My Alfa Romeo 33 rebuild - FIRST TIMER

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Brit01
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Re: My Alfa Romeo 33 rebuild - FIRST TIMER

Post by Brit01 » November 9th, 2012, 9:10 pm

Vacuum advance removed and plugged.

Much much better. No pinging under 3000 rpm. Just a hint of detonation for a split second around 3200 under WOT.
Fellow Alfa owners with Bosch distributor's had the same issues. They just drove without the vacuum advance as they proved to be too strong and advancing the curve too much too quickly under light to medium throttle opening.

Next step is to test it with the MSD connected.

Urbancamo
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Re: My Alfa Romeo 33 rebuild - FIRST TIMER

Post by Urbancamo » November 9th, 2012, 9:16 pm

Nice to hear you Chris.

And this obviously shows that OE distributors are not so accurate when they are old. And every engine is different. There is no generic pattern for ignition advance and system.

Looking forward to hear experiences with MSD ignition again.

-T
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Brit01
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Re: My Alfa Romeo 33 rebuild - FIRST TIMER

Post by Brit01 » November 17th, 2012, 11:30 pm

In heavy traffic testing the MSD and something burnt and had to get bystanders to help push the car to the side!

I'm guessing it's the coil as it was hot to touch.

If it's just the coil and the 6A is ok then I'll use an original coil with the 6A. Hope it's not the 6A that blew!

luckily it was a quick switch to the old coil and it was running again.

The MSD coil is made in China!

Brit01
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Re: My Alfa Romeo 33 rebuild - FIRST TIMER

Post by Brit01 » December 20th, 2012, 3:19 pm

As some of you may know I've been experiencing some detonation issues.

I have the 6A running now on a stock coil.

I tested the car up a very steep incline yesterday and with a full load of passengers!

In 2nd and 3rd on its limit it experienced no detonation.

ONLY when I accelerate fast 3/4-full throttle I hear detonation even with a light load on a level road. (2500-3200 rpm).

Do you think the detonation is occurring due to a lean mixture under the wide throttle opening? (due to the steep hill load test showing no detonation).
Or the distributor springs are advancing too quickly under fast acceleration?

Thanks

Brit01
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Re: My Alfa Romeo 33 rebuild - FIRST TIMER

Post by Brit01 » January 16th, 2013, 12:34 pm

6A with old stock coil all running smoothly still.

It was sat unused for 2 weeks in the garage. Started straight up and idled smooth as silk like it was warmed up already.

Had a couple of electronic gremlins to fix. One I fixed last night was a damaged fuse resulting in the failure of the warning lights, but the indicators were still working. They use the same relay so the fuse didn't cross my mind at first.

Other is the engine overheating sensor. The light is flickering on and off. Appears that the wire is grounding itself somewhere along the wiring loom. I intend to bypass the wire from the instrument cluster as trying to trace it through the wiring loom is a nightmare.

Strut pan bearings need replacing I believe and brake fluid needs changing.
Still waiting for new distributor springs.

Brit01
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Re: My Alfa Romeo 33 rebuild - FIRST TIMER

Post by Brit01 » January 30th, 2013, 12:25 am

Bosch 0237 005 004 dismantled this evening to see what's going on inside.
Used a protractor (Home DIY method) to measure the advance of the springs. Trick from a bosch manual.

Found that the total deflection was about 15-16 degrees!! lets say 15.5 * 2 = 31
31 + 8 degrees static = 39 degrees.

the max advance of this engine should be 36 degrees!!
Maybe the method wasn't the most accurate but it could give an indication of the detonation issues I've been having.

I have been sent a used set of springs from an Alfa dealer in UK.
The primary spring is visibly thicker than my current one.

I have installed the new springs and also moved the stop pegs a little to reduce the max advance.

I will test this hopefully tomorrow once installed.

May take a little trial and error especially without the access to a SUN distributor testing machine.
(unfortunately I've been unable to find a workshop with one of these. I have no idea how they test distributor's here. Most likely they don't)

Hopefully I can achieve a good static advance and reasonable curve without the recent detonation issues at the 3000 rpm range.

Brit01
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Re: My Alfa Romeo 33 rebuild - FIRST TIMER

Post by Brit01 » January 30th, 2013, 11:06 pm

Just been for a test drive with the thicker primary spring in.

Better still. First part of the power curve is very nice.
At about 3300 rpm under WOT in 3rd I get a touch of detonation so I need a slightly stronger secondary spring (in the post). I don't want to reduce the static anymore. It just gets hot when idling.

