360 build, hp and compression thoughts!

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chris17

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Hello folks, well i built my first motor, and just curious what your thoughts on my horsepower and compression might be???

Its a 1973 360 out of a motorhome, i did a rebuild and these are my specs.

KB107 pistons.
COMP.XE268 cam, lifters, pushrods and double spring kit all shimmed within .004 of each other.
Edelbrock performer intake.
Holley 4160 600CFM
MSD 6AL BOX
MSD Pro billet distributor
MSD 8.5mm wires
MSD blaster 2 coil
340 heads, 2.02 valves
Hooker comp. headers
3" exhaust all the way out
Flowmaster series 10 mufflers
Both cables Lokar
Melling hi volume oil pump
Gasket matched everything
Hughes 2000 stall
Transgo -2 shift kit
Aluminum radiator


I have approx 135 miles on it so far, compression checks 150-152 on all 8.
Running the 2 light silver springs on distributor with black bushing.

The plugs seem a little light, curious about maybe a little bigger jet?
 
You should be able to figure the comp ratio by yourself and since you don't know, stabbing in a cam is probably not the smartest thing you did.

You ratio is figured out be KNOWING how far down the hole the slug sits, bore size, gasket thickness and bore size and finally the cylinder head cc amount.

Take it to a on line calc.

HP? 214! LOL!

Go ahead and ***** at me.
 
It sounds like a common combo, the piston and cam choice is what many people migrate to. My guess would be somewhere in the 310 to 330HP range. I'm not a fan of the 4160 carbs. A nice Holley 650DP 4777 would be my choice.
 
breakstuff said:
It sounds like a common combo, the piston and cam choice is what many people migrate to. My guess would be somewhere in the 310 to 330HP range. I'm not a fan of the 4160 carbs. A nice Holley 650DP 4777 would be my choice.
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Thanks for taking the time to share your thoughts, i have all of the measurements for doing the compression calc. except the cc.volume on the heads. But was just curious on others thoughts.
 
Looks like a nice build Chris. Not sure if your running X or J 340 heads, chamber size?, but with the 107's you got some compression over stock and 150ish cranking with that cam ain't bad. Not sure what your rear gear is, but with that converter, it sounds like a good average combo. Just play with your timing so you can get the most out of it and I think you'll be happy.
 
OldmanRick said:
Looks like a nice build Chris. Not sure if your running X or J 340 heads, chamber size?, but with the 107's you got some compression over stock and 150ish cranking with that cam ain't bad. Not sure what your rear gear is, but with that converter, it sounds like a good average combo. Just play with your timing so you can get the most out of it and I think you'll be happy.
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Hello Rick, yeah the heads have a casting # of 3418915 if that helps. I know I should have c.c. them but hey, if that's the only mistake I made I feel like I did ok. The rearend is the peanut 7 1/4" with 2.76, I am thinking of changing that to a 3.91 ratio when I come up with the 8.25 or 8.75. It seems to run great, yep I have been playing with the timing and I think I have it nailed.thanks for the input.
 
chris17 said:
Hello Rick, yeah the heads have a casting # of 3418915 if that helps. I know I should have c.c. them but hey, if that's the only mistake I made I feel like I did ok. The rearend is the peanut 7 1/4" with 2.76, I am thinking of changing that to a 3.91 ratio when I come up with the 8.25 or 8.75. It seems to run great, yep I have been playing with the timing and I think I have it nailed.thanks for the input.
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The 915's are "J" heads and the chambers are around 72cc's stock. With just a mild deck cleanup, i'd probably figure about 70/71. At this point it's not really a issue, you got a nice pump gas engine with the 150ish cranking comp. As far as the gear, 3.91's will give you more performance, but if you run across a 3.55 for sale at a good price, i wouldn't turn it down with your current combo. Now if your thinking of some intake, carb, cam upgrades in the future? The 3.91's might be the way to go?
 
Should make 330-350hp and 380-400tq with 9.5:1 static comp, good tune up and proper assembly.

You should never install a camshaft without degreeing it. If you did degree, great, if not, you should.
 
2000 stall converter?
get one custom built from Dynamic...that car will be a little rocket!
 
you have the makings for sweet street combo. a few tweaks here and there is all you need. enjoy and have fun.
 
You were curious about your plugs......Well, there a little harder to read with the various pump blends that are out there. But I can see with a 10% ethanol blend, which a lot of the country runs, that one number up may be in the ballpark for you on that 600. If you post the list# off the air horn (choke housing), I can look up the jetting/secd. plate, on your exact carb to give you a idea of where to go next?
 
crackedback said:
Should make 330-350hp and 380-400tq with 9.5:1 static comp, good tune up and proper assembly.

You should never install a camshaft without degreeing it. If you did degree, great, if not, you should.
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this^^^^^^^^^^^^
 
I'm confused, you rebuild the motor and after finishing the rebuild you want to know what your compression ratio is??? This is usually calculated before you start building...I mean, not all blocks have the exact same deck height...just buying a set of KB107 pistons does not mean you will be at zero deck, or have a specific compression ratio...you have to take measurements, some of which can't be done now that the engine is assembled. We can all guesstimate a ball park figure, but that's about it.

