3.4l iron head valve size question...

[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.

[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.

[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

[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]

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...

[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...

[ssdurango]

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

[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!

[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.

[BillS]

but i have a question... since no one anywhere can answer this... how much higher if any will the compression be if i use flat top pis instead of factory dish pistons with 3500 head gaskets?

You have already said you are using flat tops. Why would you say that if you don't even know what compression it would give you? You just like the name flat top, or......

[oxrabidus]

but if i just get 10 hp frm gasket matching the ports the 8mm valves, plus the lighter weight of the valves... thats pretty bad...
but i have a question... since no one anywhere can answer this... how much higher if any will the compression be if i use flat top pis instead of factory dish pistons with 3500 head gaskets?

[geoffinbc]

There is only a .028" difference in stem size. Its not going to net you a ton of power. But it is a low cost mod. If i had time to dick around when I built my engine I would have done it.

[oxrabidus]

15-20 is doubtful. 10 if your lucky.

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

[geoffinbc]

15-20 is doubtful. 10 if your lucky.

[oxrabidus]

oh and im also getting flat top 0cc pistons instead of the stock dish type... so i imagine i could stand to lose a pinch of compression...