Build me an engine

Duke5A

Well-Known Member
Joined
Apr 6, 2018
Messages
1,637
Reaction score
852
Location
Michigan
The LA motor is going to have toilet bowl compression, the Mag motor will have something in the 9's. This is why I'm saying you should start with the Magnum. It's an all around better platform when comparing it to its predecessors. When you start replacing parts in the motors then the advantage evaporates and the LA becomes viable again.

Don't mill heads for compression. I mean, you can, but only do it for small gains. To be able to make up an entire point of compression you'll mill the shit out of them and then need to mill the intake side of the head. Just a bad can of worms...

KB107 pistons are kind of the goto for mild builds in small blocks. The compression height of the piston is taller, thus increasing the compression ration (that and different surface setups).

Compression is another reason why I recommended not going with that previous cam recommendation. Hotter cams introduce more valve overlap and this bleads compression off in the lower RPM range. Hence the moving of the power curve higher and the soggy low RPM performance. If you don't have a high enough compression to compensate for this the motor is an all around turd.

Either direction you decide to go build the Magnum motor. You're not going to get any decent compression out of the LA with factory parts.

EDIT:

Everything needs to be matched. All your parts have operating ranges where they develop power. Hotter cams need a higher stall converter, more compression, more gear, different intakes.

RPM Air-Gap intake is a good piece. It starts making power at 1500 RPM and is the defacto standard intake for street and mild bracket setups.

Whatever you decide to build, match your parts. Mismatched combos will be dogs in the entire RPM range.
 
Last edited:

9secRR

Well-Known Member
Joined
Jan 14, 2012
Messages
814
Reaction score
494
Location
Saskatchewan, Canada
The LA motor is going to have toilet bowl compression, the Mag motor will have something in the 9's. This is why I'm saying you should start with the Magnum. It's an all around better platform when comparing it to its predecessors. When you start replacing parts in the motors then the advantage evaporates and the LA becomes viable again.

Don't mill heads for compression. I mean, you can, but only do it for small gains. To be able to make up an entire point of compression you'll mill the shit out of them and then need to mill the intake side of the head. Just a bad can of worms...

KB107 pistons are kind of the goto for mild builds in small blocks. The compression height of the piston is taller, thus increasing the compression ration (that and different surface setups).

Compression is another reason why I recommended not going with that previous cam recommendation. Hotter cams introduce more valve overlap and this bleads compression off in the lower RPM range. Hence the moving of the power curve higher and the soggy low RPM performance. If you don't have a high enough compression to compensate for this the motor is an all around turd.

Either direction you decide to go build the Magnum motor. You're not going to get any decent compression out of the LA with factory parts.

EDIT:

Everything needs to be matched. All your parts have operating ranges where they develop power. Hotter cams need a higher stall converter, more compression, more gear, different intakes.

RPM Air-Gap intake is a good piece. It starts making power at 1500 RPM and is the defacto standard intake for street and mild bracket setups.

Whatever you decide to build, match your parts. Mismatched combos will be dogs in the entire RPM range.

if i'm reading this correctly, you want the OP to put in a thumper cam and keep the rest of the engine stock?

to build a decent street engine, you will need a bigger cam, bigger stall, 9:1 comp, air gap intake..... the list goes on.

i don't know where the soggy bottom end comes to play with the cam i recommended? i used 9.5:1 compression with a 615 lift cam and it had great bottom end. it was no turd. 1.68 60' with 3.55 gears and stock 1979 suspension at 3920 lbs kinda proves it.

take my current engine in my Volare. i have aries pistons to bump compression to 11:1. otherwise stock 1974 360 bottom end. W2 heads, just over 600 lift solid cam. it makes around 500 hp according to my time slips. nothing fancy at all and if my car was street legal, would it be a blast on the street.
 

