backfire on overrun and timing etc

[Ren]

I was looking at a friends B t-5 and found that two mixture screws had been wound all the way in. I adjusted his zenith carbs so they are set up right and then pointed out taht his dizzy was on backwards. I tried to put it round the right way but found that his dizzy gear is not horizontal to the block when on OT number 1. I turned the dizzy gear bit one notch and set the dizzy back to wear it should be for static timing and then with a timing light checked it at idle. One spring is missing in his dizzy and the advance mech was maing his engine timing go way up so I retarded the timing abit to try and compensate while waiting for new springs (which I have just read are not strong enough from Stoddards). He took the car for a blast and came back with a big smile. "its never gone like that before". I took it for a blast and adjusted another mixture screw and gave it back to him. He drove it again but it did backfire when he gave it a heavy amount of foot to the floor.

Am I right that its the worn out dizzy causing the problem?
Why would the last person to build his engine (Stoddard) turn the dizzy gear so it would not line up with the case at OT?
Would the mixture screws all the way in hide bad timing?

Lots of questions.

Has anyone else used the Stoddard dizzy springs?

[roy mawbey]

Mixture screws wound fully in is a real no, no. The resulting weak mixture I would have thought would make the engine tune so bad it would hardly have run at all. The standard one and a half turns out on each to start with and after adjustments then to synchronize them with the tester would no doubt as you found made it run better.

I have heard also of some advance springs being on the weak side but to run with only one would again be something I just wouldn't do. I am not surprised it still backfired. Sounds to me he should get the engine and distributor checked out properly. Just how long has been driving it like that?
If your friend possibly can't do it himself, better to spend some money now with one of the recognised 356 service companies rather than wait till some damage occurs and cost escalate. ( they have the special tools and testing equipment to do that )

Let us know how he gets on,

Roy

[Ren]

Hi Roy, good to hear from you. The owner only drives his car once in a blue moon. He knew it was not right but had been told that it was the best it can be set up too. I said no that is not right and started fiddling about and straight away the owner said it was better than it has ever run but I told him its still not right. I will fit new dizzy springs and see how that helps - or not.

Anyone rebuilt there dizzy?

Any hints?

[Paul @ P R Services]

Yes.

Make sure that the skid plate is in good order, they are normally worn which holds the bob weights up and sometimes won't let them return (ever wondered why your cars holds the revs on tick over and then drops suddenly)

The only way to tell if it is any good is to map it on a machine or put it in the hole and test drive it.
Sometimes you can watch a distributor hold up on a strobe and then jump to max advance.
Sometimes they won't advance enough and you have to compromise the timing depending on your driving style.

We have rebuilt units in stock but as usual they are not cheap.
It takes a lot of time to keep re-working a distributor to get a good curve.

P

[Ren]

Hi Paul, thanks for the info. His driving style has become more exuberant since I tweaked his engine. May be I should tell him its no 911 and to easy off a bit, then it should drive lovely. It does drive lovely when I drive it like a granny. Its only a little "dame" 60hp.

[roy mawbey]

Ren,

Paul is so right about the skid plate and an idle that is not always going back to the same rpm. Very good tip for everyone there.

If you look on www.glenn-ring.com then click on the site Bosch 010 distributor rebuild you will see what is entailed in a range of photos.

A good idea then can be had on the work involved.

Roy

[Ren]

Roy, that link is just what I was looking for. Thank you.