distributor curve

[356robo]

How is a "correct" curve determined for a distributor? How is the curve changed?

Thanks in advance,

Robo
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[mjmoran]

Find an old repair show that has a SUN distributor machine to check the curve. The weights and springs can be adjusted to change out the advance.

[356robo]

A follow up question: If the advance is not correct, could it cause hesitation on acceleration at low RPM?

[mjmoran]

Yes, it is VERY difficult to get anything right when the advance is wrong. I am guessing this is for your 70T? If so, do you have the Marelli or Bosch unit? If Bosch, then checking the advance and adding a pertronix ignitor to replace the points will fix some ilks. If Marelli, then find a Bosch replacement.

You should be able to find someone with a dist. machine near you to find out what is going on...where are you located?

[356robo]

Michael,

Its a Bosch distributor with Petronix. My questions are because the T engine was rebuilt with S pistons and cylinders, 2mm of porting on the heads, a slightly modified E cam and Webers. The car really runs well and pulls hard especially when the cam comes on at about 4800. My only complaint is that if I jump on the throttle, even a little, under 3,000 rpm, there's a slight hesitation (bog) for a moment and then she really runs great. Before I get into trying to change the jets in the webers, I thought I should learn about how the distributor my be causing the problem.

How can I curve a distributor on a machine on a modified engine?

Rob

[mjmoran]

There are a few guys on this forum that do recurving. I think Rennsport Systems in Portland and Jerry Woods may be a good source for this as well.

What jetting are you using? Is this a 2.2 still? Did you change out the crank for a balanced one?

Part of the issue could be this new "gas" and I use the word lightly. It requires a bit of changing in the carbs...

[356robo]

Michael,

Yes, it's still a 2.2. It's a T crank. I'm not sure about the jets because the Webers were rebuilt before the engine and engine rebuild paperwork doesn't list the Carb specs.

I thought I would be sure about the distributor before I start messing with the carbs. Is that the correct order?

I'm near San Luis Obispo, CA----Half way between LA and SF near the coast.

Rob

[Flieger]

I will be heading down to 1000 Oaks tomorrow afternoon. I can deliver your distributor to Marco at TLG Auto or Dave at TRE Motorsports if you want.

edit: I just saw they are heading up here for the weekend.

[356robo]

Thanks Max, but how can someone curve the distributor on a machine when it is from a modified engine?

rob

[Flieger]

I am no expert by any means in this area of expertise, however...

I think the SUN machines work as a dyno of sorts, spinning up the distributor and recording the opening and closing points. Therefore, the expert will anaylze the dynamics of the engine the distributor is part of and will then adjust it based on his knowledge. The car does not matter much, if I understand the process correctly. I think the SUN machine is mainly a measuring tool.

Experts, please correct me where I am wrong.