sprice
Active Member
Have an extra set of HP manifolds and will be refreshening my 73’ Imperial. Would anybody know if they will fit? Thanks.
73’ Imperial - will HP manifolds fit?
- Thread starter sprice
- Start date
yes but of course you will have to get the pipes modified or new ones fabbed up
I do not think it is worth the hassle to install. The hp manifolds don't offer any power gains on the dyno tests I have seen. I also think you may have interference at the steering column.
polara71
Old Man with a Hat
So are you saying Chrysler made a variation of their exhaust manifolds for a whole bunch of engines and body lines that Offered NO benefit in flow or performance?
I might suggest searching for some of Nick's dyno tests as I seem to recall some comparisons he did on that subject.
In one respect, the basic length of the main section of the cast iron HP manifolds is longer than the normal manifolds, but otherwise not much difference. That length and smoother shapes might be where the advantage is, plus possibly a little bit of additional internal diameter and exit hole? Possibly there IS something to the shape or Chevy would not have copied them for their 1990s LT1 motors in Caprices and Roadmasters, burying them under two levels of heat shielding
Look at the 300J exhaust manifolds from that engine Nick did. Those things look archaic compared to the later HP manifolds, but they apparently worked with their longer runners to compliment what was going on on the intake side of things. As Chrysler did some things back then, it seems that they tended to "stumbled onto" things which fit together and just worked. As the 1958-era RB 2x4 intake that helped one motor to massive power levels not known back then.
The main issue on the Imperial and the exhaust manifolds which never ccame on it would be the steering components (lh) and torsion bars (rh). Unless the exit pipe holes are 2.5", no real benefits (or minor benefits) of the HP manifolds (time and money it getting them installed) would be justifiable for anything other than the "WOW!" factor. In an Imperial, torque is needed more than 5000rpm horsepower gains. On the other hand, seeing them would be more difficult with all of the other stuff under the hood.
For "something better", possibly the 1975-era larger cross section B/RB C-body manifolds with larger lead pipes and rearward?
Just some thoughts,
CBODY67
In one respect, the basic length of the main section of the cast iron HP manifolds is longer than the normal manifolds, but otherwise not much difference. That length and smoother shapes might be where the advantage is, plus possibly a little bit of additional internal diameter and exit hole? Possibly there IS something to the shape or Chevy would not have copied them for their 1990s LT1 motors in Caprices and Roadmasters, burying them under two levels of heat shielding
Look at the 300J exhaust manifolds from that engine Nick did. Those things look archaic compared to the later HP manifolds, but they apparently worked with their longer runners to compliment what was going on on the intake side of things. As Chrysler did some things back then, it seems that they tended to "stumbled onto" things which fit together and just worked. As the 1958-era RB 2x4 intake that helped one motor to massive power levels not known back then.
The main issue on the Imperial and the exhaust manifolds which never ccame on it would be the steering components (lh) and torsion bars (rh). Unless the exit pipe holes are 2.5", no real benefits (or minor benefits) of the HP manifolds (time and money it getting them installed) would be justifiable for anything other than the "WOW!" factor. In an Imperial, torque is needed more than 5000rpm horsepower gains. On the other hand, seeing them would be more difficult with all of the other stuff under the hood.
For "something better", possibly the 1975-era larger cross section B/RB C-body manifolds with larger lead pipes and rearward?
Just some thoughts,
CBODY67
sprice
Active Member
Thanks for responses. Its just I have these sitting on the shelf whereas is probably my last Mopar rebuild/freshen. Some of it is the WOW factor and not expecting any real difference in performance. Will be adding TTI duals, bump up the cam, maybe some head work, if it all makes sense, and then the fun of trying something different and getting rid of parts on the shelf.
68 4spd Fury
Senior Member
Not sure about fit. I do remember dyne tests on graveyard cars, (take it with a grain of salt there), but the HP manifolds were as good as all but the best headers on the market at that time and even those, not a huge difference. Now, what difference they'd make on a 73 smog motor is undetermined.
Given the subframe within the stubframe on Imperials to further enhance smoothness and sound isolation, nothing under the hood on those models is easily done. Putting on those exhaust manifolds is virtually certain to be a major headache.
This is a dyno test that has been posted on various mopar forums. Here is a link to one posting. Doing a little dyno testing on a low compression 440.
I have read the original post about the stock 440 dyno pulls, easy search.
Maybe if you have a high compression (10.5:1) you might get a better outcome, but your 440 is low compression as mine is, and why I went looking for results a few years ago.
