New 1500 build + new 5 speed install

Fundamental carb tuning discovery today, aided by bright sunlight in the driveway: One of SteveC's older posts suggests matching butterfly angles on both DCNF's by observing relative angles at WOT (wide open throttle). In doing so could clearly see all four aux jets working well - good. Seemed like like the butterfly angles weren't perfectly matched carb to carb, which led to the discovery that the funky interlink was actually holding both butterflies from closing completely. Backed the screws off and made that right.

Went for a drive, runs better, less of the low end bog issue. Still chirping, popping and backfiring. Happy though, pulls great.

Searching for air leaks with carb cleaner: manifold to head area on the right side must be leaking. And possibly throttle shafts. Manifolds are going to come off again for another go at fitting while awaiting synchrometer adapter, o-ring, and jets arrival.

I don't believe I have clogs or fuel delivery issues. Hoping the air leak solution and proper balancing is the path to glory.
 
Just a thought here Jim and I'm sure most of this could be taken up by the gasket but is it possible that the intake to head mating surface might be an issue? Mine was warped like crazy. I'm sure you had the head port side cleaned up during machining but could the intake side be a problem? I mean as far as leaking is concerned?
 
CnC79X19 said:
Just a thought here Jim and I'm sure most of this could be taken up by the gasket but is it possible that the intake to head mating surface might be an issue? Mine was warped like crazy. I'm sure you had the head port side cleaned up during machining but could the intake side be a problem? I mean as far as leaking is concerned?
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Could be - will review and report. I suspect in thinking back on the last two mounting attempts that the Alquati casting doesn’t precisely match the factory Euro head stud positions. And/or the mating to the aftermarket header. A bit of Dremel relief, if speculation is correct, may be in order. And close look at the shoulder washers. Another member’s older thread describes this exact issue.

I continue to learn the value of close observation - both of the way the machine behaves, It’s assembly and components.

How the space station or an aircraft carriers gets done? Seems impossible.
 
With a telescopic mirror and new batteries in an LED flashlight, closely inspected the bottom portion of the intake manifold where previously I had ground off the points that interfered with the header flange. Didn't seem like more grinding would help, particularly on the side closest to #1 and #2 cylinders where the manifold exhibited air leakage.

Then took a very close look at the shoulder washers. Swapped the fabbed shoulder washer holding both the intake and exhaust on the far right side for a thick flat washer (stock component), and did the same for the washers under the intake that share contact with both manifolds. Visually, it appeared to improve the fit of the manifold at the gasket joint on that right side.

Huge improvement, very little chirps / pops now, and much quieter off throttle / downhill. Pulls much better from low revs with far less hesitation, though still not perfect. There had definitely been an air leak.

Much looking forward to the synchrometer adapter and o-rings. And much more driving.

Question: Have any of you removed the butterfly spindle end nuts, and packed the spindle bearings with grease to reduce air leakage there? And if so what were your results?
 
fiatfactory said:
turn the bolt around on the cambox lever and it may not touch the camcover....

F36 will be better than f25, so a good step.

45/47/50/52 idle jets on hand is always number one tuning tool for dcnf/dcnva etc... they spend a lot of time in the idle circuit so this is important and affects (nearly) the whole range of operation as they also control the progression and also spill fuel at wot... remember its cross section that matter for flow of fluids, and the difference/ increase in area/cross secton between 45/47/50/52 is quite a lot and not linear (as Pi is involved)

edit. I just grabbed an image from earlier in the thread and had a close look... your webers look to be the type with idle mix screws wth the cupped washer below the tension spring... in this image it kinda looks like the cup washer is cradling the spring... that's wrong. the cupped washer should be keeping the idle miture screw O ring in place. There are also maybe four different styles of idle mix screw (different taper and also different O ring positions) and check the tips of the idle mix screws, they get bent/ mashed up if someone is ham fisted and tightens them way too much

