View Full Version : Swapping intakes

12-17-2004, 12:39 AM
Well in my quest to get my recently purchased used boat ready for next summer, I've run into my share of issues. Here's the most recent: I was putting the intake manifold back on after finding a possible failed spot on one of the gaskets, and noticed that it's an intake manifold for a 302 (based on the configuration shown in the PCM manual). Up to this point, all the markings and tags on the engine have indicated the engine is the 351. I even verified this with PCM based on the information on the tag attached to the intake manifold. This tells me the previous owner may have switched the intake manifold with one from a 302 for whatever reason and transferred the engine tag.

So how will this effect the engine? I know that the intake manifolds on the 302's and 351's can be swapped, but there has to be some kind of difference. Otherwise, there wouldn't be different intakes for the different engines.

Will I be okay running this intake, or is this the next item going on my shopping list?

12-17-2004, 01:54 AM
Actually, you can't swap intake manifolds from a 302 to a 351W. The 302 would be too small for the 351W. In other words, the 351W is taller than the 302. This means the intake ports on the heads will be further apart than they would on a SHORTER 302. They can't be interchanged, just won't work. Exhaust manifolds on the other had, can be interchanged.

east tx skier
12-17-2004, 10:24 AM
iokua, I just left my old 351W manifold with my mechanic, but it might not be too late to get it back. It came off a 93 MC w/ 351W HO (92 Indmar/Ford Engine). If you want it, and assuming I can still get it back, just pay me for the shipping and it's yours. Let me know.

Update: You want it, it's yours for the shipping.

12-17-2004, 10:36 AM
Well now isn't this getting interesting; I put the manifold back on last night and it does look a little low to me, but it seemed to fit okay. Although I didn't really check to see if the holes in the head and manifold lined up. After posting last night, I went to the Skidim website to see how much a 351 manifold would cost. The picture they had was identical to mine. The difference indicated in the PCM manual is that for the 302 there are 12 mounting bolts; 16 for the 351.

East tx skier: Thanks a lot for the offer! I would jump all over that if I knew for sure I needed it; as of this morning, I'm not sure based off what martini said, and what I saw on Skidim. I guess it wouldn't hurt to see if you can still get it back - just let me know what you find out.

Edit: Just saw your "update"; how long do I have to decide?

Can anyone send me a pic of their intake manifold on a 351?

Does anyone know if the 351 manifold has undergone any changes since 1985?

east tx skier
12-17-2004, 10:41 AM
iokua, I probably won't have it back until Monday (but I could have it today). Take your time. But let me know either way as I'll put it on ebay if you or nobody else here says he wants it. It's in really good shape (from the brief look I gave it) with very little rust for an 11 year old manifold (just a little surface rust near the bolt holes from what I saw). If you use it, just make sure the gasket has the restrictor plate (see skidim).

12-17-2004, 04:03 PM
Well now isn't this getting interesting; I put the manifold back on last night and it does look a little low to me, but it seemed to fit okay.

Martini is correct; the 302 intake won't bolt onto a 351 block and heads. It's not a matter of it being "close" and you making it work, it won't fit at all. If you dropped a 302 intake onto a 351 longblock, there'd be about a 3/4" gap between the intake flange and one of the head flanges.

Unlike the SBC, the SBF used two different block heights on the Windsor small block, which results in a different intake.

east tx skier
12-17-2004, 04:54 PM
Thomas, I presume he has an early 80s boat since it's PCM. Would he be able to use my old intake?

12-17-2004, 05:12 PM
He should. As long as it's a 351W, they're al the same regardless of year.

iokua: Here are some pics for you to compare;

289 and 302 intake:

351 intake:



12-19-2004, 11:57 PM
Sweet. OK, thanks guys. My intake definitely looks more like the Edelbrock pictured for a 351. I'm still confused about what the PCM manual is showing (as far as # of bolts), but it doesn't sound like the intakes are swappable anyway. So I'm not going to sweat it.

For clarification, it's an '85 with 351 PCM. The previous owner (as I'm told by his son, who sold me the boat), was a "motorhead". However, he did some funky things to it, so I'm a little skeptical when things don't add up.

EDIT: East tx skier: Thanks a lot for the offer of your intake! I was about to tell you that I won't be needing it, but I'm wondering if it's any different than the one I currently have? Would it benefit me to change mine out with your old one?

12-20-2004, 11:36 AM
Oil pans will not swap between 302 and 351W either. Main bearings/seals are larger on the 351.

east tx skier
12-20-2004, 11:45 AM
If yours is a 351, then you ought to be able to use mine. Just let me know. I'm picking it up in about an hour.

east tx skier
12-21-2004, 11:50 AM
Okay, having spoken to Josh, if anyone wants an intake manifold for a 351W, shoot me an email. It's yours for the shipping cost (shipping won't be cheap due to weight, but it may prove cheaper than buying one). It'll be in my attic.