I found this discussion right here on FCBO. Max wedge vs HP manifolds vs Headers Test!!
www.forabodiesonly.com
Yep, put a 1972 440 on the dyno today to test out a few ideas, you know, like headers, camshafts, intakes, carburetors and heads. The first pull had it set up like this, '72 440 with .040" overbore for 448 ci, cast crank, cast pistons .160" down in the bore for 7.45:1 compression ratio, 906 heads, 1972 cast iron intake manifold, 1967 600 cfm Carter 4bbl, Summit Racing SUM-6400 camshaft 214/224 @ .050 .444"/466" lift 112 LS 106 ICL, 1964 stock cast iron exhaust manifolds. Results,
RPM...............TQ................HP
2500.............414...............197
2600.............402...............199
2700.............403...............207
2800.............402...............215
2900.............399...............220
3000.............403...............230
3100.............397...............235
3200.............399...............243
3300.............399...............251
3400.............391...............253
3500.............385...............257
3600.............380...............261
3700.............371...............262
3800.............365...............264
3900.............358...............266
4000.............350...............266
4100.............348...............271
4200.............336...............268
4300.............332...............272
4400.............323...............271
4500.............313...............268
4600.............304...............266
4700.............295...............264
4800.............283...............259
4900.............267...............249
5000.............260...............248
5100.............249...............241
5200.............231...............229
5300.............225...............227
5400.............214...............220
5500.............204...............214
The second pull today was with the HP exhaust manifolds, nothing much to report other than they lost 1 lb-ft of torque and gained 4 horsepower. Don't waste your money unless you are doing a restoration.
So, if you want to hang on, we'll take you through some bolt-on's we did today that took us to 463 lb-ft and 440 HP while NEVER taking the compression ratio beyond 7.8:1. We went to headers, bigger carb, aluminum intake, camshaft, even bigger carb and then ported 516 factory iron heads.
I have read the original post about the stock 440 dyno pulls, easy search.
Maybe if you have a high compression (10.5:1) you might get a better outcome, but your 440 is low compression as mine is, and why I went looking for results a few years ago.
I found this discussion right here on FCBO. Max wedge vs HP manifolds vs Headers Test!!
Dyno testing a stock(?) 1972 440
We're doing a dyno exhibition for the locals on Saturday the 14th so they can see what an engine dyno is and what it may be useful for. We pulled a 440 engine from a 1978 New Yorker, that turned out to be a 1972 440, .040" over with 906 heads. Pistons are .160" down from the deck, so with the...
www.forabodiesonly.com
Yep, put a 1972 440 on the dyno today to test out a few ideas, you know, like headers, camshafts, intakes, carburetors and heads. The first pull had it set up like this, '72 440 with .040" overbore for 448 ci, cast crank, cast pistons .160" down in the bore for 7.45:1 compression ratio, 906 heads, 1972 cast iron intake manifold, 1967 600 cfm Carter 4bbl, Summit Racing SUM-6400 camshaft 214/224 @ .050 .444"/466" lift 112 LS 106 ICL, 1964 stock cast iron exhaust manifolds. Results,
RPM...............TQ................HP
2500.............414...............197
2600.............402...............199
2700.............403...............207
2800.............402...............215
2900.............399...............220
3000.............403...............230
3100.............397...............235
3200.............399...............243
3300.............399...............251
3400.............391...............253
3500.............385...............257
3600.............380...............261
3700.............371...............262
3800.............365...............264
3900.............358...............266
4000.............350...............266
4100.............348...............271
4200.............336...............268
4300.............332...............272
4400.............323...............271
4500.............313...............268
4600.............304...............266
4700.............295...............264
4800.............283...............259
4900.............267...............249
5000.............260...............248
5100.............249...............241
5200.............231...............229
5300.............225...............227
5400.............214...............220
5500.............204...............214
The second pull today was with the HP exhaust manifolds, nothing much to report other than they lost 1 lb-ft of torque and gained 4 horsepower. Don't waste your money unless you are doing a restoration.
So, if you want to hang on, we'll take you through some bolt-on's we did today that took us to 463 lb-ft and 440 HP while NEVER taking the compression ratio beyond 7.8:1. We went to headers, bigger carb, aluminum intake, camshaft, even bigger carb and then ported 516 factory iron heads.
Last edited:
lemondana
Active Member
The 70-71 HP C Body 440 manifolds should fit. The left C Body 70-71 383 HP manifold won't interchange with the 440 manifold. You must have that 70-71 HP 440 C Body left manifold. Then TTI from there.
Clover
Well-Known Member
sprice
Active Member
Hi Lemondana, would you happen to know what the casting number is for the 70 to 71 manifold might be? I checked TTi website and could see a manifold specific to that date. Thanks.
sprice
Active Member
Google search is indicating #3418352. Would this be correct?
lemondana
Active Member
The 3418352 is the part number, the casting number which is what you need, is 3418351. On a lot of Mopar stuff, the part number and the casting numbers are one or two digits off. I have a pair of NOS 906 big block heads in the original boxes and the last 3 digits are 904
lemondana
Active Member
Like I said before, the HP 383 and the HP 440 used a different left manifold.
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