Here's a ? for early model (2.7) tuners

[d.a.autry]

Hmmm. . .

Okay, 2.7L early exhaust, air pump deleted, still running CIS, Bosch distributor.

Specs say .012 gap on points (dwell 38 +-3), 5 ATDC @ 900.

I'm having to go at app. .010 on points to get dwell. . . . . and almost 10 ATDC for drivability (starts stumbling at 4k + and has a BAD backfire if I use 5 ATDC)

Any thoughts here??

I'm going to upgrade to the Ignitor II and new coil next week.

Also, going to have Storz (Love Bob and Mike!!) check the distributor and advance curves when I do this.

[d.a.autry]

Not even one thought?.

What are the other early model guys running. Anyone still running points??

[stlrj]

The first thing I would check is the rotor alignment to the notch on the distributor rim at TDC.

Cheers,

Joe

[kodioneill]

Check for side play in the rotor shaft. check the bushings in the dist. also the breaker plate to see if it's free (not binding). Are the points new?

[frosty2]

Try contacting Aaron at rennwerks@hotmail.com. I just had him rebuild
my distributor for a 911t 2.4 and he recurved it to a 2.7 spec and suggested
I set my timing at 8-12 (8-10 for warm weather and 10-12 for cooler temps).
He did not mention my points gap but you may check with him

Thanks
Mike

[Bill Verburg]

is the vacuum hooked up to the distributor?

[T77911S]

you might state the year. are you sure it is not fuel related?

have you checked timing at 6K? that will tell you if your advance is working.

i dont worry about dwell. the points are just a switch for ground to the CD unit. dwell not as important as a conventional ignition system.

[d.a.autry]

Update and a more questions.

Okay, I pulled the airbox and intakes yesterday; (boots were rotted) and insured there were no vacuum leaks. . . new boots, gaskets, resealed the airbox seam just for good measure, insured no leaks around injectors. . . during this I found #6 injector wasn't seated properly.

I also replaced the distributor with a known good unit I had lying around. (Mike from Storz okayed it) Also checked the mechanical to insure springs and bushings were on correctly and that vacuum was working right.

All great ideas above guys, and to hit them point by point:


1.) Static timing is good, of course.

2.) Little side play was why I swapped distributors, points are good but not new. Breaker plate (for vacuum adv.) is free.

3.) Frosty, I'm assuming that's 8 - 12 ATDC?. . . Guys at Storz suggested same on timing, but indicated this was more what you'd see on an unmolested (i.e. air injection still on, restrictive exhaust, etc.). . . but it is definately what I'm seeing here. I'm at app. 8 now and still get the slightest stumble when attempting to maintain a constant 3k on highway. . . I'll try 10 tonight.

4.) Yes, vacuum is hooked up, but there's a splitter inline. I'm referencing vacuum diagrams in a few moments.

5.) T77. . . it's a '76, but as stated, early mod SSI exhaust, air injection deleted. . . . now, here's where I make myself sound really stupid. . . how exactly do you check advance at 6k???. . . surely you don't spin it unloaded to 6k?? Other than that, I haven't checked pressure on the CIS. I'll do that soon, . . . I'll also pull injectors and put each one in a graduated cylinder and do a 'poor man's' balance check. . . . Also, you say to ignore dwell? Book states .012 on the points (bosch dist.) and it should render a dwell of 38 +-3. . When set at .012 I get app. 28. . . so I'll try .012 and ignore the dwell later tonight.

Thanks all in 'advance' (yuk yuk) for answers to my latest round of ??'s. . . . . Maybe I need to flush the radiator.

[kodioneill]

Injectors on my 2.7 were bad and created a surging and poor overall performance. You'll be able to see the patterns and volume of spray when checking the injectors. Make sure you pull all injectors out and put them in tin cans or the like, to test them.

[d.a.autry]

Originally Posted by kodioneill

Make sure you pull all injectors out and put them in tin cans or the like, to test them.

Yeah. . .I thought I had 6 of the same type of graduated cylinder. .but I don't. I'll find something similar, then measure the amount in each. This will have to wait until next week though. The Warden's getting upset about my ignoring the grounds LOL.

[kodioneill]

I'll be interested to see the results, please keep us posted.

