Technical Jesus, would someone help?

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Technical Jesus, would someone help?

Grubeguy

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I started a full restoration on my '72 850 spider in 2014, and stopped totally because of an inability to get the thing to run right. It frankly won't start without a great deal of cranking and it idles like crap.

Thus far, I've:
-replaced the points with a pertronix (this allowed the car to start)
-sent my carbs off for a full re-bore and rebuild, to include bushings, etc
-cap, plugs, wires, rotors replaced
-installed a high torque starter

The engine was rebuilt in '15 with a hotter cam, as was the distributor.

The fact that it wouldn't start at all with points, but barely starts with the pertronix, makes me wonder if timing is off. The engine rebuilder (the guru in Connecticut) set the timing for me before I picked up the car, so I have confidence it's more or less correct.

I'm tired of throwing $$ at it and I'd like to actually run the thing. I saw a video on youtube about a barn find 850 that started, idled and ran, and it occurred to me that mine should start that quickly too.

Any ideas?
 
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Hi Grubeboy

couple of questions.

does the pertronix system use a condenser,

the carb rebuild did this include removing and cleaning all run and idle jets.

can you smell petrol in the exhaust after you have tried to start it

how hot is the cam and when you say the timing was set by the guru do you mean camshaft timing or distributor timing.

Tim
 
Pertronix doesn't use a condenser, no.

Carb rebuild was everything - jets, bushings, shafts, seals, etc. I've tried another carb, one that I rebuilt myself, and the results are the same.

Smell of petrol - no, but it seems to run a little rich. I've got the idle mixture just about as lean as it can get too...

Hot cam - legal in the US without a lumpy idle. I'd have to go back to paperwork to see the specifics though. The cam timing and the distributor timing were both set by the rebuilder. Once the car is running and warmed up, I've fiddled with that as well, without much luck.

I've also replaced the fuel pump, and installed an electric pump in line with it. The car runs equally badly with the electric one energized or off...
 
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Hi Grubeboy

I run a number of 850's the one that always runs really smooth is only 265 degree cams. The lombardi i run has 304 degree cam, goes like stick over 4000 revs but smells and runs lumpy under 1400 revs, so it does make a difference as to what the spec is.

Tim
 
OK - I'll have to find the documentation and let you know. When it starts, it idles around 1800-2000 rpm. The best I've ever had it was 1500 rpm at idle.

Will a hotter cam make it tougher to start?
 
The carb jets were wholly replaced. I had a total rebuild done at Pierce Manifolds that included replacement of everything, bigger throttle shafts and bushings as appropriate and setting up the thing to work on the 903 engine.

I've attached the cam info as well as a few pics of the carb as it sits on the engine. I've got the drip pan, and I've blocked off various inlets (I have the emissions controls stuff but none of it is installed (my locale doesn't have air pollution regs)).


I'd love some mentorship on what it is I blocked off and whether that would have an effect on it not wanting to start easily.

As a reminder, it'll start but only if I use starting fluid, and it doesn't idle worth crap.
 

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Hi Grubeguy

Yes the 282 cam should work reasonably well and that timing isnt too wild. so please remind me how many jets were replaced.

My Ex South Carolina car had the emission equipment on it but during its restoration i changed it to European spec so sadly cant help on that bit.

Tim
 
Hi Grubeguy

Photo 659 there seems to be a hose outlet with nothing connected to it, its not the same as my european spec but should that be blocked off too.

the idle mix screw is fully home and tight would that have an effect on your issue, ie blocking the idle.

Tim
 
You'd be better off asking me for a process specification on aircraft hydraulic repair. I sent the thing to Pierce Manifolds for a total rebuild, including replacement of the idle jet and what I'm assuming are two others. I know next to nothing about that carb, including the inlet shown in picture 159 (I *think* that's a vacuum break, but I don't know where it would get hooked up to).

For what it's worth, I received a rebuilt carb with the rebuilt engine, and it started/idled with those same issues on that first carb.

I've blocked off all those other ports at the behest of another, almost defunct 850 forum, but I'm not sure what they'd go to. Will they effect how it starts/runs?
 
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Hi Grubeguy

Yes I fit and repair double glazing for a living.

So

photo 659 middle of the photo is a slotted brass screw, remove it then gently pull it apart into two parts, with the half that is not visible in the photo it should have a 0.45mm hole through the middle but it may be blocked with a small piece of debris, blow it through with an airline if you have one. gently reassemble it and refit. directly across the carb at the same height there is another one the same, remove and clean and refit that one too.
photo 720 60% across the photo from left to right at the bottom of the carb is a small screw with a spring being used as a washer underneath its head, remove it and wipe it, refit it and screw it in about 6 to 8 turns.
photo 159 cap off the "vacuum break" i dont know what that is for as its US emission spec,
try starting. if it seems to start and run better then once you have normal temperatures reduce the idle speed as close to 1000 revs as you can with the throttle offset screw, then turn the idle mix screw in until the speed drops then wind it out 3/4 of a turn.