AJ/FormS

Well-Known Member
Joined
Apr 26, 2016
Messages
1,291
Reaction score
305
Location
On the Circle of the earth, Southern Man,Canada
for a streeter,IMO, time slips mean as good as nothing.
A streeter probably spends 98% of it's life below 4000 rpm, so I can't see a good reason to saddle it with a big cam.
And a streeter will spend most of it's life below 65/70 mph, so I can't see a good reason for big-number gears or 4000 hi-stall TCs.
If your build is too far oriented towards 1/4M drag-racing, I might bet 90% of us will be unhappy about it.
And If your build is too far oriented towards making torque, you will just have so much tirespin that you can never really open the throttle very far on take-off.

So, IMO, you should think about where you want the power, and then build the ENTIRE combo around that point.
If your VP gets to be too high, first gear will get to be a throw away gear, no matter what gears you run. So you end up boiling the treads off the tires to get to second gear. And then second gear gets to be where the fun is, so you might as well build the engine around that fact.
But if your cam gets to be too big, then the bottom-end, with iron heads, goes soft, and it gets to be embarrassing until the rpm gets up into the 3500/4000 zone. So now, to get around that, you end up with a hi-stall and 4 series rear gears, and that puts and end to a lot of a streeter's activities.

With just a $3500 dollar budget, there is not much you can do. Oh sure you can build an engine, but that is only a part of the project.
And if you mess up on the parts choices, then you get nothing but disappointment from the rest of the project.
but honestly, there is NO good reason for 400 hp in a zero to 60 application; except if you just want to excessively burn rubber. From zero to 60mph, on the street, 340hp with the right chassis, can be every bit as quick, without all the smokeshow.

My rule of thumb for fun is 10 pounds per cubic inch, and 1hp per cubic inch. So a 3600 pound package, car and driver, will require 360 cubes and 360 hp.
more cubes will allow less power, but will be harder to marry to the tires without wheelspin.
More hp, will usually soften the bottom end too much for street gears and a regular stall TC. And with a budget of just $3500, a good hi-stall TC is just not there.
But your rear gears should be chosen first. Cuz if your budget eats up the whole of the 3500, then the rear gears may never get done, and all the days of the 360HO will be spent in disappointment.
Next, your transmission should be chosen, because a wide-ratio trans, requires a different cam from a close ratio. If you only have $3500 to spend, then you only have whatever you got for a trans, and when you go to pick your cam, you have to keep that trans in mind.
Next you have to marry whatever gear you chose, to the engines operating rpm.
If you chose 4.10s, then 60 mph, is about 7800rpm in first/4600 in second... so you won't be in first gear,lol, with a 3500 budget, and that means there is no point in having a 6000 rpm cam in an engine that is rarely gonna do more than 4600.
But if you choose 3.55s, then 60mph will be about 6800 in first/4000 in second so you need a cam that makes good power at 4000, not 5000 nor 6000. It doesn't have to make PEAK power at 4000, but it shouldn't be too much higher, because every 200 rpm higher ( about 1 cam size) will steal about half that much operating rpm off the bottom, and so about every second cam size, you end up needing a new TC, to maintain low-rpm performance.

If your combo has 2.45 rear gears or 2.76s, then part of your $3500 has to be set aside for gears. If 360 cubes is all you got,there is no getting around that.
If you have to buy gears, AND you intend on some hiway miles, more than just occasionally, then 3.23s should be your first go-to; not 3.55s. And then you build your engine to like those 3.23s.
I like 2.94s because you can hit 60 mph at the top of first gear with those, and 28" tires , at ~5400. And that requires a cam with a power peak of about 5100 which can be done with a 224*Cam and good heads, or a 230* and any old heads. I really like the 224*FTH cam.
To cinch the deal, and to get some bottom end back, you will need a lotta cylinder pressure, and that means closed-chamber alloy heads. And not fancy big-valve heads, either, cuz we're only going to 5400.
Ok so now, with closed chamber heads, you can install those KB107s and get a deck clearance of about .012. And you add a gasket of .028 for a Quench of .040 and now you have an engine that is very pumpgas friendly.
What you don't do is any other machining than boring to fit the new pistons.
So what you end up with is about a 10.7 Scr engine With 63cc chambers, this is where it falls together at.
Now with a fast rate HFT cam that 223* cam could be a 268/276 and because we don't care about powerband, this being a one gear to 60 combo, I chose an LSA of 108 installed at 102, this gets you overlap of 56* pretty good; and
Static compression ratio of 10.7:1.
In at 102, and 760 ft elevation
Effective stroke is 2.88 inches.
Your dynamic compression ratio is 8.80:1 .
Your dynamic cranking pressure is 181PSI.
V/P (Volume to Pressure Index) is 160

