I was wondering if its possible to run a newer style split exhaust manifold on my 82 300 i-6 with out changing the intake or carb. my old 6 to 1 manifold [or whatever you call it]is rusty and is leaking where the manifold connects to the downtube. my current exhaust setup is 2 1/4 inch straight pipe with a trush glasspack it exits threw a 3 inch chrome tip infront of the right rear tire. I figure if the split manifold would fit, I could rig up a new 2 into 1 downtube, or pick up some more pipe and a second glasspack and run true duels, have anouther big tip if front of the other tire

 

What you're talking about is a pretty common swap. The later EFI manifolds flow much better than your stock log manifold and will bolt right up. The later EFI heads had a few more bolt holes in them than the earlier carb'd heads but the EFI manifolds will bolt up just fine. If you don't feel like making a new y-pipe you can buy the Walker down-pipe from J C Whitney or look for them on E-Bay. Good Luck, Matt.

 

They will fit but I did need to grind some off the bolt tabs on both the intake and exhaust. If you use an aftermarket intake you don't need to grind anything!

 

5_labs brings up a good point about the grinding. I used an Offy and I didn't have to grind on the EFI's but I did just to make it easier to installl. Do a couple of dry runs to see how it's going to fit so that you get the feel of it before putting a gasket and any sealer on it.

 

I've a set of the E.M.'s that you are looking for.
You give me the price I paid for them plus S&H & they are yours.
Contact via P.M.

Cheers
Colonel Flashman

 

I just completed the EFI manifold swap on my '85. Highly recomended! I changed the entire exhaust system, Walker downpipe, high flown cat (2.5" I/O) and Dynomax dual tailpipe cat-back system. Both tailpipes exit after the passenger rear tire (looks stock, except the 2.25" diameter pipes!) The Dynomax system cleared my 31 inch spare tire (in factory location) and class III trailer hitch with pleanty of room to spare. Muffler has nice deep tone, not loud at all.

Now the 300 spins freely to 3000+ RPM and no more exhaust leaks from the head/exhaust manifold junction, heat riser valve, intake/exhaust manifold junction and exhaust pipe flange. Do it and forget it!

Grinding of the EFI's is required, I needed to grind a bump off of the rear manifold and one unused bolt tang off of one of 'um. No grinding of the intake was required. Do a search, I think this topic is pretty well documented.

FYI, the alternator top (pivot) bolt needs to be reworked as it is removed rearward. First, drill the threads out of the front of the alternator bracket then either helicoil the rear hole or use a longer bolt and locking nut. If you do not make this mod, look forward to removing your front exhaust manifold when you need to change the alternator.

It took me a while to get off my a$$ and do the job but it was well worth the effort.

Let us know what you decide.

 

You can put the alternator on the bracket and mount the bracket to the motor without a problem.

 

This is what I did for my alternator. No problem.

But yeah, upgrading the exhaust is well worth it. I went EFI manifolds, Walker downpipe, magnaflow high flow cat, flowmaster 50 series with 2.5" duals.

I also went with the offy intake and Holley 390. I was sick of messing with 1 barrles. The performance difference is unreal. A neighbor drove my truck recently and commented that it felt like a v-8 under the hood and not a 6!

 

Does anybody know if the Walker downpipes will clear the inner fenders, etc on the earlier trucks, specifically 67-72?

 

I picked up a set of efi manifolds, 13 bucks from the junk yard, as soon as it warms up outside I can start putting it together

 

13 is a killer price. When I was shoping for a set everyone wanted 50 - 60.

 

Got mine free! They replaced an engine in a van and replaced the manifolds. They were going to put them in the trash. Nothing wrong with them.