What do I need to know about installing a more aggressive cam?

A

aarpcard

True Classic
So I'm in the middle of an engine rebuild, and I figured now would be the best time to replace the stock cam with something more aggressive (motor is a stock 1.5 FI). Ultimately I settled on the 223 Degree Duration Regrind Street Cam available at MWB. I'm not looking for massive gains in the power department, but I would like to wake the motor up a bit.

I know I'll need (likely thicker) valve shims which I'll order after getting the cam and taking measurements.

What I don't know is how will this affect anything else; like the fuel injection system. WIll I have to run different timing than stock? Is there anything else I should know that wouldn't make this a fairly simple bolt on upgrade?
 
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Tweaking the cam timing is about it. Of course that means buying an adjustable gear. Besides that,nothing to adjust or alter, I’d say.
 
I recently installed this very same cam in my 85 x. I didn't do a rebuild I just installed the new cam and everything is great I did install an adjustable cam gear but it is set at 0 and the timing is set to factory specs and everything is great it runs very well the only drawback is I am running the thickest shims available 5.5mm which is working fine but you may want to consider milling the cam box or using the cup spacers as well
 
skully said:
I recently installed this very same cam in my 85 x. I didn't do a rebuild I just installed the new cam and everything is great I did install an adjustable cam gear but it is set at 0 and the timing is set to factory specs and everything is great it runs very well the only drawback is I am running the thickest shims available 5.5mm which is working fine but you may want to consider milling the cam box or using the cup spacers as well
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I lapped my valves too so my clearances are all on the tight end now. I don't anticipate on needing shims that thick, but we'll see once I measure with the new cam.

How's your performance before and after the install?
 
By the way - if your cam box seals are original- you really should replace the rear gasket and front cam seal while you are there.

....and technically the belt too, however if that was replaced in the last 5k or 2-3years I wouldn’t necessarily change it unless evidence of dry rot/ tooth wear or cracking is present
 
lookforjoe said:
By the way - if your cam box seals are original- you really should replace the rear gasket and front cam seal while you are there.

....and technically the belt too, however if that was replaced in the last 5k or 2-3years I wouldn’t necessarily change it unless evidence of dry rot/ tooth wear or cracking is present
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Thanks - yeah I'm replacing probably 90% of the gaskets on the engine, all the seals except for the rear main, timing belt, idler, piston rings, rod bearings, crank bearings (only if they're worn - haven't measured yet), camshaft, shims, lapped the valves and seats, resurfaced the head, lots of misc stuff too.

My head gasket blew about a month ago. Turned out the head was warped too. Figured if I'm taking it this far apart, I might as well do a whole refresh.
 
Has there been any comparison between the "reground" cam you intend to use (as referenced in your initial post) and the similar "new" billet one from the other well known vendor? Trying to interpret advertised cam specs is not easy, perhaps one of our cam experts can enlighten us how the two would compare in application.

I'm also curious if one has a different base circle than the other (both are reduced size), therefore not requiring quite as much additional shim thickness? Related to that, how much material would need to be skimmed off the box to bring either cam back to using 'standard' thickness shims (opposed to the common practice of over-skimming for reduced thickness shims)?
 
aarpcard said:
Thanks - yeah I'm replacing probably 90% of the gaskets on the engine, all the seals except for the rear main, timing belt, idler, piston rings, rod bearings, crank bearings (only if they're worn - haven't measured yet), camshaft, shims, lapped the valves and seats, resurfaced the head, lots of misc stuff too.
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As long as you have the engine out for rebuild I would replace the main seals, super easy to do while the engine is out, a pain to do after it's all back in the car. When I go into an engine I just do it all, bearings, rings, seals and gaskets. Cheap insurance.
 
Andy said:
When I go into an engine I just do it all, bearings, rings, seals and gaskets. Cheap insurance.
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Very, very wise advice Andy!! Yep, now with the engine out, time to do all the "housekeeping" maintenance! Certainly saves any tears and aggro later on if something kinda minor fails, and you have to pull the engine just to fix that problem! :mad:

cheers, IanL - NZ
 
aarpcard said:
I lapped my valves too so my clearances are all on the tight end now. I don't anticipate on needing shims that thick, but we'll see once I measure with the new cam.

How's your performance before and after the install?
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There is a very noticeable increase in the lower end or take off power . I am quite happy with the results although I wish I would have done other improvements such as bigger valves and porting which I think would really make this cam even better
 
skully said:
There is a very noticeable increase in the lower end or take off power
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Very interesting that this increased cam (over stock) would be felt mostly in the lower end / power take off. Just generally speaking, usually a performance cam tends to effect the top end range more and can actually decrease lower end power (as a trade off, increasing "horse power" tends to decrease "torque"). So I'm glad to hear that isn't the case here; in my opinion retaining good torque is vital for a street tuned engine. The result you describe follows the reference of this cam to being like the "Euro spec" factory cam.
 
I run the same cam. Take cam box and have it machined / shaved to regain near stock shim use, install 1300 timing belt tensioner pulley. timing will not be exact but I do not find it to be that much of a problem.
 