Oh Lordy getaload of that VP, 440s barely make that. So now you have a real low-rpm powerhouse, to work with those 2.94s and very likely even with a 2000TC. Yes you will get tirespin, just the right amount, not frying the tires tho. I can predict 280 ftlbs at 2000rpm.
If that is true and your TC can muster 1.7 ratio TM, then
280x1.7x2.45x2.94=3430 ftlbs at zero mph, far in access to get the tires spinning. Then,you immediately get the revs to 3000, and pick up the torque to say 340, and the TC has dropped to 1.2, and so
340x1.2x2.45x2.94=2940 so still spinning the tires, you are gonna have to back off and let the tires catch pavement.
At 35 mph, you will be cruising at 1800(zero-slip) in second gear. When the trans kicks into first, the Rs will rise to 3200 , closing in on peak torque which might come as early as 3400. And it might be pushing 400ftlbs; so
400x1.2x2.45x2.94=3460, so when the secondaries kick in, your tires will again be screaming.
This is what makes a streeter fun for me, always having the right amount of torque.
How much power will that combo make?
IDK and I don't care because it has fun written all over it, and the bonus is 65=2300(zero-slip)
But notice, it all started with the gears, then the trans, then the cam and heads. The Scr took care of itself....But can you fit it all into $3500USd, IDK.
I ran this engine combo with 3.23s and 3.55s but with a clutch, so no help from the TC. For 4 years I hammered on that engine, until one day it started dropping lobes. I replaced that 223 with a 230, and was immediately sorry. To get the bottom-end back cost me a lotta lotta money. Yes, I could have swapped to more rear gear, but those 3.55s were already murder on the hiway.
I even ran this engine with 2.76s; but that didn't turn out as acceptable as I had thought it would.
This engine got the 68 Barracuda just into the 12s at 3650 pounds and 930 ft elevation, on the only successful run (of 4) it ever made; she hit 106 and change at 12.9 seconds, which, if I recall worked out to ~340 hp.
 

9secRR

Well-Known Member
Joined
Jan 14, 2012
Messages
814
Reaction score
494
Location
Saskatchewan, Canada
i helped a friend build his 340 Demon back in 1998. stock bottom end 340 with flat top pistons. 10.8:1 compression. 587 lift solid flat tappet (248* @ .050), eddie air gap dual plane intake, 750 DP holley, X heads ported and with 2.02/1.60 valves. heads were shaved .050 to bump compression up, 4000 stall, 3.55 gears. ran 12.2's but was his only car for 12 years. every day it was street driven and i can tell you it was no dog on the bottom. perfect street manners.

i build my first 360 basically the same way a few years later but with 9.5:1 compression. i also went with a tunnel ram and 2-450 holleys, and yes for street driving
 

Duke5A

Well-Known Member
Joined
Apr 6, 2018
Messages
1,637
Reaction score
852
Location
Michigan
if i'm reading this correctly, you want the OP to put in a thumper cam and keep the rest of the engine stock?

to build a decent street engine, you will need a bigger cam, bigger stall, 9:1 comp, air gap intake..... the list goes on.

i don't know where the soggy bottom end comes to play with the cam i recommended? i used 9.5:1 compression with a 615 lift cam and it had great bottom end. it was no turd. 1.68 60' with 3.55 gears and stock 1979 suspension at 3920 lbs kinda proves it.

take my current engine in my Volare. i have aries pistons to bump compression to 11:1. otherwise stock 1974 360 bottom end. W2 heads, just over 600 lift solid cam. it makes around 500 hp according to my time slips. nothing fancy at all and if my car was street legal, would it be a blast on the street.

