Race Engine Forum UK

timinator wrote:Hi Chris,

Shame I don't have an adjustable vacuum advance with an Allen key

There are other ways to limit vacuum advance. Could you put up a picture of the distributor without the cap on. Also a pic of the vacuum canister off the point plate. Fixes range from a short piece of vacuum hose on the actuator rod, or a vacuum bleed, to building a vernier.

Hi,

not sure when I'll get the chance to do this now as the misses is busy using the car and summer is over so no access to the beach house for easy access to the engine.
vacuum bleed could be an idea. possibly using some simple fish tank air pump valves I have. I have a vacuum gauge and can experiment with that to reduce the vacuum somewhat. No need to remove the distributor for this.
It has lost some of the initial power below 1500 rpm due to the vacuum disconnected.

Thanks
Chris

Chris

Initial power under 1500 rpm?

Is it a diesel?

:)

Tommi

Urbancamo wrote:Chris

Initial power under 1500 rpm?

Is it a diesel?

:)

Tommi

lol no but the Alfa always has good torque at low revs 1-2500 rpm (the 8v carb version was always known for its low end torque compared to the 16v more modern version). Just loses a little with the vacuum advance disconnected.
Made a T connection from a brass piece I had, some vacuum tube and a small plastic air valve for bleeding some air out.
Will try with various openings of the valve so I get a little vacuum when the throttle opens but not too much that it advances a lot at 1/2 throttle or so.

Was busy giving the Alfa its pre-winter paint treatment today. hot wash, rinse, clay bar, wash, and final wax. 2.5 hours in total!

oh boy do I have the urge to rebuild another engine!!

Looking through my old archives and I want to dismantle another engine and improve upon my first experience.

Decided to dig into my wallet again and buy a 16v oil pump. Used but in very good condition. Good gears and no lateral play.

Mine is a smaller pump for the 8v version.
Both have exactly the same specs except the 16v has larger higher gears than can pump more to provide all 4 cams with oil instead of the standard 2.

I hope this will enable me to use the normal 10w40 or 15w50 oils and give a better hot idle OP.

Also picked up a cheap Bosch distributor which is going to ignition specialists for a total rebuild and re-map.

New wideband O2 sensor already in my possession so I'll be able to see the AFR values again very soon.

thank you

Chris

Yup, that's how it happens: you sniff enough petrol so it gets into your blood. Then gradually you get these urges, uncontrollable urges...

TomLouwrier wrote:Yup, that's how it happens: you sniff enough petrol so it gets into your blood. Then gradually you get these urges, uncontrollable urges...

I sweat the stuff now!! Coming out of my pores.

New pump arrived. Difference between new and old gears.

I can assure you that you have wasted your time buying a 16v oil pump. No manufacturer in history - to the best of my knowledge - has ever specified an oil pump that is too_small.

The output of the 8v pump is not merely governed by the pumping capacity of the gears but the relief valve. With no relief valve the pump would either a) blow the crank and cam seals out their housings or b) break the oil pump shaft.

The uncontrolled output of even an old-fashioned 8v gear pump like yours is like a fire hose. If you have an oil-pressure problem I can guarantee it is not the oil pump size, per-se.

Sorry!

G

You are usually right Guy.

The common issues I'm trying to solve.
Common issues with this engine is low pressure at idle.
min OP is 15 psi recommended by Alfa romeo. Common pressure as low as 10 psi with many drivers.

2 big ends share the same oil channel feed off the crank. Other 2 have individual feeds. Former two tend to wear faster due to less oil flow.
I understand flow will be higher if the oil is a little thinner.

Also the lobe on this new oil pump that drives the fuel pump has never been used.
My old worn has hardly any lift. I'm using an electric fuel pump right now.

From the Alfa discussions the 16v pump is a common upgrade to the 8v engine.

As you know I checked the big end and main clearances and all were good but still had issues of low OP at idle and low revs when hot.

Well we'll see in a few weeks once I get it installed.

I know that I can sell either pump here in Uruguay and cover my costs and make a small profit if I have made a mistake buying it.

Regards

Chris

Experimented with the distributor this week.
Will receive the newly restored one from h&h in a couple of months.

I installed the tubing on the stops for the weights as you can see in the photo.
To reduce the max advance. I still measured the advance as 16 degrees with a protractor with this stop.
There was zero detonation during a 60 mile trip. Previously I was getting detonation around 3400 rpm.
I had lost some power but it goes to show the original curve of this old bosch needed adjusting.
The new curve is noted on th h&h thread.

Wideband up and running.
Mains circuit on the lean side dipping to 15.2 on occasion such as climbing up hills on the motorway at high speeds.
Idle circuit good on the rich side just a little.

Also a big thanks to Tom for putting together this spreadsheet with the timing of the new distributor I had prepared by H&H.
You can see the advance of the old unit is topping out at 36 degrees at 3600 rpm.
I was getting detonation at around 3500.

So the new advance is 4 degrees less but still a healthy 32.

Brit01 wrote:Mains circuit on the lean side dipping to 15.2 on occasion such as climbing up hills on the motorway at high speeds.

I bet if you try to tune that spot much more richer you end up to situation where your mains are too rich in acceleration and in lower speeds. If you find mains wich are maybe 0.02 or 0.03 smaller it might bit better.
In street use I always aim at bit leanish side especially in light acceleration/light throttle to produce reasonable MPG.

I always see compromises with dual carburettors. When I adjust them I always trust both feeling and A/F gauge. When it feels nice and crisp it's usually good in A/F too.

T

Urbancamo wrote:

Brit01 wrote:Mains circuit on the lean side dipping to 15.2 on occasion such as climbing up hills on the motorway at high speeds.

I bet if you try to tune that spot much more richer you end up to situation where your mains are too rich in acceleration and in lower speeds. If you find mains wich are maybe 0.02 or 0.03 smaller it might bit better.
In street use I always aim at bit leanish side especially in light acceleration/light throttle to produce reasonable MPG.

I always see compromises with dual carburettors. When I adjust them I always trust both feeling and A/F gauge. When it feels nice and crisp it's usually good in A/F too.

T

I am not so interested in fuel economy here.
Thought that being on borderline rich you improved the power somewhat.
Mains start to kick in at about 2500 rpm?

It is rich on the idle circuit but if I try going down one idle size I experience those annoying flat spots.

Peaking at 15.2 at higher speeds when accelerating hard I thought was really asking for a lean mixture disaster.

Thanks for your input T. Appreciate it.

thank you
Chris