Some remembrances from when Paul Thompson and I took my car down to Sigma Engineering in Dorset (UK) for a rolling road tune and test. We spent 5 hours (£125!) with this chap who specialised in Holleys. Possibly ten years ago?
If you want to see the set up go to the GTD club website (
www.gtd40club.co.uk) and then click on The Car is The Star (part of the picture gallery section), scroll right down to the photo section and there she be!
We managed 306 rear wheel bhp with the following setup;
Dart 2 cast iron heads
roller rockers
Rhodes hydraulic lifters
TRW forged pistons
10:1 CR (I can't remember the exact figure)
1.75 inch primary cross over exhaust
brand new out the box 650 double pumper
mega cam 280 camshaft
torquer 2 inlet manifold
Accel electronic distributor and coil
one oily rag (used)
This was my very first engine and had initially been timed up by me badly, like constant 57 degrees advanced! Oooops! But still good enough to record my best ever (still best ever) 1/4 mile at Brighton at 12.61secs!
The dymo chap (sorry can't remember his name) was unimpressed by the list of parts above. This engine had been spec'ed by a freind and myself based on his Chevy powered Cobra replica. All these parts in Chevy form on his car worked a real treat and kicked ass. So we thought we would try teh Ford versions. The Dart 2 heads had only just made it to the UK and were quite new back then. But they still weigh as much now as they did back then!
However as a package things really worked well and we acheived the 306 rwbhp.
The carb was straight out the box and from the comments above I am that 1 in 100! We set float levels and that is all I ever done to that carb in all the time I have used it. It is still on the car today. But now on a Ron Earp/Dave Milham spec'ed engine.
We took the the vacuum advance system off the Accel dizzy, which took a little butchering if I remember rightly. Poorer fuel consumption but who notices that in a 40?
Our main problem was with the spark plugs. The raised top pistons and head/valve combo with the plugs we started with had negative clearance. The gap on the plugs used to get hit and squashed shut causing very poor sparking! Reduced lenght plugs and indexing them to avoid fouling eventually solved that problem until I could find an equivalent plug that was the right fit and rating, which I now run all the time.
The driving difference before and after was very different ie much more power.
Anyway that is my experience of dyno testng for what it is worth. I spoke with Paul this morning who may still have the video of the power runs. If he is minded to post it I have no problems with that.
The wheels were 15 inch with Comp TA2 tyres on which actually worked well on the rollers with a very even contact patch. We got them good and hot! All gears were used but I do remember getting quite concerned at the noise and movement of everything whilst the car was stationary. Scary stuff to a dyno virgin.
My only other thought would be that if guys are thinking of doing bench runs and then a rolling road run we should at least get a better idea of transmission loss. I continue to beleive in the loss being about 40 bhp with some variation for heat and friction increases and not a percentage of engine power. Its a lonely corner!
I do fancy putting my current engine on a rolling road but other priorities call. Maybe another day.
Hoping you find the secret to unlock your engine, Fali
Malcolm
