3400/3500 hybrid project

[orangecky2k]

Okay so the motor is completly apart i am working on cleaning it at the moment. I put it through the hot tank and took some solvant to it and its starting to look good!
Im going to order my 3400 and 3500 intakes and 3500 heads and the turbo cam. And the valves and springs. Then after that i will be purchasing the forged pistons and rods after Im ready to start honing and boaring. Im thinking about going 20 over not sure yet though.
Im really missing driving the car though any comments from anyone is very apreciated if you have any ideas on the motor build or prep for my turbo build. Thanks for looking.
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[orangecky2k]

Okay so update I got all my ARP bolts today waiting on the pistons and rods to start boring and honing.(20 over) I am taking the the crank to get turned for my double roller timing chain I will have in the near future. I was wanting to get the rotating assembly balanced while i get my mains bored/ honed for the main studs but am starting to run out of time for my class and i need the rods to balance. My questions is for you guys that have turbo'd 3400's. Did you have your rotating assembley balanced? Should i push my luck and just wait for the rods to come then get it balanced or should I just forget about it?

[mfuller]

Okay so update I got all my ARP bolts today waiting on the pistons and rods to start boring and honing.(20 over) I am taking the the crank to get turned for my double roller timing chain I will have in the near future. I was wanting to get the rotating assembly balanced while i get my mains bored/ honed for the main studs but am starting to run out of time for my class and i need the rods to balance. My questions is for you guys that have turbo'd 3400's. Did you have your rotating assembley balanced? Should i push my luck and just wait for the rods to come then get it balanced or should I just forget about it?

Regardless of whether or not you use forced induction, balancing is always recommended when doing a rebuild but especially when replacing anything in the reciprocating assembly (like pistons and rods).

[orangecky2k]

Okay I guess I will run it over as soon as I get the rods and stuff.

[diabolical1]

The 3400 bottom end has a lot of options for compression without going forged.

old thread, i know, but i'm interested in hearing about some of those options. also, would i have a similar pool of options if i were to bore the block to accept LX9 pistons?

[SappySE107]

3.4 DOHC and 3.4 iron head are you 2 options for higher compression. You will need to figure out what quench you want vs compression using gaskets and milling. The calculator on this site has the specs for both engines. I don't know what options you would have with a 94mm bore with the right pin height and pin size vs a rod to use with said pistons.

[diabolical1]

3.4 DOHC and 3.4 iron head are you 2 options for higher compression. You will need to figure out what quench you want vs compression using gaskets and milling.

thanks. however, with 9.5 and 9.0, there's nothing to gain over my LA1. which already has 9.5s. if i keep the stock bore, i guess i'll keep the stock pistons, too.

I don't know what options you would have with a 94mm bore with the right pin height and pin size vs a rod to use with said pistons.

no worries. it was just curiosity as i'm still learning what's what with these GM engines. i'm not building a pseudo-racer or anything. stock LX9 stuff is the way i'd really like to go. basically swap LX9 guts into my LA1 block and then swap over a complete LX9 top to go with it.

thank you.

[SappySE107]

um...ok. Well, if you are telling me I don't know what im talking about, thats cool. Good luck.

[diabolical1]

i've re-read my response a few times and i guess i can make a stretch and see where you'd get that from, but i assure you, i'm NOT saying you don't know what you're talking about. so if that's how it came across to you, you have my apologies.

i will start my own thread in a few days and i'll get to explain what i'm trying to do in it's own context and i'll have more pointed questions then.

[carbon]

Ben grumpy... grrr...

But you misunderstood too, Diabolical1... the flat top iron head pistons and the DOHC pistons when combined with the 3400 LA1 heads do not yeild the same compression ratio of the respective original engine. The piston dome volume on the 3.4 pistons is 8cc and the DOHC is 5cc, stock 3400 is 28.6cc.

93-95 3.4 flat top pistons in an LA1 3400:
With 3.4 head gaskets -- 12.34:1 <- quench is OK at 0.05 (optimal 0.04")
With 3400 head gaskets - 11.57:1 <- quench is outside of optimal at 0.07"
With 3500 head gaskets - 11.51:1 <- quench is outside of optimal at 0.07"

91-95 DOHC pistons in an LA1 3400 (same quench issues as above):
With 3.4 head gaskets -- 13.08:1
With 3400 head gaskets - 12.20:1
With 3500 head gaskets - 12.14:1

Maybe Ben can comment on the effect of quench as I am still unclear on how significant it is... but if 0.04" is optimal, 0.07 is 75% out of spec, which seems like a long way statistically.

[pocket-rocket]

Quench has an effect on flame propagation. If there is a huge area (too large of quench) the flame will take a long time to travel across the cylinder resulting in poor performance and high emissions. Too little quench probably results in poor flame spread and not burning all the fuel and air resulting in poor performance and high emissions.

TBH, this is how I see quench working in my mind and I'm probably wrong so someone may chime in to correct me.

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[SappySE107]

3.4 iron head is .010 in the hole. 3.4 DOHC is 0 deck. With 3.4 DOHC heads and 3.4 iron head gaskets using 3400 heads, its 15.4:1. Quench is the distance from the head to the piston, and you can call it squish. When you have .040 or tighter, you get more squish action, which does exactly what Jon said above. It makes the flame travel much faster to get a more complete burn.

If you used the calculator on the site, you could see all of the numbers and play with it. 3.4 DOHC isn't 5cc, its 2.5. I didn't write the calculator so I can't edit it.

[diabolical1]

But you misunderstood too, Diabolical1... the flat top iron head pistons and the DOHC pistons when combined with the 3400 LA1 heads do not yeild the same compression ratio of the respective original engine.

you're quite right. as you correctly pointed out, i overlooked keeping the static compression numbers in the right context - which would be comparing pistons ONLY to their respective engines since other factors go into calculating CR. i posting without thinking. not a real shining moment for me.

also, thank you for taking the time to type all of that. it is appreciated. i will be adding it all to my notes.

[carbon]

If you used the calculator on the site, you could see all of the numbers and play with it. 3.4 DOHC isn't 5cc, its 2.5. I didn't write the calculator so I can't edit it.

Ahh... I just used the calc cause everyone says to use the calc... so... I used the calc.

[carbon]

you're quite right. as you correctly pointed out, i overlooked keeping the static compression numbers in the right context - which would be comparing pistons ONLY to their respective engines since other factors go into calculating CR. i posting without thinking. not a real shining moment for me.

also, thank you for taking the time to type all of that. it is appreciated. i will be adding it all to my notes.

Be sure to note Ben's correction for the DOHC pistons... the numbers are MUCH higher than what I posted.