cfair

With a new Taylor HEI distributor and today's fresh coolant & hoses, I'm on the hunt for your timing & vacuum setups.

I'd like to avoid the ported/manifold vacuum debate, if possible. If you like your setup, I'd just like to hear what you've done.

I have a nice running 66 Starfire with HEI, with a smooth RV cam, but it pings/rattles at WOT. Which makes me nut when I nail it. I could add race gas but I'd have to go to Infineon raceway at every fill up, not convenient, or cheap. Xylene is gone from CA and Octane booster is $10 per tank for not enough boost.

I think this means I need to take some mechanical advance out to run it on 91 octane pump gas. Even when I turn the adjustable vacuum advance all the way retarded, I can't get the ping out - which leads me to retarding the mechanical/centrifugal advance.

I think my target is 10-12 BTDC at idle ~700 and timing "all in" at ~3200.

>> Does that sound right?

My Mr. Gasket 929 advance kit has various spring & lighter weights.

>>Will the lighter weights give less total advance since they won't swing out as far? The lighter springs seem to bring the mechanical advance in quicker. I thought I'd try stiff/heavy and move lighter if I hear no ping/rattle - does that sound right?

There's also an adjustable vacuum advance to mess with. Taylor recommends starting with it all the way clockwise closed, then back off (counterclockwise) if you hear a ping. Others say start at 5 turns counterclockwise from closed and advance (clockwise) until you hear a ping.

>> What have you done with these adjustable vacuum advance units?

MSD Timing tape is on the way from Jeg's. I'm working with a 1970 455 block and also have a 1966 (originally) 425 block.

>> Do all Olds 425/455's have a 6" balancer? Or is the size year/block specific?

Looking forward to your answers. If you have links where this is covered, please copy'n'paste.

Warm Regards,
cf

oldcutlass

Which Taylor HEI do you have? In the instructions it will tell you how many degrees of mechanical advance it has. Please post that. I can't find an instruction sheet for it.

You need to get an idea on how timing works. Read this for a start:
http://www.73-87.com/7387garage/drivetrain/hei.htm

Fun71

Vacuum advance will be zero at WOT, so forget about that for now.

If you want to get rid of the pinging, you will need to reduce the amount of total advance, either by setting the initial lower or reducing the amount of mechanical advance.

As oldcutlass posted, you need to figure out what you currently have so you can then decide how to bring the total advance to a lower number.

oldcutlass

In some cases there can be vacuum advance at full throttle. For now I would disconnect the vacuum advance and plug the line until you get your distributor dialed in.

olds 307 and 403

Is it the Blueprint or Performance replacement?

cfair

We're talking Taylor blueprint. I stabbed it in not using instructions. I'm a guy. So I'll have to see if I can find a PDF...

I'm trying to hit initial timing of 10-12 degrees BTDC _and_ reduce total timing.

So far, I can either have great initial timing and pinging _or_ retard the initial, run hot, and get rid of the ping.

Sounds like I'm on the right track to reduce total mechanical advance. Cool. Hence the need for a recurve kit...

Let's continue....

Cf

oldcutlass

The recurve kit is not going to reduce the amount of mechanical timing, it will change the rate. Adjusting your vac advance unit will not reduce the amount of vac advance, it will change the amount of vacuum required for the canister to deploy. If you adjust the spring pressure too high it may lower the amount of advance but it will be erratic. If the HEI does not have full battery voltage it will not work right also.

So no, you are not on the right track.

RetroRanger

Msd sells a vacuum ax value limiting device for Hei Iirc its about $10 on ebay

olds 307 and 403

From what I found, the Blueprint distributor has an adjustable mechanical advance and a better module. I could not find instructions anywhere, you might have to contact Taylor.

cfair

Many thanks fro your help. It's great.

olds cutlass - HEI Definintely has 12v, no problem there. Agree that the kits focus on the rate of mechanical advance, not the total

Retro ranger -- do you have a part name or number? Couldn't find one on eBay or jeg's.

Olds 307/403 - are you sure the _mechanical_ advance is adjustable? The vacuum certainly is.

cfair

The chevy people have all kinds of backyard tweaks for reducing HEI mechanical advance.

All involve putting a stop of some kind in the inner hole of the plate the rotor screws into. Like this:

Approach 1 is drive a screw in the inner hole and grind the top to suit your timing preference. I tapped a spare HEI this morning for a #10/32 screw just to size the hole and to know what kind of screw to get.

Approach 2 is put a zip tie in the inner hole securing it on the underside of the rotor mount so it won't interfere with the other distributor operation. I can't imagine a zip tie would last long being constantly hit by the advance mechanism.

Have any of you tried this? Did you like the results?

oldcutlass

First find out what your mechanical advance is, then we can come up with some settings. I've never done the tie wrap thing, but have used a screw. Did you read the link I provided?

I use this one in my distributor:
http://www.jegs.com/pt/Vacuum+Advance+Stop+Plate

Others have used this:
https://www.summitracing.com/parts/CRN-99619-1/

RetroRanger

My bad I was thinking of the vac limiting device and wrote mechanical, I edited my reply.

I have used the vac limiting bracket but haven't reduced max mechical in any way.

Fun71

The HEI mechanical advance is dictated by the mating surfaces of the weights and the center bar. Some recurve kits have different weight/center bar profiles so they change the amount of mechanical advance, but my experience they give MORE advance and not less (the Moroso kit gives 24º mechanical advance). This is great if you want to retain the points-style advance curve with a lower initial and more mechanical.

From what I have read over the years, limiting the travel of the advance plate by shortening the slots will limit the amount of advance but can cause timing bounce when the posts hit the ends of the slots.

cfair

I'm starting conservative with tighter springs to see if they get me where I want to go. If the spring range with the original taylor weights fails (pings) , then I'll test the Mr. Gasket kit which has lighter weights and a range of springs.

As an aside, i test fitted the mr. gasket center post on my test distributor and had to hog out the holes to even get it to sit correctly. Makes me very suspicious of using it "in the field" as they used to say. The mr. gasket weights were sloppy too compared to the Taylor weights which were heavier, and secured with an E clip. Advantage Taylor...

The hard part here is when I have the initial advance where it idles great/cool, it pings at WOT and sometimes under load. But when I retard the initial timing to get the high RPM ping out, it idles worse and hotter.

Damned if you do, damned if you don't.

The timing experiments continue.

olds 307 and 403

The screw trick works but you must cover the bottom of the distributor to keep filings out of the magnetic pick up. You must also pick the right side of the distributor, I picked the wrong one, could not get my timing below 40 degrees. Try the stiffest springs and let us know.

oldcutlass

What are the timing settings? Did you figure out how much mechanical timing your distributor is working with?

cfair

I'm waiting for timing tape as we speak (well, write).

The stiffer spring experiment begins today just to keep things moving.

My hypothesis is stiff enough springs may keep the weights from swinging all the way out at WOT. I've got just 3 or so stiffer sets than the Taylor came with, so that's the path.

If that doesn't work to my satisfaction, on to mix & match with springs of differing stiffness.

Timing tape should be here in a few days or a week and I can carry on when it gets here.

Many thanks again for your interest & guidance on this one.

oldcutlass

Stiffer springs extends the rpm range of your timing curve. It may limit the upper end, but it will be inconsistent/erratic on where it may top out. Not the best way to set your distributor up.