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Needles and Seats

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jhorton3

jhorton3

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I'd never been happy with my HS2 carbs, just couldn't seem to get them right. I was contemplating a conversion to Mikuni HSR 42mm carb, but that's another story. As a last resort I decided to get new needle and seat By the way these were rebuilt carbs I acquired a few years back.

Pull the front float chamber apart and the needle looks like a viton tip, which is the type I bought. I replace it anyway. By the way it'd been three weeks since I'd run the car and there was about 1/4 chamber full of fuel.

Move to the rear carb's chamber. Chamber nearly empty of fuel. Pull float and look at the needle. It's a flimsy plastic bit with a weird shaped nose. Go to remove the seat and it's a larger diameter size than what was in the front carb.

Now it's all back together. I fired it up and just at idle and revving in the driveway I could tell a difference. I've still got to tidy things up before a test drive.
 
Sounds like you may have fixed a problem. I had mis-matched HS 2 carbs on mine when I bought the car. Now have rebuilt carbs and M needles. Car runs great now
Which needles did you buy?
 
I changed over to viton tipped float needles. She now runs a little rich so I need to make adjustments. I did take it out for a test drive and I was able to get her up around 80 which is a record and she liked it there. 70 is about all she would do and that would be going downhill with a tail wind. One problem I always had was backfiring a lot on downshifts. I maybe heard one small pop the entire trip out today.
 
Decel backfiring is usually an air leak at the manifold, sucking in oxygen and igniting the unburnt fuel in the exhaust, at least that's been my experience....FWIW!
I'm anxiously awaiting the opportunity to reinstall some HS2s, carbs have sat for 20 years but stored well, cleaned up well but have grose jets, I'm under the impression the original Grose jets were great, then got cheapened up when bought out by someone, now are made by someone else and good again. I'm going to try mine as they are.....I've got SO much work to do first though....I should get started......
 
I've checked for leaks with WD 40 spraying around and could not find any. My theory is that the back carb was starved for fuel and causing an unbalanced mixture. If it was too lean a mixture then that might cause the pop.

I'm curious to hear your experience with new Grose jets. I had bad experiences with them in the mid-90's. They wouldn't hold pressure, caused my carbs to overflow and turned my charcoal canister into a petrol fountain. Replaced them with original style and that problem went away.
 
Yeah, I don't know the vintage of these grose jets though, according to PO's receipts the Weber kit was purchased in '86, I assume the Grose jets to be at least that old. I should probably just put the viton stuff in there but I'll wait and see first. I plan on doing a few tests to check operation but if they pass then I'll try them, if I suspect issues I'll ditch them.
Backfiring could be loose exhaust too. I had it severely until I resealed the manifolds to head. No intake leak, just the exhaust, of course I have a crappy Pacesetter header with different flange thickness than the intake, so getting both to seal is a pain. Maybe even the joint between exhaust manifold and downpipe. You'd think you'd hear that though.
 
With my hs2's and the M needles I can easily get 80 MPH....85 and still climbing was the fastest I've been though. A bit scary but great fun when passing all the new BIGGER vehicles on the road. Love lookin at the faces when they see me pass 'em...
 
80 MPH was a bit scary yesterday, especially on a two-lane blacktop. She felt like a wobbly goblin with the wind blowing. Part of that thought I still believe is a need for better wheels/tires and tweaking the suspension a bit more.
 
Whenever I've experienced backfire on decel it has been from an exhaust leak. It doesn't have to be at the manifold, it can be at any joint in the pipes where the exhaust is still hot enough to burn.

I replaced the Grose Jets in both the GT6 and the Mini. In the GT6 they had a tendency to stick closed. With the Mini they never shut off. I now have Viton tipped needles in both. However, I've had the Viton needles stick closed once or twice in the Mini. When the carbs are due for float valves again I'm going back to the metal-on-metal valves.
 
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