Deane, how would you describe this cam compared to the stock one in terms of driving characteristics?
 
car is 79 carb, 34DAT carb with cleaned up intake manifold. no smog equipment. Allison header with magna flow muffler. Lots more pull from 3k to red line plus. Idles nice at 1k. Fun on the street. If I want fast I go out on my YZFR1.
 
well, this is most interesting to hear this (if i'm reading correctly) is a nice upgrade even in an otherwise stock 1.5. I could almost talk myself into doing it on my '85....
 
My otherwise-bone-stock X loves 15 degrees of ignition timing, compared to the factory spec of 10 degrees. Not that it has knocked once ever, either before or after I jacked the ig timing to 15, but just to be safe I run the mid grade gas available in my area, 89.
 
Got the cam in the mail. Did a test install to measure the shim clearance. I'll definitely need thicker shims ranging from 4.70mm to 4.95mm . . . or I'll get the box shaved. Not sure which is better. I'm not looking for large gains - just want to wake the motor up a bit. Won't be running it at high rpm very often so I'm not too worried about valve float. I measured the stock cam and it was actually in good shape - everything was in spec. If I didn't shave the box, it'd be easier to go back to stock if I wanted to.

Another stupid question though. How would I go about determining how far to advanced/retard the cam timing? Some responses in the thread said they left it at 0 with good results. Elsewhere I've found that the cam regrinder will list it with the cam documentation - I don't see that info for this cam.

Is this something that can be determined by measuring or is it something that you have to experiment with on a dyno? I've never installed a cam with a modified profile in a car before.

Andy said:
As long as you have the engine out for rebuild I would replace the main seals, super easy to do while the engine is out, a pain to do after it's all back in the car. When I go into an engine I just do it all, bearings, rings, seals and gaskets. Cheap insurance.
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Unfortunately the block is still in the car. I don't really have a place to put it if I took it out. I can still replace everything except for the rear main seal, main bearings (and a few other gaskets).

After I'm done with the engine, I'm going to tackle the transmission. I'll do the rear main seal, related gaskets, and main bearings (if needed) then. Yeah it creates some double work, but there's really no other way for me to do it.
 
As for 'degreeing' the cam, I guess there are three ways of looking at it:

1) If the reground cam was designed with the same zero degrees alignment as the stock cam, and if you do not mill (shave) the head (for compression gains) or cam box (i.e. you use thicker shims instead), then in theory you should be able to install the new cam with the stock cam sprocket set at the stock zero specs (as per the workshop manual) and be good.

2) On the other hand, if you don't trust the reground cam's alignment specs, or you shave the cam box and/or head, then you will need to 'degree the cam' (find true zero) and use an adjustable cam sprocket to get it back to a zero setting.

3) If you want to set your cam (new or otherwise) to any setting other than the stock zero degrees spec (for performance characteristic changes), then you will also need to degree the cam.

To degree the cam for either item 2 or 3 above, a "degree wheel" on the end of the crankshaft and a dial indicator and stand on the cam lobes are used. The procedure isn't that difficult to do. There is likely a detailed explanation somewhere on this forum, or Google "how to degree a cam".
 
Is 4.95 the max end of the shim range? I would suppose having a shaved box with custom cam along with stock/stock isn't unreasonable. MWB sells shaved boxes I see. I think I have a spare or two, but buying one already cut may be more cost effective if I assign a value to my time, though I do need to check one friend who has "an awesome set of tools." As that would not be a big PITA & time suck to do...
 
Dr.Jeff said:
As for 'degreeing' the cam, I guess there are three ways of looking at it:

1) If the reground cam was designed with the same zero degrees alignment as the stock cam, and if you do not mill (shave) the head (for compression gains) or cam box (i.e. you use thicker shims instead), then in theory you should be able to install the new cam with the stock cam sprocket set at the stock zero specs (as per the workshop manual) and be good.

2) On the other hand, if you don't trust the reground cam's alignment specs, or you shave the cam box and/or head, then you will need to 'degree the cam' (find true zero) and use an adjustable cam sprocket to get it back to a zero setting.

3) If you want to set your cam (new or otherwise) to any setting other than the stock zero degrees spec (for performance characteristic changes), then you will also need to degree the cam.

To degree the cam for either item 2 or 3 above, a "degree wheel" on the end of the crankshaft and a dial indicator and stand on the cam lobes are used. The procedure isn't that difficult to do. There is likely a detailed explanation somewhere on this forum, or Google "how to degree a cam".
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Ahh I think I get it now. You'd degree the cam to get the 0 degree alignment to match back to the stock cam profile if the new cam is off.

Why would shaving the head or box result in you needing to degree the cam to get it back to zero? I'm don't quite see how the geometry changes so that would be required. Shaving the head will increase CR, but not change the relative cam to crank angle . . . same as shaving the box. Sorry if I'm asking obvious questions.

Fiataccompli said:
Is 4.95 the max end of the shim range? I would suppose having a shaved box with custom cam along with stock/stock isn't unreasonable. MWB sells shaved boxes I see. I think I have a spare or two, but buying one already cut may be more cost effective if I assign a value to my time, though I do need to check one friend who has "an awesome set of tools." As that would not be a big PITA & time suck to do...
Click to expand...

The max end of the range is 5.05mm. I noticed that MWB sells shaved boxes too. Didn't really want to go that route unless it made sense for my use case as they're kind of pricey and I'd have to buy new shims either way. (not worried about valve float because I don't plan on high revving the motor often. Although I don't really know at what rpm valve float would begin to be an issue.)
 
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