SteveC
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Successfully sourced correct o-ring gaskets for the idle mixture screws (CarbsUnlimited). They are a dark green material and incorporate a molded channel on the faces. Th channel there I think to mate with the cupped washers. Addition of these gaskets seems to again help with air leaks, they are installed. To your point Steve, having those cupped washers with the concave side toward the carby is correct. It's also important to have them in the first place! All four of mine were not present, so I went and searched high and low to source. Nearly gave up and bought complete sets of DCOE idle screws complete with springs, gaskets and cup washers from eBay, when I discovered:

Weber Mixture Screw Cups are available at
Partsklassik
827 State Route 82
Suite 10251
Hopewell Junction, NY 12533
Phone: 928-255-2824

No affiliation with vendor, just want you all to be aware. $1.05 each.

 
Agnelli said:
Successfully sourced correct o-ring gaskets for the idle mixture screws (CarbsUnlimited). They are a dark green material and incorporate a molded channel on the faces. Th channel there I think to mate with the cupped washers. Addition of these gaskets seems to again help with air leaks, they are installed. To your point Steve, having those cupped washers with the concave side toward the carby is correct. It's also important to have them in the first place! All four of mine were not present, so I went and searched high and low to source. Nearly gave up and bought complete sets of DCOE idle screws complete with springs, gaskets and cup washers from eBay, when I discovered:

Weber Mixture Screw Cups are available at
Partsklassik
827 State Route 82
Suite 10251
Hopewell Junction, NY 12533
Phone: 928-255-2824

No affiliation with vendor, just want you all to be aware. $1.05 each.

Click to expand...
I'm rather curious about the o-rings on the idle mixture screws. My carbs, which came new from Weber in 1980, never had o-rings at that location. The Haynes Weber manual does not show them either in the DCNF section. That being said, my DCNFs have the idle mixture screws mounted differently than yours (the screw heads point to the left rear of the car on both barrels). Perhaps some models use them and some do not?

Since I've recently developed symptoms of an air leak (backfires), I'm wondering if that could be a possible source. What size o-rings did you end up with?
 
Don -

dllubin said:
I'm rather curious about the o-rings on the idle mixture screws. My carbs, which came new from Weber in 1980, never had o-rings at that location. The Haynes Weber manual does not show them either in the DCNF section. That being said, my DCNFs have the idle mixture screws mounted differently than yours (the screw heads point to the left rear of the car on both barrels). Perhaps some models use them and some do not?

Since I've recently developed symptoms of an air leak (backfires), I'm wondering if that could be a possible source. What size o-rings did you end up with?
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I measured the round light green O-rings that came with a parts stash that seem to work with the idle jets (though did not for the idle mixture screws without the soon to arrive cupped washers. They appear to be quite similar in dimension to the new squarish edged O-rings from Carbs Unlimited.

Dimensions are 8mm OD, 5mm ID, 2mm thick. Hope that helps. I'd have to do yet a third order w/ McMasters to ascertain if generics in those dimensions would work. The good news is McMasters Carr must have a fulfillment depot close to our locations in NorCal because both of my prior orders arrived the next day, these were orders placed in the afternoon. Remarkable.
 
there are at least three different designs of fuel mixture screws for DCNF that I know of, some have the O ring fitted to a groove in the shaft of the screw, some have it external under a cupped washer. There has to be something to seal air ingress, threads dont seal and air will get pulled down the threads and upset the metering of the carb

The green material is probably Viton (a fluoridated elastomer) and it's resistant to most things , so a good choice.

SteveC
 
fiatfactory said:
there are at least three different designs of fuel mixture screws for DCNF that I know of, some have the O ring fitted to a groove in the shaft of the screw, some have it external under a cupped washer. There has to be something to seal air ingress, threads dont seal and air will get pulled down the threads and upset the metering of the carb

The green material is probably Viton (a fluoridated elastomer) and it's resistant to most things , so a good choice.

