My wife said that we can probably pick up some new rocker arms from the Fiero Store at tax time and so I was looking at what they offer. I have all new valve springs, lifters, pushrods, cam, etc... all I need now is the rocker arms, I'm just not sure what to go with. My cylinder head is a Falconer Racing prepped P&P setup with titanium valves. I have ported lower, middle and upper intake manifolds, and eventually I will finally get around to installing my dual throttle body intake manifold. I have ceramic coated FOCOA headers... and all of this is bolted to a '95 Camaro 3.4L PR with a crane H-272-2 camshaft.
Here are my three options from the Fiero Store: 1. $159.95 COMPETITION CAMS 1.52:1 ROLLER TIP ROCKERS
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Competition Cams Magnum roller rockers offer an accurate 1.52 rocker ratio. Stock stamped rocker ratios can vary from 1.46 to 1.50. With Magnum Rockers at 1.52 it effectively increases a standard .420 lift cam to .432 lift. With the increased lift and the friction reduction at the valve horsepower increases and rev's are quicker.
2. $169.95 COMPETITION CAMS 1.6:1 ROLLER TIP ROCKERS
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Magnum Rockers at 1.60:1 will increase valve even further than the 1.52:1 ratio rocker for even more HP out of a stock or performance camshaft. The roller tip also reduces friction for easier rev's.
3. $329.95 CRANE GOLD ROLLER ROCKER SET
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Stock stamped rocker ratios can vary from 1.46 to 1.50. These Crane Cams Gold series roller rockers are 1.60 ratio for increase valve lift. With the increased lift and the friction reduction from these full roller rockers, horsepower will increase and the engine will rev quicker. These rockers have a narrow body (not self-aligning) for valve cover clearance. The special 10mm x 1.50 bottom x 3/8" x 24 top rocker arm studs are included so no machining is required to the heads.
I would personally go with the second set. They are 1.6 as well as the gold ones, so theoretically they should offer the same performance. The gold ones may be somewhat stronger, and even if they do offer better performance being a true roller setup, its not almost-double-the-money better. Of course it all comes down to how you want to use the engine and what your personal preference is.
Also consider that the higher ratio means that you will have to recheck your coil bind and retainer to valveguide/seal clearance. If you chassis dyno this combo then make two pulls. Do it first with the 1.6 ratio on the intakes and the exhaust side stock. then do it with 1.6's on all the valves.
Oftentimes you will find that the peak hp comparison is nearly the same but usually there is noticeably more torque using the smaller ratio on the exhaust side which would make for an all around better car. Allot plays into this like valve sizes, cam selection, pipe diameters, and flow numbers so I cant be sure of the results but for only an extra half hours effort you will have an idea which side of your engine is out flowing the other. This info is then very important for any future changes so that you can target improvements where they are needed most.
I have a set of 1.6 roller tips. They work very well and lower the pitch of the exhaust. The 1.6 adds lift and it kind of depends how much lift your cam has. If you go too high you can get binding in the springs. Crane cams has some good info on their website.
Arn
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07:25 PM
Jan 27th, 2008
Oreif Member
Posts: 16460 From: Schaumburg, IL Registered: Jan 2000
Since you have a Crane 272, Not only do you have to recheck valve springs for binding, But now piston to valve clearence could be an issue. Your max lift goes from .480 to .513 if you use a 1.6 ratio rocker.
Unless you plan on spending a lot of time at WOT or racing every weekend, The full-roller rockers will not have much of an effect over the roller tipped ones.
I would go with the Comp Cams 1.52 and their heavy duty pushrods. More accurate lift with stronger and better oiling pushrods.
Another vote for the Comp roller tip 1.52s. I'm running the same thing in my 3.4 w/ the 272 cam.
As mentioned, if you go with the 1.6s, check your clearances. The 1.52s will also be easier on your cam and lifters. Never a bad thing with the 272, from what I've heard.
So then why with this build would the decision be for a race prepped head with titanium valves but then decide to alter the direction of the build in favor of less lift to avoid A POSSIBILITY FOR INTERFEARENCE when interference may not exist at all and then decide that longevity is now the primary consideration in spite of the titanium valves and other high flow mods?
