Tatton and New Engine Start

[RichDyne]

Thanks for the advice Pete - will let you know how it went on Thursday evening.

Hose pipe at the ready - radiator pointing out the front of the garage!!

[RichDyne]

Diagnosis???

The engine got through the cam break in today without any major problems at all. Did not even overheat so was very happy.

Only problem we noticed is a loud "blatting" noise (for want of a better word) on one of the banks ( right hand bank as seen from cockpit). The noise is internal and it only when the engine is on load / acceleration. It almost sounds like one of the bores is not firing right!?!

Generally she feels powerful and smooth however this noise is worrying. One thought came to mind that it could simply be the new cam and because of the higher profile I may just not be used to that type of sound. We spent most of the day playing with the timing however no adjustment makes it go away. We finally returned it to static timing std settings (6 deg BTDC).

In addition we disconnected the accelerator pump (Edelbrock 500) as even on its leanest setting it was pumping too much fuel in on acceleration (black smoke). If I am right all this is for is to help the carb transition from the idle circuit to the primary circuit. Without the pump she seems to transition very smoothly already so assume no problem disconnecting.

Any idea on what this noise could be (am worried it is something more serious than timing, but am hoping its normal)

MOT in the morning so hope its not a reason to fail it otherwise I wont be at the Tatton show in Sat/Sun.

Thanks
Rich

[RichDyne]

Forgot to mention - I did check all the plugs for spark etc and its all ok so I dont think its missfiring on one cylinder...

[Sidecarbod]

Originally Posted by RichDyne

Diagnosis???

The engine got through the cam break in today without any major problems at all. Did not even overheat so was very happy.

Only problem we noticed is a loud "blatting" noise (for want of a better word) on one of the banks ( right hand bank as seen from cockpit). The noise is internal and it only when the engine is on load / acceleration. It almost sounds like one of the bores is not firing right!?!

Generally she feels powerful and smooth however this noise is worrying. One thought came to mind that it could simply be the new cam and because of the higher profile I may just not be used to that type of sound. We spent most of the day playing with the timing however no adjustment makes it go away. We finally returned it to static timing std settings (6 deg BTDC).

In addition we disconnected the accelerator pump (Edelbrock 500) as even on its leanest setting it was pumping too much fuel in on acceleration (black smoke). If I am right all this is for is to help the carb transition from the idle circuit to the primary circuit. Without the pump she seems to transition very smoothly already so assume no problem disconnecting.

Any idea on what this noise could be (am worried it is something more serious than timing, but am hoping its normal)

MOT in the morning so hope its not a reason to fail it otherwise I wont be at the Tatton show in Sat/Sun.

Thanks
Rich

Hi Rich,

The noise does sound a bit worrying but then I do tend to look on the gloomy side of things! It comes from my racing past, nothing was a simple, cheap fix! Rover lumps on the other hand can often give you a nice surprise!

Its not that you've messed up the HT leads is it?

The black smoke is bad and normal for a 500 carb on the standard settings. Assuming that the fuel pressure is not too high then you can lean out the mixture by fitting the 67x55 needles but you'll need to get hold of them ASAP. Also check the pilot screws, I've found that around 1+3/4 (or maybe 1/8 more) is OK on a standard 3.5 lump. My old 3.5 running a typhoon cam needed them open alot more but the bores were knackered hence no vaccum.

You could open them say 3 turns (if it slows at three turns try 2.5) then slowly wind each one in until the engine just starts to slow down, open the screw up 1/4 turn from that. Do the same with the other then kill the motor and wind both in make a note of the number of turns, then reset them (If they are not quite the same for each I usually just even them up so that I only have one number to write down!) This method is a little rough but it will get your A/F ratio around 13.5:1 which is more than clean enough for the MOT.


What cam have you got in the lump?

Regards,

Pete

[Sidecarbod]

I see you've got a hurricane. There is not supposed to be any issues with sticking one of them into a standard lump so as long as you timed it up OK its not going to be a valve hitting the valve guide or piston issue. (which is nice!)

Pete

Edit....Its not a leaking header is it? that could "blat" when you put the ngine under load but be OK-ish under no load

[RichDyne]

Thanks Pete - will double check the leads but am sure they are correct.

Have cyl one next to the distributor then running on the left hand back (as seen from cockpit) 1,3,5,7 and on the other 2,4,6,8. HT leads are set up in same firing order as per the Haynes manual for the SD1.

I think I have the idle screws at about 1.75 turns - will follow your guidance in the morning to get a little bit closer to reality.

For the cam the rockers were shimmed to get preload clearance to 40 thou by the engine builder so don't think that is the problem.

What spark plugs do you use? I have NGK BP5E (and a 6ES that needs changing).

Will see what the guys think at the MOT station (Paul Sheards in Congleton race MX5's in their spare time and am sure they have experience with RV8s as its a relatively normal conversion for am MX5.

[RichDyne]

hmm - I thought I got the headers nice and tight (as tough as that is with so little space) but will double check those in the morning.

[Sidecarbod]

Originally Posted by RichDyne

Thanks Pete - will double check the leads but am sure they are correct.

Have cyl one next to the distributor then running on the left hand back (as seen from cockpit) 1,3,5,7 and on the other 2,4,6,8. HT leads are set up in same firing order as per the Haynes manual for the SD1.

I think I have the idle screws at about 1.75 turns - will follow your guidance in the morning to get a little bit closer to reality.

For the cam the rockers were shimmed to get preload clearance to 40 thou by the engine builder so don't think that is the problem.

What spark plugs do you use? I have NGK BP5E (and a 6ES that needs changing).

Will see what the guys think at the MOT station (Paul Sheards in Congleton race MX5's in their spare time and am sure they have experience with RV8s as its a relatively normal conversion for am MX5.

I think my plugs are 5's or 6's can't quite rememeber! Either will be OK at this stage, in fact 5's may help with all that fuel that the carb is dumping into the bores. Make sure that they are the correct reach though, if your running an SD1 then they won't be too long but too short is no good either!

Shims are OK-ish and 40 thou is OK, its what Real Steel recommend. 20 thou is better at high revs (over 5.5 K rpm) but you'll have a job getting them all at that with shims. Adjustable pushrods are better as the valve train geometry gets a bit messed up with shims. (Don't worry though loads of people run with shims and for the mileage that our cars do it probably makes sod all difference!)

let us know how it goes at the MOT.

Pete

[Sidecarbod]

Originally Posted by RichDyne

hmm - I thought I got the headers nice and tight (as tough as that is with so little space) but will double check those in the morning.

They could be tight as you like but if they're warped they'll blow like a prossie on a Friday night!

[RichDyne]

LMAO - They seemed ok before the we took the engine out so don't expect anything to have happened. To be honest it sounds more internal than air moving.

Something went through my head before (rare but it does happen now and again). Could it be possible that such a noise would come about from a hydraulic tapet not being filled correctly with oil? If it is how could I check this - I assume its possible to move a push rod with the rocker off......

Might whip a rocker cover off in the morning and check if there is something obviously wrong going on.

Cheers Pete.
Rich