3.4l iron head valve size question...

[87S10]

wow... almost makes it pointless to spend the money...
that is even with the 8mm stem?

Those valves should yield a gain of 5 to 8 CFM's(also depends on who's massaging the seats) of your net gain plus they offer less resistance as the mixture is being pulled by the thicker valve margin,simply giving a longer path for the mixture to travel. There's a reason why GM choose those valves to be used in those heads. Those iron heads are pretty restrictive from what I've read,you may wanna take it a step further and clean up the casting flaws as bit.

[oxrabidus]

Those valves should yield a gain of 5 to 8 CFM's(also depends on who's massaging the seats) of your net gain plus they offer less resistance as the mixture is being pulled by the thicker valve margin,simply giving a longer path for the mixture to travel. There's a reason why GM choose those valves to be used in those heads. Those iron heads are pretty restrictive from what I've read,you may wanna take it a step further and clean up the casting flaws as bit.

well where are some of the flaws? i am already gasket matchng the ports which i was told was a big help, i may do the 8mm valves as well...
the reason why i ask about the pistons is because when i opened the engine up, i saw the pistons were dished, i cant find anywhere a combustion chamber size for the iron heads to see the difference in comp.ression or the size of the dish, and i (kinda rashly..) ordered the pistons before i checked, i figured they used flat tops from the factory, ive been asking around and no one has told me, i want to be able to still run pump gas...

would anyone know what was the most seen out of the 3.4l with iron heads? im also useing my intake out of my 86 camaro which i heard was better than the 94 camaro intake, so how much of a gain would it be to port that? and would one of the 62mm TB's fit the intake? just curious really about that...
thank you!

[ssdurango]

What makes the 86 camaro intake manifold better then the 94? (upper or lower intake?)

[oxrabidus]

from what i was told the plenum (upper and middle piece) is better... because the runners are all the same length and size... the 4th gen camaro intakes two rear runners are shorter and narrower... its not a huge difference but they sid it would gain me a few extra ponies...

[oxrabidus]

and you could see the difference of the two rear runners from the outside of the manifold... whether or not it will gain me anything i dunno... but im gonna use it because it fits it came with my car plus i think it looks prettier haha...

[BillS]

If you are lucky, and you ordered Fiero style pistons, the flat top will net you around 9.5:1 which is fine.

I wouldn't want to run much more than 10 or 10.5 on the street unless you are up for carrying additive.

Sorry I don't have my combustion chamber volume data handy - it's been a few years since I did the turbo engine (where ratio was critical). I am sure some of the guys here will have it readily available and can tell you much more accurately what ratio you will get with the flat top pistons - if they know the installed deck height.

Be aware that it isn't just crown shape, as some engines (Chrysler big block) use flat top pistons for most of their variants, altering compression ratios by simply adjusting deck height, that is dropping the piston down the bore for lower compression engines.

[oxrabidus]

9.5 is right around were i would like to be... i believe deck clearance with the pistons is like .01 or something.... they have a comp height of 1.464 with 1.2/1.5/4 rings... i was thinking turbo for a bit... then had some cash problems and that fell through...
i looked for valve guides... the only ones that i knew for 8mm valves were 80 bucks for a set (which were ls style guides)... if anyone knows of any cheaper please let me know... and the valves and stuff were 140.... could i use regular retainers? or would i have to get specific stuff? thank you

[geoffinbc]

You don't just "buy guides" They are not like aluminum heads where they use bronze guides from factory. On iron heads the valve rides right on the iron casting. When its time to rebuild the heads the iron is drilled out and an insert is pressed in and then that is drilled to to provide the proper stem clearance. So a machine shop should easily be able to install and machine an insert for you which will accept an 8mm stem.

[bszopi]

Use the site's CR calculator (found in the left hand menus) to find all the values you should need to determine what your CR is going to be. Go through the stock values of the various engines to get all the numbers you need, and then do a custom calculation by inserting the appropriate values where they need to go.

[SappySE107]

Aluminum heads use iron guides and iron heads have iron guides. Aluminum is a PITA to change guides because of the angle and the fact that aluminum likes to gall when you press guides in and out. Then you have the damn size difference between stock guides and aftermarket. Bleh...sucks.

Iron heads you should be able to press the guides out but that still leaves the task of the right OD with 8mm ID. I have no idea if this is available. If you run a bronze liner, then it won't matter because the guide is just machined anyway.

[oxrabidus]

well thats good to know... would i need taller springs or specific valve retainers/locks? what else is needed to make them work? i was thinking yellow ls6 springs with matching retaiers and locks but those are kinda out of my reach at this particular moment... im gonna gt me slightly bigger cam maybe... but dont know which one yet... something to compliment the head work... i saw a 56 mm throttle body for the 3100 could i use this one my 3.4l wi my factory wiring? if anyone would kow thanks guys for the info

[oxrabidus]

it would cost me 400 bucks to have those valves installed with gasket matching etc etc... thats quite a bit... does anyone know is total seal piston rings are worth the power they claim? and if i could use that 56mm throttle body?

[geoffinbc]

With gasket matching and on 2 heads is not a bad deal. I paid $400 for a pair of stock rebuilt heads. All they did was the guides, grind the valves and mill the surface flat. They did not charge me any extra to install my comp springs and install exhaust valve stem seals.

[jerome]

you guys seem to have some knowledge on the iron heads, I was curious if you would know how much can be milled off the heads before you would have piston to valve interference. on an 87 2.8 liter using 95 3.4 liter heads with the larger valves.

[geoffinbc]

A ton. But I would not advise removing more than .010"