I think we're talking past one another. I could have done a better job articulating my previous post. I'm just giving my reasoning for using the Magnum motor instead of his LA since the Magnum will already have the required compression to build with. The LA will need heads or pistons to raise its toilet bowl compression - wouldn't be surprised if it's as low as 8:1.
 

Oldiron440

Well-Known Member
Joined
Apr 25, 2017
Messages
3,048
Reaction score
738
Location
Iowa
for a streeter,IMO, time slips mean as good as nothing.
A streeter probably spends 98% of it's life below 4000 rpm, so I can't see a good reason to saddle it with a big cam.
And a streeter will spend most of it's life below 65/70 mph, so I can't see a good reason for big-number gears or 4000 hi-stall TCs.
If your build is too far oriented towards 1/4M drag-racing, I might bet 90% of us will be unhappy about it.
And If your build is too far oriented towards making torque, you will just have so much tirespin that you can never really open the throttle very far on take-off.

So, IMO, you should think about where you want the power, and then build the ENTIRE combo around that point.
If your VP gets to be too high, first gear will get to be a throw away gear, no matter what gears you run. So you end up boiling the treads off the tires to get to second gear. And then second gear gets to be where the fun is, so you might as well build the engine around that fact.
But if your cam gets to be too big, then the bottom-end, with iron heads, goes soft, and it gets to be embarrassing until the rpm gets up into the 3500/4000 zone. So now, to get around that, you end up with a hi-stall and 4 series rear gears, and that puts and end to a lot of a streeter's activities.

With just a $3500 dollar budget, there is not much you can do. Oh sure you can build an engine, but that is only a part of the project.
And if you mess up on the parts choices, then you get nothing but disappointment from the rest of the project.
but honestly, there is NO good reason for 400 hp in a zero to 60 application; except if you just want to excessively burn rubber. From zero to 60mph, on the street, 340hp with the right chassis, can be every bit as quick, without all the smokeshow.

My rule of thumb for fun is 10 pounds per cubic inch, and 1hp per cubic inch. So a 3600 pound package, car and driver, will require 360 cubes and 360 hp.
more cubes will allow less power, but will be harder to marry to the tires without wheelspin.
More hp, will usually soften the bottom end too much for street gears and a regular stall TC. And with a budget of just $3500, a good hi-stall TC is just not there.
But your rear gears should be chosen first. Cuz if your budget eats up the whole of the 3500, then the rear gears may never get done, and all the days of the 360HO will be spent in disappointment.
Next, your transmission should be chosen, because a wide-ratio trans, requires a different cam from a close ratio. If you only have $3500 to spend, then you only have whatever you got for a trans, and when you go to pick your cam, you have to keep that trans in mind.
Next you have to marry whatever gear you chose, to the engines operating rpm.
If you chose 4.10s, then 60 mph, is about 7800rpm in first/4600 in second... so you won't be in first gear,lol, with a 3500 budget, and that means there is no point in having a 6000 rpm cam in an engine that is rarely gonna do more than 4600.
But if you choose 3.55s, then 60mph will be about 6800 in first/4000 in second so you need a cam that makes good power at 4000, not 5000 nor 6000. It doesn't have to make PEAK power at 4000, but it shouldn't be too much higher, because every 200 rpm higher ( about 1 cam size) will steal about half that much operating rpm off the bottom, and so about every second cam size, you end up needing a new TC, to maintain low-rpm performance.

If your combo has 2.45 rear gears or 2.76s, then part of your $3500 has to be set aside for gears. If 360 cubes is all you got,there is no getting around that.
If you have to buy gears, AND you intend on some hiway miles, more than just occasionally, then 3.23s should be your first go-to; not 3.55s. And then you build your engine to like those 3.23s.
I like 2.94s because you can hit 60 mph at the top of first gear with those, and 28" tires , at ~5400. And that requires a cam with a power peak of about 5100 which can be done with a 224*Cam and good heads, or a 230* and any old heads. I really like the 224*FTH cam.
To cinch the deal, and to get some bottom end back, you will need a lotta cylinder pressure, and that means closed-chamber alloy heads. And not fancy big-valve heads, either, cuz we're only going to 5400.
Ok so now, with closed chamber heads, you can install those KB107s and get a deck clearance of about .012. And you add a gasket of .028 for a Quench of .040 and now you have an engine that is very pumpgas friendly.
What you don't do is any other machining than boring to fit the new pistons.
So what you end up with is about a 10.7 Scr engine With 63cc chambers, this is where it falls together at.
Now with a fast rate HFT cam that 223* cam could be a 268/276 and because we don't care about powerband, this being a one gear to 60 combo, I chose an LSA of 108 installed at 102, this gets you overlap of 56* pretty good; and
Static compression ratio of 10.7:1.
In at 102, and 760 ft elevation
Effective stroke is 2.88 inches.
Your dynamic compression ratio is 8.80:1 .
Your dynamic cranking pressure is 181PSI.
V/P (Volume to Pressure Index) is 160

