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Author Subject: Kent PT81 cams
braymond

Seasoned Pro

Location: Brighton

Registered: 20 Aug 2008

Posts: 1,163

Status: Offline
Post #1
I have done a search on this, before anyone starts peeling back the lid on a can of woopass...

Couple of questions -
1- I understand that this is the most 'agressive' cam you can get BEFORE you need to machine pockets into the pistons. this is correct yes? But it sounds like this carries with it risks becasue of the tight tollerance. Is there a risk, and if so, a risk of what?

2- other than an ECU remap, is there anything else that would need to be done/modified to run this setup?

________________________________________

Rallye-R

Nurburgring article
Posted 19th Oct 2009 at 16:52
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daveyboy

aka Jim Davey

Location: Southampton

Registered: 01 Oct 2007

Posts: 8,648

Status: Offline
Post #2
braymond wrote:
I have done a search on this, before anyone starts peeling back the lid on a can of woopass...

Couple of questions -
1- I understand that this is the most 'agressive' cam you can get BEFORE you need to machine pockets into the pistons. this is correct yes? But it sounds like this carries with it risks becasue of the tight tollerance. Is there a risk, and if so, a risk of what?

2- other than an ECU remap, is there anything else that would need to be done/modified to run this setup?


The major risk is that without verniers it is difficult to get the cams timed exactly in relation to the crank, this coupled to the minimal clearance (even more minimal if the head has had a skim in the past) leaves you vulnerable to valves colliding with the piston.

Many on here will say you can run these milder cams without detriment on the original map and it was discussed quite heatedley at the time. Trusted opinion however would suggest the original ECU will run rich at low rpm (bore wear issues later on) and lean up top (again not really very healthy) but if set properly and clearances are there and checked these can be run successfuly with no modifications to the engine and a remap is reccommended.

________________________________________

R H Davey Welding Supplies. I sell new and used welding equipment in the Hampshire area. I take on welding jobs in the evenings, ally casting repairs are one of my specialities but I can weld pretty much anything. PM me with your requirements.

Some of my services: (See my for sale threads)
Engine mount/chassis repair
Solid Beam Mounts BACK IN PRODUCTION
Harness bars
Posted 19th Oct 2009 at 17:16
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ryangti6

Seasoned Pro

Location: Pontypool

Registered: 01 Sep 2006

Posts: 1,839

Status: Offline
Post #3
braymond wrote:
I have done a search on this, before anyone starts peeling back the lid on a can of woopass...

Couple of questions -
1- I understand that this is the most 'agressive' cam you can get BEFORE you need to machine pockets into the pistons. this is correct yes? But it sounds like this carries with it risks becasue of the tight tollerance. Is there a risk, and if so, a risk of what?

2- other than an ECU remap, is there anything else that would need to be done/modified to run this setup?


Hi,

I've been looking into cams recently and from what I have seen yes there is a risk with them. This seems to be down to different peoples opinions though as some say they are fine but others say they are only fine if they are fitted without going for max lift.

You need to watch the max lift on the cam at Tdc, on these engines valve-piston clearance is close as standard so if set incorrectly you could see valve-piston contact.

Tbh though, if they are dialled in correctly it should be fine.

________________________________________

Ryan
Posted 19th Oct 2009 at 17:19
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braymond

Seasoned Pro

Location: Brighton

Registered: 20 Aug 2008

Posts: 1,163

Status: Offline
Post #4
Thanks for your replies


daveyboy wrote:


The major risk is that without verniers it is difficult to get the cams timed exactly in relation to the crank, this coupled to the minimal clearance (even more minimal if the head has had a skim in the past) leaves you vulnerable to valves colliding with the piston.



Mine has been skimmed twice (to my knowledge) so would that put me even more in the 'danger zone' Shock
If so, would you recommend a different cam? I dont really want to go through the palava of changing the cams for a bearly discernable gain in performance, but equally im not fully sold on the idea of getting involved in machine the pistons... Hmm

________________________________________

Rallye-R

Nurburgring article
Posted 19th Oct 2009 at 18:58
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daveyboy

aka Jim Davey

Location: Southampton

Registered: 01 Oct 2007

Posts: 8,648

Status: Offline
Post #5
braymond wrote:
Thanks for your replies


daveyboy wrote:


The major risk is that without verniers it is difficult to get the cams timed exactly in relation to the crank, this coupled to the minimal clearance (even more minimal if the head has had a skim in the past) leaves you vulnerable to valves colliding with the piston.



Mine has been skimmed twice (to my knowledge) so would that put me even more in the 'danger zone' Shock
If so, would you recommend a different cam? I dont really want to go through the palava of changing the cams for a bearly discernable gain in performance, but equally im not fully sold on the idea of getting involved in machine the pistons... Hmm


Problem is you may not have the clearance now to fit the PT81s, for every fraction of a mm you take off the head, you obviously bring the valve that much closer to the top of the piston. If you have had 2 skims you are on very dodgy ground. Looks like maybe some deeper pockets on the pistons will be in order. It may be more cost effective to go for big pockets and a lairier cam (PT82) to make this worthwile for the effort/money versus the relatively small gain you would get from the PT81s.