Horsepower is a little easier at this point. Take it to a drag strip and run it. Knowing the cars weight and MPH through the 1/4 mile will tell the story (or you can chassis dyno it).
 
Ok, so i should have stated that i had taken measurements, and the only thing i was missing or failed to do was to c.c. chheck the heads as they were not the ones originally on the motor. So to the people that want to keep raggin on me great, enjoy yourselves, i am sure you are all mechanical engineers and everything you have ever built is the "best" and you more than likely have never made a mistake either.

As for the people that are willing to accept the fact that i did not c.c. the heads, and thats the only thing holding me back from a accurate compression ratio calculation, and are willing to offer there POSITIVE thoughts and opinions, much appreciated, thank you.
 
OldmanRick said:
You were curious about your plugs......Well, there a little harder to read with the various pump blends that are out there. But I can see with a 10% ethanol blend, which a lot of the country runs, that one number up may be in the ballpark for you on that 600. If you post the list# off the air horn (choke housing), I can look up the jetting/secd. plate, on your exact carb to give you a idea of where to go next?
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I will check that out after work Rick and get back to you, thanks.
 
nice job for a first build. drive it & enjoy it. i'm guessing you are worried about comp ratio because of a chance of detonation or whatever.

best bet: run premium gas
keep it cool. if you have an old radiator, change it out when you get a chance. you dont need a $400 aluminum. a stock replacement from napa/autozone/etc will be fine for now. get the one for a car with A/C. it's more important that the car runs cool so she will run for a long time.

good luck with her! nice job bro
 
moparlover said:
nice job for a first build. drive it & enjoy it. i'm guessing you are worried about comp ratio because of a chance of detonation or whatever.

best bet: run premium gas
keep it cool. if you have an old radiator, change it out when you get a chance. you dont need a $400 aluminum. a stock replacement from napa/autozone/etc will be fine for now. get the one for a car with A/C. it's more important that the car runs cool so she will run for a long time.

good luck with her! nice job bro
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Thanks man, really enjoying it so far!
 
I'm going to guess it's a little lower than 9.5:1. Which is not a problem. That's why you have 150psi and can run the two light silvers. You might want to try this tho: replace one light silver with one blue, replace the black bushing with blue, and reset the initial to 17. Then re-tune the carb. Reson being your carb is a little small (IMO) and you don't need all that advance so early. Over advancing down low on pump fuel can be a problem because it burns so quickly compared to non-oxygenated, non-ethanol-added fuels.
As far as your questions - I think it's around 9:1 and the horsepower is probably 325ish. Not too shabby - but a track visit will tell you more.
 
moper said:
I'm going to guess it's a little lower than 9.5:1. Which is not a problem. That's why you have 150psi and can run the two light silvers. You might want to try this tho: replace one light silver with one blue, replace the black bushing with blue, and reset the initial to 17. Then re-tune the carb. Reson being your carb is a little small (IMO) and you don't need all that advance so early. Over advancing down low on pump fuel can be a problem because it burns so quickly compared to non-oxygenated, non-ethanol-added fuels.
As far as your questions - I think it's around 9:1 and the horsepower is probably 325ish. Not too shabby - but a track visit will tell you more.
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Thats a good thought there Moper, i will give that a shot, quick work and a test drive, will let you know how it goes. Most likely wont be till the weekend due to our wind and rain storm. Thanks though.
 
Sorry Chris17, I'm not trying to bust your chops, I was just saying that determining the compression is normally thought about in the planning stages of a motor build. I would imagine your are somewhere in the 9-9.5:1 compression range. With that, I would also guesstimate that your motor is in the 280-300hp range as well. It should be a fun street car.

If you ever want to squeeze a little more out of it, try switching to a performer RPM, or RPM Air-gap intake and a 750dp carb. Those two changes would probably get you up into the 350hp range....but this is all just guesstimating over the internet, take it to the track and find out what you've got.
 
107's with 72 cc, 4.125-.040 gasket, .010 in the hole will be ~9.5 static. With a .050 gasket it's ~9.35.

I'd leave the black bushing on the distributor. I pretty much use nothing but the black bushing anymore.

A 1" open spacer would really wake up the performer intake. Would require jetting up the carb a bit.

The car would like more converter without a doubt, a true 2500 would be good, if you want it to really make a move in the 1/4 or 1/8, 3000-3500.

It all a learning experience. Some are a gruff, some tactful.
 
flyfish said:
Sorry Chris17, I'm not trying to bust your chops, I was just saying that determining the compression is normally thought about in the planning stages of a motor build. I would imagine your are somewhere in the 9-9.5:1 compression range. With that, I would also guesstimate that your motor is in the 280-300hp range as well. It should be a fun street car.

If you ever want to squeeze a little more out of it, try switching to a performer RPM, or RPM Air-gap intake and a 750dp carb. Those two changes would probably get you up into the 350hp range....but this is all just guesstimating over the internet, take it to the track and find out what you've got.
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Thanks for your thoughts, i wanted a different intake but i picked the heads and the intake up for $100, but i have been looking for a rpm or air gap, 750dp huh, i have a buddy who has one of those that i believe is up for sale!
 
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