Mild 360 engine rebuild recommendations

[Plymouth65]

I have a stock 73 Dart 318 automatic that I would like to get a little more out of it. I am not interested in fixing up the 318 at this time. I have gathered the following parts, an 86 360 that needs to be bored 40 over. 360 heads with 202 valves, Edelbrock dual plane intake, Edelbrock 600 carb, Roller Rockers 1.5, MSD Distributor & MSD 6AL2 box and coil, Headers & 8 3/4 Suregrip 3:55 gears. I am looking for a mild build. I am looking for recommendations for pistons and cam.

 

[crackedback]

Simple build - KB107's and something like a Voodoo 268 or comp XE268 will get you around 350ish hp A little porting on the 2.02's and it will get closer to 385-400

Easy driver engine capable of moving an A body to the 12's

 

[4eighteener]

Is that a roller block, and do you have the roller lifters, dog bones, and spider to reuse?
What heads # do you have.
You can't go wrong with the aforementioned kb107 pistons for price, but even though not a big horsepower loss, I still personally avoid 5/64 ring packs anymore

 

[RustyRatRod]

Is the 86 engine a flat tappet or roller LA? If roller, that's a lot of territory already covered.

 

[PRH]

Keep in mind that pretty much any “performance oriented” piston will be enough lighter than the OE pistons that the crank will need balancing.

The kb107 and the xe268 are proven pieces for a mild street build.

 

[MOPAROFFICIAL]

I have a stock 73 Dart 318 automatic that I would like to get a little more out of it. I am not interested in fixing up the 318 at this time. I have gathered the following parts, an 86 360 that needs to be bored 40 over. 360 heads with 202 valves, Edelbrock dual plane intake, Edelbrock 600 carb, Roller Rockers 1.5, MSD Distributor & MSD 6AL2 box and coil, Headers & 8 3/4 Suregrip 3:55 gears. I am looking for a mild build. I am looking for recommendations for pistons and cam.

Stock 340 cam, head work.
Mild.

The valve job and bowl blending will be half the power and key in this type of a build.

 

[aaronk785]

Speed pro h116cp are duplicate weight. They should give you about 9.5 to 1 with stock type heads. Just food for thought. Mine were within 7 grams of the stock pistons so I didn’t balance. Engine ran smooth. The ex 268 is a great street cam.

 

[Plymouth65]

Is that a roller block, and do you have the roller lifters, dog bones, and spider to reuse?
What heads # do you have.
You can't go wrong with the aforementioned kb107 pistons for price, but even though not a big horsepower loss, I still personally avoid 5/64 ring packs anymore

Not a roller block, no roller lifters, roller rockers

 

[Plymouth65]

Is the 86 engine a flat tappet or roller LA? If roller, that's a lot of territory already covered.

Flat tappet

 

[273]

Here's a 360 build stock to mild, but low cr with decent cr the mods would make a little more say add 3-4%.

 

[RustyRatRod]

Flat tappet

SO it doesn't have provisions in the valley for the spider retainer? It should. They will be bosses with drilled and tapped holes.

 

[AJ/FormS]

360 heads are open chambers. You cannot get any Squish/Quench out of that combination, with flat tops; which means, that the engine will be somewhat pressure limited, to prevent detonation.
Pressure makes heat, makes torque, which, times rpm, equals power.
IE, lack of pressure is lack of power; especially at lower rpms.
To "get some bottom end back", you will need;
A) a higher stall convertor, so the engine doesn't have to operate in the marshmallow zone, and
B) higher ratio rear gears, so the engine can spool up into the power zone and sorta hover in the powerband, after the shifts.
Neither of those are cheap.
C) IMHO, if you want to keep those heads, you'll need to get some specialty-pistons with machinable Q-pads, cuz without Quench,typically yur engine pressure will be limited due to detonation.

Here's the deal;
Early 340s were rated at 10.5Scr.
They weren't that.
At best maybe 9.8, and they had forged pistons/forged cranks, and a pressure bleeding camshaft, which all worked together to try to prevent detonation, even with best leaded gasoline of the day.
If you copy that deal with; hypers, a cast crank, a tight LSA street-cam, and todays gas ............. you could be in for a world of hurt.
Yur plan is pretty good, but I'll never run open chambers again. And if you machine yours, you always take a chance that the machine shop will get all the angles right. I would trim some fat off your parts list and go straight for some closed chamber heads, and since I have had such a great experience with alloys at up to 195psi/still on 87E10 pump gas, how can I not recommend them...........

 

[Plymouth65]

360 heads are open chambers. You cannot get any Squish/Quench out of that combination, with flat tops; which means, that the engine will be somewhat pressure limited, to prevent detonation.
Pressure makes heat, makes torque, which, times rpm, equals power.
IE, lack of pressure is lack of power; especially at lower rpms.
To "get some bottom end back", you will need;
A) a higher stall convertor, so the engine doesn't have to operate in the marshmallow zone, and
B) higher ratio rear gears, so the engine can spool up into the power zone and sorta hover in the powerband, after the shifts.
Neither of those are cheap.
C) IMHO, if you want to keep those heads, you'll need to get some specialty-pistons with machinable Q-pads, cuz without Quench,typically yur engine pressure will be limited due to detonation.

Here's the deal;
Early 340s were rated at 10.5Scr.
They weren't that.
At best maybe 9.8, and they had forged pistons/forged cranks, and a pressure bleeding camshaft, which all worked together to try to prevent detonation, even with best leaded gasoline of the day.
If you copy that deal with; hypers, a cast crank, a tight LSA street-cam, and todays gas ............. you could be in for a world of hurt.
Yur plan is pretty good, but I'll never run open chambers again. And if you machine yours, you always take a chance that the machine shop will get all the angles right. I would trim some fat off your parts list and go straight for some closed chamber heads, and since I have had such a great experience with alloys at up to 195psi/still on 87E10 pump gas, how can I not recommend them...........

