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HD8 carb on Healey 3000

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I've have been following this interesting discussion and have a couple of thoughts.

I agree with OWD724 that the length of the damper rods is not important as long as the piston can achieve full travel. However, I have found slightly different 'dampening resistance' in various dampers so if you have an assortment to choose from, I suggest making sure they both feel the same resistance.

As to AUSMHLY's question "Did all the HD8 have the AUC 2053 pistons?" The Healey HD8s I have had all used the AUC 2053.
However, several years ago I bought a pair of HD8s for $50 at a swap meet that were off of a Rover 2000TC. Seemed like a nice cheap way to upgrade from HD6 to HD8 until I got them home and disassembled them - the old adage 'if it seems too good to be true, it probably is' applied. The pistons in these HD8s are AUC 1278 and entirely different than the pistons we are familiar with in the HD6 and HD8 as found on Healeys.
IMG_3701_LI (2).jpgIMG_3703_LI (3).jpg
I marked in red the vacuum ports that carry the intake vacuum to the top side of the piston. The AUC 2053 type have two fairly large holes that go directly into the bottom of the piston where the spring rests but these AUC 1278 have a different shaped entry port on the bottom, a very small drilling thru the side that goes all the way into the area where the spring is, and two fairly small ports in the top flange (also this vacuum is applied between the two 'rings' at the top of the piston).

I have no idea why they are made like this (possibly because they were on a 4 cylinder and the vacuum pulses were larger so the smaller vacuum ports smoothed out the rise of the pistons?? - I do think a pair of HD8s on a 2 liter 4 could be considered over-carbureted...) but it does show that there were definitely more than a couple of HD8 versions made for different applications... and that SU knew more than most of us ever will.

I do believe it is usually best to not mix & match parts from different carbs unless you have damaged parts but definitely the pistons & cambers should stay paired.

Dave
 
To continue this saga a bit, I thought I would order a pair of new piston springs for the HD8s. I did so for no particular reason other than to install a new component. I ordered them from Moss Motors. AUC 4826 red/green springs for 2ā€ SUs. I was surprised at the difference between the new springs and the springs that were in the carbs. I am pretty sure the springs in the carbs were also red/green but a bit hard to tell as most of the paint is long gone.

Anyway, the springs in the carbs are 230mm long while the new springs are 268mm long. The wire diameter on the springs in the carbs is 1.25mm while the wire on the new springs is 1.1mm. The diameter of the coil appears to be the same.

I have not installed the new springs yet. I am curious about the thoughts of the group regarding the spring differences. Did I have the proper springs to begin with? If so, why the change?
B89E6B89-F53E-4627-A1CD-70275C872769.jpg
 
The spring that is most common in the HD8 on Jags is the BLUE/BLACK that is lighter in compression. The wire is thinner.
i bet yours is that one. The GREEN/RED is considerably heavier and stronger. But, it goes all the way back to my original comments as to why the Healey 3000 has non vented dome, vented cap and this heavy spring. It is correct according to the SU book, but no one has given an explanation why when most have vented dome, non vented damper and far lighter spring ? The red green is over 11oz compression but the blue black is just over 4 oz. The Burlen SU book is contradictory as near the beginning of the book it states all HD8ā€™s are internally vented and require non vented damper. I do have a brand new set of green red and they are 242mm long and 1.21 mm thick.
 
OWD724 said:
The spring that is most common in the HD8 on Jags is the BLUE/BLACK that is lighter in compression. The wire is thinner.
i bet yours is that one. The GREEN/RED is considerably heavier and stronger. ....
Click to expand...
According to Burlen, the light blue/black springs are for the competition Healeys with three HD8s and the red/green springs are for "normal street" Healeys.

The key way to tell what a spring is, if the paint has worn off is the compression of 11.25 oz at 8.875". The wire size may have changed due to a change in material specification.
 
Yes, the E Type also has 3 HD8ā€™s with the blue black.

The picture of the new spring from Moss and its colour look strange to me.

I have brand new ones from Burlen in an open packet unused and the green is different and the length as I described before.
 
OWD724 said:
The spring that is most common in the HD8 on Jags is the BLUE/BLACK that is lighter in compression. The wire is thinner.
i bet yours is that one. The GREEN/RED is considerably heavier and stronger. But, it goes all the way back to my original comments as to why the Healey 3000 has non vented dome, vented cap and this heavy spring. It is correct according to the SU book, but no one has given an explanation why when most have vented dome, non vented damper and far lighter spring ? The red green is over 11oz compression but the blue black is just over 4 oz. The Burlen SU book is contradictory as near the beginning of the book it states all HD8ā€™s are internally vented and require non vented damper. I do have a brand new set of green red and they are 242mm long and 1.21 mm thick.
Click to expand...

I wonder if there's a lost archive of high-level SU information, accumulated by people long-dead that has the answers to our questions.

It seems to me we're all operating at a level where we have contradictory bits of information, but not the whole picture, which, unfortunately is lost in the mists of time. Much like monks in the middle ages trying to rediscover the secrets of the ancients. Dave's pictures of a Rover 2000 HD8 give us a glimpse of this.
 