Oh Lordy getaload of that VP, 440s barely make that. So now you have a real low-rpm powerhouse, to work with those 2.94s and very likely even with a 2000TC. Yes you will get tirespin, just the right amount, not frying the tires tho. I can predict 280 ftlbs at 2000rpm.
If that is true and your TC can muster 1.7 ratio TM, then
280x1.7x2.45x2.94=3430 ftlbs at zero mph, far in access to get the tires spinning. Then,you immediately get the revs to 3000, and pick up the torque to say 340, and the TC has dropped to 1.2, and so
340x1.2x2.45x2.94=2940 so still spinning the tires, you are gonna have to back off and let the tires catch pavement.
At 35 mph, you will be cruising at 1800(zero-slip) in second gear. When the trans kicks into first, the Rs will rise to 3200 , closing in on peak torque which might come as early as 3400. And it might be pushing 400ftlbs; so
400x1.2x2.45x2.94=3460, so when the secondaries kick in, your tires will again be screaming.
This is what makes a streeter fun for me, always having the right amount of torque.
How much power will that combo make?
IDK and I don't care because it has fun written all over it, and the bonus is 65=2300(zero-slip)
But notice, it all started with the gears, then the trans, then the cam and heads. The Scr took care of itself....But can you fit it all into $3500USd, IDK.
I ran this engine combo with 3.23s and 3.55s but with a clutch, so no help from the TC. For 4 years I hammered on that engine, until one day it started dropping lobes. I replaced that 223 with a 230, and was immediately sorry. To get the bottom-end back cost me a lotta lotta money. Yes, I could have swapped to more rear gear, but those 3.55s were already murder on the hiway.
I even ran this engine with 2.76s; but that didn't turn out as acceptable as I had thought it would.
This engine got the 68 Barracuda just into the 12s at 3650 pounds and 930 ft elevation, on the only successful run (of 4) it ever made; she hit 106 and change at 12.9 seconds, which, if I recall worked out to ~340 hp.
Aj I'd bet you have reasoned yourself out of a truly fast car your entire life.
I'll drive a temperamental hotrod around for the ability to light the tires in any gear at any speed. Bolt the slicks on at the track and you can feel the weight of your eye balls on the hit.
The best motor for the street is probably a stocker but how flipping boring is that.
 

TheSkunk

Well-Known Member
Joined
Jan 12, 2020
Messages
59
Reaction score
26
Location
Indiana
Sorry guys works been picking back up and turkey season has me distracted atm.

but I agree I don’t wanna go to radical but I want a nice healthy engine trying to use what I have available the only reason I’m nervous of going with theMag block is it has 230k on the bottom end the heads were replaced about 500 miles ago. That’s why I’m trying to use the heads n am Leary of the bottom end. But I’m open to all opinions at this point in time.
 

Duke5A

Well-Known Member
Joined
Apr 6, 2018
Messages
1,637
Reaction score
852
Location
Michigan
Sorry guys works been picking back up and turkey season has me distracted atm.

but I agree I don’t wanna go to radical but I want a nice healthy engine trying to use what I have available the only reason I’m nervous of going with theMag block is it has 230k on the bottom end the heads were replaced about 500 miles ago. That’s why I’m trying to use the heads n am Leary of the bottom end. But I’m open to all opinions at this point in time.