I see nothing wrong with the advice that is being given if that's the direction that you now want to go but you could have saved cost and improved longevity in the beginning if earlier decisions with in the build had been made that had the same priority.
I assume that you have lash caps on those titanium valves but if you don't then you should get the full roller tips so they don't wear the valves severely.
[This message has been edited by big block fiero (edited 01-30-2008).]
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09:38 AM
Blacktree Member
Posts: 20770 From: Central Florida Registered: Dec 2001
So then why with this build would the decision be for a race prepped head with titanium valves but then decide to alter the direction of the build in favor of less lift to avoid A POSSIBILITY FOR INTERFEARENCE when interference may not exist at all and then decide that longevity is now the primary consideration in spite of the titanium valves and other high flow mods?
A couple things:
1) The possibility of mechanical interference using the Crane Cams H272 with 1.6:1 rockers is very high. With this setup, the lift at the valves will exceed 0.500" on the exhaust side. That will require special springs, and possibly even some head work. As mentioned above, in addition to valve spring bind, there also exists a very real possibility for valve-to-piston interference. Only a fool would stick these parts into an engine and just cross his fingers.
2) Keep in mind that the 1.52:1 ratio rockers will still provide a slight improvement in valve lift (and a more accurate ratio) compared to the stock stamped rockers. But at least in this case, the increase in lift won't be enough to trash the engine.
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11:09 AM
The_Stickman2 Member
Posts: 1030 From: Lehigh Valley Pa. Registered: Sep 2007
yes, it really does come down to what springs you are using, if you want to go for the 1.6 rockers I have had springs bind with just the 1.52 rockers & the Crane 272, using the Crane springs you've mentioned the titanium valves - but said nothing about the springs. if stock - forget it. waste of time. the valves will float before you reach peak power.
I guess my point still isn't clear, in summary if your building a racing engine then make all the steps necessary to complete it even if that means putting an isky valve clearancing tool down some valve guides on a spare head to notch the pistons. It isn't that hard, adds just a little overbalance (good) and that's what any knowledgeable engine builder would do to complete this goal. When an engine revs to the moon and if there is a little valve float it is always the exhaust valves that will hit the pistons, never the intake valves. The best performance will likely be seen with the smaller rockers on the exhaust side anyway which would add clearance where it is needed most. The intake side doesn't require as much clearance and that is the side that would likely benefit from the bigger rocker so it all works out fairly well. Obviously your springs and springpads should be matched to the rest of the assembly so there isn't any float, coilbind, etc, and those titanium valves were selected to reduce reciprocating weight to prevent valve float but this is all part of job of making all the steps necessary to complete a racing engine.
I would highly recommend that anyone interested should read "chevrolet small-block v-8 camshafts and valvetrains" by david vizard. He is very smart, simply the best, and explains these dynamics in much greater detail with by far more content then you will find by any other author. This info is as usefull for any engine as it is for a small-block chevy.
[This message has been edited by big block fiero (edited 01-30-2008).]
Orief posted some pushrods that look like they should work, but at one third of the cost of the ones I got. All of these parts were what was recommended to me by Summit Racing support. Should I return them for something else?
Also, I am going to start with roller tipped 1.52 rockers and do a baseline dyno, and then swap them out for full roller rockers, at 1.52 ratio later for another dyno. Should be interesting.
Lots of good info ,,also You need to check the "match" of the rollers to the stem.especially if you go with the more extreme ratio.. this info should be available on the cam sites.. Do not ignore this critical check,,The simplest methods are to just mark the stem with a marker.. you can eyeball the 1.5 any other CHECK!
[This message has been edited by uhlanstan (edited 01-31-2008).]
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01:03 AM
Pyrthian Member
Posts: 29569 From: Detroit, MI Registered: Jul 2002
ok, the "usual" instal height of Fiero valve springs is 1.700 these springs bind at 1.153 that means at most 0.547 lift. with ZERO tolerance.
now, being these be alum heads, and have probably been machined - but many Fiero heads need the valve seat machined down, because they dont quite reach the 1.700 valve spring install height.
for anything over 0.500" lift - which 1.6 rockers will give ya - I'd say go for some taller springs, and lower the valve spring seats.
