'Performance' cams, worth fitting?

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nickp
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Joined: October 23rd, 2007, 8:42 pm
Location: Barnsley, South Yorks. UK (A)
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'Performance' cams, worth fitting?

Post by nickp »

Hi Guy,

My Monte's currently running std cams but has a DIY modded Volumex head and twin DCNFs, it has 150bhp at 6krpm / 142 ft/lb at 4.5krpm so goes pretty well. I'm not in a position to buy a pair of steel billet cams at the moment with too many other projects on the go. However, I've just picked up a pair of 'performance' cams for not much money. They were apparently reground (I know, I know, they never work!!) by an employee of a well known tuning company for his own engine and allegedly made 160bhp in a 1600, which sounded a tad optimistic to me. Rather than just steam in and fit these unknown cams I thought I'd plot one against a std 2.0 131 cam that I had laid about to see what I've got. I've got to say I'm less than blown away by the profile. Yes it's got more lift, about 10% up everywhere, but has only gained about 5deg of duration and the progressive opening / closing ramps of the std cam are missing. The base circle has been reduced by 2mm to gain the lift, down to about 24mm now.

Sorry I haven't had chance to plot it onto a graph, but here's the figures at 5deg intervals-

DEG / STD 131 / ‘Performance’ PROFILE

0-----0
5-----0.1
10----0.2
15----0.3
20----0.35
25----0.4
30----0.5---------0
35----0.55-------- 0.15
40----0.85-------- 0.8
45----1.8--------- 2.0
50----2.9--------- 3.3
55----4.1--------- 4.55
60----5.2--------- 5.7
65----6.2--------- 6.8
70----7.0--------- 7.75
75----7.8--------- 8.6
80----8.4--------- 9.25
85----8.9--------- 9.75
90----9.25-------- 10.15
95----9.45-------- 10.4
100----9.5--------- 10.5
105---9.45-------- 10.45
110---9.25--------- 10.25
115---8.85-------- 10.00
120---8.4-------- 9.5
125---7.7-------- 8.9
130---7.0--------- 8.15
135---6.0--------- 7.35
140---4.9--------- 6.35
145---3.75--------- 5.3
150---2.45--------- 4.2
155---1.3-------- 3.0
160---0.65-------- 1.7
165---0.5--------- 0.65
170---0.45-------- 0.1
175---0.4--------- 0
180---0.3
185---0.25
190---0.15
195---0.05
200---0


Std cam duration (0.8-0.6mm lift) 120deg.
'Perf' cam duration (0.8-0.6mm lift) 125deg.

Please give your honest opinion if it's worth my time and effort to fit these, it's not the end of the world if I don't fit them. I wouldn't be looking/expecting miracles from them, but would probably go ahead if I thought there was 10-15bhp to be gained.

Thanks in advance,
Nick
Robert
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Joined: August 20th, 2006, 8:17 am
Location: France
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Re: 'Performance' cams, worth fitting?

Post by Robert »

Hello Nick (from Yorkshire),

Find attached the file showing your cam profiles from the data you indicated (I transformed the angle in crank angle explaining the factor 2).
At a first glance there is quite no ramp in the "perf" cams, there is also an asymmetry of the profile.

I calculated also the lift integral for information if the cam is usable (I wonder it is difficult to run with quite no ramp).
You can note that with the 0.4mm lash (generally recommended) the "perf" gives 16% increase value.

Of course I don't want to interfere with Guy answer, I just would give information to help.

Regards

Robert Montecarlisto
Attachments
Nickp.xls
Graph and lift integral
(37.5 KiB) Downloaded 359 times
GC_131
nickp
Posts: 54
Joined: October 23rd, 2007, 8:42 pm
Location: Barnsley, South Yorks. UK (A)
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Re: 'Performance' cams, worth fitting?

Post by nickp »

Bonjour Robert (from France),

C'est magnifique!!

Thanks for putting it onto a graph for me mate, that's perfect. Like you say it is assymetric, maybe the peak would need advancing slightly to even it out?

Thanks again,

Nick
TomLouwrier
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Location: Leiden, The Netherlands
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Re: 'Performance' cams, worth fitting?

Post by TomLouwrier »

Well now, it seems some of us have the same hobby on a Sunday morning.
nickp profile plot.png
nickp profile plot.png (49.06 KiB) Viewed 6665 times
Here's mine, same comments as you guys. The 'performance' can has no ramps and seems slightly asymmetric. That might be hysteresis in the measuring setup??
No idea about power, but I think it will be quite harsh on the valvetrain.

regards
Tom
Attachments
nokkenprofiel 130tc.xls
created as '.ods' but site won't allow me to upload that format. xls may not work for everyone.
(12.5 KiB) Downloaded 672 times
GC_29
nickp
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Location: Barnsley, South Yorks. UK (A)
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Re: 'Performance' cams, worth fitting?

Post by nickp »

Thanks Tom, will see what Guy says about its lack of ramps. It's not ideal, but is it a disaster? I don't know.
Guy Croft
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Re: 'Performance' cams, worth fitting?

Post by Guy Croft »

Nice try by all concerned but sorry complete & utter waste of time mapping out a regrind in this case. Whether you can superimpose a new profile and achieve any measure of performance gain depends on how much bulk the existing cam has - in the case of the TC not a lot. That being because the cam has to if thru a housing and the available space is thus tightly constrained.

So we have a map. So what? You can only prove-out a cam's worth by accurate bench dyno test.

I've been saying this since I ever first tried a pair in my own TC (124CSA), L14 profile. What a torque disaster and well-done (not) the race engine shop who supplied them. Standard 1800 124 CSA on 44 IDF - 128bhp. My expensive gasflowed head, 10.2/1 , 44/38mm valve combo and L14 regrinds - 137bhp and chronically poor torque. All done years before I learned how to do it all this myself. + 9bhp. What a mess!

Here are some of the things you can look forward to with regrinds in the 8V TC:

1. Lousy torque - even compared with standard cams
2. Fuel standoff at the carb (the more radical the cams the worse it gets)
3. Broken valve springs
4. Valves and seats hammered to bits

The best place for 8V TC regrinds is in the scrap bin.

I speak as a race engine pro - for anyone who thinks I am a bit, er, 'harsh'.

GC
Guy Croft, owner
nickp
Posts: 54
Joined: October 23rd, 2007, 8:42 pm
Location: Barnsley, South Yorks. UK (A)
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Re: 'Performance' cams, worth fitting?

Post by nickp »

Thanks for the reply Guy.

I thought they actually looked quite promising for regrinds, but the lack of opening / closing ramps does concern me. I presume this is what would lead to the broken valve spring / battered seats that you've mentioned? I'm not going to disagree with you ( I know better than that!!) but I am still thinking of trying them. If I do then I'll try to take it back to the same rollers I went to initially so I get a decent comparison of std v 'dodgy regrinds'.

thank you,
Nick
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