Sheepy
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| posted on 22/4/03 at 10:15 AM |
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Engine drinks like an alcoholic fish
Hi,
A couple of questions and advice please. I've just picked up a car with a 1700cc X-flow with twin 40s and a kent cam (checking which one
tonight). I've been out all weekend and have an average of 17-25mpg with 25 being a long gentle run. Before people start saying "well what
do you expect with 40s and a kent cam..." I've bought it with it all in and was expect a little more perhaps. I'm about to change
the points and plugs because they've been sitting for a while and will be checking timing and such asap because the exhaust seems to run very
hot and get very hot very quickly i.e. too hot to touch from cold within 10-15 seconds. I appreciate that it must be set up correctly first with
respect to timing and balancing carbs, I've got them closer than they were before I can take true readings. Can anybody tell me what sort of mpg
they get with a 1700cc X-flow, twin 40s and kent cam before I go hunting for an impossibility. Don't get me wrong, the power/noise and
everything else is great-I love it but would prefer something I could use more often in terms of drinking my money away. Thanks Gaz
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Deckman001
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| posted on 22/4/03 at 10:39 AM |
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I had a 1700x/flow in a mkII escort with twin 40's and a fast road cam, it was on 1300 gearing and went like sh*t off a shovel up to about
95mph. Like your engine mine did about 20mpg on a run, but dropped to about 12 yes 12 mpg when i wanted to put a smile on my face !!
Locodude might be another party with experience of this sort of thing, but he has defected to the BEC sections now !! 
Jason
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stephen_gusterson
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| posted on 22/4/03 at 11:21 AM |
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dave ashurst runs a 1700 - think hes got twin carbs and a high tube head - not sure about cam - perhaps he can help you.
atb
steve
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Dave Ashurst
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| posted on 22/4/03 at 12:36 PM |
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Indeed.
I monitored fuel economy for about 4 weeks recently and was getting 25 to 30mpg. My car has a tuned 1700 crossflow with twin DCOE 40's, a kent
234 camshaft, a very nice big valve head and an aftermarket optical electronic ignition system. It's used daily for a 25-miles-each-way
enthusiastic commuting adventure through warwickshire B roads.
If your engine, cooling system and transmission are in a condition to take the stress then I suggest getting the carbs and timing tuned on a rolling
road by someone who knows what they're doing. It works wonders.
Tell them what sort of drive you want to achieve.
If you are anywhere near Birmingham I recommend Hi-Tech Motorsport in Cradley Heath for reasonable cost and good results.
Dave
[Edited on 22/4/03 by Dave Ashurst]
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Rob Lane
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| posted on 22/4/03 at 04:47 PM |
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When I had a 1700 with twin 40's and a 244 cam fitted it would only return 25mpg at best, less with a lead right foot.
This engine was very carefully set up on a rolling road (6 hours) and so was at peak tune.
This is what I would expect with a 244 cam and perhaps slightly more mpg with a 234 milder cam.
The exhaust getting hot suggests that the cam is too advanced. They do take very careful setting up for timing, many a builder will just fit the
original cam wheel on to a tuned cam and not check the timing. This will usually result in the cam being out by a number of degrees.
There are two methods of setting the timing on the wheel, one is by offset dowel on original wheel, other is a cam vernier wheel, much simpler.
It is possible to check but not adjust the cam timing by using a dial guage on the rocker arms, against the lower crank pulley timing mark.
Adjusting the timing can be done in car but is very difficult that way. The engine has to be drained of oil and water and the pulley and cam cover
removed, in the latter taking care with sump gasket.
It usually means resealing with silicone and the remnants of old gasket.
Otherwise it's a engine out, sump off job.
Rob Lane
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jollygreengiant
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| posted on 22/4/03 at 08:08 PM |
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There was a very old trick that used to be used many years ago and that was to adjust your cam timing by careful adjustment of the valve clearances,
but this it must be said was only suitable for small adjusments and fine tuning to compensate for variations between cylinders.
Enjoy.
Beware of the Goldfish in the tulip mines. The ONLY defence against them is smoking peanut butter sandwiches.
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Dave Ashurst
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| posted on 22/4/03 at 08:11 PM |
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Got me thinking now. I haven't calibrated the trip meter, but as I recall my speedo read 10% fast at SVA and I haven't corrected for
that.
Last measured fill-up after general use gave 28.13 uncorrected mpg. So correct it to around 25mpg.
Dave
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david walker
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| posted on 22/4/03 at 08:45 PM |
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Unless it's a really wild cam or unless it's come from a poor cam grinder then valve timing error on a X'Flow will be insignificant
and won't really affect running temperature. Too high compression for fuel octane being used or ignition timing errors would have a greater
effect.