Tim
 
Hi Grubeguy

Yes I fit and repair double glazing for a living.

So

photo 659 middle of the photo is a slotted brass screw, remove it then gently pull it apart into two parts, with the half that is not visible in the photo it should have a 0.45mm hole through the middle but it may be blocked with a small piece of debris, blow it through with an airline if you have one. gently reassemble it and refit. directly across the carb at the same height there is another one the same, remove and clean and refit that one too.
photo 720 60% across the photo from left to right at the bottom of the carb is a small screw with a spring being used as a washer underneath its head, remove it and wipe it, refit it and screw it in about 6 to 8 turns.
photo 159 cap off the "vacuum break" i dont know what that is for as its US emission spec,
Try starting. if it seems to start and run better then once you have normal temperatures reduce the idle speed as close to 1000 revs as you can with the throttle offset screw(middle of photo 720), then turn the idle mix screw in until the speed drops then wind it out 3/4 of a turn.

Tim
 
Hi Grubeguy

Also you have an important part missing that would let an about of air into the manifold below the carb. this would have an effect on the intake

the part missing is in photo 720, below the clip on throttle linkage there is a hole in the steel plate which has a piece of rubber tube jammed into it. this should have a steel plunger in it, when the throttle is closed this is blocked, when the throttle is opened it opens up and connects to the underneath of the air filter to draw through oil vapour(on UK/European cars) have a look in your workshop manual for this small plunger.

you could temporarily put some gaffer tape over the hole to test the difference, do this before the previous process on my previous post, but still do all processes described

Tim
 
Hi Grubeguy

looking at the photos, the carb as it stands has the choke lever pulled out so as to do a cold start, as it stands it doesn't seem to give any throttle offset whilst on choke, this would be difficult to start without using the accelerator.

Whats your car/classic history

Tim
 
Is there an adjustment for the offset? I didn't see one that was intuitively obvious to me...

My classic car history - Saab 96 (3 cylinder, 2-stroke) when I was 16, a '68 MGB after that, somewhat modern stuff after that (Camaro, a Ford Probe GT, Saturn Coupe), a '64 Mercedes 220seB, a '72 Mercedes 280C, a '73 Mercedes 280SE 4.5, a '58 MGA, the Fiat in discussion, and in the near future, a rather modified '75 Porsche 914.


My strengths are in wiring and body work, but not in carbs.



Hi Grubeguy. looking at the photos, the carb as it stands has the choke lever pulled out so as to do a cold start, as it stands it doesn't seem to give any throttle offset whilst on choke, this would be difficult to start without using the accelerator.

Whats your car/classic history

Tim
 
Hi Grubeguy


I spotted your message, yes there is a way of getting more choke on throttle offset, the linkage that goes from the main throttle lever at the bottom up to the link at the top can be made from straight to S shaped this will effectively shorten its length, be careful as the ends are quite delicate.

I wouldn't worry too much about the throttle offset just yet until you've got the idle down.

my first thing would be block the hole in the steel plate then do the top jets then adjust the idle screw.in that order.

Tim
 
So to recap the day's events, I've pulled both jets and blew through them (no junk inside). The left side one was .40, the right side one was .45. I removed the idle mixture screw, cleaned it and reinserted the thing to 7 full turns (360 degrees of change). While I was at it, I also cleaned out the fuel filter.

No change to how it runs or starts.

I did discover that with that front piece (covered with a black cap) off, it would start, and then die as if fuel starved.

I also capped off that front vertical piece (where a small piston goes), to no effect.

I made a quick video of the thing running. See [ame]https://youtu.be/TYWRR7mxfKQ[/ame]

With the choke fully in, I couldn't get the car to idle at all - I had to feather the gas to ensure it didn't die, but it died. It would only start with the aid of starting fluid after that.

Does this carb have an accelerator pump? When manually actuating the throttle, with the electric fuel pump running, I see no gas getting squirted into the intake.
 

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Hi Grubeguy

its photo 720 and it is the linkage that goes up at an angle the same as a clock at 11 O'clock this will adjust the amount of throttle you get when you pull the choke out

Tim
 
Hi Grubeguy

the throttle squirt pump is the part nearest to the radiator hose.

having watched the video it does sound like your getting too much air in at low revs, did you manage to block the hole in the plate.

hopefully attached should be a photo of the workshop manual, the piston you are missing is in the hole below lever no 23.

20200116_010209.jpg

I couldn't work out however what the comment meant at the end of the video

Tim
 
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