I took of both exhaust manifolds. I found some restriction in air flow. Not so much on the left manifold. But check out the firewall side manifold



Cylinder 2 and 4 are like this. It surprises me this passed QC.. Oh well time to get out the Dremel.

quote Originally posted by Ramon: I took of both exhaust manifolds. I found some restriction in air flow.

Yep, common knowledge in the Fiero world. It's rather puzzling why Pontiac would allow them to be built in that manner. Get rid of those obstructions and you'll gain a few ponies.

quote Originally posted by Patrick in This thread: My buddy has a Hole Saw kit (similar to what's pictured below) which includes a cutter which is the exact same size as the inside of the manifold ports. It takes about ten seconds per port to do a perfect job! I'm not kidding. I'm surprised more people don't use this method.

[This message has been edited by Patrick (edited 05-05-2015).]

Weld the flanges all the way around the tubes on the outside first (they always crack there), then cut and or grind the obstructions away.

Patrick, is there a one-off hole saw size available?? The entire set might be too pricey. Any special material the saw should be made of? Do you need a drill press with the close fit or is a hand drill still ok?

quote Originally posted by tesmith66: Weld the flanges all the way around the tubes on the outside first (they always crack there), then cut and or grind the obstructions away.

Perhaps the problem is more pronounced with some sets of exhaust manifolds, but when we ported mine (using the method posted above), we felt we didn't need to do any reinforcement welding. A year and a half later, all is still good.

quote Originally posted by Notorio: Patrick, is there a one-off hole saw size available?? The entire set might be too pricey. Any special material the saw should be made of? Do you need a drill press with the close fit or is a hand drill still ok?

I don't know if individual cutters can be bought, but yes, I can certainly understand why you wouldn't wish to buy a whole set just for the one size needed for this task. I don't recall the size, but the cutter fits perfectly in the manifold holes. We just used a hand drill with the manifold held securely in a bench vice. I don't believe there's anything "special" about the cutter, but the set's not mine, so I'm not all that familiar with it.

quote Originally posted by Notorio: Patrick, is there a one-off hole saw size available?? The entire set might be too pricey. Any special material the saw should be made of? Do you need a drill press with the close fit or is a hand drill still ok?

Harbor Freight has a set of hole saws that should work, which is fairly cheap.

Thanks guys, I will check on those. Judging by my spare set it might be the 1 and 1/8" size.

Ramon, sorry for the detour.

I used dremel tool with the oxide drum--ground all that off---car sounds great!!

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Pat Jones

quote Originally posted by Notorio: Patrick, is there a one-off hole saw size available?? The entire set might be too pricey. Any special material the saw should be made of? Do you need a drill press with the close fit or is a hand drill still ok?

Most hardware stores sell them singly, buy the mandrel and whatever size saw you want, so you will need to know what size obviously if you buy just one. Unless some one knows the right one wait until you measure it.

Steve

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Technology is great when it works,
and one big pain in the ass when it doesn't



Detroit iron rules all the rest are just toys.

I picked up a diamond plated grinding bit at HF today I'm going to give it a try in the morning. I'm looking forward to see if I get a decent performance increase. id like to pick up some FS headers, but man $$$$$.

quote Originally posted by tesmith66: Weld the flanges all the way around the tubes on the outside first (they always crack there), then cut and or grind the obstructions away.

Be careful welding the manifolds off the head. To much weld heat can and will warp them. Trust me I know. It is my belief that the obstructions are a major contributing factor that causes the cracking therefore if you take care of the obstructions welding is not necessary unless you already have a crack. IMHO