First, let me mention that the engine, when spitting and coughing, is
spitting and coughing BLACK smoke. And the plugs keep turning a nice deep
velvet black. The kind any theater major would be happy to acheive. I've
installed a new fuel filter, and just rebuilt these carbies. I reset the
floats to the recommended height and have good flow from the hoses. I think
we can put off any comments of running too lean.
Secondly, The car had been running fine through the winter on the HIF's I
pulled off the maroon while rebuilding the HS4's, albeit with a rather high
idle (go figure - they're HIF's). It even ran okay on the HS4's until I
pulled them off because the throttle shafts needed help. It ran okay until I;
1. Put the HS4's back on,
2. Replaced the exhaust with the alledged oversize stainless
3. Put in new plugs
4. Adjusted the valves
5. Replaced the oil filter and changed the oil
6. Replaced points and condensor and gapped them
7. Replaced the fuel filter
8. Checked the timing
9. Watched my wife clean the birdshit off it
10. Got my son's car fixed
11. Stared tuning the newly rebuilt HS4's
Things I promise I will check if it doesn't rain tomorrow;
1. If I didn't get the plug wires mixed up tho I've checked 3 times already
2. If having taken the diz apart and really cleaned it won't help
3. If there's enough beer in the fridge (this has been a problem in the past)
Now, back to my original question. I seem to remember when I put the
alledged oversize exhaust on the maroon in the first place, that I got a
power boost at the low end and kept the blip in the 3500 rpm area. The
maroon always had a spot right around 3k to 3.5k where it just didn't run
smooth. Anything above or below that was fine. Installing the new exhaust
seemed to localize it right at 3.5k but didn't affect it any other way. I
just learned to drive around it.
The primrose has always had a steady curve with no blips all the way up and
down but with very little low end torque. I don't get startup torque until I
start getting over 1500 rpm. The recent compression check tells me that at
120 psi on a high compression engine, I'm possibly due for some deep engine
work in the future, but for a daily driver and occasional tourer it's okay.
I was HOPING that putting the same system on the prim that I had on the
maroon, I could pick up a little low end.
Now to respond to some of the comments I've been recieving:
Larry Unger writes:
>The real issue is that the match the vaccum type
>to the dizzy/vacuum advance not the carbs ... do
>ya know if the dizzy/vacuum advance is original
>and whether it requires manifold or ported vaccum?
>
>Have you checked the mechanical advance springs
>to make sure that they are OK? (Connected and not
>stretched)
I replaced the dizzy when I first got the car with a unit that I had peiced
together from about four other units I had laying around the house. It's
still a 25D and all the parts came from 25D's. The maroon ('74) had a
manifold vacuum and the prim ('69) came with ported. When I put the HIF's on
I swapped over to the manifold since the HIF's had no port and the only
performance difference was a high idle, which I've always just written down
to HIF's. I think it's a worthwhile suggestion, though and if the clean diz
doesn't pay off I'll try that next.
The advance springs are okay, but I do notice they are of the same size, as
were all the other springs in the other four units I raped to build this
one. I remeber threads about unequal springs, so I wanted to head that off.
This diz has worked fine but the top plate seemed to be stiff so I cleaned
it up last night.
John McEwan and Todd Mullins write:
>John McEwen writes:
>
>> On a motorcycle, when any changes are made to increase the flow of exhaust
>> gases, the carbs must be richened to accommodate the increased air flow
>> through the engine. You may have created an excessively lean engine with
>> the new system. While you can adjust it at idle, the carbs cannot
>> accommodate higher revs.
>
>I must disagree. Within a certain usable range, the CD nature of SU
>carbs automatically compensates for changes in flow.
>
>Right?
>
>- --
>
>Todd Mullins
*Wait! You're BOTH right! It's a candy mint AND a breath mint!
A motorcycle engine, being a much smaller unit, is going to respond more
readily to large changes than an auto engine, but the logic would apply,
IMO. And the CD nature of the carbs should apply to the mixture going INTO
the chamber but don't have anything to do with the other half of the
equation. I know that exhaust tuning is a black art practiced by Druid
preists at the soltices, but there must be some kind of basic bylaws we the
laypeople can live by that we can make heads or tails of our next purchase
and get better crops next season.
John M. Trindle writes:
>No, it's not the headers. I have the same size and the car ran fine with
>a massive leak in the exhaust. (I now have it all welded, a "free flow"
>Ansa exhaust). You might see a small torque reduction below 1500-200 RPM
>but the power should be noticeably >better< at 2500 and above. Sounds
>like it doesn't get there.
See above Reply. And like I say, when I put this same system in the maroon,
I got a good low end push but it did nothing for the high end. Now I can't
even TUNE the damn prim and can't believe it's the exhaust pipe. But I'm not
a Druid priest.
If it doesn't rain tomorrow I'll let you all know how the clean diz worked
and what else I've tried.
Glenn "Starting a large rock collection" Schnittke
-----------------------------------------
No one in Tuna knows what I do for a living.
Why should they care what I say?
Glenn Schnittke Recovering Musician
Nashville TN 615-385-2800
schnittke@mindspring.com
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