C&S Evo7 said:
...I would definitely consider RDT. But worry about his possible lack of experience ...
No lack of experience here!
Parksy, Dependant on which cams you go for, the VTC mechanism can either be removed in exchange for a fixed set of adjustable pulleys or you can modift the VTC actuator to limit the cam advance for your application which is the best option. ...since these standard engines can advance the cam upto 25*degrees you may not want that with a much higher duration cam. The VTC mechanism is a wonderful creation, so why not use it! When you can get really high fuel economy an great power + smoothness, then why not.!? If you do use it though make sur eyou check the adjustable cam pulley centerline against the limited VTC actuator centreline as Ive seen it many a time when aftermarket pulley centerlines are not the same as the OEM. Never assume!
The best way to check the clearances on the K-series is for your engine builder to use an adjustable cam pulley on the intake side as well and dial the cam in at the 1mm lift datum‘s with the vtec mechanism locked either by v.high air pressure (this doesn‘t work if you have a lot of miles on the engines! In which case you lock the mechanism mechanically. Along with the use of low pressure valve springs piston to valve clearance can be checked very simply. if you're using a quality DTi (I only use Mitutoyo instruments myself here!) put it in difference mode when you‘re at each 1mm datum (opening/closing) then simply press down on the roller rocker assembly with your index finger until it touches the piston, Then write down the indicated clearance on the DTI. This can be different across the cylinders so it is worth checking on every one. (e.g. bentcrankshafts (seen this on the skyline engines a couple of times!/badly manufactured cams etc.)
There‘s a common misconception that claying an engine is the way to check the piston to valve clearances. This isnt the case, it is an outdated P2V checking method but its real purpose is for RADIAL clearance. I.E. making sure the valve fits into the pocket of the piston, and with oversized valves this is often a minor issue that needs to be addressed. In which case you have a special 'scribe' punch made of an old valve stem machined to a point. With the piston at TDC you make a valve centre-point on top of the piston and then dis-assemble the engine again. Take the pistons to the machine shop, with your valves and specify the radial clearance you require. Bearing in mind that as your valve-guids wear over time you have to have a safety margin slightly exceeding the Honda valve-end-play service limit!
Another element of confusion here is the compression rating of a piston. Pistons don‘t have compression, but engines do. Pistons do however have displacement volumes. The static compression ratio is the result of the displacement of the piston in relation to the deck surface of the engine, the heads combustion chamber volume along with the along with the swept area of cylinder (basically largest volume too smallest volume in the chamber). There is also some finicky details that come into play like the area above the top ring to the crown surface of the piston and the volume this space has. The only accurate way to work-out the compression of an engine is with a burette. So you can literally measure the volume of the heads combustion chamber & the displacement or volume of the pistons dome accurately in order to calculate the static compression. Alot of piston manufactures assume the volume of the heads combustion chamber being stock along with stock valves and a stock spark plug. So there can certainly be a great deal of variation between advertised and actual. Never assume anything with engines as that will be your first mistake. Everything‘s measurable and quantifiable.