________________________________________

R H Davey Welding Supplies. I sell new and used welding equipment in the Hampshire area. I take on welding jobs in the evenings, ally casting repairs are one of my specialities but I can weld pretty much anything. PM me with your requirements.

Some of my services: (See my for sale threads)
Engine mount/chassis repair
Solid Beam Mounts BACK IN PRODUCTION
Harness bars
Posted 19th Oct 2009 at 19:09
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braymond

Seasoned Pro

Location: Brighton

Registered: 20 Aug 2008

Posts: 1,163

Status: Offline
Post #6
daveyboy wrote:


Problem is you may not have the clearance now to fit the PT81s, for every fraction of a mm you take off the head, you obviously bring the valve that much closer to the top of the piston. If you have had 2 skims you are on very dodgy ground. Looks like maybe some deeper pockets on the pistons will be in order. It may be more cost effective to go for big pockets and a lairier cam (PT82) to make this worthwile for the effort/money versus the relatively small gain you would get from the PT81s.


You make a good point. Which leads me to another question - Am I being foolhardy to consider putting any aftermarket cams into and 94k engine, whatever their profile?? would this be a recipe for a premature disaster??

________________________________________

Rallye-R

Nurburgring article
Posted 19th Oct 2009 at 19:32
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daveyboy

aka Jim Davey

Location: Southampton

Registered: 01 Oct 2007

Posts: 8,648

Status: Offline
Post #7
braymond wrote:
daveyboy wrote:


Problem is you may not have the clearance now to fit the PT81s, for every fraction of a mm you take off the head, you obviously bring the valve that much closer to the top of the piston. If you have had 2 skims you are on very dodgy ground. Looks like maybe some deeper pockets on the pistons will be in order. It may be more cost effective to go for big pockets and a lairier cam (PT82) to make this worthwile for the effort/money versus the relatively small gain you would get from the PT81s.


You make a good point. Which leads me to another question - Am I being foolhardy to consider putting any aftermarket cams into and 94k engine, whatever their profile?? would this be a recipe for a premature disaster??


Not really, however revving the tits off it to get all of the extra top end power might not be such a good idea. Maybe getting hold of some decent rod bolts and investing in some high quality oil would be a sensible precaution.

________________________________________

R H Davey Welding Supplies. I sell new and used welding equipment in the Hampshire area. I take on welding jobs in the evenings, ally casting repairs are one of my specialities but I can weld pretty much anything. PM me with your requirements.

Some of my services: (See my for sale threads)
Engine mount/chassis repair
Solid Beam Mounts BACK IN PRODUCTION
Harness bars
Posted 19th Oct 2009 at 19:37
Profile
braymond

Seasoned Pro

Location: Brighton

Registered: 20 Aug 2008

Posts: 1,163

Status: Offline
Post #8
Cheers. You've given me plenty to think about!

you're car sounds like quite a machine - i might have to drop you a message next time in in the southampton area. not far from me!

________________________________________

Rallye-R

Nurburgring article
Posted 19th Oct 2009 at 19:45
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daveyboy

aka Jim Davey

Location: Southampton

Registered: 01 Oct 2007

Posts: 8,648

Status: Offline
Post #9
braymond wrote:
Cheers. You've given me plenty to think about!

you're car sounds like quite a machine - i might have to drop you a message next time in in the southampton area. not far from me!


It's bust at the moment. You are pretty close, we have a branch in Arundel as it happens, called Arun Welding Supplies. Smile

________________________________________

R H Davey Welding Supplies. I sell new and used welding equipment in the Hampshire area. I take on welding jobs in the evenings, ally casting repairs are one of my specialities but I can weld pretty much anything. PM me with your requirements.

Some of my services: (See my for sale threads)
Engine mount/chassis repair
Solid Beam Mounts BACK IN PRODUCTION
Harness bars
Posted 19th Oct 2009 at 20:50
Profile
braymond

Seasoned Pro

Location: Brighton

Registered: 20 Aug 2008

Posts: 1,163

Status: Offline
Post #10
Ahh i was in Arundel just the other weekend enjoying a few local ales Cheers

didnt have need for any welding that day though..

________________________________________

Rallye-R

Nurburgring article
Posted 19th Oct 2009 at 21:12
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crf450

Senior User

Location: belper

Registered: 23 Mar 2005

Posts: 502

Status: Offline
Post #11
I fitted a set of PT81's to an engine that had has never been apart so I knew that the head hadn't been skimmed.Timed them in to the manufactures spec's meticulously. Ran the engine for approximately 2000 miles and had need to take the head off and discovered although there wasn't any damage, all the inlet valves had been kissing the pistons. Now when I fit PT81's I don't do it without pocketing the pistons.

________________________________________


Quote "da g man!"
"You've only got to watch the "306 vs ringtaxi" video & you soon realise how good these mod's are! That guy is running Ash's 30mm ARB, Solid Mounts & 23mm Torsion Bars & some adjustments on the camber. Admittedly, the guy is an awesome driver, but it just go's to show how well these cars can handle with the right modification's
Posted 21st Oct 2009 at 21:29
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sandy

Junior User

Location: Truro

Registered: 02 Oct 2005

Posts: 70

Status: Offline
Post #12
Lucky!
Posted 27th Oct 2009 at 00:40
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