How easy is a cam change?
 

In the CIS and Aggressive Cams thread John Dougherty very kindly answered my question regarding what is the most aggressive cam you can use with a std 3.2 Motronic engine:

"3.0 with cis would be the 964 grind.

3.2 motronic gets the super cup grind

3.2 with factory pistons and aftermarket management my DC24 grind (Valve to piston clearance will be close and need piston notching)

3.2 with JE pistons and motec? anything goes

Remember hotter cams need more compression


__________________
John Dougherty
http://www.drcamshafts.com"

So, the next question is, how much work is involved in changing to a 993 Supercup grind cam? Nobody in the UK seems to have expereince with this cam in this engine. 964 cam grind, sure, but Supercup, never done it. My mechanic asked what the installed valve spring length would be? And also asked about preload on valve springs.

The thing is, I don't need to do a top end rebuild. My 1989 72,000 mile engine burns virtually zero oil and seems very strong compared to other cars. I just want more horsepower after years of DEing it in std form and more lately with stiff suspension and big brakes. The car will get SSIs and sport exhaust with a custom burned remap at the same time.

What do you guys think? What should I do? Any thoughts gratefully received.

Richard

John and others will know if you even need to change your springs, but simply swapping cams wouldn't be that tough. Some may say that it'd be safer to go with a stronger spring since the more aggressive cam will leave you more vulnerable to valve/piston interferance in an over-rev, but it may not be 'necessary.'

You 'could' get by with a partial engine drop. Then pull your chain covers and valve covers. Pull all the rockers and send them out to be reconditioned. With the rockers off, you can remove the chain sprockets and slide the cams out. Reinstall cams and rockers, re-time your cams, reassmeble and you're off and running.

It might be easier to do with a full engine drop, but it can be pretty quick and easy.

An aftermarket valve spring is good insurance for sure. With the Super cup or 964 cam the factory spring will work, but it is on the edge.
What RPM will you be shifting at?

I have the Clubsport rev limit with the current chip - 6850rpm IIRC - but rarely see higher than 6400rpm as there seems to be little benefit. I think I could happily live with a 6500rpm limit but I am not sure if the better breathing with cams and exhaust change would tempt me higher. I was thinking of changing to Ti retainers as a little extra "insurance".

I may have misunderstood things but it sounded like I could have cams changed without the heads coming off but valve springs, guides etc is a whole lot more work. Did I understand this correctly? Sounds like it from the post above. I am changing the clutch at the same time so it will be a full drop.

Many thanks,
Richard

To swap cams only, you don't need to pull the heads. If you're doing springs and valve guides, this would require pulling the heads. Yes, that's a bunch more work and is pretty much a top-end rebuild.

Richard:
I just completed the work you are considering and I'm not a professional. My son's engine is a 1985 3.2L. I replaced the cams and installed racing springs, seats and TI keepers.
You don't need to teardown the engine. Performance Products and others (Pelican?) sell the tools (exhaust/intake) to remove and replace
valve springs on engine. However, you will need to apply shop air to the cylinder to hold the valves closed. Your basic tester will not work as the plugs are recessed. I modified an engine cylinder compression tester that has a section of hose (my 911/VW engine compression tester). Mine was purchased at Sears years ago.
This engine will run in a few months with chip, adjustable fuel pressure, flowmeter, cams, springs and TI keepers, headers, Flowmaster muffler.
John is extremely knowledgeable, his quality is excellent, and I trust his recommendations enough I bought EVO cams and racing spring set, TI keepers for the 3.6L engine destined for my '73.
Marty

I guess, the simple answer is that if I keep a sensible rev limit, I can just swap the cams. Yes?

Richard:
I would say no. First, assume the factory specifys adequate spring pressure for control to the stock rev limit and stock lift. Then assume the miles weaken all the springs and a few more than others. Given these conditions, I think you need new springs to allow proper seating on all cylinders at increased revs and increased lift. Ti retainers may be considered a luxury but if you go the step of changing the springs why not the keepers also. Afterall weight reduction to an admitted heavy valvetrain is a step in the right direction.
Marty

You can swap in the Ti retainers without taking the heads off if you have right tool (so I'm told). So, what I should have said is cams + retainers + sensible rev limit and you can leave the springs alone? I am guessing, so opinions welcome.

If you are going with the Super Cup grind, you will be tempted to keep it coming on rpm wise as this cam just keeps making pawer up thru 7k. If you are in a DE, and in the heat of battle so to speak, don't be surprised to find yourself comfortable up in the higher rpm range.

Point being is, as John D. said above, with stock springs you are right on the edge with the factory 3.2L 6250 rpm limit.

Also be aware that with the factory S.C. grind, higher compression makes the power come on in a lower rpm range, hence if you have the euro 3.2 p/c if I remember correctly, you should start to feel the power band at approx 4k.

I just went thru the same decisions you are facing now, although I went with a slightly less aggressive grind (WebCam 20/21) I approached this in a "systems" type way.

So in preparation for the new cams, I had a racing valve job, 9k springs w. Ti retainers and all new rockers installed.

It's easier said than done, but go the extra distance so you only have to do this once.

Good Luck!!

You're opening up a can of worms when you upgrade the cams. If you go with upgraded cams, springs, titanium retainers etc. You'll want to rev higher. If you rev higher with the stock 3.2 rod bolts you'll break a rod bolt eventully. Now your talking about a full top end rebuild at a minimum just to upgrade the cams.

-Andy

Well, I am not ready to undertake a full rebuild. Given that premise, rod bolts are not going to be changed at this point in time. I think the UK specialists are perhaps a little less conservative than you guys in the US. This is a road car that does a few DEs remember and max 3,000 miles a year. A number of shops building competition motors have advised that the rod bolts are good for 280hp engines as long as rev limits are keep close to normal.

A guess what I really want is to modify in a way that compliments the SSI exhaust but also does not limit future mods or have to be redone. For this reason I like the Supercup cam (more than 964 or 20/21). In the ideal world I would complete a full rebuild out to 3.4 with ITBs and Motec ECU - which I think would be a great motor. Given the streetable goal, the SSIs and Supercam cam fit with this "dream" and with a custom chip burned should give a nice little horsepower lift for the time being on their own. Given I need a clutch and the engine is coming out anyway, well why not change the cams? If I have to run at a rev limit that precludes getting the full benefit right now then so be it.

I think you guys have help me develop my thinking around this and clarify what I want to achieve - so many thanks for that. I will be getting some prices for a top end rebuild to see if the budget stretches to that (I completely agree that it would be better to do valve springs, guides, retainers etc). I am moving house in March so that is draining funds at a frightening rate - thanks to the wife for that!

Richard