OHV engines benefit more from adjustable cam timing gear for the purposes of tweaking the power characteristics of a race cam. By advancing or
retarding the timing the dyno operator can move the power band up or down the rev range. On an A2/BCF3/KC234 type profile a degree or two either way
of specified figure will not be noticable.
The BCF3 cam in my X'Flow is within a couple of degrees of spec without a vernier. (And anyone who claims he can set a vernier to better than 1
to 2 degrees has never built an engine).
I'm not wanting to be controversial but another viewpoint on a related subject concerns the use of Duplex gear on X'Flows. Using modern
chains and modest cams (of the above type) how many have you seen snap? Before you answer, bear in mind that the Lotus TC, of which there are many
running wild cams and putting out approaching 200bhp, use the same chain profile but it's about 3 feet long! No duplex kit available for them. I
feel that over the years the marketing men have created too many "must have" add ons and it's not as though they are cheap.
On the contrary vernier, or adjustable pulleys are nearly always necessary with OHC engines - particularly where the block has been decked or the head
skimmed.
On the fuel front my 1700 X'Flow gets well thrashed about and is used mainly on short runs and I doubt I get 20mpg!
BTW - Don't all headers get hot after 10 to 15 secs? - then again what do we mean by hot?
Dave Walker, Race Engine Services - 07957 454659 or 01636 671277
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jollygreengiant
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| posted on 23/4/03 at 05:54 AM |
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Spot on David.
Enjoy.
Beware of the Goldfish in the tulip mines. The ONLY defence against them is smoking peanut butter sandwiches.
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Sheepy
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| posted on 23/4/03 at 08:34 AM |
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Drinking again
Hi,
Thanks for all the responses, loads of very interesting points. Some more info for you. In terms of how hot is hot...it'll take skin off your
legs without much trouble after 30 seconds or so, I'm used to working with zetec 1.8 on a dyno and they don't kick out half as much
heat.
Anyway, I've had a look through the paperwork I've got with the car and it reads like this; 243 kent high lift cam (yes it says two four
three, could this be a 234 or 244 or is there a 243 out there?). it has been fully gas flowed, everything skimmed and hardened throughout. it mentions
9 3/4 lbs compression. I've seen somewhere the mention of a 120 jet and 10 degree timing at 4500 rpm, twin weber 40 dcoe and tuned in mid
1990's for max power via Colin Blower Garages LTD but thats about it.
I put a timing gun on it last night before going home, at idle the pulley marker shows TDC and increases to a max of 12 BTDC at 3500-4000 rpm. It
apparently has a lucas electronic ignition , all I can see at the moment under the webers is something like AIDON and the words electronic, I'm
checking on this now. There doesn't seem to be a vacuum of any sort which should confirm the electronic ignition but the fact that its sitting
at TDC is puzzling me. I've read in loads of places that this type of engine should be at 8 BDTC or there abouts and then talk of advance figure
in the twenties or low thirties...what am I missing here? Can anybody shed some light on what I should be seeing on the timing gun with all of the
add on bits. I'm used to standard engines but tweaking with something I haven't set up isn't something I want to do without lots
more info....any help please...thanks again for all the responses...Gaz
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Dave Ashurst
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| posted on 23/4/03 at 12:52 PM |
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David Walker's 1700 crossflow advice will supersede mine which is based on my experience with this car only.
Again I would encourage you go to a decent tuner with a rolling road to set up the carbs and timing up on your new car.
I don't know about the 243? camshaft.
But the Kent 234 is a nice profile which should give good all round performance for fast road use.
I don't know what the 9 3/4 lbs compression means. Someone else will though.
Your timing sounds miles retarded to me, makes me wonder how it works like that. I guess that could push burning gas out into the exhaust system.
My timing is set to 34 degrees max advance (which is there by around 3500rpm) and static timing is of the order of 12 degrees (which is a bit heavy to
start but it then idles beautifully) and I have no vacuum advance.
Yours is an Aldon Automotive distributor I'm sure. Aldon modify Lucas distributors for use with modified engines. (Burton sell them for
example) Aldon are a reputable if expensive tuning outfit and Weber carb dealer based in Brierley Hill in Birmingham. They have a rolling road
tuning facility, refurbish carbs etc.
120 jets might be ok for your set up but a rolling road tuning session would establish that My weber 40s are now set up with 30mm diameter chokes and
135 main jets in f16 emulsion tubes which all suit the flow characteristic of engine and exhaust system very well. Paradoxically, combinations with
bigger chokes gave less top end power in my case. Yours will be different no doubt.
Dave
[Edited on 23/4/03 by Dave Ashurst]
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