I hope this will answer any and all questions, else just email me.
(Patience, it's fairly long, but complete)
(NB: As per list rules, this text is copyright Bert Sager)
As an engine turns, it turns the camshaft which pushes on pushrods (little sticks going up in the block which push on the rockers which push on the valves. (the valve stem is parallel to the pushrod) Valves are used to let the air/fuel mixture into the combustion chamber. How much gets in influences how much power the engine makes.
The most common way of letting more mix in the cylinder is to install a camshaft with more lift (valves open higher) and duration (valves open longer)
Now looking at the fiero, I personally don't like changing chips, and a cam with different duration would definitely require one. That leaves higher lift (timing is unaffected). I also don't like pulling the engine out of my car, and to change a cam, you must.
Fieros have a rocker ratio of 1.5:1 (and that's if you're lucky) These rockers chan be relatively easily and cheaply obtained and installed. This in reality provides a substantial increase in lift (someone on the list calculated the exact figure, but I can't re- member it). With 1.6 ratio rockers, you can expect a 10% increase in horsepower on a stock fiero engine almost through the whole range.
Where to buy the rockers:
Go to any machine shop, ask for regular 1.6 rockers that'll fit a 60 degree 2.8 chevy V6, you'll get rockers for a small block chevy V8. They fit but you'll have to re-use your nuts and bearings as the new ones will be SAE and won't fit your studs. They cost me 10$ a pair (Canadian currency, about 6.75 US$)
What you'll need:
A metric ratchet set, a metric wrench set, a flat screwdriver.
A torx set, including a 35 or 40 (?) for the throttle body.
(I remember my set didn't include it and I went to buy it)
A long thin inflexible stick.
Upper plenum gasket, lower plenum gasket, valve cover gaskets.
(I reused mine but then again, my engine is new)
Coloured electrical tape (yellow is good), a pen (for labeling)
Clean rags (I use disposable Scott(tm) ShopTowels)
EGR tube if yours is broken or breaks during the job.
How I did it:
Disconnect Battery NEGATIVE. (Most ppl disconnect positive, but by disconnecting the ground, you run no chance of accidentally grounding something, especially when working a ratchet close to the battery) (Big sparks!)
Label and remove sparkplug wires, remove distributor cap after marking the location for wire #1. Inspect cap/rotor to see if they need replacing.
Remove the rubber tube connecting the airbox to the throttle body and set it aside (you may want to clean it)
Unscrew the 2 torx holding the throttle body to the plenum. Unscrew all the chrome bolts from the plenum. Carefully lift the plenum out, unhook all vacuums and label them. (I have no EGR, but you may have trouble with the tube, I recommend unscrewing it from the EGR valve) Stick rags in lower plenum holes so no screws/dirt fall in there. Thoroughly wash the inside of the upper plenum, make it shiny.
Unscrew the 2 Throttle Body coolant lines from the rubber hoses on the right side of the car, by the thermostat housing. Now flip the Throttle Body/tubes out of the way so you have more room. Unplug the wires for the IAC and TPS, no need to label them, they're unique.
Remove the whole array of vacuum lines in one pack, labeling each so you'll know where they go. (You might want to repair some with flexible vacuum tubing)
Unscrew the cap on the fuel entry, press the valve to relieve pressure. Unscrew that little box held with 2 torx, careful, there's a copper washer, don't lose it, you can re-use it , I did, no leaks. Flip this box to the side, out of the way. here's a metal loop tube (mine's blue/green) bringing gas to the cold start injector, unscrew the nut holding it, and gently pull the tube out of the fuel rail (without breaking it), some gas will leak out but no problem.
Remove and label the wires for the injectors. Simply press the clip in and pull. The fuel rail is held with 2 bolts, note where they are (front/back) because the lower plenum bolts in both ways and you'll notice you did it wrong when you can't bolt in the fuel rail or the line don't match anymore. There's an arrow on the plenum, that might be useful Remove the fuel rail, rocking it back and forth until the injectors pop out. Plug the holes with pieces of rags. Remove the fuel rail disconnecting and labeling the vacuum hose for the regulator. Careful, it's full of gas, drain it before lighting that cigarette.
Unscrew the bolts holding the lower plenum, and lift it off. Plug the intake holes with rags. Thoroughly clean the plenum, make it shine (inside).
Looking at the passenger side rocker cover, you'll notice a black bracket, you need to remove it in order to get the rocker cover off. Remove both rocker covers, remove sparkplugs, plug the holes with rags (notice how easy it is to get at the sparkplugs now!) Note: while you're here, you may want to remove the exhaust manifolds and grind out the restrictions, you'll want and need the extra breathing ability. Just look inside from the port, you'll see what to do, it's obvious.
Now for the tricky part: Remove all the rags so they don't get sucked into the engine during the next step. Using a ratchet and a 15(?)mm socket, connect to the crank pulley nut. It's a tight fit and you might get a few scratches, but it's feasible. Turn the crank clockwise (you should see the distributor rotor's finger turn clockwise) while feeling for compression in cylinder 1 (it helps a lot to have the car in neutral here). Note: front bank, left to right: 6,4,2, rear bank: 5,3,1. Insert the stick in the plug hole, and feel it coming up while you slowly turn the crank (very slowly, one degree at a time). You're looking for the moment when you turn the crank and the piston doesn't move. Move back and repeat if you have to, we're looking to be exactly at top dead center. Remove both rockers for cylinder one. install the new ones one at a time, using your old bolts and bearings. this is how to tighten them: Turn the pushrod with your fingers, tighten the nut untill you cannot turn it anymore, at that point, tighten exactly between 1/2 and 3/4 turns more. repeat for the other rocker.
Now turn the crank for one whole distributor rotation, feeling for any resistance (such as a valve touching), this is only a precaution, and shouldn't happen, but if it does, you might have a cam in there and the starter motor would be powerful enough to bend a valve. IMPORTANT: if you feel something blocking, don't force, remove the rocker and reinstall the old one. Again, on a stock fiero engine, this shouldn't be a problem, I have shaved heads and special high compression pistons and everything cleared nicely.
Now bring cylinder 2 to TDC and repeat the process for all the other rockers. Reinstall the sparkplugs, and the rags for the intake holes until you're ready to put the next part on.
Voila! reassembly is the reverse, and goes a lot quicker. Just make sure you put the lower plenum in right, I had to take it off and turn it around, and use the new gaskets. Make sure nothing's missing, that you have no bolts left, and that your cleaned plenums are dry.
Now when I first started my engine, it went toc, toc, toc for a while this was because I had pulled a pushrod out and that drained a lifter of it's oil, the toc went away once the lifter filled.
The difference is imediately noticeable, the sound is louder, and the rpms climb much faster. I don't have a water separator and the intake hiss is significantly louder since the rocker change. My catless exhaust also pumps out much more gases. Note: the next logical mod would be to grind out the exhaust manifold restrictions, because more air in means more air out, and you'll need the exhaust with this setup.
Total power gains:
I'll get a dyno test this summer, in the meantime, here's some ideas:
Polishing the intake plenum did smoothen airflow, so that's good for something, probably much more than adding a k&n filter which is good for nothing.
1.6 rockers: 10% hp increase
Grinding exhaust manifolds: 5% hp increase
No cat: 5% hp increase.
Strangely, the higher (10:1) compression didn't affect my dyno results (peak hp)at all though I can definitely feel the car has more punch. I think with all that, I'm looking at a wheel dyno result somewhere in the 125-130hp at the wheels, we'll see. (Stock is around 100) Should my 4.1:1 differential affect that?
From: Bert Sager
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