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My BJ8 [MK III] hesitates and spits when accelerating

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rcflyer

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Hi everyone, Hope you can help here. I have a 1965 BJ8 (HD8's) and it is a new car to me last July, Nice car...just working out some grimlins. When I accelerate (Not always) it will hesitate then kind of spit and go pow (maybe pow is overkill!) for a short time...then run fine. Seems to do it more when cold., but does it anytime. Seems to be more after a stop then go at a light or sign. Is it a Healey standard feature...or can it be fixed?? Thanks...Also, anyone tell me how to do new lines in this editor? Lee:rapture:
 
Am guessing here. Add oil to your carb dashpots. Use ATF or other thin oil. Motor oil also OK.

I had a problem with bucking and missing accelerating from a stop sign - turned out to be the coil.

Your problems not a feature - car should run fine.
 
Steve, Thanks...I think there is oil in the dashpots...at least there was a month ago after I got through rebuilding the carbs,,,but I'll check, AND maybe I have too thick of oil in there...I think I used engine oil (20-50). Also, I do have a new coil and I could swap it to see if it fixes it. I have a MGA 1600 as well so I thought I should have a coil as a spare for either if I take a trip somewhere kind of far away. Also, I have a brand new SU electronic fule pump (the new model supposed to be better on fuel W/alcohol0 I got from Healey Surgeons....and it is very noisey compared the the old one..but the car doesn't quit on me anymore -:smile:
 
rcflyer said:
Steve, Thanks...I think there is oil in the dashpots...at least there was a month ago after I got through rebuilding the carbs,,,but I'll check, AND maybe I have too thick of oil in there...I think I used engine oil (20-50). Also, I do have a new coil and I could swap it to see if it fixes it. I have a MGA 1600 as well so I thought I should have a coil as a spare for either if I take a trip somewhere kind of far away. Also, I have a brand new SU electronic fule pump (the new model supposed to be better on fuel W/alcohol0 I got from Healey Surgeons....and it is very noisey compared the the old one..but the car doesn't quit on me anymore -:smile:
Click to expand...
The spit and pow can also be the sign of carb(s) too lean. Easy to check. Buy SU carb oil or Marvel Mystery Oil for carb dashpots(go ahead and laugh...but it works and is great for upper end wear!).
 
I believe the shop manual recommends 20W oil. '3-in-1' (sewing machine) oil is 20W. I've used 3-in-1, 20W-50, ATF and SU carb oil and didn't notice much difference.
 
I forgot to mention, when I got my rebuild kit from Joe Curto...he recommended needles 1 size larger due to unleaded/alcohol gas we have to use today, so if anything they should run slightly richer than stock Lee
 
If it doesn't do it when it's hot, it's just a tiny bit weak when cold. Check float heights are correct, butterflies are synchronised and that main jets are 35-38 thou down from the jet bridge.
 
Well, it did it some Monday when I took a 40 mile trip. It was cool outside and the engine was at 165 deg. the whole time. I will double check those settings, but I think they are good as when I rebuilt the carbs and set up everything I took my time (I used the vacuum snchro. tool) I have and use the SU tool kit also. Not sure how to check the fuel level from the bridge, but I know the fuel is slightly below the bridge (otherwise serious flooding occurs :smile:.....Thanks, Lee
 
EV2239 said:
If it doesn't do it when it's hot, it's just a tiny bit weak when cold. Check float heights are correct, butterflies are synchronised and that main jets are 35-38 thou down from the jet bridge.
Click to expand...

That's interesting - my HD8s are set at 90 thou down. Two friends' HD6s are at 55.

Are you using rich needles?
 
Lee wrote:
Not sure how to check the fuel level from the bridge, but I know the fuel is slightly below the bridge (otherwise serious flooding occurs :smile:

You're checking the position of the jet below the bridge with a dial caliper. Not the fuel.
 
Ah...so that is a better way to set the mixture than the method in the manual (lift the pistons slightly and watch for small increase in RPM)? OK, I see, yes I can use my dial caliper to check the level of the jet as compared to the bridge. Anyone else want to chime in on how far down the jets should be???Thanks, Lee
 
rcflyer said:
Ah...so that is a better way to set the mixture than the method in the manual (lift the pistons slightly and watch for small increase in RPM)? OK, I see, yes I can use my dial caliper to check the level of the jet as compared to the bridge. Anyone else want to chime in on how far down the jets should be???Thanks, Lee
Click to expand...

Tune the car using the lifting pin and/or ColorTune etc. Then use a dial caliper to average the jet drop. For example, if one is .060" and the other is .050", set both to .055".

This is the method advocated by APT.
https://www.aptfast.com/
 
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