SMELLY - De-camming for de-smelling ?

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Dave999
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Re: SMELLY - De-camming for de-smelling ?

Post by Dave999 »

black bushings and 2 light sliver springs. i think you have every chance of making it work its just hard work when you potentially have a few things not quite right

my cam 248/252 at 0.050 109 LSA 596/605 lift just my intake opens 34 BTDC i chased the richness away up the rpm range eventually
but as i say still work to be done i still make eyes water...;)


i have a megajolt igntion to go on built it about 10 years ago and never got round to fitting it because i had money in a modified (welded up) dizzy, to achieve what you can do with bushes and springs. I have the choice of 2 dizzys original BOSCH or a Chinese copy, which made things a bit awkward as neither lends itself to curve modification like a mopar one and the chinese ones have ball bearings in which put me off, DO not need them in the sump :) .

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Re: SMELLY - De-camming for de-smelling ?

Post by morgan »

I'll recurve it; its the quickest of the jobs to try and easiest to put back. Should know in 30 mins if its done anything.
Need to check plugs I think the are xk5s (which are like 7s). They dont seem to be doing anything horrible; dirty but not foul.

Yes, ball bearings in the sump. Closest I came was I dropped the dizzy clamp bolt down the dizzy hole. It sat there precariously and I had to get one of those bendy-grab things and control the shake in my hand to retrieve. That could have been very VERY irritating. But I got it.

Next update - "I changed the timing, I've blown the air cleaner off"... coming soon.
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Re: SMELLY - De-camming for de-smelling ?

Post by morgan »

Ok - update.

Springs changed, curve like the Eiger.
Tricky to measure initial as advance starts before idle ( which is what I wanted) - but can confirm all in by 1900rpm at 35 deg.

On idle it reads 21ish - so that’s a couple of degrees of advance in the springs as soon as it starts. EDIT - 4ish deg. Advance stop bushing 18deg, so must be 17ish initial.

Smells better ( still juicy but not quite as bad).
Performance is better too.

Will leave at that and get exhaust sniffed next ( sensor!).


Thanks chaps. A step forward I think.
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Re: SMELLY - De-camming for de-smelling ?

Post by Dave999 »

progress

now you have changed its ignition advance at idle the idle mix screws will need a tweak again

gunson colour tune or Lambda senser time.

once all done its vacuum advance time again. highest vaccum setting so it pulls in some degrees only if you snap close the throttle when doing high RPM

when you lift off at 70 at the mo. you will feel the car slow in an obvious way. if you get the vaccum advance right every lift off at 70 will feel more like you are on your bike as a kid....on a nice HILL... (going down obviously) the slowing of the car won't be as noticeable as the very thin mixture (throttle closed 3500 rpm++ ) will now be being ignited rather than washing the bores.

needs to be stiff enough not to come in as you open the throttle at less than X000 rpm (you will have to approach it from above by making the vacuum can less stiff) just want it for high speed cruise big RPM, big vacuum, tiny throttle not small rpm medium vacuum tiny throttle

before it came in every time the throttle was in the first 1/4 of opening regardless. i.e on acceleration from low rpm to higher

a smoother/ restrictor as used on a alfa sud may work

look up "Vacuum Advance Anti Pulse Distributor Valve APV001"

slows the vaccum can action down so it comes in, on average vacuum rather than pulsing. might help avoid the old problem of loads of degrees getting pulled in every time you touch the throttle



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Re: SMELLY - De-camming for de-smelling ?

Post by morgan »

Well, now THERES an interesting thought.

SO (cast you mind back) I have NEVER been able to run vacuum on any engine /carb - I concluded my can was shot. I bought and fitted an adjustable vac can, so I can now screw it right down. Made not a JOT of difference - the second I connected it to the carb BANGBANGCOUGHBANG ! - even on this engine with naff all vacuum. I decided its just not meant to be. (ties in with your 'loads of advance every time you touch the throttle)

I'll dig the 'ol colortune out and make sure I am still blue and lovely. (I was before). Overrun largely cured now I have cracked the secondaries open and transfer slot is visible. So maybe it is time to try again with vacuum. Never made it work yet... But... :think:
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Re: SMELLY - De-camming for de-smelling ?

Post by morgan »

Edit - Feels worth a £20 shot doesnt it ? I waste that much every time I drive her without one :)
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Re: SMELLY - De-camming for de-smelling ?

