What’s your guesses on horse power?

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moparjoe71

4speeder
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My rear main seal started leaking so I pulled out my 17 year old 360 for a freshen up. New rings bearings gaskets and a cam shaft. Here is what I have
78 360 block .030 over
Balanced stock bottom end the crank and rods were turned .010
Speed pro 116 pistons set at close to zero deck height.( not 100% certain on that measurement)according to speed pro they make 9.2-10.0 depending on heads
The cam shaft is a Lunati .520/.520 240@.050 lift 106 lobe separation
The heads are ported and polished 2.02/1.60 j castings with a good valve job
Intake is a Holley strip dominator that is port matched with a 750 double pumper
Dougs headers recurved dizzy and electronic ignition


After tear down I found a cam lobe that was in bad shape which in turn chewed up a main bearing and I assume the cause of the rear main seal giving up. This combo was a ton of fun for a lot of years but I honestly have no idea what kinda power I’m really making. Any guesses? It’s in a 71 duster with an 8.75 with 3:55 and an over drive 4 speed. I haven’t ever put this thing on the track but any day of the week I can lay a spanking down on my buddies 12.20 chevelle on the street
 
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Do you have an actual true measured compression ratio? If not, give us a cranking compression test. If you have an actual 10:1 compression ratio, that set up should make 450hp.
 
Do you have an actual true measured compression ratio? If not, give us a cranking compression test. If you have an actual 10:1 compression ratio, that set up should make 450hp.
Before we pulled the engine I did a dry compression test and the average psi was 155. That was with a different camshaft it measured 502/522 234@.050 lift 108 lobe seperation I would have to believe with factory heads I would be closer to 9-9.5:1
 
My guesstimating formula

Torque is the easiest to guess most street to mild street strip are gonna be 1.15-1.25 lbs-ft.

So minimum of 1.15 x 365 cid is 420 lbs-ft, The trick is guessing where peak power is gonna occur, I’d say 5500 for your combo depending how well ported the heads. Torque at peak hp is usually down 10% ish.

So 378 lbs-ft.

378 x 5500 / 5252 = 396 hp.

So minimum 396 hp @ 5500 and 420 lbs-ft @ 4000 to max 429 hp @ 5500 and 456 lbs-ft @ 4000.
 
My guesstimating formula

Torque is the easiest to guess most street to mild street strip are gonna be 1.15-1.25 lbs-ft.

So minimum of 1.15 x 365 cid is 420 lbs-ft, The trick is guessing where peak power is gonna occur, I’d say 5500 for your combo depending how well ported the heads. Torque at peak hp is usually down 10% ish.

So 378 lbs-ft.

378 x 5500 / 5252 = 396 hp.

So minimum 396 hp @ 5500 and 420 lbs-ft @ 4000 to max 429 hp @ 5500 and 456 lbs-ft @ 4000.
My heads are opened way up
 
If you have flow numbers that would let us get things a little more accurately.
 
Take it to the strip and work on getting it to hook and then run consistently, but short of that I’d guess about 325
 
Take it to the strip and work on getting it to hook and then run consistently.
That’s the plan! I recently upgraded to super stock springs from stock saggy six cylinder springs and sub frame connectors. The increase in traction and how straight it launches is impressive
 
My rear main seal started leaking so I pulled out my 17 year old 360 for a freshen up. New rings bearings gaskets and a cam shaft. Here is what I have
78 360 block .030 over
Balanced stock bottom end the crank and rods were turned .010
Speed pro 116 pistons set at close to zero deck height.( not 100% certain on that measurement)according to speed pro they make 9.2-10.0 depending on heads
The cam shaft is a Lunati .520/.520 240@.050 lift 106 lobe separation
The heads are ported and polished 2.02/1.60 j castings with a good valve job
Intake is a Holley strip dominator that is port matched with a 750 double pumper
Dougs headers recurved dizzy and electronic ignition


After tear down I found a cam lobe that was in bad shape which in turn chewed up a main bearing and I assume the cause of the rear main seal giving up. This combo was a ton of fun for a lot of years but I honestly have no idea what kinda power I’m really making. Any guesses? It’s in a 71 duster with an 8.75 with 3:55 and an over drive 4 speed. I haven’t ever put this thing on the track but any day of the week I can lay a spanking down on my buddies 12.20 chevelle on the street

If the tune is right on, 2.02 J with decent work done, you should have about 425-435hp.
 
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Thanks for all of your input guys! When I built this engine the for the first time I cared a lot less about a real number and more about seat of the pants performance, but the older I get the less time I spend at wife open throttle lol. Any guesses as to where I would be in the quarter mile with my garbage gears and o/d four speed? My near future plans include better gears and an iron case 833
 
Thanks for all of your input guys! When I built this engine the for the first time I cared a lot less about a real number and more about seat of the pants performance, but the older I get the less time I spend at wife open throttle lol. Any guesses as to where I would be in the quarter mile with my garbage gears and o/d four speed? My near future plans include better gears and an iron case 833
As I've mentioned before, had about the same as you but no real head work and x heads made 392hp. I think that's a fair comparison.
 
My rear main seal started leaking so I pulled out my 17 year old 360 for a freshen up. New rings bearings gaskets and a cam shaft. Here is what I have
78 360 block .030 over
Balanced stock bottom end the crank and rods were turned .010
Speed pro 116 pistons set at close to zero deck height.( not 100% certain on that measurement)according to speed pro they make 9.2-10.0 depending on heads
The cam shaft is a Lunati .520/.520 240@.050 lift 106 lobe separation
The heads are ported and polished 2.02/1.60 j castings with a good valve job
Intake is a Holley strip dominator that is port matched with a 750 double pumper
Dougs headers recurved dizzy and electronic ignition


After tear down I found a cam lobe that was in bad shape which in turn chewed up a main bearing and I assume the cause of the rear main seal giving up. This combo was a ton of fun for a lot of years but I honestly have no idea what kinda power I’m really making. Any guesses? It’s in a 71 duster with an 8.75 with 3:55 and an over drive 4 speed. I haven’t ever put this thing on the track but any day of the week I can lay a spanking down on my buddies 12.20 chevelle on the street
425 I make 400 plus you have a bigger cam than I do. So I say 425 is a pretty accurate and that’s quick with 355s
 
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