2ltr Cambelt Query

[keith m 131]

Hi TAS

I have not fitted the new plugs (NGK BP6RES), and coil ( type listed below) etc yet. I said that if the valves dont make a marked difference then I will change the electrical components one by one and see if the problem is there. Your correct I did mention plug leads but I will some, what type do you recommend?

You say that the valve clearance is not the issue and that may be but since I have the cam box covers off I might aswell change the shims for correct size even just to eliminate something else. And the only reason I am looking at the valves is because I did start looking at the carb first and this is what I found.

I did take the top off the carb (34ADF 54/250) and checked the float dept which is set at 6mm. I replaced the float needle valve, checked all jets were correct and not blocked.
 
I re-checked the idle mixture screw and it is 2 & 1/8 turns out from seated.
The spark plugs are FIAT 1L45J, I got them from a Fiat dealer,  The plugs are a mid brown colour.
The coil is Motaquip RPC-115 BN17 for electronic ignition.
primary idle jet is 50
Secondary idle jet is 90
Primary emulsion tube is F20
Secondary emulsion tube F5
Primary air corrector jet is 170
Secondary air corrector jet is 175
Accelerator pump nozzle is 45

Air filter is a K&N set up. Which I washed and blew through with some low pressure compressed air.

So now you can see why I am stumped as to what is happening or not happening as the case may be. I also checked the inline fuel filters but I will check them again.

So I am not just focused on the complex parts of the engine, as I said I found myself looking there because everything else appears to be ok, but then again something cant ok.

Really appreciate your comments so please keep them comming.

Regards

Keith  

[Tas131]

Yep, while the cam covers are off it's prudent to do the shims. Measure the gaps, the shims you've got, and work out what size shims you require. You can usually mix and match some of the shims you've got, so you only have to buy a couple of shims, or if the planets align correctly, none.
Once you've exhausted all your options, if you're still not happy with the performance and you're still scratching your head, it might be worth throwing it on a rolling road and getting some data of what it's doing in real time.

[mirafioriman]

Thinking outside the box here:

1) Is the speedo accurate ie are you doing just 80 MPH or are you actually doing more (even if the speedo is at the 10% legal limit for inaccuracy you could theoretically be doing 88 MPH)

2) What's going on with the gearing. Is it possible for the engine to pull more than 4000 rpm in 5th with the current gearing? What happens when you go flat out in third and fourth gears? Does it rev to the redline in these lower gears?

[keith m 131]

Hi chaps,

Mirafioriman,...I checked the speedo against my sat nav and with the speedo reading 82 the sat nav read 79, so not much difference there.

All running gear is from the same standard car so no alterations to gear ratios etc to gearbox or diff.

I have taken it to 5000 rpm from 2nd through to 5th gear up to just past 80. What do you mean by redlining it? What rpm does that mean? It is not running at the mo, I will be doing the shims tomorrow so after that I can carry out any road tests you recommend.

Tas131.....I was thinking about going on a rolling road but wanted to try and sort out all the obvious possibilities before doing that. A Rolling road can be quite expensive.

Hopefully over the next few days and with the help of you all on here we can get to the bottom of this.

Thanks again

Keith

PS. David that is a super collection of cars you have there.

[Tas131]

5th gear is an overdrive, I've read old magazine write ups that state 4th is better for top speed. Revving to 6k/rpm through the gears occasionally hasn't hurt my car over the years. It would be interesting to see what speed your car will pull in 4th gear.

[david]

You can rev the bollocks of these engines as long as they are properly mantained theres no problem as they are bullet proof.
The only time I knew of one of these failing was when it was being red lined in the wet and the driver went through a large puddle and spun up the rear and the revs went stratospheric and a valve broke and mashed the cylinder but this was a badly maintained car (no oil changes) and wouldn't have happened if he had dropped the revs a bit in the wet.

[keith m 131]

Thanks for that David, you've filled me with confidence.

