24 replies to this topic

[nicklouse]

Losing 60 bhp through the drivetrain? Thats a lot!

 dragging brakes? incorrect tracking?

[Raggedroy]

What timing did you end up with?.  Combination of plugs ( first choice) and advanced timing  .. ( good for power but may be too early for idle)?  300 degree cam is going to be lumpy, was it warm?,, again combination with plugs.  NGK 8s is more in keeping with a NA 'race' motor ( ie sits over 5000rpm all of its life).  Hope you get it sorted. Drive train loss for 120 at flywheel  ,,,maybe down to 85 -80 at the wheels

the timing and plugs are identicle to the setup I was running when I had the single 1 3/4 fitted. It ran sweet like that for years. It ran quite good and without the hunting before the rolling road tune on the twin HS4s. The rolling road tune may not have caused the fault. Any other ideas what it might be?

[Retroman]

I would be using BP7's the BP8 is too cold, make sure they are gapped too.

 

If its hunting its probably a bit lean.

 

Speak to your RR man, you should have a test drive before leaving, then you know you are happy....

 

not spending X amount and leaving with an issue

 

The mixture needs checking / adjusting again

 

AND you need to find where you are loosing all that power in the transmission...

[racingbob]

my old engine gave 73 at fly 61 at wheels. why not ring him ask to be run up again

[Raggedroy]

Im speaking to the rolling road again on Wednesday. If I richen it up the symptoms get less but are still there. Ive been right through the ignition system from new coil, plug leads, borrowed another distributor, tried BP6 plugs, put a permanent 12v to coil. Compression test is still good, I have had the carbs off and put on a new manifold gasket. Im wondering if its dash pot spring problems. When I put my foot to the floor it pulls great. The problem is when it is on steady throttle.

 

Edited by Raggedroy, 06 May 2018 - 05:35 PM.

[carbon]

OP, the compression pressure of 180psi across all cylinders is consistent, but seems to me to be on the low side. But this could be because I am used to seeing results of 195-210psi using the much milder MD266 profile with only 260 degrees of intake duration.

 

Out of interest what compression ratio are you using with your 300 degree cam profile?

[Spider]

OP, the compression pressure of 180psi across all cylinders is consistent, but seems to me to be on the low side. But this could be because I am used to seeing results of 195-210psi using the much milder MD266 profile with only 260 degrees of intake duration.

 

Out of interest what compression ratio are you using with your 300 degree cam profile?

 

I know we've been here before Carbon, however, IMO, 180 psi on a 300 degree Cam to me sounds good to probably too good.

[nicklouse]

 

OP, the compression pressure of 180psi across all cylinders is consistent, but seems to me to be on the low side. But this could be because I am used to seeing results of 195-210psi using the much milder MD266 profile with only 260 degrees of intake duration.

 

Out of interest what compression ratio are you using with your 300 degree cam profile?

 

I know we've been here before Carbon, however, IMO, 180 psi on a 300 degree Cam to me sounds good to probably too good.

 

mmmm interesting i get 225psi on a 290/300 duration cam.

[racingbob]

my 300 duration cam gave 245

[Raggedroy]

Its looking like its running lean in the mid range.