318 to 390?

Posted By: Tinmans21

318 to 390? - 10/05/12 01:05 AM

Ok I have an 85 Dodge diplomat salon 4 door that im making into a sleeper. I want to take the 318 i have an bore it .40 over an make it a 390 stroker. I've read that it is possible to make 360 heads flow better than the stock 340 x heads heres the link http://www.moparmusclemagazine.com/techa...ng/viewall.html So i was considering doing the exact same thing an putting them on the 390 stroker. As for a cam and intake im not sure. I want the car to be streetable but also have a hefty amount of power. The car is planned to be a sleeper an intended to blow the doors off of teenage kids who think they are on top of the world. I also have a 650 holley double pumper laying around. Would that be to much depending on the cam an intake? Does anyone have experience with this kind of motor build an have advice for cam an intake based on what iv said? Please any advice is amazing!!!

Posted By: radar

Re: 318 to 390? - 10/05/12 01:13 AM

The teenage kids on top of the world in my neighborhood have three hundred horsepower turbo all wheel drive subarus. Good luck with that!

My 408 with ootb eddy heads, MP 557 cam, airgap, 750dp, and small headers puts down 400tq 350hp at the wheels. A mildish 390 (xe275hl cam?) will step on every fart-canner but you'll have to know how to drive for the ones who's parents have money haha!

Don't be like me and plan for 400-500 horses at the crank with a cast stroker and sir rods. I am already planning a forged crank build...

Posted By: Tinmans21

Re: 318 to 390? - 10/05/12 01:50 AM

I also have a virgin block 383 bb but my concern is if i could handle it cuz id be going all out on the motor. 496 stroker kit from 440 source along with the super stealth aluminum heads. cams an intake are once again unkown. im to familiar with the upper part of the motor. but im learning more everyday. I think it might be better for me to work my way up to that kind of power unless of course im just being a pansy. lol. I can handle an srt-8 just fine but i want more power than that. lol An yes i want it in a diplomat lol

Posted By: Moparmal

Re: 318 to 390? - 10/05/12 05:01 AM

Ran a 392 for 18 mths till the Eagle cast crank let go.

I used ported 360 heads peak flow to 240cfm at .550 lift.

Off the shelf headers, M1 SP off the shelf, comp xs282s sold (520 , 245@.50)

3.89 gears, 3400 stall, RMVB. 800 AVS carb, 3650lbs with me in it.

Ran a best of 12.3 at 111mph with a dogs$&t 60 ft of 1.86,

Loved the torque for street duty and there was def more in it.

Just use a decent brand crankshaft and forged slugs.....Icon 846/847 are good.

Posted By: patrick

Re: 318 to 390? - 10/05/12 02:49 PM

don't use an eagle cast crank, go with a scat. balance it to 360 external if you need a lot of heavy metal for internal balancing

skip the 360 heads, go straight to magnums...either junkyard pieces or these from hughes

http://www.hughesengines.com/Index/produ...mp;partid=25702

if you go stockers, use the hughes #1110 springs and their retainers anyway..

your '85 should be a roller block/cam. you'll need new magnum roller lifters (about $85 set) since the '85's don't have pushrod oiling provisions. for a heavy car like a dippy (I hotrodded a 5th ave) don't go too big on the cam. look for a roller cam in the [Email]218-224@.050[/Email] range, with about .340" lobe lift (nets approx. .540" valve lift).

edelbrock RPM air gap, and I'd probably look at the new demon thermoquad clones for street use, or an 800 cfm eddie AVS. run headers, and this should be a 425-450hp combo pretty easily. if you want fun, I'd use an iron case A body A833OD manual and 3.23's or 3.55's out back. should be a low, low 13/high 12 second car.

Posted By: Moparmal

Re: 318 to 390? - 10/06/12 07:22 AM

Quote:

don't use an eagle cast crank, go with a scat.

I agree!

Posted By: Chris'sBarracuda

Re: 318 to 390? - 10/06/12 07:32 AM

You might want to think that over carefully..

https://board.moparts.org/ubbthreads/show...rue#Post7384092

This was a 318/390..

Chris..

Posted By: Moparmal

Re: 318 to 390? - 10/06/12 07:49 AM

Quote:

You might want to think that over carefully..

https://board.moparts.org/ubbthreads/show...rue#Post7384092

This was a 318/390..

Chris..

Was this addressed to me?

Id certainly never recommend anything "Eagle" ever again...so not sure what you're saying?

Posted By: Chris'sBarracuda

Re: 318 to 390? - 10/06/12 07:59 AM

Quote:

Quote:

You might want to think that over carefully..

https://board.moparts.org/ubbthreads/show...rue#Post7384092

This was a 318/390..

Chris..

Was this addressed to me?

Id certainly never recommend anything "Eagle" ever again...so not sure what you're saying?

Nope..

To the OP.. Dustin's build was 318/390..

Just giving him something to think about...

Chris..

Posted By: AdamR

Re: 318 to 390? - 10/06/12 02:29 PM

Quote:

You might want to think that over carefully..

https://board.moparts.org/ubbthreads/show...rue#Post7384092

This was a 318/390..

Chris..

Seems the valve failed and caused the carnage. That could happen with any motor.

