Hi-Po Manifolds

tx65coupe · Apr 21, 2009

Is anyone running Hi Po K code manifolds on a 302 with Edelbrock heads?

I was thinking of running Hi Po manifolds on my 65, because I don't want to deal with ill fitting headers any more.

If I do this I plan on using Percy's gaskets between the heads and manifolds. I was going to use them with my headers, but the headers don't fit right.

Is this a decent idea?

I don't want long tubes because of my clutch cable and I don't want to smash the collectors on speed bumps.

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Rusty67 · Apr 22, 2009

I don't know if the HiPo manifolds will clear a clutch cable setup or not. If they do, then port them out for improved flow. I just run RTV on mine, no gasket.

tx65coupe · Apr 22, 2009

From everything I have heard a gasket needs to be used with cast iron manifolds if bolting them to an aluminum head. I'm not sure though.

Do the Hi Po manifolds flow enough for a built 302? My engine is not radical but it is making over 300 hp.

Has anyone else run Hi Po manifolds with a clutch cable from MD?

BornInAFord · Apr 23, 2009

I currently have Hi-Po manifolds on my 66 and like them pretty well. I also have Edelbrock Performer heads, but only 2" dual exhausts. I didn't go all out for power, but the car still performs pretty good.

I use Remflex gaskets (which I would recommend) and have ported out the primaries and some of the collector. The Hi-Po manifolds fit well, but the ports needed work and the collector was too small for my tastes as cast. My bolt holes lined up well, but some of the recent castings have had issues with the manifold to head bolt holes not being well aligned. The fix for that is a little dremel work to enlarge the bolt hole if and where needed. Here a few pictures comparing my Hi-Po manifolds to my original 1966 stock log-style California smog manifolds with the indents to clear the air tubes (thermactor fittings). Note the differences in shape and port sizes between stock log-style and Hi-Po and also differences in the diameter of the collector to H-pipe. You can port it out to ~2 1/4", maybe a little more, for better flow yet. Sorry for the size of the pics--I wanted to show details not available in thumbnail sizes.

Collector size difference

Port size difference after a little porting on the Hi-Po. The Hi-Pos started out bigger, but porting will help with the port shape. The carbon deposits in the stock manifold on the left is the size of the Edelbrock exhaust port. YES, I had a leak at the corner, but these were only used to break in the engine.

Passenger side

Driver side

Daniel

BornInAFord · Apr 23, 2009

Oh, and I run the Hi-Po manifolds and H-pipe with a Ron Morris cable clutch. No problems, and there is well over 4" of clearance at the closest point.

tx65coupe · Apr 23, 2009

Thanks for the comparision pictures.

That is really intersting to see them side by side like that.

I'm still not totally sure what I am going to do just yet. I would like to run the JBA midlength headers I have. To make them fit it looks like I will have to change out my 66 style motor mounts to the Ron Morris adjustable ones.

Rapid · Apr 24, 2009

If you already have JBA's get the RM mounts.

If you are starting from scratch be aware that repo HiPo mainfolds are a hair narrower than originals and mounts may need to be modified, y pipes might be a little wide if made to stock specs etc.

I found this out talking to Ron Morriss about their mounts.

Edster · Apr 24, 2009

I went from headers to HiPo manifolds to tri Ys. I liked the tri Ys better than the manifolds as far as performance goes. Tri Ys had no clearance issues... as long as you get the drop bracket for the power steering (if you have it).

tx65coupe · Apr 24, 2009

The RMP adjustable mounts should be here today. Hopefully I will be able to move the engine back 3/8 to 1/2 inch. If I can do that I think everything will work out. The MD crossmember for the T5 still has a bit of room for adjustment at the mount and the shifter is centered right now, so it can also move back a bit.

I originally wanted to run Tri-Y's but they won't work with the Modern Driveline clutch cable setup. At least that is what MD says as well as others that have their setup.

BornInAFord · Apr 25, 2009

The inner tube (primary collector of the 5 and 7 primaries) of reproduction SBF tri-y headers occupies the same real estate that the cable wants to pass through. Tri-ys (and many long tubes also have this problem. I've tried several types of longtubes and either they completely interfere with or rest against the cable. I know some longtubes work, but the reproduction tri-ys (like Patriot) won't work with cable clutches. The tri-ys which have the driver's side collectors stacked vertically (like they are on the passenger's side) instead of side by side may work, though. I think JBA has this design.

Here are some pictures of Jet-hot coated reproduction tri-y headers for illustrating the stacked passenger and side-by-side driver's side collectors. The dent is to clear the steering box. These headers didn't work with cable clutches.

Here is a picture of JBA SBF tri-ys that have the 5/7 collector tuck in and under the 6/8 collector and y's vertically. Even then, JBA says only for z-bar linkage or auto mustangs.

Rusty67 · Apr 25, 2009

My mid length Tri-Y's fit perfectly.... then again they were custom built.

It seems to me that the #1 problem of all the T5 swaps using cable setups is header clearance. Doesn't Dougs make a set that is designed for this swap ?

tx65coupe · Apr 28, 2009

I got my JBA 1650SJS mid length headers to fit. The H pipe is installed as well. The RMP mounts solved almost all of the problems. I decided to grind a hair off of the corncer of the steering box just incase though.

jonfor · May 9, 2009

tx65coupe said:
From everything I have heard a gasket needs to be used with cast iron manifolds if bolting them to an aluminum head. I'm not sure though.

Do the Hi Po manifolds flow enough for a built 302? My engine is not radical but it is making over 300 hp.

Has anyone else run Hi Po manifolds with a clutch cable from MD?

+1 on that question??

also, if i understand correctly, the collector is 2" and not 2-1/4"????

i like the way they look , but i would like to eventually make it to 250-300hp to the tires without paying for an exhaust system twice.

2+2GT · May 9, 2009

jonfor said:
+1 on that question??

also, if i understand correctly, the collector is 2" and not 2-1/4"????

i like the way they look , but i would like to eventually make it to 250-300hp to the tires without paying for an exhaust system twice.

Yes, the 289 High Performance featured a 2" exhaust system. I used to run headers but tired of the disadvantages. They didn't leak, but they did reduce ground clearance somewhat, I did have to tighten the occasional flange bolt, but mostly they just gave off a lot of heat. I switched to HP manifolds and was never sorry. The engine is a ported 289HP, although I have used a variety of intakes and carbs.

BornInAFord · May 10, 2009

jonfor said:
+1 on that question??

also, if i understand correctly, the collector is 2" and not 2-1/4"????

i like the way they look , but i would like to eventually make it to 250-300hp to the tires without paying for an exhaust system twice.

If you look at my pictures above, you'll see the collectors were enlarged enough to fit a 2 1/4" exhaust. That's about the largest you can go with these, though. Depending on heads, intake and cam, 2 1/4" dual exhausts should flow plenty to meet the ~300HP goal.
Daniel

2+2GT · May 10, 2009

BornInAFord said:
If you look at my pictures above, you'll see the collectors were enlarged enough to fit a 2 1/4" exhaust. That's about the largest you can go with these, though. Depending on heads, intake and cam, 2 1/4" dual exhausts should flow plenty to meet the ~300HP goal.
Daniel

Well I'll be, so it is. That's a slick and subtle upgrade. The tricky part would be an H-pipe. Motive makes a 289HP H-pipe in 2.25", but necks it down to 2" at the flange. I'm sure they could be persuaded to make one with 2.25" flanges, it would actually be less work for them. Did you machine the outlets yourself?

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