The stronger primary spring has improved the curve definitely but the static idle is still at about 8 degrees, just a touch less in fact. Shouldn't be pinging with this and with the vacuum advance disconnected.

Soon as I get the other springs I'll install a stronger secondary spring.
Shame they aren't easily available. Eager to get this fixed.
But it was great to feel the car accelerate better today.
Attachments
001.JPG
First spring on the left controls the advance up to 1500 rpm, then the second kicks in.
001.JPG (89.83 KiB) Viewed 4975 times

Brit01
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Re: My Alfa Romeo 33 rebuild - FIRST TIMER

Post by Brit01 » March 6th, 2013, 5:54 pm

Another little detail I want to address.

It's in regards to the pump jets on my Dellorto DRLA carbs.

I hadn't paid too much attention to my pump jets to be honest, just making sure they all pump a nice squirt down the barrels.

I was looking more closely the other night, but at the small nut that attaches to the end of the pushrod that levers the diaphragm.

I noticed the nut on the left carb was screwed in much less than the right carb, it was showing about 2-3mm less thread than the other.

I screwed that in a couple of turns and I think it felt a bit smoother under acceleration.
I didn't have time to play around with it (kid in car), or make a drastic change in 1 step.

Do these nuts ideally need to show the same amount of thread (ie be turned in equally, left and right carbs)?

Thanks

TomLouwrier
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Re: My Alfa Romeo 33 rebuild - FIRST TIMER

Post by TomLouwrier » March 6th, 2013, 8:10 pm

hi Chris,

Been following your adventures with ignition curves and doubtful fuel, but haven't commented since you're exploring paths I've never been on myself.

Looking at some pictures of the DRLA I see they have the same arrangement as many Solexes had. You open the throttle, the rod slides through the pump lever and the spring behind the lever, around the rod, gets compressed and thus pushes the pump lever, giving you the squirt you need.
To be honest I've always found this an iffy construction since the hole in the pump lever tends to wear out rapidly and so does that nut you mention. The result is a pump that stops working correctly, or stops working at all.
The nut governs how far you retract the pump lever and thus the membrane when releasing the throttle. This defines the amount of fuel in the pump, so the maximum amount you can squirt.
It also governs the pretension in the spring, which relates to the force on the pump arm. The more force, the stronger and quicker the squirt of course.

Pump timing (start of squirt) is not affected much, as it would be with the pump cam on a Weber IDF.
BTW: an early IDF has a spring between the pump arm and the membrane: if not it would be a stiff system and your pedal travel would be limited by the discharge of the pump. The newer IDF's (Spanish version??) have a similar setup as yours I see now. Probably part of a rationalisation, making simpler and cheaper parts common to as many models as possible. Me no like.

Of course it is completely logical to have both pumps set up identically. Assuming the springs are identical (same free length, same force @ a certain compression or same compression @ a certain force) the distance between the spring seat and the pump arm should be the same on both. This gives identical preload and pump stroke.
The ultimate test of course is measuring both carbs' pump yield. You should not only make the same amount of full strokes on both, but also make the strokes at about the same speed, closing fast enough not to completely empty the pumps.
Personally I think setting up the springs identically is enough, provided you have the same jets etc in both acceleration circuits of course.

regards
Tom
Last edited by TomLouwrier on March 6th, 2013, 8:25 pm, edited 1 time in total.
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Brit01
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Re: My Alfa Romeo 33 rebuild - FIRST TIMER

Post by Brit01 » March 6th, 2013, 8:24 pm

TomLouwrier wrote:hi Chris,

Been following your adventures with ignition curves and doubtful fuel, but haven't commented since you're exploring paths I've never been on myself.

Looking at some pictures of the DRLA I see they have the same arrangement as many Solexes had. You open the throttle, the arm slides through the pump lever and the spring behind the arm gets compressed and thus pushes the pump lever in, giving you the squirt you need.
To be honest I've always found this an iffy construction since the hole in the pump lever tends to wear out rapidly and so does that nut you mention. The result is a pump that stops working correctly, or stops working at all.
The nut governs how far you retract the pump lever and thus membrane. This defines the amount of fuel in the pump, so the maximum amount you can squirt.
It also governs the pretension in the spring, which relates to the force on the pump arm. The more force, the stronger and quicker the squirt of course.