Post by Adam »

Are you still running the Rhoads lifters?
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Re: SMELLY - De-camming for de-smelling ?

Post by morgan »

Quick answer - no idea. If thats what Bob had, yes ! (got a pic somewhere).

EDIT - Yes, seems I am, looking at the build sheet for engine. "Rhodes Variable Duration"
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Re: SMELLY - De-camming for de-smelling ?

Post by Dave999 »

Vacuum thing you can find em cheaper...

the other thing to check is that the rod from the vacuum can when connected doesn't move the timing plate unless the can is seeing vacuum.

i had one where te flat lever was wonky and as soon as i slipped it on and put the circlip back it lifted the advance plate off one of its brass feet just enough to alter the gap between the sensor and the spiky ring the precise gap was now wedge shaped. just shoddy old junk but explained why the teeth on the the spiky bit were shiny at 1 end... at full suck it caused a minor collision of parts that should never meet


one other thing as you seem to be heading in the right direction.... how big are these bushes you fit?

could they be made bigger? sleeved by judicious application of a carefully cut section of felt tip/ biro pen lid.

once you get it right find a bored man with a lathe and give him a stick of nylon, or get some plastic printed in bigger sizes

i.e restrict total a bit more
add in a smidge more initial
and then you can run springs that are not actively stretching at idle, next ones up. ideally idle timing should be rock solid mechanical (as set) only, with the weights and springs coming in only once off idle...

special motor needs a good bit of bodge using pen tops or bits of ally tube from the Wickes emporium, fine "hardware and bits of metal you will never use" Rack ....

mine now has bits of Wickes in it. cheap and just round most corners, or pay double at homebase..

you only need to do one bushing to try it out...

mine uses the thickness of the pins that the springs connect to, to limit how far the advance weights swing out. making them thicker, just where the Bananarama!, reduced advance

a right old faff

why it is bananaramaring w e i gh ts and the word Hit i have no idea


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Re: SMELLY - De-camming for de-smelling ?

Post by Blue »

Make sure you are connecting to manifold vacuum (on manifold itself or carb baseplate) rather than on the carb metering block.
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Re: SMELLY - De-camming for de-smelling ?

Post by morgan »

Yeah, that would work (the make a bushing) - its literally a thick washer with a mm diff per size or something. Trouble is I dont think I'll want to go bigger as there will be too much initial to start the car. At the moment it works as I get 17 and then it pops up to 21. 21 from the off feels ambitious...

Now the question Adam raised is interesting. As I understand it, the point of these Rhoads lifters is to 'soften' a lumpy cam - and make it smoother at idle and give a bit of Vac. So perhaps Bob DID set the motor up for a bit of vacuum. (If thats true, then they dont work as far as I can see :) BUT I must admit I didnt pay much attention to that last night - I've got sort of used to no brakes on idle - it might be better now.) HOWEVER - it may mean that there is some vacuum. I'll have to get the ol' gauge on it and see...
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Re: SMELLY - De-camming for de-smelling ?

Post by morgan »

Blue wrote: Mon Apr 19, 21 5:42 pm Make sure you are connecting to manifold vacuum (on manifold itself or carb baseplate) rather than on the carb metering block.
Been there. Done that. :oops:
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Re: SMELLY - De-camming for de-smelling ?

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morgan wrote: Mon Apr 19, 21 5:46 pm Yeah, that would work (the make a bushing) - its literally a thick washer with a mm diff per size or something. Trouble is I dont think I'll want to go bigger as there will be too much initial to start the car. At the moment it works as I get 17 and then it pops up to 21. 21 from the off feels ambitious...
yeah but the initial needs to be right.... getting that right dictates the rest

so if yours wants 17* that's cool the other end of things is currently an arbitrary point 35* because that's where it landed....just treat that as a maximum for mechanical advance

it doesn't have to be that it could be that 28 30 32 34.

you have a high compression motor with lifters that have the potential to alter the cam timing slightly by not pumping up at Low RPM
if they don't pump up at low RPM what do they do at High rpm. they pump up.... but the mechanism to allow the former will impact the latter also

so at high rpm you have a cam and lifter that will be providing just a bit more duration and a bit more overlap. Your Dynamic compression changes..you haven't got VVT but you have a wiff of it in your motor...

if at higher RPM your motor becomes more efficient you need less ignition advance than you would expect. the rule of thumb works on standard motors no more than 34... why have so much faith in it for you none standard motor

