8v Cam/Piston Query

19th March 2010, 17:25

Before we begin if all your going to say is 16v it then I'm glad to say GTFO of this thread... gracias (The same goes if you have nothing constructive...

I've been meaning to ask this a while back but anyways.....

Ok, so I'm now collecting parts for my build which to cut a long story short is a throttle bodied 8v. And I've hit my dilemma, a while back I posted in the Cams thread looking for some advice but I'm after a little bit more so to speak....

Originally I was going to settle for some PH3's which are the following spec:

Clearance [cl] INLET 0.008 / 0.203 EXHAUST: 0.010 / 0.254
Duration [1.0mm + cl] INLET: 270, EXHAUST: 270
Valve Lift [cl=0] INLET 0.415 / 10.53 EXHAUST: 0.411 / 10.44
Cam Lift INLET 0.237 / 6.02 EXHAUST: 0.235 / 5.96
Timing [1.0mm + cl] INLET: 25-65 EXHAUST: 65-25
Lift at TDC [cl=0] INLET: 110 EXHAUST: 110

But I was swiftly moved away from these thanks to LeeumH (irrc) as in the silvertop engine these are not wild enough for bodies. I was then recommended these Kent PT41 cams which are the below spec:

Power Band - 2500-7000
Cam Lift(mm) - 7.03
Valve Lift(mm) - 12.03
Duration - 292 Deg
Timing - 38/74 80/32
Full Lift - 108 Deg
VC (mm) - 0.25
LTDC - I 3.05mm

Ok so here is were I'm struggling as I cant seem to find a spec sheet of the standard cam to try work out my clearances etc. So if anyone can shed some light I would be greatly appreciated.

As I have a feeling that the PT41 cams will require forged components, either cam I will fit new piper valve springs and caps as it is a silvertop afterall...

But.... If I do have to go forged I have found to potential options either:

These

Or..

These But I was wondering if these would fit as they are actually for a 1.6 xsi 8v?!?

So yes if anyone can be of any assistance it would be greatly appreciated..

19th March 2010, 17:55

8v engine needs dif pistons than the ones you are looking at ,also to get any serious lift you will need forged pistons with deep cut outs ,that brings another problem ,if building a high power 8v you don,t want to be using silver top rods ,or rocker gear .
ring me when you know excatly what power you want--bear in mind a highly cameed 8v will NEVER pass REAL mot

19th March 2010, 21:43

Will do

thanks for the reply and how comes the piston will not be adequate? As they are for the engine its just the pictures is a representation not the real thing...

Also are you a Piper cams dealer as I was thinking of purchasing the springs and caps from yourself.. But I will give you a call at some stage next week if you don't mind to run through a couple of things....

Oh and to be honest I'm not pushing for high power I just want a pleasurable daily driver which can be used on the occasional track day as you may know power isn't necessary to have fun, but I'd rather run a bit of a wilder cam if it's a tad more beneficial.

19th March 2010, 21:59

Sorry for the hijack but why wont a high power 8v pass a mot? Would a 16v with a similar spec pass? Im guessing its down to emissions but surely A 16v would be the same, If not worse?

19th March 2010, 22:05

Any highly cammed car will struggle to pass iirc.?

19th March 2010, 22:18

Yeah thats what I thought lol. I just wondered why he said I highly cammed 8v wont pass rather than a highly cammed car. Thought I was missing something lol.

19th March 2010, 22:23

Lol it could have been misleading but I think he was just referring to this example....

20th March 2010, 19:40

BUMP can do with some help guys...

20th March 2010, 19:44

Quote:

Originally Posted by SaxoMuffin

Any highly cammed car will struggle to pass iirc.?

Yes, I suppose the difference with this is that a cammed and bodied vts (eg with 708s) can be made to go through emissions, whereas the same power 8v would almost certainly not I'd imagine.

20th March 2010, 20:38

I always found a pre cat block on the logbook and pulling a single injector plug off would tend to get you past.

20th March 2010, 22:38

16v engines for run less duration than 8v,s as they have more valve area ,therfore there is less overlap .
anything over a 285 cam on an 8v has no chance of a REAL mot pass .
why is everything I post challenged --fi you don,t think i know what i,m on about ,
just ignore my reply

I,ve been tuning these TU engines since 1990--

20th March 2010, 22:51

MOT's and emissions are not a problem, just want to get the parts sorted....

Do you think it may be worth just running a PH3 cam then for safety on the engine?

As like I've said I'm not pushing for figures... just something fun and fruity to drive

20th March 2010, 23:39

Quote:

Originally Posted by axsaxoman

why is everything I post challenged --fi you don,t think i know what i,m on about ,

I don't think any one had this time John. Well apart from me now I guess

I think most of the posts were people were just genially interested in what you had to say and wanted to know more. My post was agreeing with you as an example of the extent you may have to go to if you have to pass at all on a gass test with a wilder cam in a 8v. As you point out running on 3 is bending the regs some what and you have had it if you get a road side test.

20th March 2010, 23:43

Fitting a Newman PH3 with a closer ratio gearbox to compliment should be a fairly fun setup imo.

21st March 2010, 00:40

Sorry if it came across that I was challenging your knowlege, I was genuinely interested on the subject.

21st March 2010, 00:57

Quote:

Originally Posted by axsaxoman

16v engines for run less duration than 8v,s as they have more valve area ,therfore there is less overlap .
anything over a 285 cam on an 8v has no chance of a REAL mot pass .
why is everything I post challenged --fi you don,t think i know what i,m on about ,
just ignore my reply

I,ve been tuning these TU engines since 1990--

I think people are mainly intrigued as to why, not questioning your knowledge.

21st March 2010, 08:53

maybe its me getting old +cranky --but as i have been tuning cars +running my own biz for 50 years and physics has not changed --only the technology to control things better has changed + the ability to measure the results ,