Installing Flowtech “ram horn” headers on a SBC

[ggeezer]

Factory Five’s Hot Rod Small Block Chevy Installation Instructions, Rev. F, dated 6/29/2020 on page 9 says “Attach the headers to the engine.” That’s it, other than two photos. I decided to do this write-up mainly to consolidate some part numbers in one place and perhaps save someone a little bit of frustration.

I installed a Blueprint Engine 400 c.i. small block Chevy in my ‘35 truck. The engine came with HP8103 aluminum heads which have exhaust ports measuring about 1.5” wide and 1.4” tall. Per FFR’s recommendation I bought a set of Flowtech (Holley) 11704 exhaust manifolds, aka ram horn headers. A couple of comments about these headers:

1) Fit and finish on mine (I got the silver ceramic because I had read that the chrome ones turn blue) was pretty good, although the tapped holes in the collector flange were kind of rough, so I chased the threads with a 3/8-16 tap.

2) The hardware kit included with the headers was rubbish. All the bolts were too long, there were too many of one size and too few of the other size. Also, there were about a gazillion or so split and flat washers – way too many. Maybe you’re supposed to use a few dozen washers under each bolt head? Perhaps this hardware kit is for another type or style of Flowtech header, but it clearly will not work for the ram horns. For a $400 item I would have expected Flowtech/Holley to do a better job with the hardware. That said, the studs for the collector flange were the right length so I did use those. Do yourself a favor and buy the Dorman 675-006 studs. They are 4” long and you get a set of 10, which means you’ll have to buy a pair of 3.5” studs to have a complete set of 12 studs (Dorman 03113). Since the header casting is not as thick at the ends you’ll need a total of four 3.5” studs so I cut down two of the 4” studs to use in the end mounting holes. I used brass nuts with lock-washers so I could remove the headers down the road if I need to.

Now on to the installation.

3) If you don’t have any anti-seize on hand, go to Harbor Freight and get their Permatex anti-seize. It’s about $10, and cheaper than any of my LAPS. Coat your studs on the short threaded end where they screw into the head, but be careful with this stuff – it seems to get on everything and it’s hard to get off! Screw your two short (3.5”) studs into the outer header mounting holes on the head (in my case these were NOT the outermost holes on the head). I used Remflex 2081 gaskets, which are the correct port size and hole spacing for the BPE heads. I used Remflex gaskets before on my Cobra build, so I was familiar with the product and never had an issue. Carefully hang the gasket on the two studs.

4) I used the FFR-supplied donut gasket (Walker 31398). The metal end fits into the collector on the header and the graphite end fits down into the flare on the J-pipe when they get bolted up. I used a small block of wood and a rubber mallet to gently tap the donut into place.

5) Install the collector flange studs, again using anti-seize. (You may have to drop your J-pipe slightly to get the header into place.)

6) Fit the ram horn over the two studs and run nuts on the studs temporarily so the header doesn’t accidentally slide off.

7) Grab a couple of the 4” studs and lube ‘em up with anti-seize. Thread them through the header and gasket into the holes in the head. Repeat until you’ve got all the studs in place. Now apply some anti-seize to the end of each stud and install a lock-washer and brass nut on each. Then go back and remove the temporary nuts you put on the outermost studs, coat with anti-seize, the install lock-washers and brass nuts on these studs. Tighten all the nuts finger-tight for now.

8) Pull the triangular flange on your J-pipe up to the flare, then carefully fit the flare over the donut and the triangular flange over the three studs you installed earlier. BTW, you don’t need the triangular gasket FFR supplies with the kit – the donut seals the collector and J-pipe up very nicely. Again, slather the studs with anti-seize, install the lock-washers and nuts, and finger-tighten.

9) Now tighten everything up. For their aluminum heads Blueprint recommends 18 ft.-lbs for 5/16” hardware and 25 ft.-lbs for 3/8” hardware. OTOH, Remflex says 20 ft.-lbs is the correct torque for their gaskets, so that’s what I went with. Work you way up to 20 ft.-lbs, starting with the inner-most nuts and moving your way to the outer ones.

10) After the header is torqued to spec, next tighten the nuts on the collector to J-pipe studs. The triangular flange on the J-pipe will not go all the way up to meet the collector – this is why you don’t need the triangular gasket, and also why there is no torque spec. Just tighten all three nuts evenly until they are snug. Your goal is not to crush the donut, just to get it to seat fully in the J-pipe flare. I used a small metal ruler (a machinist’s rule I believe it is called) which was about ½” across to get the gap between the triangular piece and the collector to be even all the way around. You could use anything about ½” thick (e.g. a nut or a bolt) to check your gap. In the end, my gap between the J-pipe and header collector flange was about ½” all the way around.

11) Repeat on the other side and viola you’re done!

12) Heat cycle the engine and re-check your nut torque. Re-check the torque again after a couple of hundred miles.

If something is not clear or you think could have been phrased more gooder, please hesitate to let me know.

[RoadRacer]

> but be careful with this stuff – it seems to get on everything and it’s hard to get off!

You're not kidding about that! I'm still finding it.

Love to see a pic of the final look of these?

[KippRacing]

Nice write up with part numbers. Wish I could find a set of headers for this application. I'm getting close to having to buy the flotech's.

[ggeezer]

> Love to see a pic of the final look of these?

Here you go:

header4.JPGheader3.JPGheader2.JPGheader1.JPG

[ggeezer]

Nice write up with part numbers. Wish I could find a set of headers for this application. I'm getting close to having to buy the flotech's.

I tried a set of the Summit SUM-G9200S headers but they hug the block too much so the FFR-supplied J-pipes don't meet up at all -- I think I would have needed a set of "extension tubes" which means more connections and thus more chances of a leak. I've seen Sanderson headers mentioned in other posts, but have never looked into them.

[Grandpas Garage]

I tried a set of the Summit SUM-G9200S headers but they hug the block too much so the FFR-supplied J-pipes don't meet up at all -- I think I would have needed a set of "extension tubes" which means more connections and thus more chances of a leak. I've seen Sanderson headers mentioned in other posts, but have never looked into them.

I also used the Summit G9200S headers on my 383 SBC and the J pipes supplied by FFR fit up perfectly.

[ggeezer]

I also used the Summit G9200S headers on my 383 SBC and the J pipes supplied by FFR fit up perfectly.

My heads are "23 degree AFR something something." Maybe that's why the G9200S didn't fit. I couldn't get the J-pipe in (toward the block) and up enough to get them to mate. I guess I could have moved some of the exhaust bracketry, but I'm lazy and the Flowtech just bolted right up.

[KippRacing]

Just got my flow tech rams horns yesterday. i'm planning on wrapping mine.

[GoDadGo]

Speedway Motors sells a similar set that have been extremely popular for quite a few years.
They come in cast iron, cast stainless and cast polished stainless.
They even make them for the LS and BBC platforms.

https://www.speedwaymotors.com/Searc...am%20manifolds