 

[Plymouth65]

I also have a set of standard 360 heads that have had he valves done, would I be better off with them?

 

[273]

Here's the dyno graph from the video I posted #10 if you noticed all the mods gained around 50 lbs-ft down low without doing anything about the compression ratio.

Final mods xe268h airgap headers pocket port 2.02 heads 1.6 rockers etc.. Top red line

Stock 2bbl lonely blues lines at the bottom.

 

[273]

I also have a set of standard 360 heads that have had he valves done, would I be better off with them?

your heads are fine, he's obsess with cr.

 

[273]

Depending on your cam choice, a mild cam will generally be happy with around 8.8-9.2 to 1.

 

[Illahe]

Flat tappet

Use a quality hydraulic lifter like Howards 91711. Better yet, run a mild solid flat tappet with 273 rockers.

Ken @ Oregon Cams has the 268XE in his pattern catalog Pn. 1179. He can grind it on an OEM Chrysler cam core too!

 

[Plymouth65]

Keep in mind that pretty much any “performance oriented” piston will be enough lighter than the OE pistons that the crank will need balancing.

The kb107 and the xe268 are proven pieces for a mild street build.

The machine shop suggested flat top pistons

 

[Illahe]

The machine shop suggested flat top pistons

Considering your in Fl. spend another $200 and get a forged flat top piston.

Icon FHR Pistons IC10028-STD Fits SB Chrysler 360 Flat Top 7cc​

Low $400 bucks at CNC Motorsports

 

[rumblefish360]

I have a stock 73 Dart 318 automatic that I would like to get a little more out of it. I am not interested in fixing up the 318 at this time. I have gathered the following parts, an 86 360 that needs to be bored 40 over. 360 heads with 202 valves, Edelbrock dual plane intake, Edelbrock 600 carb, Roller Rockers 1.5, MSD Distributor & MSD 6AL2 box and coil, Headers & 8 3/4 Suregrip 3:55 gears. I am looking for a mild build. I am looking for recommendations for pistons and cam.

KB-107’s or the Federal Mogul side coated piston that are like the KB-107’s. not zero decked, zero decking can possible lead to a 9.8-1 - 93 octane user.
I have found a 226@050 cam very good with 3.55’s. Largest tire I’d use is at 27” in diameter. 26 is better.
A small converter is recommended. If a converter is not in the cards, back the cam duration down to 216@050. The 226@040 is a little large for a stock converter.
You’ll only need .500 lift unless you start working on the heads.
Look for an LSA @108

 

[rumblefish360]

Considering your in Fl. spend another $200 and get a forged flat top piston.

Icon FHR Pistons IC10028-STD Fits SB Chrysler 360 Flat Top 7cc​

Low $400 bucks at CNC Motorsports

Great price!!!!

 

[Illahe]

your heads are fine, he's obsess with cr.

Like: Compression Obsession: More Power

 

[rumblefish360]

360 heads are open chambers. You cannot get any Squish/Quench out of that combination, with flat tops; which means, that the engine will be somewhat pressure limited, to prevent detonation.

False

Pressure makes heat, makes torque, which, times rpm, equals power.
IE, lack of pressure is lack of power; especially at lower rpms.
To "get some bottom end back", you will need;
A) a higher stall convertor, so the engine doesn't have to operate in the marshmallow zone, and

Only if the camshaft is too large for the stall converter and gear set/tire combined. The last factor is weight of the car.

B) higher ratio rear gears, so the engine can spool up into the power zone and sorta hover in the powerband, after the shifts.
Neither of those are cheap.

Agree-ish

C) IMHO, if you want to keep those heads, you'll need to get some specialty-pistons with machinable Q-pads, cuz without Quench,typically yur engine pressure will be limited due to detonation.

False X‘S 2. Small done pistons are readily available.
He doesn’t NEED to go there. The KB-107’s machined to a zero deck height and proper head gasket can net a 9.8-1 ratio.

Here's the deal;
Early 340s were rated at 10.5Scr.
They weren't that.
At best maybe 9.8, and they had forged pistons/forged cranks, and a pressure bleeding camshaft, which all worked together to try to prevent detonation, even with best leaded gasoline of the day.

Disagree. The camshaft was at a wide 114 LSA.

If you copy that deal with; hypers, a cast crank, a tight LSA street-cam, and todays gas ............. you could be in for a world of hurt.

Disagree. But I’d rather run 87 than 93 for an easy and possible everyday driver.

Yur plan is pretty good, but I'll never run open chambers again. And if you machine yours, you always take a chance that the machine shop will get all the angles right. I would trim some fat off your parts list and go straight for some closed chamber heads, and since I have had such a great experience with alloys at up to 195psi/still on 87E10 pump gas, how can I not recommend them...........

I also have a set of standard 360 heads that have had he valves done, would I be better off with them?

Use the best set. If the 2.02’s are the better set, use them. I’d like to say moving the 2.02’s to the smaller 1.88 valve head is good but now it’s a cost issue. This is up to you and I don’t see the worth unless the 2.02 heads are shot out and garbage.

 

[rumblefish360]

Here's the dyno graph from the video I posted #10 if you noticed all the mods gained around 50 lbs-ft down low without doing anything about the compression ratio.

Final mods xe268h airgap headers pocket port 2.02 heads 1.6 rockers etc.. Top red line

Stock 2bbl lonely blues lines at the bottom.

View attachment 1716478483

What cam is the red lines?