Porting suggestions/pics for 3x00 heads

[IsaacHayes]

If the mark isn't all the way across the gasket surface area I wouldn't worry about it. Just as long as the rubber seals it. I'm using 3400 upper gaskets and they are paper on the bottom with silicone on top. The paper style will melt into stuff like that better. You can take some RTV and use a razor blade to wipe it across it to seal it though no problem. I actually did that on my pitted LIM on the 3100 once and it held great on the coolant jackets!!

Thanks for the info on the rasps.

For the central pneumatic die grinder, it has a safety catch so it doesn't turn on if you drop it. I took some masking tape and wrapped it flat to defeat it. It's so much easier to use then.

[ForcedFirebird]

If the mark isn't all the way across the gasket surface area I wouldn't worry about it. Just as long as the rubber seals it. I'm using 3400 upper gaskets and they are paper on the bottom with silicone on top. The paper style will melt into stuff like that better. You can take some RTV and use a razor blade to wipe it across it to seal it though no problem. I actually did that on my pitted LIM on the 3100 once and it held great on the coolant jackets!!

Yes, it went all the way across, but with hardley any pressure on the stone - just enough to scratch it. Like I said, not overly concerned because it's between the UIM and LIM. I'm going to follow your advice on the tape for the bottom side - we all know we don't need any help with leaks there . I'm going to use some silver tape (aluminum) that I have for sealing A/C plenums, this way one layer is tough enough to take a little abuse.

[IsaacHayes]

Ah yes that tape will work. Even when I had to go back to clearance my LIM for my rockers some more (since I did it first by eyeballing pictures online) I covered the ports, and coolant jackets and valve cover areas. A slip going that far would be a stretch, but I didn't want to chance it.

[Superdave]

I don't have any final pics of my combustion chambers but i did round off the parts around the spark plug, then sanded everything to about 800 grit and used the crossbuffs to get them very shiney.

my exhaust ports were opened up to a little bit under the 3400 gasket port size (since i used 3400 header flanges). I didn't go all the way because i was worried about losing port velocity.

my intake ports were matched to the LIM gasket with a little "fluff" room for the gasket crush, same as my LIM lower ports. i sanded the intake tracks in the LIM to about 800 grit all the way to about where the injectors were then crossbuffed to a shine. The intake ports in the heads were sanded to about 120 iirc.

Upper ports were matched to the 3500 metal gasket like you've done, same as the plenum, and i rounded off every sharp edge i could reach in the plenum.


I use a carbide cutter for most of the shape work then sanding cones to make everything blend in nicely, then crossbuffs for the bling.

mine will be coming apart this winter, i plan on stripping the heads back down and doing a little more work to the intake ports.. (with a few other small changes to the engine)

[IsaacHayes]

I noticed the casting on my 3400 lower was smooth like smooth garage floor concrete. The casting on my 3100 lower was rough like rough driveway concrete. I didn't polish the 3400 insides because it was all ready pretty smooth. The 3500 plenum was rough inside though but I couldn't really get to all of that.

[SappySE107]

I can't stress enough how little you should touch the 3500 heads.

[IsaacHayes]

Touching them kills the velocity eh?

[3400-95-Modified]

Is anything I did bad?

I just matched them, intake side only, which wasnt much.

[SappySE107]

The port entrance shouldn't screw anything up if you gasket match. I prefer to leave the floor alone, or just barely go over it to make it look nicer. I can't say any more on this subject.

[ForcedFirebird]

I can't say any more on this subject.

Because you said what you have to, or because you don't want to know your secrets , JK I'll take any advice I can since this is my first port job on a 660.

[Superdave]

yes, just sand the floor lightly. Don't change the short side radius of the port at all.

[ForcedFirebird]

And the exhaust? You said, Dave, to port to the 3400 gaskets? I also need velocity on the exhaust side because this motor will be feeding a turbo soon. Where did you get said gaskets?

[Superdave]

for you, i don't know how much i'd cut out of the exhaust ports. they are pretty large as it is. If i remember right the middle port is offset slightly on the 3500 VS the 3400 gaskets so I adjusted the shape of that one a little.

i used stock Felpro gaskets for a 3400, had to adjust them a little to clear the header flanges but that's easy.


here is the stock 3400 gasket on the 3500 head The far left port is how far I ported them out, the other 2 are stock:

[ForcedFirebird]

for you, i don't know how much i'd cut out of the exhaust ports. they are pretty large as it is. If i remember right the middle port is offset slightly on the 3500 VS the 3400 gaskets so I adjusted the shape of that one a little.

Why for me? Because I'm going with boost? I know I don't want to loose velocity, but at the same time the turbo is going to need all the gas/heat I can get to it.


Yeah, I saw a little difference betweent the 3400 and 3500 heads when I was comparing the two sets I had here. I thought all three of the 3500 ports looked like they were more vertical, but didn't actually measure it.

Also, I saw you used 1 5/8" primaries? Could they be beat close to the shape of the ports? I think I have some 1 5/8" in the garge, was going to experiment before I spent a bunch of money on 180* mendrels.

[3400-95-Modified]

The port entrance shouldn't screw anything up if you gasket match. I prefer to leave the floor alone, or just barely go over it to make it look nicer. I can't say any more on this subject.

You have your secrets as you very well should, Bill Gates doesn't release his windows code for the same reason