Hi I've just got my engime going after my first rebuild including going from 1600 to 1776. All seems ok and power is up as I'd hoped runs nicely (just done 200 mile round trip to coast) but idle is ropey. Being a pessimist I've decided it might be cam timing cos this is the worst thing it could be . . . I have cam data for the one I installed, it say intake opens at 14.5 degs & lash=0.008". I don't have a degree wheel but calculate pulley is 180 dia so 1 deg = 1.571mm round the wheel so inlet opens 14.9mm before 5 deg idle timing mark. It's nearer 55mm !!! What have I done wrong in the checking or alternatively how would an engine run with the cam a tooth (or 2) out ? Should I be checking timing with 008 lash ? I'm now bricking it with 2 weeks to go before the big trip to Ireland so any help will be great. Cheers !
Nope stock 34 pct-3 so far but the next move is to fit a 32-36 progressive. I wanted to do this upgrade one step at a time. I was expecting the carb to be a bit lacking but thought it would at least get me going.
You Pict carb should be perfect for the job and drive very nicely. Have you checked the choke and the cut-off work and that the idle jet is clear?
Uprated cam will give a lumpier idle, if the cam timing was that far out you wouldn't have made 200mm let alone 200 miles. My money would be with Zed on carb settings, an 11% increase in capacity is going to warrant SOME carb setting changes but a Pict 34 should be plenty for the job with minor tweaks.
Also don't forget that the cam runs at half the crankshaft speed... So 1 full rotation of the crankshaft is only half a rotation of the cam
What make/model is your cam (which I don't think is the problem - your engine would run like sh*te if the cam timing was out).
It's from The Engine Shop. I believe they get their own ground, it's their TES 8 Fast Road Camshaft. Been looking at can grinds generally and none are anywhere near th 14.5 degree inlet opening value most are in the 30s. so perhaps that value is wrong. Anyway it looks to be close to symetrical so I'm going to check the split overlap tonight and if that's near or on TDC I'll sleep easy tonight. Cheers.
Split overlap checked out fine (found a really simple method on the Isky cams site that made it even easier). Down to carbs like you've all suggested but I needed to know - I'm an engineer dammit !
