Is my bargain 'Hot' cam actually just a standard one?

[PersonaGrata]

I think I might have been 'sold a pup' but don't have the experience to know for sure..

I bought a pair of secondhand cams for my Mitsi/Proton 4G93 DOHC which were advertised as RPW 'Stage 2' billet cams out of a Mitsibushi Colt Gti. The bloke I bought them off bought them for a song himself (£80) but didn't use them because he went turbo instead of NA. He wouldn't sell them for less than £150 though, but I still thought that a bit of a bargain since they are £600 new. They came with a set of modified lifters to replace the hydraulic ones that come as standard.

This fella seemed like a trustworthy sort and often trades bits on the Proton forum without any obvious 'comeback'. I really want to build a quick engine but couldn't afford to spend hundreds on ones with obvious and reliable lineage - so I decided to take a risk. To this day I don't believe that the seller thought that these cams were anything other than genuine.

However, given that the vital statistics and provenance of these cams were uncertain I decided to measure them. I used a dial gauge with the probe normal to the axis of the cam and rotated the cams by hand taking measurements as I went. The slightly fat nose of the probe is going to give an apparent width to the profiles (and longer duration I guess) than they dont actually have. However since this was more for comparison, and that both profiles would be affected equally, I thought it unimportant.

There will be some error on the rotational intervals.

Here is the plot for the inlet lobes.

InletProfiles.jpg (59.77 KiB) Viewed 5997 times

And here is the plot for the exhaust lobes

ExhProfs.jpg (63.3 KiB) Viewed 5997 times

There isn't a great deal of difference that I can see unless the difference between standard and 'hot' is much subtler than my slightly crude measurements would spot.

RPW themselves state that cams with profiles beyond Stage 1 have increases in both duration and lift. There may be a slight difference in lift on the exhaust lobes but there is certainly none on the inlets.

Finally, both the 'hot' and standard cams use the same format of serial number stamped in exactly the same places.

You will probably know instantly Guy. Are these cams standard?

Regards
Iain McLean

[Guy Croft]

The clue here is the serial number. Notwithstanding your careful plots the easiest way to determine the state of the cams is to put them between vee blocks and measure the cam peak lift standard vs 'other'. Also measure the distance from the base circle to the bearings. Record this in a data table.

It is remotely possible that factory raw billets have been used and a billet profile of non-OE origin ground on to them. More likely (?) is they've been reprofiled. In either case you will see more lift and if reprofiled this will have been achieved by grinding the base circle of a std prodn cam smaller.

Another indicator is to put the cams in the head with valve and measure the valve open/close position with a protactor and compare with standard. You need to have the follower in place because point lift with a dti will differ markedly from that with cam against a flat follower. You can overlay the two cam types with, say, IVO in the same place - the position of FL is unimportant, you're just looking for a difference in nominal duration (ie: not allowing for running clearance).

Somemore work to do perhaps but hope this helps some,

GC

[PersonaGrata]

Thanks for your reply Guy,
Could I just clear up a couple of points??

If I understand you correctly, we cannot tell what the difference is simply by plotting one DTI plot over the other (the diagrams in the first post show both standard against 'RPW', one line is blue and the other red, and there is so little difference visible just from a strictly visual assessment). The only way to actually understand what the difference is is by working out the angles where the valves open and close. Is that correct?

In order to do this the valve train needs to be fitted including the fulcrum (I don't know what engine term to use here - 'lifter', 'bucket'?? its the fulcrum of the pivot system formed by the follower, cam etc). In the 4G93 this is a hydraulic item and so will subject to some variability in operation. If we want to understand the differences between the cams then we need the fulcrum height to be a constant. Is that correct also?

RPW cams are always billet so the base circle is always a 30mm diameter so we cannot tell from comparison of this attribute alone unfortunately.

You will have to forgive my ignorance here but could you tell me what the acronyms are - FL, IVO? I could guess at Full Lift for FL and Initial Valve Opening for IVO??

Thanks again

[Guy Croft]

Ooops.

I'm awfully sorry - the profiles as plotted (blue and red) are so close together until now I did not realise the plots are actually the overlays we need. I really I should take more time over these things.

Looking again - and given the care you've taken to do the plots - it's clear the 'new cams' no different from the old ones. There would be a very marked difference in the profiles if any additional, er 'performance' was built into them, would show up very visibly in nose profile.

Kind of you to read my post in rather more detail than I read (studied?) yours!

GC

[PersonaGrata]

No problem Guy, you're very busy.

So, I've just got to confirm the serial numbers with RPW then it looks like I've got a bit of a problem to deal with.

Oh well. Such is life.

[Guy Croft]

If you want supporting evidence send them to Kent Cams and ask for them to be mapped.

GC

[PersonaGrata]

<From RPW> They would definitly be fake then as our units don't have any numbers like that marked on them. They would have markings on the back of the cams inscribed like S2T being stage 2 Turbo etc.

----- Original Message -----
From: Iain McLean
To: rpwinfo@iinet.net.au
Cc: Iain McLean
Sent: Tuesday, January 19, 2010 6:31 AM
Subject: FAKE RPW Camshafts


Hello there,
I would really, really appreciate it if you could just take a moment to confirm something I have suspected for some weeks now.

I bought some cams that were supposedly RPW Stage -2 cams for the 4G93.

I'm pretty sure they are fakes as I've mapped them out with a Dial Test Indicator against standard and can see no difference.

The serial numbers are identical in format and position to the standard ones and differ only in the actual number. They are:

208311432 E
208312300 E

Was I right to be suspicious?

Many thanks in anticpation.
Regards
Iain McLean
Lancashire
England.

The cams did turn out to be fakes. See quoted text above lifted from an email reply from RPW

They say that late January is the most miserable time of year - certainly proving true for me right now.

[Guy Croft]

Yup. It's the way it is now and well done to RPW for replying.

Provenance and 'traceability' is EVERYTHING these days when so many purport to be 'specialist' or 'expert'.

I insist on absolute traceability for all my parts, whether OE or competition and go to great lengths to assure that I will get exactly what it says 'on the box' before I buy.

Well done for checking your parts and finding out the truth.

GC