SteveC
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It would make sense to insure there is a good seal there. However, the parts diagrams I've got show nothing in the way of a seal at that location. In the Haynes manual, there is actually a photo (5.40) of an idle mixture screw being removed and there is no seal shown. My carbs came new from Weber and I never saw seals on the idle mixture screws. Maybe I'll have a closer look at the screws and the holes they go in to. I should also give it a spray there with the engine running and see if it affects the idle.
 
Steve and Don -

Concur with your thinking and observations.

While awaiting cupped washers, F24 emulsion tubes, mains and air correctors, figured it would be good to test drive and get a bit more time on the engine. Started instantly, and took a longer run this time including freeway time. X ran quite well up the road to first destination, very little popping / chirping and quite consistent. Some hesitation at the transition from idle to mains, but driveable and still eager to rev. Pops and chirps increased with the stops I made. Will continue to run down air leaks. Did adjust idle speed down during the drive.

SteveH transaxle is fantastic, working well in all gears. Grateful.

Back in the driveway, powered up the new timing light and applied it. To view the strobe illuminating the flywheel mark, required activating the throttle above idle, so I do need to move the distributor to dial in the timing. It'll be interesting to see how advancing timing improves power.

Can't wait to get the carby flow meter adapter to actually tune the carbs. Zeroing in on a good running car.
 
dllubin said:
It would make sense to insure there is a good seal there. However, the parts diagrams I've got show nothing in the way of a seal at that location. In the Haynes manual, there is actually a photo (5.40) of an idle mixture screw being removed and there is no seal shown. My carbs came new from Weber and I never saw seals on the idle mixture screws. Maybe I'll have a closer look at the screws and the holes they go in to. I should also give it a spray there with the engine running and see if it affects the idle.
Click to expand...

I had look thru my original Weber literature, and you're right... early diagrams from the 1976 dated bible doesn't show an O rng in that position... but a later copy dated 1982 does. Perhaps it was a misprint or omission, perhaps it was designed without an O ring?... but I really can't see that

When I've found dcnf/dcnva/dcnvh etc carbs without a O ring I simply assumed that someone had lost / left them out (believe me it happens a lot) and fitted replacements (same deal on IDF's they went from internal O ring to external at that position)

buy 4 of the cupped washers and 4 O rings and fit them. It can't hurt.

SteveC
 
fiatfactory said:
I had look thru my original Weber literature, and you're right... early diagrams from the 1976 dated bible doesn't show an O rng in that position... but a later copy dated 1982 does. Perhaps it was a misprint or omission, perhaps it was designed without an O ring?... but I really can't see that

When I've found dcnf/dcnva/dcnvh etc carbs without a O ring I simply assumed that someone had lost / left them out (believe me it happens a lot) and fitted replacements (same deal on IDF's they went from internal O ring to external at that position)

buy 4 of the cupped washers and 4 O rings and fit them. It can't hurt.

SteveC
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Totally agree. For the good of the order, attached here is an image of earlier referenced o-rings and cupped washers, the latter just arrived. Upper left dark green o rings are from Carbs Unlimited. Lower left black o ring was on the carbys when acquired, at the idle jet mounting. Second from lower left light green o ring was in a DCNF spares box that arrived with my 128. Cupped washers from Partsklassik who specialize in early Porsches. I've already installed the cupped washers and dark green o rings on the idle mixtures screws. The fit indicates they will seal, which is to be proven upon next drive.

cupped washers.JPG
 
fiatfactory said:
I had look thru my original Weber literature, and you're right... early diagrams from the 1976 dated bible doesn't show an O rng in that position... but a later copy dated 1982 does. Perhaps it was a misprint or omission, perhaps it was designed without an O ring?... but I really can't see that

When I've found dcnf/dcnva/dcnvh etc carbs without a O ring I simply assumed that someone had lost / left them out (believe me it happens a lot) and fitted replacements (same deal on IDF's they went from internal O ring to external at that position)

buy 4 of the cupped washers and 4 O rings and fit them. It can't hurt.