Pump timing (start of squirt) is not affected much, as it would be with the ramp on a Weber IDF. (BTW: an early IDF has a spring between the pump arm and the membrane: if not it would be a stiff system and your pedal travel would be limited by the discharge of the pump. They need an extra spring inside the pump to push out the membrane on the refill-stroke though, so it's a bit more complex. The newer IDF's (Spanish version??) have a similar setup as yours I see. Me no like.)

Of course it is completely logical to have both pumps set up identically. Assuming the springs are identical (same free length, same force @ a certain compression or same compression @ a certain force) the distance between the spring seat and the pump arm should be the same on both. This gives identical preload and pump stroke.
The ultimate test of course is measuring both carbs' pump yield. You should not only make the same amount of full strokes on both, but also make the strokes at about the same speed.

regards
Tom
Thanks Tom.
Yes I think I made good progress with my advance curve. The engine feels much smoother now without any knocking. It's so relieving to know I can use WOT without any apparent knocking resulting in damage and loss of power. The fun begins now! I certainly find myself exceeding speed limits easily (under safe conditions of course)! lol

I think you have good points in regards to the pump jet set ups.
A lot of mechanical parts that wear over time and result in iffy accuracy.

The best way to measure the pump volume IMO would be to hang 4 identical containers in each barrel at the same time and press down the throttle 20 times so we're not changing any variables.
Now what DIY containers(x4) could I use I wonder to catch the fuel?

Regards

Chris

TomLouwrier
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Re: My Alfa Romeo 33 rebuild - FIRST TIMER

Post by TomLouwrier » March 6th, 2013, 8:29 pm

Chris,

I just edited my post a bit regarding the testing, your reply crossed it meanwhile.
Nice timing ;-)
Now what DIY containers(x4) could I use I wonder to catch the fuel?
Anything that's transparent and identical in size and shape I'd say. The small beakers you get with coughing syrup? Test tubes? Syringes (blocked)?
You'd have to get the carbs off the manifold anyway.

You did mention a somewhat higher engine temperature and lower oil pressure. I wondered if you're not simply getting more power from your engine and using it too. That would be a very simple explanation for both, rather than bore wash etc.

regards
Tom
Last edited by TomLouwrier on March 6th, 2013, 8:36 pm, edited 1 time in total.
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Brit01
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Re: My Alfa Romeo 33 rebuild - FIRST TIMER

Post by Brit01 » March 6th, 2013, 8:35 pm

TomLouwrier wrote:Chris,

I just edited my post a bit regarding the testing, your reply crossed it meanwhile.
Nice timing ;-)

You did mention a somewhat higher engine temperature and lower oil pressure. I wondered if you're not simply getting more power from your engine and using it too. That would be a very simple explanation for both, rather than bore wash etc.

regards
Tom

I thought the same about the engine temperatures (great minds think alike as they say!). Before I was more reserved with the throttle especially around the knocking zone. Now I'm thrashing it much more!
My wife used it the other day and the temp/OP was back to normal which is always a good test as she probably drove it the same as before.

Just ordered some projected plugs also as I found these superior to the standard recessed ones.

I will unscrew one of the nuts in increments to match the other and test in between to see if I feel any difference first.
Looking down the carbs to see if they squirt at the same time is impossible due to the boxer design and width between them.
Only way is to use the graduated containers in each.

Regards

Chris

Brit01
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Re: My Alfa Romeo 33 rebuild - FIRST TIMER

Post by Brit01 » March 8th, 2013, 2:57 pm

Unscrewed the pump jet nuts until they had the same number of turns from the end of the threaded shaft.

She felt a little hesitant (lean). Last night a couple of turns in and much better.
Got a trip out tonight so I'll have the chance to give her a good spin.

Increased the hot idle speed a little to about 875/900 too. was a little low at 750/800 when hot and 600 when cold.
This will help to bump up the hot idle OP too a little.

Regards

Brit01
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Re: My Alfa Romeo 33 rebuild - FIRST TIMER

Post by Brit01 » April 24th, 2013, 1:23 am

Back to bad petrol and timing.

I think the vacuum advance is going to stay disconnected. It's most definitely giving too much advance, in 2nd/3rd gear at 3500 rpm.
Disconnected and fine. I have to increase the static advance a little but still an improvement.

Shame I don't have an adjustable vacuum advance with an Allen key. Guess I could adjust it internally but that will be hit and miss. It's a really strong advance even under higher throttle.

timinator
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Re: My Alfa Romeo 33 rebuild - FIRST TIMER

Post by timinator » April 27th, 2013, 9:08 pm

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.

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