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

I'll ask the dumb question, but I don't know....might you use cap on some but not all valves? I mean for what I think was the OP's situation; street performance improvement, not racing.

(Sometimes discussion of more pedestrian/less exotic applications are quite valuable)
 
Fiataccompli said:
I'll ask the dumb question, but I don't know....might you use cap on some but not all valves? I mean for what I think was the OP's situation; street performance improvement, not racing.

(Sometimes discussion of more pedestrian/less exotic applications are quite valuable)
Click to expand...

Tyler aka "AARPCard" :) did state: "Did a test install to measure the shim clearance. I'll definitely need thicker shims ranging from 4.70mm to 4.95mm..."

For those numbers, using a 1.5mm lash cap on all valves would seem to work out almost perfectly. 4.90 - 1.5 = 3.40 and 4.70 - 1.5 = 3.20. So any valve whose clearance would be more than the low end of his range, standard shims would work normally. For the valves that come in needing a 4.70 shim, he would have to dress the valve tip with a very light kiss of the tip grinding stone on the valve grinding machine to pick up the .05mm needed to fall into standard shim thickness territory.
 
In my younger days (25 years ago) I had my engine rebuilt by reknown Fiat builder Remo Tagliani (father or racer Alex) in Montréal. He regrinded my can and installed Alfa shims to complement the stock shims. It was a "common" modification at that time. I think that's what you are referring as "lash caps". Alfa shims are much smaller and fit Inside the tappet. A year later, in my oïl change, I discovered some parts of one of these shims. Don't know how it falled into the engine and survived to be large enough so I could identify it... but I would never use them anymore.
 
Daniel, Alfa shims and Lash caps are very different animals.
Lash caps are small 8mm caps that fit on the top of the valve stem under the buckets.
Like So:
lashcap.jpg
 
Dan Sarandrea (Phila) said:
he would have to dress the valve tip with a very light kiss of the tip grinding stone on the valve grinding machine to pick up the .05mm needed to fall into standard shim thickness territory.
Click to expand...

Everyone keeps referencing grinding the valve stem tip, I was under the (possibly mistaken) impression that this was a big no-no, the tip is hardened and you don't want to grind through that. Does Fiat not harden valve tips? Or does no one do it and I am just misinformed? :confused: Always a possibility I will admit.

Pete
 
In many applications and with some materials, valve tips are hardened. For example, a lot of American high performance engine aftermarket valves are stainless steel, which is not all that hard, so the tips are usually hardened during the manufacturing process. Titanium valves have to have hardened tips. And in classic American pushrod v8 engines, often the rocker arm contact patch pressure is concentrated on a point on the valve tip, or in the case of roller rockers, a moving contact patch, so hardening would be advantageous.

Typically lash caps themselves are hardened because it is assumed that they will be receiving point loads as described above.
​
In our SOHCs, the buckets pretty much exert full and even contact pressure on the tips of the valves, so much less of a point load than in the examples above. Not to mention on the SOHC, the valve spring loads are pretty light which means less force is needed to open the valves, thereby stressing the valve tip less. So absent any definitive info or actual factory specs, my guess would be that in the SOHC the valve tips are not hardened over and above the natural hardness of the valve stem material.

I would think that with a hardened lash cap on a non-hardened valve tip, if the valve tip were soft enough to suffer say mushrooming from the force, the encapsulating effect of the lash cap would work to contain the mushrooming. Logically, the evidence of such mushrooming would be something like the lash cap being difficult to remove from the tip, or perhaps in extreme cases the mushrooming would expand the cap to where its collar would crack and the cap would break into pieces.
 
Well, I have build American engines in the past, I guess that's where that memory is coming from.

You talk about "point loading", for that reason alone I would be leery to grind valve stem tips. I just don't believe that they can be ground by hand to a flat, perpendicular surface, so the result is going to be an uneven spread of the load. In my mind, best outcome is that the high spots eventually get pounded down, during which time your lash will change. Worst outcome is that it causes the cap or the shim to spit out because of the uneven load. I have seen the shim spit situation before, albeit on a DOHC motor, but with no lash caps, just the usual hardware.

Pete
 
My experience in this (bty no means expert) is that fiat valve stems are not hardened. I recall using a hand file with no effort to remove a small amount of the tip to get my valves in spec. As stated prior, this was in an autocross engine, I ran high revs for the most part, there was no mushrooming of the stems, the caps stayed where they belonged, and the engine showed no adverse conditions after several years of use, or should I say abuse.

I am not suggesting that anyone follow my footsteps, merely offering my personal experience with lash caps. Would I use them again? Absolutely, if needed.
 
In reference to Pete's and Dan's comments above. I tend to side with Pete, I'd prefer to NOT grind any contact surface in the valve train, including the valve stems and the adjustment shims, hardened or not. However IF you do grind the valve stems, then definitely do as Dan suggests and have them ground on a proper valve refinishing machine designed to do it accurately (square and even to exact tolerance). No offense Andy, but I would not hand file them as it leaves too much open to error. And IF it came down to having to grind something (again, preferably not), then I'd grind the valve stems (to add lash caps) before I'd grind the shims, also for the reasons Dan describes. But I think there is an even better solution to grinding any valve train components (below).

