FMS 351w swap headers, questions

281pony · Dec 4, 2011

i had a 393 stroker fall into my lap basically. i can also get some fms swap headers for a 351 for free. i did some quick searches online, how horrible are these really if anyone has used them? i haven't seen them in person.

appears they are 1.75 primary to 2.5 collectors? i was also told they are designed to work with factory/302 style midpipes. so if i replaced my equal 302 shortys with these, the rest bolts up.

can anyone confirm or denie some of this for me? remember.. they are free. how bad are they.

ID89GT · Dec 4, 2011

If they are free I would take them. Even if you don't end up using them you can just sell them

281pony · Dec 5, 2011

ID89GT said:
If they are free I would take them. Even if you don't end up using them you can just sell them

they are from a friend. i am not gonna take parts to flip them like that.

the reviews i found (from 2002) implied they were so ty it wasn't even worth taking them.

Three50won · Dec 5, 2011

281pony...look at it this way, you can buy some brand new LT headers and exhaust using the money you're saving from getting the 351 stroker for dirt cheap. If you did that then you'd still be ahead a few bucks. On the other hand, you can use the headers he gave you.

The problem I see with them is that the primaries may be too small, the collectors are only 2.5, and they're short style headers. So they're not gonna flow enough for a built 393. Expect to leave some power on the table with this set-up. Now you can use them just to get the car running but if you do then I'd suggest getting rid of them first chance you get. Ideally you want something like a LT 1 3/4 or LT 1 7/8 primary with 3" collectors into a 3" exhaust...IMO. But that kind of engine is gonna get choked off by your current exhaust.

281pony · Dec 5, 2011

Three50won said:
281pony...look at it this way, you can buy some brand new LT headers and exhaust using the money you're saving from getting the 351 stroker for dirt cheap. If you did that then you'd still be ahead a few bucks. On the other hand, you can use the headers he gave you.

The problem I see with them is that the primaries may be too small, the collectors are only 2.5, and they're short style headers. So they're not gonna flow enough for a built 393. Expect to leave some power on the table with this set-up. Now you can use them just to get the car running but if you do then I'd suggest getting rid of them first chance you get. Ideally you want something like a LT 1 3/4 or LT 1 7/8 primary with 3" collectors into a 3" exhaust...IMO. But that kind of engine is gonna get choked off by your current exhaust.

yeah. i will be running my si-blower on this engine eventually also. which will help things along, but lt's and mid-pipe will cause my catback not to work also. so it goes from 0 cost to around $1000 for decent stuff. pretty big investment, for how much gain?

Three50won · Dec 5, 2011

It would be a pretty significant gain just on the 393 alone. Add a blower to it and you're really gonna choke it off with that set-up. It's still gonna be fast mind you, however that set-up isn't even optimal for a 302 with a good HCI combination. I wouldn't use it. A good set of LTs with a 3" exhaust would be very well worth the money.

Cobra912 · Dec 6, 2011

if you can test fit them try it. I have a set of hooker super comp conversion headers and they were a nighmare

281pony · Dec 7, 2011

awesome.. i'm workin on some mid-length headers, pro chamber and catback. 1.75 to 3" all the way back.

FMS 351w swap headers, questions

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