21 replies to this topic

[Dave33]

ok looks like im joining the club aswell then,lol!
After rebuilding my 1380 i have the same prob,anything below 2500rpm on a part or closed throttle and it judders,if you accelerate its fine.
have tried different timing and advancing and retarding cam timing all to no avail.
The only thing that helps a bit(it doesnt go away completely) is leaning the mixture off,but then it hasnt got the go it had.
The only couple of things i changed spec wise was 1.5 rockers,and light steel flywheel and backplate,along with new bearings and pistons etc.
Spec is
1380
A series
longman fast road/rally head(standard size valves)
1.5 roller tip rockers
Aldon AY100 vaccum dizzy(running points)
BP8ES plugs
10.5/1 compression
kent 286 scatter cam
stage 2 maniflow lcb
Rc40
mk2 metro rad,thermostat blanking sleeve(water temp 75)
Hif44,k and n filter,mg metro inlet(carb and manny modded to vizard spec)
3.2 to 1 FD
It never did this before,but whereas it used to make power from 2000 to 5500 it now is 2500 to 7000rpm.
Am running on super unleaded with redline lead additive.
Bit of a mystery,i put it down to the cam spec and 1.5 rockers but seeing as others have this prob on a fairly standard motor im not too sure.
Be good to know what it is.
dave

[Pigeonto]

[quote name='Dave33' date='Jul 23 2010, 11:05 PM' post='1889285']
ok looks like im joining the club aswell then,lol!
Thanks a bunch 33!! I have ordered pistons etc for my rebuild(not saying which capacity it will be as Cooperman will tell me off,but big).Now I'm really concerned as I may just have a bigger engine with same prob.SOMEONE must have the answer.I posted this prob on "ask Doddy" a few weeks back but got no where too.Not having association with any racers( would love to have a go-anyone??) I wondered if they suffer this but keep above 3000 so it doesnt matter and that was what I asked Doddy but he didnt pick up on that part.I wondered if the carb piston was jumping around and tried a thick oil,guess what, no.Do SUs draw in a rich mix on deceleration caused by the big vaccuum made which may pull fuel out of the jet?no idea but my std engine didnt so probably not that.Perhaps I'll try a Webber.Not really,but I will be putting on twin HS 2s to try.Off to work now.

[Pauly]

Wow, think ive opened up a can of worms here .

Will be poping round bud666's today, so we can have a faf.

[Carlzilla]

No last minute decisions either paul!

[Pigeonto]

Wow, think ive opened up a can of worms here .

Will be poping round bud666's today, so we can have a faf.

OK, I've decided to open up this can of worms again. If any of the members who responded are on,did you resolve this??And of course anyone reading who didnt see all this last time. I was building my replacement engine at that time and its now in.And of course absolutely no different. So there must be a common link.I tried different head,carb,cam at the time and now I have to wonder what has been transferred to this build which was on the last one.One thought being the vernier set and double chain. I am now questioning the timing chain-as I have asked on here before- ref the tensioner.You cant use one reliably with a duplex set up and this means a fair amount of slack.So I'm wondering if the chain flaps about at lower RPM and causes this??I dont bother with double or heavy valve springs and have no issues at high revs so I'm going to try the simplex set up with tensioner. Any thoughts?

[Mr Joshua]

When you rev the engine does the ignition light come on very dull? If so its the loom from the ignion barrel down to the connector causing your woes.

This is not a hard and fast check but when the engine is running does the wires leading to the ignition barrel get warm if so then the above stands.

Mine would do it below 1200rpm engine was trying to kick its way out of the engine bay.

Edited by Mr Joshua, 06 September 2010 - 02:03 PM.

[Pigeonto]

When you rev the engine does the ignition light come on very dull? If so its the loom from the ignion barrel down to the connector causing your woes.

This is not a hard and fast check but when the engine is running does the wires leading to the ignition barrel get warm if so then the above stands.

Mine would do it below 1200rpm engine was trying to kick its way out of the engine bay.

Mine tries to get out of engine bay too. Really hard to drive in traffic. Just seen this and now off again. I will certainly try all suggestions. No to the ignition light though.Timing chain still foremost in my mind,specially as it is now noisy( done only 3000m, kept it to pre-empt the situation of it wearing-in and retarding the cam timing)Of course if it did flap about,cam AND ign timing are affected I just realised......Any of the original post(ers) sorted theirs out?