You need to pull both of them apart for inspection anyways. If you've got them out and they're of unknown quantity then disassemble. Uncle Tony has a very good build series going on right now on refurbing short blocks on the cheap. He's doing a late model LA 360. Give it a look.
 

M_Body_Coupe

Well-Known Member
Joined
Aug 19, 2013
Messages
621
Reaction score
293
Location
Windsor, ON, Canada
Oh wow...I missed the start of this "party"!!! lol

I love the big cams, and by that I mean: high valve list and the rate of that lift, not necessairly the long duration most cams require to get there.

I would have to agree with Duke re: cam recommendation. Take it from someone who's running a Hughes HE3844AL hydraulic flat tappet in a 360 motor. Awesome grind, but boy, the car didn't really wake up until I stuck a nice 4K converter in there, and that was originally with 3.91 rear end. Having gone to 4.10 last summer I have to say this is absolutely a BEAST on the street. But that is with a Performer RPM intake, heavily ported heads, 10.5:1 static CR, etc, etc...

So if you're looking for something that just flat out delivers consistently all the time (across a wide powerband) Duke's ideas will get you there. But if you want that "holy shit, I thik I need a change of my undies" feeling, and it comes on fast and it's very violent, than I would suggest you follow AspenRT's advice. From a power-point perspective that'll make you much happier, but you'll have to live with all the other nuances of driving this on the street...sure, can be done, but you need to make a committment.
 

greyghost

Well-Known Member
Joined
Aug 14, 2014
Messages
146
Reaction score
25
Location
Roscoe, IL
Hey Skunk, is this goin' in your '78 LeBaron (I seen it in your list)? I'm following this because I'm looking to do the same thing with my '79 LeBaron. I have a '74 360 LA that I just had re-machined (bored 30 over) and refurbished stock heads but have not started assembly because I'm contemplating a roller cam. In the interim I bought a '79 300 (Cordoba) for parts that has a running 360 that has magnum heads on it and an M1 intake. It also has a 727 TF and 9 1/4" rear end in it that'll take some modding to fit it into the Grey Ghost.
 

TheSkunk

Well-Known Member
Joined
Jan 12, 2020
Messages
59
Reaction score
26
Location
Indiana
Yes this will be built for my Lebaron. I’m waiting to get the rest of the magnum block from my buddys and getting the heads checked out before I go much farther my heads and block are going to be the determining factor. If I gotta clean up the bores I’m gonna go ahead and get it decked as well and probably try to reuse stock pistons if they will work with my heads. If that sounds okay lol.

Trying to do this as budget friendly as possible my 3500 budget is a very broad ballpark number but as always if I can use what I have and achieve my goal then I’m gonna give it a shot. Being my first “build” if this fucker Grenades I don’t wanna be out a fortune. I have the confidence that I’ll be able to put it together I just don’t know what combination is gonna meet my goals.
 

TheSkunk

Well-Known Member
Joined
Jan 12, 2020
Messages
59
Reaction score
26
Location
Indiana
Alright guys rather then start a new thread I’ll just add to this one. I just picked up a 74 360.. complete 1.88 j heads performer intake, .30 over h405P pistons, 3418645 rods, with some sort of cam that’s looks like it ran a month ago!!
What do I need to do to retrofit roller cam set up from my roller block(crank needs turned and needs bored over)? I really think this new 360 is gonna be my ticket with minimal block work.
 

Duke5A

Well-Known Member
Joined
Apr 6, 2018
Messages
1,637
Reaction score
852
Location
Michigan
Alright guys rather then start a new thread I’ll just add to this one. I just picked up a 74 360.. complete 1.88 j heads performer intake, .30 over h405P pistons, 3418645 rods, with some sort of cam that’s looks like it ran a month ago!!
What do I need to do to retrofit roller cam set up from my roller block(crank needs turned and needs bored over)? I really think this new 360 is gonna be my ticket with minimal block work.

None of the factory roller parts from the newer block swap over. You need aftermarket and that entails about $1400 from top to bottom (rockers, springs, pushrods, lifters, cam). This is why factory roller blocks are so appealing.
 
Back
Top