Per the example in this discussion, needing 4.70 - 4.95 shims to accommodate the reduced base circle cam. As Dan points out, a 1.5 lash cap would work for the ones needing the 4.95 shims to bring them into the lower end of the stock shim range. However for the ones needing 4.70 shims it does not work...1.5 caps are too thick, resulting in the need for undersized shims. So the 1.5 mm lash caps are not a good solution here. This is why I said I'd only use lash caps if they are available in a selection of thicknesses, allowing the use of standard unmodified shims. Perhaps lash caps that fit the SOHC are available in more than one thickness? I don't know...anyone?

Alternatively the cam box could be skimmed only enough to put these values back into the stock shim range with the 1.5 caps. With some accurate measurements and a little math you could determine the proper amount to be skimmed off and put you into that sweet-spot range for the shims, with or without lash caps (depending on the need). As I mentioned previously, these calculations would be done after all other machine work has been performed. So for the current example, the cam box could be skimmed .10 mm, use the 1.5 mm caps, then shims in the 3.30 to 3.50 range would be correct.

However I noted a moment ago there is a better solution (in my opinion):
Wouldn't it be even better yet to skim the cam box 1.6 mm, not use lash caps, and use shims in the 3.30 - 3.50 range? I tend to think so, why use lash caps if you don't need to. Adding anything to the system poses the potential for problems. As far as I know, skimming the cam box by 1.6mm would not cause any adverse effects (assuming you make the necessary cam belt adjustments to accommodate it)? By the way, my mention of skimming "1.6 mm" is assuming that was the result of the accurate measurements described. The goal is to skim only enough to put the shim thickness back into the lower end of the standard range. I suppose if it was determined a huge amount needed to be skimmed then going back to adding lash caps and only skimming enough to accommodate them would be preferred (again, in my opinion).
 
I'm no expert on Alfas but I have a race head that uses Alfa shims. The valves are 7mm and the Alfa shim assortment kit seems to be stock. I assume that means that at least some Alfas come with 7mm valves.
P1040294.JPG

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Wow, what an interesting conversation. Now, let's talk reality. A more aggressive cam by itself is probably 85 to 90% of what you are looking for. It is probably the single biggest change you can make to wake up your car. Lightened shim caps, Holy water injectors, etc are all nice, but not required and in some cases probably not noticeable given the conditions you are going to drive this in. I have done many swaps where I shaved the cam tower, suck on a 1300 idler pulley and put the stock crank wheel on the cam and went for it. Don't get to caught up in the Wow factor of some items when you will simply not see the difference. For example, the strongest running X I ever had ran stock valve sizes. Here is my suggestion:

1. Cam
2. Deck the head to increase compression
3. Get in it and drive...

These two simple things will increase your heart rate and impact to your wallet and points on your driving record in short order. Personally I always enjoyed the 34dmtr carb with a 35/75 cam. Great combo. Never saw enough of a difference to warrant a twin carb setup.

If you want more after the first two, then:

1. Lightened flywheel
2. Open up the exhaust a bit more.

Hope this helps, and good luck!
 
fastx19 said:
Oh, one other item. Valves shims for Volvo's fit as well.
Click to expand...

FIAT DOHC and SOHC engines use 33mm diameter shims, which as Eric mentioned are also used by contemporary Volvo engines. Other manufacturers have used shims for valve adjustment as well: VW, Audi, and Chrysler used 31mm shims and Toyota used 28mm shims for passenger cars and 34mm shims for trucks, Honda and Yamaha used 25mm shims in motorcycle engines, etc.
 
It seems the original question you had has been pretty much obscured by talk about how to deal with the use of reduced base circle cams. Lots of choices/solutions - simplest of which is thicker shims which you already know.

To answer your original question:

"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?"

I'll take a stab at it and say - No. That cam will work just fine with your combo. Install it, adjust your valve clearance, set your ignition timing (10' BTDC is a good starting point) and you should notice an improvement over the stock emissions cam. Fairly simple bolt on upgrade.
 
So this project stalled out due to semi unrelated circumstances - life and I bought a different X.

I'm gearing back up to tackle this along with an assortment of other things. I got to thinking, since I'm going to be removing the valve springs anyway (to replace the valve seals) is there any benefit to upgrading to stiffer valve springs at the same time?

Considering the cam I'll be using, the 223 deg duration MWB street regrind, and the fact that the only other performance mod I'd likely ever end up doing to this motor would be a performance exhaust/cat delete, I'm thinking stiffer valve springs would be largely pointless. Stiffer springs don't seem to be too expensive, bu

Do you guys think there would be any chance of valve float near the stock fuel cut considering the new cam (or without it for that matter)?
 
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