSVC Member
SSVC Member
Posts: 410
Joined: Tue Mar 07, 2006 12:54 am
Location: Near Santa pod Northants!!

Post by elliot101 »

update after tinkering tonight
thanks for the input guys :wink:
timing set a 28 deg at 3000rpm on the 009
points and valve gaps checked all ok
blocked off vacuum hole's
checked jets for blockages
idling fast at about 1400rpm , and i havent balanced them as i dont have the tool (yet)
the left manifold is hot to touch after 5 minutes of running ,the left is only just warm :?
jets sizes are:
idle 55
air 205
gas 135
accel pump 35
venturi's are 32's

are these correct for a 1776 ?
i'm quite new to performance engines so twin carbs are abit alien to me
i'd like to sort this myself as i'm a diy guy like to know how things work etc
so taking it somewhere will be plan B thanks
64 RHD 21 window devon



ImageImage

flatbeat
SSVC Member
SSVC Member
Posts: 1894
Joined: Thu Oct 04, 2007 4:06 pm
Location: Gloucester

Post by flatbeat »

One manifold getting to hot to touch could mean you're running lean on that side, or maybe sucking air( this could explain some of the snapping and popping back). Check that everything is nice and tight, manifold nuts, carb mounting nuts etc, no air leaks. You can do a good job of balancing the carbs with a feeler guage. Best to do it with them off. Measure between the butterfly and carb body and with the throttle stop screw set the butterfly with a gap of 0.004" (4 thou) on both carbs and you'll be close.
Packed a few belongings and headed out to Pirates Cove. In my buddy’s old grey Kombi we rolled until the gas got low.....

1965 11 Window aka 'Rustina'.
1961 Beetle.

elliot101
SSVC Member
SSVC Member
Posts: 410
Joined: Tue Mar 07, 2006 12:54 am
Location: Near Santa pod Northants!!

Post by elliot101 »

just thought i should add that it has no exhaust or manifold on at the moment would that change anything ? :?
thanks for the replys
64 RHD 21 window devon



ImageImage

orb
Registered user
Posts: 2474
Joined: Wed Jan 14, 2004 6:00 pm
Location: Kingston upon Thames

Post by orb »

elliot101 wrote:just thought i should add that it has no exhaust or manifold on at the moment would that change anything ? :?
thanks for the replys
it certainly won't help that's for sure - all engines really need a little back pressure to run right so I'd bolt that all up before trying to set it up further or you'll be wasting your time.

I had one that used to pop and bang a lot and it turned out the inlet manifolds just hadn't quite seated properly and were letting too much air through - if it's one side then check that first - have them off and make sure they go back on nice and snug - the simple things are the cheapest :wink:

Speak with the guys down at eurocarb http://www.dellorto.co.uk/
they should be able to give you a good baseline on the jet sizes - they know their stuff

good luck

Orb
Image

My Bus - http://www.youtube.com/watch?v=K7deu8L0ra4
PB 15.126 @ 83.26 mph EBI 2015

User avatar
maddison
SSVC Member
SSVC Member
Posts: 5536
Joined: Fri Feb 01, 2008 1:56 pm
Location: up norf
Contact:

Post by maddison »

fit an exhaust :roll:
and make sure your air bypass valves are screwed all the way down, they are the long thin brass ones, 1 each barrel. 2 per carb, next to the air mixture screw

dont need to tighten them tight, just finger tight

buy me a drink if that fixes it :wink:

i`ve got a 1776 with twin 40 dells......and i have had the whole thing stripped, new dizzy, exhaust, plugs leads, head off, carbs cleaned....still popping and firing...frustrated as hell.....just found one of the bypass screws had snapped, stuck some gum over it and bingo...smooth as a criminal :wink:

Post Reply