Difference in 427MR and 427HR

[xlr8or]

If building a period correct engine, what is the difference in the Medium Riser vs. High Riser setup? Is it just the port design?
Is there a preference?

I notice most aftermarket stuff seems to MR. Are there new intakes that fit HR heads?

[Woodz428]

Primarily it is port design, although the difference also requires a matching intake manifold. There is a lot of discussion regarding which is best, but my vote goes to the medium riser in most applications.
I believe Dove and/or Blue Thunder may make some intakes, the reason most parts you see are for medium riser is just sheer numbers. They were made in much larger quantities than the others and replacement parts were also used on other engines so they were available through the parts department.

[Excaliber]

When I rebuilt my engine I considered going with alloy heads to replace my iron 1964 OEM heads but I wanted to use my 2X4 high rise intake. I found only a couple of heads that MIGHT work with my intake, but there seemed to be some uncertainty as to port matching.

The high riser heads have really TALL (as in long) ports compared to the MR and thus require a specific intake gasket as well. There are no heat crossover ports to warm the intake on the high riser configuration. But that may be a non issue as it seems most of todays aftermarket alloy heads don't have an exhaust cross over port configuration anyway.

In the end I decided to stay with the iron 1964 date coded heads regardless of what was available. I just felt it was a good combo for my build, date coded heads and date coded intake (1964). Some say the MR's flow 'almost as much' anyway as are 'almost as good' as the HR's. I suspect that holds true under the 6500 rpm or so. The high risers continue to flow well beyond the 7000 range. My original engine did run in the 7000 plus range and pulled strong at that lofty rpm, but was to radical for the 'street' due to BIG cam profile, race only carbs and 12.5 to 1 compression.

I rebuilt using a milder cam profile (6400 or so), smaller carbs and custom pistons that provide some 'quench' as well as lower my C.R. (9.8 to 1). I doubt that I am taking advantage of the higher flow rates available with the high risers at this point. I kept them because there 'cool' and I like the idea I'm running "Tall and Terrible" high risers with a 2X4. Very street friendly now, power comes on smoother than the 'explosive' power I had before. It's about a 1/10th of a second slower in the quarter (11.90 vs 11.99) but still 'fast enough' to take your breath away. MPG almost doubled!

I think NASCAR outlawed the heads for the 1965 racing season, Ford dropped them and they were replaced with MR's.

[FFR428]

I think part of it was NASCAR changed the use of bubble or teardrop hoods. And banned the high riser heads and intakes at the end of the 64 season along with the SOHC. The MR heads were introduced in 65 and favored until the tunnelport heads came out in late 66 or early 67.

Hey Ernie do you know the Ford part number for the high riser intake gaskets? I thought I had it somewhere but apparently not. Guy on another fourm is looking for that info AND a oem set of gaskets.

Thanks,

G.

[Excaliber]

I just checked my stock, the set I have is after market with no part number.

...there not for sale.

[FFR428]

Ok thanks. BTW DSC sells HR gaskets if ya ever need them. This guy wants a oem set. Next to impossible to find I'd think. DSC's gaskets look pretty close to the oems in tunnelport version anyway. Much better than the Mr Gaskets. This guy and his Dad are building a Tbolt clone and have the original 427 HR from Tbolt #34. Pretty cool. He's gonna send me some pics. I'll pass them along if you'd like to see them.

G.

[Excaliber]

'Rumor has it' my heads and intake also came from a T-Bolt in Texas around 1986. I spoke with the guy that built the car/engine a couple of years ago. He was pretty tickled to be reminded of the car and the memories flooded back as we chatted away.

[FFR428]

Wow thanks pretty cool!! Nice to know some history on your parts. My heads are just lowly over the counter parts.

G.