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Jun 11, 2016 17:58:48 GMT
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Long story short, family member was building a kit car with a tuned crossflow. don't know spec but I seem to remember its 17-1800, expected to be over 150bhp (175 rings a bell but sounds alot for the cc), built by burton.
Has twin 40 dcoe.
Anyhow, after he died his wife had the car finished and set up.
I just took her out in it. It flies! Sounds turbo'd on lift off.
Runs great, feels over 150bhp.
Digi dash says its getting to 105 degrees when pushed.
Too much?
Idles great when cold but when hot will cut out (starts again easy) and hesitates off idle. Foot down and it takes off again.
Ive been having a look at set up guides etc but its been on rolling road so don't want to mess too much.
I also read off idle hesitation is usual with dcoe?
What I'm asking is, is it worth me pursuing this issue or just up the idle a little?
Is an engine like this going to behave any better than this?
I live 200 miles from it so will only get to tweek it occasionally but his widow (current owner) would need this car to behave if she's going to drive it.
Any thoughts?
If I owned it id drive it and tweek it amd all would be good but I'm going to get maybe an hour every 6 months to do anything with it.
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Jun 12, 2016 10:17:56 GMT
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I also read off idle hesitation is usual with dcoe? that's because 90% are not set up properly and it's more than just jets and tweaking. float height, progression hole position, and if it's the later carbs with air bleeds, as well as the idle jets will need setting to get a good light throttle drivability. progression holes are fixed but different body numbers have different position holes. the DCOEs need to be matched to the engine (and to each other if in pairs or triples). Ford usually have DCOE9 though I have drilled carb bodys before to modify progression. if they are new carbs they may be DCOE152 with three progression holes or DCOE152G with four progression holes. do you know what type are fitted? good idle when cold says to me too rich hence stalling when hot. need more info of carb type and idle jet size to be able to give more advice. |
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Jun 12, 2016 10:30:36 GMT
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I was thinking 45.
the 40 uses different numbers. 151 seems the favorite choice.
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Jun 12, 2016 13:00:23 GMT
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I don't know what type, ill try and find out.
Light throttle drivability seemed ok.
I'm not sure if there is any choke system but guess there must be. I guess its ppssible I had it left on choke.
Too rich was my guess too but its been on a rolling road so I'm assuming its pretty much right as far as jets are concerned and may just need tweeking.
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Last Edit: Jun 12, 2016 13:05:07 GMT by VW
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Jun 13, 2016 14:48:38 GMT
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In my experience rolling roads tend to focus on full load and high power, light load and idle often seem to be a bit flaky. (oh and very few understand much about carbs nowadays)
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slater
Club Retro Rides Member
Posts: 6,390
Club RR Member Number: 78
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Jun 13, 2016 15:03:19 GMT
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It mighy have a pretty lumpy cam in it to make that kind of power. Are you sure your not confusing that with bad fueling? Mighty make it hard to handle 'just off idle'
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Jun 13, 2016 19:27:22 GMT
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Maybe slater, but it drives great untill its properly up to temp.
I only drove it for about 30 mins, its a fresh engine, I was also probably poking it to hard.
Its awkward as I'm so far away from it.
It will be a few months till I see it again but I think my first step has got to be finding all the paperwork and seeing exactly what this motor is and how the carbs are currently set up.
Generaly though it feels very refined. It feels like its set up very well, just when its hot it doesnt like to idle and is flat somewhere like 1000-2000rpm.
Ill update and get back to you when I get to see it next.
Thanks.
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Jun 13, 2016 21:07:00 GMT
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It mighy have a pretty lumpy cam in it to make that kind of power. Are you sure your not confusing that with bad fueling? Mighty make it hard to handle 'just off idle' that's why carbs like that were fitted in the day. a single carb has high vacuum so a lot of reversion and charge robbing occurs. fit separate runners there can be no charge robbing and less of a vacuum gives less reversion. you could easily fit a big single carb to flow full power but they really run bad for normal driving. Webers give much better drivability on a tuned engine, they are not just for power. as I said before, there is so much more than just jetting to get the driveability correct. and it can be done but usually can take days to get right where as full power tuning can take less than an hour. iv'e drilled extra progression holes before. iv'e also drilled the butterflys to change the fueling at lower rpm (later carbs have an air bleed to do this but they are usually mistakenly set for balancing the idle. they are NOT to balance the idle). changing the float height can change light throttle tuning so you cannot always go by book height settings. I normally see off idle leanness so to counteract that you can fit an idle jet with a smaller air hole to start to see what that does. the idle jet has two holes. the one in the end for fuel and one in the side to act as a fuel brake. what happens is that as engine speed rises the engine will draw more fuel and get richer and richer. to stop this air is introduced into the fuel stream through the jet. fitting a jet with the same fuel hole size and a smaller air hole size will idle about the same but be richer off idle. i.e. 55F8 can be changed for a 55F9 (the F number never makes any sence when it comes to the size of the air bleed so get yourself a weber book) the Emulsion tube for the main jets is a much bigger version but does the same thing. they come in different widths and hole positions to bleed air into the fuel stream to alter the fueling at different throttle positions and engine speeds. but luckily you wont need to touch this part as it sounds pretty well sorted. |
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