I ordered new shims but wont get them for 10 days so cant do any road testing before then. So if I go quiet for a few days that will be why. I will be back on here when engine is running again.

Thanks guys

Regards

keith

[jasonh131]

shove a cable up the rear exhaust pipe ,i used a clutch cable . i had a pattern  back box on one 131 it  had a restricter plate in the middle of the box ? now i can get the cable 5 feet up the pipe .

[keith m 131]

Hi Jason,

Thanks for the tip I will try that tomorrow.

regards

keith

[Thotos]

• With your foot to the floor, the car gets up to 80mph and won't go any faster
  
• The car gets to 80mph in under 20 seconds
  
• At 80mph the rev counter is showing 4000rpm
  
• There's no misfiring; the car runs fine but won't go above 80mph
  

Thotos.... thats exactly right, everything as you say but stumped at 80mph

Here's my bit of thinking out loud....

It's not the shims (as most people said) since the gaps are good enough. In fact it isn't anything that will cause loss of power as the car gets to 80mph in under 20 seconds. As Dave suggested, it would be good to know if the car can actually rev to 6000rpm in lower gears (first, second, third). But it revs to 5000rpm so it's not cam timing or the cams. And it's not fuel starvation or carburettor problem if it revs beyond 4000rpm in lower gears; plus there's no loss in power.  And it's not a gearing problem as it's doing 4000rpm at 80mph in top. Like Dave, I too was thinking the speedo might be lying but the 80mph speed has been verified by Sat Nav and the rev counter. It's not a weak spark or ignition problem as that would cause misfiring. So there's only one possible reason for this problem: The engine's got the hump because it's in the wrong car!  These twin cams have feelings you know.... 

[david]

I think you cracked it there    I once knew someone who put a fiat 1800 twin cam in a mk4 cortina ! (sacrilege)  and they couldn't get it to run right, needless to say I wouldn't have anything to do with it and felt sorry for the engine.

[keith m 131]

Hi Guys

I believe the engine has got a mind of its own, Theo. And you know what it is so bloody ungrateful because I could have let it go to the scrap yard but chose to save it and this is how it repays me.

I took the shims to my local engineering company and they reduced the thickness so didnt have to wait 10 days for new ones. Busy today so tomorrow I will get her (him) not sure what to call it anymore in case it gets offended) running and do some more checks as recommended on here and then I can do some road tests and report my findings.

Theo, I havnt replaced the electrics yet, I will replace them one by one in the next few days to try and determine what is causing the problem, that way if I find the fault I will know what is was for futuer reference.

Thanks Guys

Keith

[124AC]

Hi Keith

Just a thought................

This engine was designed to live on proper 5* petrol.  I have a 124AC and that used to love decent fuel!  The later models were designed to run on 4*, with only the latest setup for unleaded.

Unleaded fuel has nothing to slow the burn and therefore ignites and burns faster.  For this reason many 80s car models had adjustments to allow a change between leaded and unleaded.  All injected Vauxhalls had a reversible plug under the bonnet.

A common problem back in the day was to run a car on unleaded without adjustment.  In extreme cases the car can run lumpy at idle, then exhibit limited power at higher advance.

Try setting the static at 5 degrees and adjust the idle mixture to match.

Take the car for a run and see how it revs in each gear.  Listen carefully and see how the engine revs.  Beyond 3/4 throttle it should come alive as the second barrel opens.


Also, do you have points or electronic?

Wrong points gap can limit spark at higher revs.


Thanks
Duncan

[keith m 131]

Hi Duncan,

I will try setting the static timing at 5* BTDC and see what happens. I have ordered a new set of HT leads so should get them tomorrow and then I can try some of the things recommended on here by yourself and others and report back.

I have electronic ignition.

Regards

keith

Edit: Jason I can get the length of the clutch cable in through the rear box. It needs a bit of jiggling but it will go through.