ziptie_engineer wrote:Perry; I've already taken the liberty of doing this and I estimate the internal thread to be circa 13mm, this was the thing that originally prompted me to question why I had 19mm plugs. I haven't had a chance to measure the valve-spring yet, but I'm thinking I might just fit the new shorter plugs I've bought as see if they make a difference. I assume it will be very lumpy/won't start if it doesn't like them.
Chris; I was going to ditch the points as the engine has been a little bit underwhelming (especially from idle) and I've systematically tried to eliminate any potential issues. So far I've fitted a facet fuel pump & regulator, completely overhauled the Holley and fitted new HT leads. These fixes have made it significantly smoother, but there is still a slightly stumble from idle. Hence why it was going to be new plugs and some form of electronic distributor.
Dave; any suggestions? I've apparently got the 'old' style points with a triangular-base. The guy from Accuspark told me the kit is a real pig to fit compared to the later SD1-style kit with the 6mm pin.
Shorter plugs are needed then
Perry Stephenson
MGB GT + Rover V8
9.62 @ 137.37mph
Now looking for 8 seconds with a SBC engine
http://www.youtube.com/watch?v=nVscbPHgue0&list=UUqIlXfSAoiZ--GyG4tfRrjw
Chris; yep the Holley originally was the problem. I fitted a new float and accelerator arm then had it tuned by the local Hot Rod Speedshop is specialise in everything old skool Amerciana engine-wise.... About a 1000 times better. However there is still a little bit of what could be described as "laziness" and he suggested fitting some form of electronic ignition.
Perry; good to know that my original guess was correct then. Just waiting the Champion L92YCs to arrive to see what difference they make. Surely the spark plugs being 5mm longer than required must make a difference! Hopefully they'll arrive today and I'll post feedback tonight. Great first name by the way (same as mine).... The only other one I've met was pushing the trolley's at Tescos (seriously).
Chris; yep the Holley originally was the problem. I fitted a new float and accelerator arm then had it tuned by the local Hot Rod Speedshop is specialise in everything old skool Amerciana engine-wise.... About a 1000 times better. However there is still a little bit of what could be described as "laziness" and he suggested fitting some form of electronic ignition.
Perry; good to know that my original guess was correct then. Just waiting the Champion L92YCs to arrive to see what difference they make. Surely the spark plugs being 5mm longer than required must make a difference! Hopefully they'll arrive today and I'll post feedback tonight. Great first name by the way (same as mine).... The only other one I've met was pushing the trolley's at Tescos (seriously).
Chris; yep the Holley originally was the problem. I fitted a new float and accelerator arm then had it tuned by the local Hot Rod Speedshop is specialise in everything old skool Amerciana engine-wise.... About a 1000 times better. However there is still a little bit of what could be described as "laziness" and he suggested fitting some form of electronic ignition.
Perry; good to know that my original guess was correct then. Just waiting the Champion L92YCs to arrive to see what difference they make. Surely the spark plugs being 5mm longer than required must make a difference! Hopefully they'll arrive today and I'll post feedback tonight. Great first name by the way (same as mine).... The only other one I've met was pushing the trolley's at Tescos (seriously).
Chris; yep the Holley originally was the problem. I fitted a new float and accelerator arm then had it tuned by the local Hot Rod Speedshop is specialise in everything old skool Amerciana engine-wise.... About a 1000 times better. However there is still a little bit of what could be described as "laziness" and he suggested fitting some form of electronic ignition.
Perry; good to know that my original guess was correct then. Just waiting the Champion L92YCs to arrive to see what difference they make. Surely the spark plugs being 5mm longer than required must make a difference! Hopefully they'll arrive today and I'll post feedback tonight. Great first name by the way (same as mine).... The only other one I've met was pushing the trolley's at Tescos (seriously).
Chris; yep the Holley originally was the problem. I fitted a new float and accelerator arm then had it tuned by the local Hot Rod Speedshop is specialise in everything old skool Amerciana engine-wise.... About a 1000 times better. However there is still a little bit of what could be described as "laziness" and he suggested fitting some form of electronic ignition.
Perry; good to know that my original guess was correct then. Just waiting the Champion L92YCs to arrive to see what difference they make. Surely the spark plugs being 5mm longer than required must make a difference! Hopefully they'll arrive today and I'll post feedback tonight. Great first name by the way (same as mine).... The only other one I've met was pushing the trolley's at Tescos (seriously).
Ran my old P6 engine on long and short reach and never noticed any difference.
If its still the original points dizzy I would look at the dizzy being worn out with regard to the ignition curve its providing as being an issue with timing. Any sort of electronic upgrade will not change the timing accuracy and that is more important than extra spark intensity.
I would run it with and without the A/R vac line fitted as the SU and the Holley deliver different signals.
Move the static around between 8 and 16 degrees to test the difference that makes at the low end.
Guys, sorry for the delay in updating this thread- really busy with work.
They are definitely P6 head (double springs the right size etc). I fitted the short plugs and the engine does seem better at high revs, although the old plugs were horrible and pinked so the difference could simply be new plugs. The "stumble" has returned and is getting worse so I suspect it's another float/needle problem..... Back to rebuilding the carb again then!
The pinking in my opinion is because the compression ratio of the P6 engine is too high for todays fuel, some modern engines (bike engines) run with similar CRs but the combustion chamber design of these engines allows for this. You have a few options here, the easy one is backing off the timing but this results in a poor performing engine, the better option would be to pull the heads off and fit composite head gaskets. This would 'knock' the CR down from 10.5:1 to 10:1. You could also fit a composite valley gasket which would hopefully mean that the manifold still fits without any bother. The only other issue is the valve train pre-load, hopefully this would still be within the acceptable range.
Edit, just re-read your post, if your engine no longer pinks with the short plugs then that's great! I think that you have been lucky in that you have managed to remove the long plugs without stripping the threads in the heads.
Thanks: Although what you've said is mostly black-magic to me!
I'm going to get it rolling road tuned at some point and get someone to look at the distributor and Holley again. Although quite frankly at the moment it runs ok(ish) doesn't drink too much fuel or leak too much so I'm happy. It's pointless seeking perfecting with a BW35 dinosaur gearbox fitted anyhow.
I suspect there may be a bit of mild threading as some of the old plugs were quite "rattle-ly" but the new ones seem tight and I gave them plenty of copper slip..... Fingers crossed!