Steve, I have never known you to be so philosophical :encouragement:

I ordered a pair of the red/green springs from Burlen. When they arrive I will do a photographic, side-to-side, comparison with the springs that were in my carbs, the Moss springs and the Burlen springs for what it is worth.
Lin
 
Latest update on the red/green spring issue for the HD8 carbs. To quickly recap. My ā€œoriginalā€ red/green vacuum chamber springs are shorter than the Moss Motors replacements that I ordered. My ā€œoriginalā€ springs do have the remnants of red/green paint and the new springs were labeled red/green and painted that way. I figured the Moss Motors springs might be incorrect (sorry Moss) and I ordered a pair from Burlen. They arrived today and they are exactly the same as the Moss springs - I assume Burlen supplies Moss, but Mossā€™s springs were packaged in their own bag - not in a Burlen wrapper.

So, I have emailed Burlen asking if there has been a change in spring specs. Failing that, I asked if they can explain the difference in the springs. These new springs are quite long! I will share their response when I get it. Sounds like I may have to do the spring compression test S. Gerow explained if I donā€™t get a reasonable explanation.
Lin
 
Hello Lin, as you know I started this whole post, three pages ago questioning why there are anomalyā€™s with the Healey 3000 HD8 in respect to vented dampers, heavy springs etc. Here attached is a picture of a brand new unused green/red spring from Burlen with the original SU packaging. As you can see it is about 240mm and the thickness of the wire is 1.20mm measured on a digital micrometer.D772574A-B501-420D-A9B6-F6B00CEE928D.jpg
 
Hello Lin, sorry picture so small, donā€™t know how to make bigger, but if you tap and save maybe you can expand size ?
 
John,
yes. Those dimensions measure up to what I have from them. I have 248mm with wire size of 1.25 mm. I am curious about the response from Burlen regarding the discrepancy in measurements between my ā€œoriginalā€ springs and those they are now selling. We will see...
 
Hello Lin, just for something to do on a Saturday, I took the springs out of my XK120 HD8ā€™s. They are the Blue/Black which is fairly normal on Jagā€™s with HD8ā€™s, they are not new but about 5 years old. Length 230mm, wire thickness 1.03mm.
My new unused in the SU packet Green/Red are length 240mm, wire thickness 1.20mm.

Looking forward to hearing your response from Burlen, but donā€™t hold out much hope for a good explanation other than they have changed suppler !! I also note the shade of green in your picture is a solid pea green. My green is more a metallic emerald.
 
Question about Colortune. I have one but have not used it yet. Do you place it in the middle cylinder for each bank. Piston 2 and 5?
 
I use two of them. #2 and #5 cylinders. Using only one makes it a little harder to judge white/blue verses yellow/blue. I find the mirror tube device worthless. Just do it a dim lit garage. You're looking for "bunsen" blue then go a tad richer. They show up on Ebay at a good price.
 
Well ..... this thread got me looking into a some details regarding my collection of various SU carburetors for big Healeys.
First, the free length, color and wire size of the spring is irrelevant. If the spring for your HD8 compresses to 11.25 oz at 3.875" height, or very close to that, than you have the right spring. Use a postage scale and compress the spring to 3.875" to see what you got. I use a 1/2" drive deep socket as a guide to keep the spring straight as I push down.
Second, the caps on dampers are either vented or non-vented caps. The HD8s have vented caps. The damper rods come in different lengths. The HD8s have rods roughly 3.3" overall. The 1-3/4 (HD6) carbs have rods a little over 3" overall and the rods on the 1-1/2" (HS4) carbs are about 2.85" long overall.
Third, there are two different weights at the ends of the rods. All of the weights are 3.35" in diameter but they are either 3.06" or 3.78" in length. The weights on my HD8 rods use the heavier version. I discovered that the weights on the HD6 rods were of the lighter version and the ones on the HS4s had the heavier version. Go figure.
There may be more variations out there but this is what I found in just checking out some of my SU stuff.
And lastly, does anyone have an orphan HD8 they would be willing to sell me? ..... I need one for parts.
 
While I think that Richard is exactly correct when it comes to what matters about the spring, I thought I would share that Burlen finally got back to me this morning. Their representative states, ā€œWe have checked our information sheets for the springs, and the spec hasnā€™t changed. I have checked with our production team and they say the new springs will function as originally intended for your application.ā€

Lin
 
Hello Lin, not really a satisfactory answer from Burlen. I think if you follow what Richard says and compress the springs you have from them and your original set, that should check whether the specifications are the same. It is strange that my brand new set as I photoā€™d In previous post in original SU packaging is different to both yours from Burlen and Moss.
Not really sure what Burlen mean by New springs ? Are they saying made by a different manufacturer? I can tell you my new unused springs are exactly the same as the ones we took out of my friends 3000 with HD8ā€™s. I have never used my Red/Greens as just bought to experiment in my 120 with the HD8ā€™s. Later today I am going to use an electronic kitchen scale to measure as Richard said. The saga continues !!
 
Ok, I was impatient to try the weight test. My Red/Greens are somewhere around 11.75oz on my pretty accurate digital kitchen scales tested against various other new food packages.
 
I think the two springs are equivalent which is some what supported by the pictures even after I enlarged them.

The top shorter spring appears to be made from a slightly larger diameter wire than the bottom spring , consequently the additional length shown in the bottom spring suggests they are of the same performance specification .--JMOP
 
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