[kent olsen]

The most important timing check is the one at 6000 rpm. Yes unloaded. Do not exceed, I think it's 36-38 degrees. You'll see those timing marks on the wheel when you bring the rpm up. Two marks as I remember. One I think is 30 and the other is max 36-38. Disregard the idle setting just take what you get.

[Bill Verburg]

To check timing @6k
disconnect vac.
spin the engine to 6k in neutral

this wouldn't be a Ca. engine would it?

[d.a.autry]

Originally Posted by Bill Verburg

this wouldn't be a Ca. engine would it?

Bill,

I'm not sure, it has no emissions information on the doorjam Only indicating it would be. Besides, the 2.7 in there now is a transplant and again, with backdated exhaust and the air injection deleted.

Were the curves different on the distributors for Ca. models?

Also, I don't have any marks for the 6k test. I'll check a few other pulleys I have. I may have to get (make) a degree wheel. All I have is TDC, 5 ATDC, then 120 and 240.

I've always heard it was a BIG no-no to spin anything up that high unloaded even for a second,. . . .perhaps a holdover from my muscle days?? I'm still sure that one would want to do that check within a few quick seconds just the same.

[Bill Verburg]

Originally Posted by d.a.autry

Bill,

I'm not sure, it has no emissions information on the doorjam Only indicating it would be. Besides, the 2.7 in there now is a transplant and again, with backdated exhaust and the air injection deleted.

Were the curves different on the distributors for Ca. models?

Also, I don't have any marks for the 6k test. I'll check a few other pulleys I have. I may have to get (make) a degree wheel. All I have is TDC, 5 ATDC, then 120 and 240.

I've always heard it was a BIG no-no to spin anything up that high unloaded even for a second,. . . .perhaps a holdover from my muscle days?? I'm still sure that one would want to do that check within a few quick seconds just the same.

post the engine # next to the fan

Ca. engines are different, 15*ATC @1krpm w/ vac connected is the spec for them

I am not at my main computer so can't look up the curves but if you swapped in a good RoW or Ro US distributor then it's a non issue anyway

[d.a.autry]

Originally Posted by Bill Verburg

post the engine # next to the fan

LOL. . . I wish it was that easy.

this is a donor case that was sent directly to Ollie's for their magic touch. The original . . .well. . . let's blame that on an unsavvy individual in Seattle (or UPS, take your pick. I choose the former).

I do however have the case my spare came from and I'll check it later today. I'm assuming there's no way to differentiate by distributor #'s eh?

This is kind of why I wanted to check curves. I thought Storz had a machine. I recall seeing one at someones shop here locally, but I forget where.

BTW. . .a neat read on "Dwell, and what it means to us old school alumni" Found this whilst trying to figure how do convert duty cycle to dwell using a RMS 87.

Dwell - what's it trying to tell me? | MG MGB Technical | British-Cars.net

[Bill Verburg]

I didn't read through the MGB link, but dwell is simply the time in degrees that the points are closed, the shorter the dwell the wider the gap and vice versa. Back in the dark ages of auto history they started specifying dwell instead of point gap because it is easier to measure accurately. Because the dwell gets bigger as the rubbing block wears I always set them up on the low end of the dwell spec.(wide end onf the gap spec.)

I always set the points on a bench, pull the distributor and place it in a vice, much easier to work on than bent over on your knees in the car.

[BURN-BROS]

There is a good posibility that the vacuum retard is not working. Block the vacuum port

Set timing to 0 deg (Z1)

Verify timing @ 6000 rpm and reply back.


If the Vac retard is not working, your engine in running severely retarded, causing the backfires.

[Otto]

set the CO, quit chasing your tail.

[d.a.autry]

@Burn,

I know the vacuum unit itself is operational. I'm wondering about the splitter in the line to it from the throttle body. I'm at work now, but if I recall it goes to a switch that in turn goes to the WUR.

@Otto,

That's forthcoming, but I need to ensure all systems are functioning correctly first. (which they could be and thus the CO would make perfect sense, but my nose tells me the burn is good. . . does that sound crazy? Can one really have that keen of a smell? . . only if it's VP113? LOL )

It's running much, much better. But as Bill and Frosty have posted here, and as verified with other sources, there was a tendency for these 2.7 CIS's to have an idle timing app. 5 deg more retarded than specs.

I'm going to need to make a degree wheel to check the 6k, . . .or just mark the pulley. . . I'd rather make it complicated though, LOL.

Understand, much of this query is more about my own education than that of being O/C about specs