You need to identify the minimum it wants at 2500+ rpm any more doesn't help..

why?

if you set off the mix before it is properly tumbled and compressed it burns in small whirl pools and and some unburnt goes out the exhaust

if you hit it with a spark at the point where the piston has compressed it just enough it will go off like a war head . it burns in 1 almighty wumpfff quick effective perfect rolling front of combustion across the piston head , piston in right place valves shut ...all good.

if you are too late its still burning when the exhaust valve opens. the under bonnet temps go sky high and the opening of the valve puts out the fire in the cylinder. so you get un burnt out the exhaust think of a backdraft in a fire situation. burning house, open window air rushes in and a few second later a sheet of flame engulfs you. the massive change in pressure and new air causes the fire to shrink rapidly then expand rapidly to 10 time its size in an explosive way

in the case of a motor you don't get the oxygen/air you get unburnt fuel and exhaust gas from the last cylinder to go off i.e you belatedly quench the fire in the port and header. you create heat in the headers and exhaust valve and you set up the next cycle badly

what i'm getting at is there may be a degree 2 degrees maybe 5 ther will be some variance that helps at the top of the curve
worry about the bottom first ..

the more efficient the motor is the narrower range of ignition advance you need

i got so hung up on 15 BTDC initial and 34 Total, now my experience may be unique i can't promise that it wasn't just some Australian engine aberration... but once i let go of that... ahhhhhhh.... life got better.

and i went through this with both igntion and weber config. once i threw everything that seemed to be THE LAW out i made progress, and backed it up with the fastest leisurely drive down a flat bit of road at santa pod i've managed, until my ignition module went bad :)


It wants what it wants and it probably won't want what you have learned to expect
sorry i'm sounding more and more like an arrogant asshole but this caused me so much frustration :)

standing there for 1/2 hour at a time fuming... worse than the car... then going for another think and a cup of tea.



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Re: SMELLY - De-camming for de-smelling ?

Post by Dave999 »

PS if all else fails

4 hole spacer under carb
if that works then maybe....

stick this in your manifold

https://www.aussiespeedshop.com/product ... -manifold/


turns a race only manifold into something that works better on the street

i.e if you find a 4 hole spacer under the carb makes things better then this is the next step

better distribution at low RPM with only a small impact at higher RPM but obviously has an impact on WOT all out race operation in the 5000+ range where plenum size/space is king


i.e better fuel distribution at low the rpms that the motor wasn't designed for will mean a change to initial advance and a re tune of carb settings

it just makes things a bit more street and strip rather than strip


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Re: SMELLY - De-camming for de-smelling ?

Post by morgan »

All good learning as always Dave, thanks.

Took her out again last night. Stinky when cold (but MAYBE not as bad) but I do think better when underway.
Under full load higher revs (and this thing comes ALIVE past 4,500 and is still pulling hard at 6) there was the slightest crackle of pinking (bang in line with what you say). Which brings me back to the point you say. I could clearly use a degree of so off the top, but I dont want to drop the bottom off. One thing though - the 35 is not because thats where it landed, the 17 is because thats where it landed - because I can measure initial (it starts advancing too early) the 17 is CALCULATED from the total which I deliberately set to 35. (i.e. I know total is running at 35 so initial must be 35 - 18 = 17) - I had to do it backward.

So feels like a) restrict the movement further with a larger advance bushing or b) Get the vac can working (something I have never managed).
I really didnt understand the rhoads lifters thing - but as Pete pointed out, I wonder if its all part of the '5 degree' thing on the earlier page ? It doesnt get full lobe poke until the revs get up - quite a neat solution if it works.

Your other point about colossal under bonnet heat, had that. All seems to be leaning the same way doesnt it ?

Just to add further variables I have not 100% eliminated ignition/plug/lead questions. I've noticed a funny thing where the 'idle' (haha) is choppy and 800rpmish sometimes and 1,000 rpm and smoother at others. I know its not the springs/throttle so I have half a nag that I have a dodgy/intermittent lead or plug. That would also cause it to smell unburnt of course... :-k

I really appreciate the sounding board, team. Just working ideas through. It has the potential to be a hooligan with street manners I think. The hooligan part is working fine already :)
Last edited by morgan on Tue Apr 20, 21 11:20 am, edited 2 times in total.
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