OK question do the 3400 & 3500 main caps made for cross bolting if so why hasn't any one used them on the 3.4DOHC engine with the oil pan . the 3500 has a forge steel crank and 5.9 center to center powder metal forge rods correct so why not use them ? and can the 3500 pistons be used just need to bore the block and cut new valve notches ?

[This message has been edited by engine man (edited 02-24-2011).]

The oil pan doesn't fit, it's quite difficult to retrofit the pan or the block to make that work, the majority of the bolt holes don't line up. The caps do fit and they are stronger, but you would need to line hone the caps once installed, as they need to be mated.

Oil pan fitment pictures:






Cap comparison:




Thats all well and good, but the 3.4 DOHC has not proven to need any of this, there are a few running in the 400+ horsepower range, and they aren't having any bottom end related issues.

As for 3500 pistons... Well, you can bore the engine to 3.7" from the 3.622, but thats .078" overbore. That's pretty extreme, the cylinders may be compromised. .060" is a generally accepted limit. But the real issue is that the 3.4 DOHC's combustion chamber is inside the head. In the 3500, the combustion chamber volume is split between the head and the inside the heavily dished pistons. So if you combine the 3500 pistons and the 3.4 DOHC heads. You lose a ton of compression.

You can use the 3500 crank, you have to change the reluctor wheel out for a custom one that mimics the original. You do gain a seriously strong crank with 2.25" crank pins. The block does need to be clearanced for this, but only a little.

so we would need a reluctor wheel change custom pistons i think if the LX9 rods are longer or am i wrong on that and if those caps are used line honed and customize the oil pan then the bottom end should be strong enough to really put the boost to it

If you want the 3500 internals, why don't you just build a 3500.

best flowing heads are on the 3.4 DOHC they flow 277 cfm at .400 lift although the 3500'S heads are not bad if i recall like 260 CFM at like .600 lift but really want 4 valve DOHC engine only if it where all aluminum

this is a link to a calculator that will tel you how much HP and at what rpm the flow is good for theoretically
http://www.bgsoflex.com/flowcalc1.html

[This message has been edited by engine man (edited 02-25-2011).]

quote Originally posted by engine man: best flowing heads are on the 3.4 DOHC they flow 277 cfm at .400 lift although the 3500'S heads are not bad if i recall like 260 CFM at like .600 lift but really want 4 valve DOHC engine only if it where all aluminum

Then get a Northstar. Or a Shortstar. Or a High Feature V6. You can't just take random parts from random engines and throw them together. AFAICT, you keep asking the same questions over and over, and ignoring the facts, and way too worried about how much CFM part of the heads flow.

Like was already said, there are people with 400+ hp 3.4 DOHCs in their Fieros. If that's not enough for you, then you need to move to something else. If you want lots of power, having a DOHC isn't necessarily going to get you there.

did i say i would take random parts and through them together no the crank form a 3500 fits and is the same stroke as the 3.4 but you need the reluctor wheel the caps fit the block but you must machine the block and more CFM more power the heads are where power is made not in how strong the bottom end is thats just how long it will last making the power BTW i never asked about the bottom end before you asked why i wanted the 3.4 and i gave you the answer thats all

[This message has been edited by engine man (edited 02-25-2011).]

I didn't ask you why you wanted a 3.4. Rather, it's pretty obvious that you have no idea what engine you want. You've made a thread asking about almost every possible swap. Surprised you haven't asked about the 3.1 McLaren motor. Where's that high power 4.3 swap you were doing?

Well if you just want to try busting my balls go for it and i can change my mind on what i want to build i mean wtf are you my mom if I had the money i would have 10 fiero's with 10 different engines but for now i am trying to find out if these parts would work thats all i am doing