SteveC
Click to expand...
My guess is that it was a design change. My Webers were purchased new in 1980 and shipped without the O ring and cupped washer. I'll check for leaks in that location and add them if necessary. I'm guessing my problem lies elsewhere but it is worth checking.

I've heard people complain about the cold start devices but never got a good description of the issues they can cause. Some people block them off but I have had good luck with them starting a cold engine. Any reports of the cold start devices causing air leaks?
 
The green Viton O rings with the grooves are "the duck's nuts" and what's supplied in the best kits... (when I can find those) that is what I like to use, good to know a source I'll need to buy some.

SteveC
 
cold start plunger / valve not sealing will spill fuel not air, it's simply an enrichment device, it's more of a problem child with older IDF's.

it really only happens on older carbs that have been exposed to corrosion damage, as most times (well a lot of the time) when you lift the plunger valves in an IDF, they are quite stuck and show signs of corrosion at the taper seat in the bottom of the well... if they are like that the best fix is to block them at the carby base (as I dont have and I dont know anyone that does have the correct tool to recut the seat)

SteveC
 
Updates:
(1) swapped in new F24 emulsion tubes, 185 air correctors, and 120 main jets.
(2) STE-BK synchrometer adapters now very hard to acquire. First vendor issued a refund due to inability to fulfill, claims manufacturer is no longer making the adapters. Second vendor I tried also immediately refunded my order today, and was kind of enough to indicate that adapters come from Europe and are well backlogged.
(3) ordered the smaller STE-SK model which should work without an adapter for DCNF 40. Hoping Pierce can ship quickly.

Will drive and set timing tomorrow, and complete the tuning when the synch tool arrives.
 
Agnelli said:
Updates:
(1) swapped in new F24 emulsion tubes, 185 air correctors, and 120 main jets.
(2) STE-BK synchrometer adapters now very hard to acquire. First vendor issued a refund due to inability to fulfill, claims manufacturer is no longer making the adapters. Second vendor I tried also immediately refunded my order today, and was kind of enough to indicate that adapters come from Europe and are well backlogged.
(3) ordered the smaller STE-SK model which should work without an adapter for DCNF 40. Hoping Pierce can ship quickly.

Will drive and set timing tomorrow, and complete the tuning when the synch tool arrives.
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The SK model works great on my 40 DCNFs. I've had it since 1980 when I bought it after getting nowhere with a friend's UniSyn.

I'm curious as to how the F24 compares with the F36.
 
dllubin said:
The SK model works great on my 40 DCNFs. I've had it since 1980 when I bought it after getting nowhere with a friend's UniSyn.

I'm curious as to how the F24 compares with the F36.
Click to expand...
Don - great information, I have an SK due to arrive 12/15.

Meanwhile, I installed the F24s, 185 ACs, and 120 mains and drove it yesterday. Note that I have yet to synch the carbs so this feedback is with that huge caveat. First run as it warmed up the transition from idle to main seems better. The reason I opted to also try the F24s was based on a Steve C post in trying to understand emulsion tubes. That post indicated and logically so that F24s are actually leaner at part throttle and richer at full throttle than F36s, which I originally thought were leaner irrespective of throttle amounts.

Between runs I advanced the timing, first adjustment there since the rebuild. First marked the distributor and block as a reference point / baseline. Rotated the body of the distributor counterclockwise ~ 2-3 degrees. This bumped the idle up considerably, which I adjusted back down via idle speed screw. Then fiddled with the idle mixtures, backing them off about a half turn on the left carby. They are now out one full turn from closed. The right carby, idle mixtures seemed to have less effect if any, opted to match the right carb by closing them down to one turn open from full closed. This effect could be attributed to the fact that I have yet to synch the carbs, and all idle corrections are thus closed. This is as much a statement as is a question for you all.

Second run, power seems to be up, transition a little better still, and less burble downhill on compression, and a bit less light popping. Can't wait to synch, and re-check for air leaks as the next step before the SK arrives.

Moving in the right direction here.
 
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