3500 swap questions

[IsaacHayes]

Hahha yes I know it costs more but it's a project car might as well do it right and get some more power from headers! You want it to be fast right?

I think you'll have to cut off the flange and position it different or put your own flange on or something would be my guess... But modifying the downpipe isn't that hard to get it to fit compared to what it would take in an L body.

The O2 bung is in the cross over yes. Not the most ideal spot, so it would be best to weld in a nut in the down pipe somewhere for the O2 sensor(s) so they can read both banks. You can cap the cross over bung with a bolt of the right size then.

[Superdave]

S&S is usually pretty quick although they "forgot" to ship me an order a while back.. i called after a month of waiting and they overnighted it to me.

[PCGUY112887]

Well I was looking at the headers and it looks like they put the bung for the O2 right in the crossover area (far away enough from the ports for the wideband). I have also read a few posts that say the headers need no modification, and 1 that said that the flange had to be modified a bit or it would bump against the firewall.

So I just ordered the headers

Damn you Isaac... making me spend money

Anyone have any idea how long they take to ship? I have been calling them all day and I sent them an email this morning but I haven't been able to get ahold of anyone.

[IsaacHayes]

Not sure.

[PCGUY112887]

I just got my wideband in the mail today, says it needs to be at least 18" from the exhaust port...

That is no where near where the stock O2 sensor is. I planned on using this gauges simulated output to run the car, if it was 18" from a port would it still run fine?

Isaac, if I got the headers wouldn't I have to put them in after the engine was in? It doesn't look like I could bolt them up then put the whole engine in, looks like it wouldn't fit.

[IsaacHayes]

or go S&S headers...

[PCGUY112887]

Yes but I don't want to do all of this work to have less than stock HP for this engine because of restrictive manifolds.

To be honest I much rather just use my header style manifolds, but then I either gotta pay the shop to try to rig them together under the oil pan and make an O2 bung in a wye pipe somewhere (and weld shut the stock O2 bungs), or find part of a G6/malibu exhaust that connects them into 1 downpipe and see if it would fit.

[Superdave]

use 3400 gaskets and they'll work fine.

[PCGUY112887]

Do you mean the actual tubes, or the openings?

Because despite how it looks like with the black marks, the width and height of the ports from the first pic match my heads, and they match my manifolds.

[bszopi]

The first picture manifolds are not the 3500 sized. They are not fat enough. Compare the 1st picture to the 3rd picture and you should be able to see the difference.

[PCGUY112887]

So are these manis the correct size or what?

[IsaacHayes]

Gaskets usually are over sized. That's why you can gasket match parts. I gasket matched my 3400 LIM to the gaskets. The gasket was bigger than the port.

[PCGUY112887]

OK so I may have found some manifolds...

Someone here has some 04 3400 manifolds, I wasn't sure if they could be 3500 sized or not, so I asked for a pic with measurements.

Here is what I got.



So I went out and my exhaust ports on the heads are the exact same size of what is in the pic there. My "header style" manifolds are also the exact same size... however the metal gasket for my 3500 is what appears to have the super wide exhaust ports.

My exhaust pics





Does this look right? Does this mean some 3400 04 manifolds have 3500 sized ports as well, or did I somehow get heads with small ports?

[Superdave]

Header is probably heating up the starter too much causing it to not work. Electric coils/motors hate heat.

Yep.. gonna coat it in header wrap.. but that won't matter for you....

[IsaacHayes]

Header is probably heating up the starter too much causing it to not work. Electric coils/motors hate heat.