Hi guys, I've searched the cam timing stuff and can't find a thread that is simple enough for a beginner to timing like myself ... sorry if I ask stupid questions! Timing belt and water pump are due on my 8v GTI Anni soon, and i've aqcuired a PB cylinder head to scavenge bits from to lightly tweak the standard AGG engine. The plan was to use the PB cam and the associated PB followers into the AGG head whilst changing cambelt etc. My question is, how many degrees of advance timing is reliable but also possibly an improvement for an AGG engine with PB cam? The car has a drilled airbox with foam panel filter, a smooth ally intake pipe with oil breather and fuel evap lines removed for 'cleaner' intake air. The exhaust is a temporary mismatch at present but consists of a standard 8v GTI exhaust, but minus a centre box - straight through from the cat to the back-box. I have recently changed the dizzy cap, rotor arm, leads (standard) and coil for new items when i serviced the car on buying it in July. Also I am aware the PB cam will need a 5th cam-bearing grinding into it to be accepted in the later AGG head Hopefully the above info helps anyone with the knowhow to help me on my way please! Thanks, Tom
PB cam is the same as the 2E and 3A. Fitting to an AGG, all things being means equal means 115bhp @ 5400rpm and around 130lbft@2000rpm
As it's a budget mod I'd fit it and time it up to std marks then check the lift @ tdc on inlet and exhaust...If it just happens to be around 12-14 thou advanced on the inlet then leave it there. With the age of these engine's now many have been skimmed at some point so a vernier pulley could be needed to achieve the desired setting.
'the pb head flows better' is a bit of a myth from what I've seen, but even if it was better fitting one in a mk3 gti would be a massive ball ache as the mk3 inlet wont fit. so you would have to use a mk2 inlet and since its an agg you would also have to convert it to take the mk3 motorised throttle body somehow as the mk2 tb is egg shaped not round. some kind of adaptor would be required, probably negate any gains from the mk2 head if there were any. same goes for the cam, even if it was slightly better the messing about required to fit it if you do need to machine it would make it too costly, just get an aftermarket cam of some kind.
Compared to the ADY/AGG? This is shown in the table below. As per engines of that era, what is does have are valves with smaller stems and an exhaust valve that is made smaller, sitting in a seat the same size as a a 2E engine. I have not seen any flow data to be fair on any of the cylinder heads, which is really the remit of someone like Jason. On one of my former vehicles (The 8v MK2), I did a 3A/PB head swap. I have the benefit of swapping from PB to 3A/2E cylinder head on a 3A bottom end and have seem a reduction in performance when the OE 54mm single throttle was used! The only time the performance returned wwith std 3A/2E head fitted, was with the use of an ABF throttle, which has a similar area to the twin throttle. Unfortunately the single throttle was rigged up to work with the Digifant 2 ECUs switches. Mid range punch from 2100rpm-3800rpm was further enhanced with the Megasquirt SEM ECU. It was an awful lot of work to get more out of the hardware. As said by John, if a PB head + manifold is used on a MK3 Golf with a Simos ECU, an adapter will be needed to run a single adaptive throttle module, which by its size of 54mm will only strangle any performance as I indicated above. Your car though!
Aye what we need is proper flow data to know either way. I'm sure I saw some on here but cant remember if there was any 8v data or if it was just 16v...
That would be a good reference yes, however experience suggests the idea from the OP will result in not a lot of progress.
Firstly, thank you very much to all for your input to my query!! it's given more opinions in the 'marginally better : no difference' poll so that's certainly useful to hear. For the sake of a 25 PB head and also that my AGG tappets are pretty musical, i'm inclined to fit the cam for 2 reasons: i wanna get more 'involved' with internal engine tweaking (and replace those tappets/followers) and also i would like to try out my local precision engineers to see if he's got the skills for future projects! Based on your replies, standard timing is what i'll set her to. It's too tame a cam to deserve the full vernier treatment imo :/ I'm not gonna do a dyno comparison unfortunately but i will report back with my opinion on any 'improved torque at 3-4k revs' claims. Thanks again!
Firstly, thank you very much to all for your input to my query!! it's given more opinions in the 'marginally better : no difference' poll so that's certainly useful to hear. For the sake of a 25 PB head and also that my AGG tappets are pretty musical, i'm inclined to fit the cam for 2 reasons: i wanna get more 'involved' with internal engine tweaking (and replace those tappets/followers) and also i would like to try out my local precision engineers to see if he's got the skills for future projects! Based on your replies, standard timing is what i'll set her to. It's too tame a cam to deserve the full vernier treatment imo :/ I'm not gonna do a dyno comparison unfortunately but i will report back with my opinion on any 'improved torque at 3-4k revs' claims. Thanks again!