Posted By: Triple Threat

Re: 318 to 390? - 10/07/12 05:54 AM

Quote:

Quote:

You might want to think that over carefully..

https://board.moparts.org/ubbthreads/show...rue#Post7384092

This was a 318/390..

Chris..

Seems the valve failed and caused the carnage. That could happen with any motor.

Just my luck, has nothing to do with what the engine was.

Bigger Bore makes more power, unless you have a reason to stay with the 318, you're better off building a 408.

Posted By: dizuster

Re: 318 to 390? - 10/08/12 08:59 PM

You'd probably be further ahead money wise just building a stock cast crank 360. I wouldn't waste the time on a stroker 318 when 360's are so plentiful.

Posted By: AdamR

Re: 318 to 390? - 10/09/12 01:06 AM

Quote:

You'd probably be further ahead money wise just building a stock cast crank 360. I wouldn't waste the time on a stroker 318 when 360's are so plentiful.

why is that ? most guys already have the 318

Posted By: Moparmal

Re: 318 to 390? - 10/09/12 03:45 AM

I agree...and furthermore.......

Its funny how the extra 32 cubes between a 318 and 360 are "to die for", but the xtra 32 cubes between a 360 and 392 don't count for much......

Of course this position is only ever held by those who've never run a stroked 318 on the street...

Posted By: RobX4406

Re: 318 to 390? - 10/09/12 03:52 AM

Quote:

I agree...and furthermore.......

Its funny how the extra 32 cubes between a 318 and 360 are "to die for", but the xtra 32 cubes between a 360 and 392 don't count for much......

Of course this position is only ever held by those who've never run a stroked 318 on the street...

Math is hard...

Posted By: Moparmal

Re: 318 to 390? - 10/09/12 05:46 AM

Quote:

Quote:

I agree...and furthermore.......

Its funny how the extra 32 cubes between a 318 and 360 are "to die for", but the xtra 32 cubes between a 360 and 392 don't count for much......

Of course this position is only ever held by those who've never run a stroked 318 on the street...

Math is hard...

You should be having my day Cracked.....err Rob....If I could ship it FedEx to you I would.......:p

Posted By: DaytonaTurbo

Re: 318 to 390? - 10/09/12 06:00 AM

Quote:

Quote:

I agree...and furthermore.......

Its funny how the extra 32 cubes between a 318 and 360 are "to die for", but the xtra 32 cubes between a 360 and 392 don't count for much......

Of course this position is only ever held by those who've never run a stroked 318 on the street...

Math is hard...

It must be, because 360-318 = 42 cubes, not 32. Buy a core 360 for $300, then add in your new pistons, redone rods, recondition crank, new bearings and you're easy at the 1k or over mark. Could kick in a bit of extra cash and have stroked the 318 from the start. Which is worth it is up to you. I thought I saw complete 390 kits on sale for 1300 or 1400 bucks.

Posted By: RobX4406

Re: 318 to 390? - 10/09/12 06:25 AM

Quote:

Quote:

Quote:

I agree...and furthermore.......

Its funny how the extra 32 cubes between a 318 and 360 are "to die for", but the xtra 32 cubes between a 360 and 392 don't count for much......

Of course this position is only ever held by those who've never run a stroked 318 on the street...

Math is hard...

You should be having my day Cracked.....err Rob....If I could ship it FedEx to you I would.......:p

Just having a bit of fun. Hope your day gets better,

Posted By: Moparmal

Re: 318 to 390? - 10/09/12 11:36 AM

Quote:

It must be, because 360-318 = 42 cubes, not 32.

yeah got that - argument is still valid -

Cubes has always been the "pitch" the 360 boys bring to the mound - but when the 318/392 combo gets mentioned torque per cui is suddenly "relegated to the minors".

I prefer this equation:

392 cu. in. ...1 hp per cu. in....392 hp (4" stroke)(torque Monster)

360 cu. in. ...1.08 hp per cu. in. 392 hp (3.580 Stroke)(medium Torque)

340 cu. in. ...1.152 hp per cu. in 392 hp (3.310 Stroke)(no torque)

318 cu in. ...1.23 hp per cu. in. 392 hp (3.310 Stroke)(no torque)

Which is most streetable to run and easiest to achieve ?

Batter up!

Posted By: patrick

Re: 318 to 390? - 10/09/12 02:44 PM

one HUGE advantage of stroking the 318 vs. building a 360 is his '85 318 has a factory roller cam. that allows you to use either a reground factory or an aftermarket hydraulic roller cam with the very depandable and cheap OEM hydraulic roller lifters.

and a dippy is a heavy car. my 5th ave was 3950 lbs w/o me once I added the A500 tranny, big sway bars, 8 3/4" rear and 5 leaf rear springs (and deleting all the emissions crap, going to an aluminum intake). Torque is your friend, and torque is directly proportional to displacement. built identically except for displacement, I'd expect the 390 CID stroked 318 to make ~8%, or about 25-30 more lb-ft of torque than a 360.

the economics of it are use your existing 318 block, and spend $300 on a SCAT 4" crank, or spend $300 on a 360 core motor....otherwise the build costs will be very similar if you were planning on aftermarket pistons/rods/heads

for a car like this, that's going to be a street car primarily, don't look at peak HP, look at ave torque and torque peak, and let the HP fall where it may. a 420HP engine with say, 450 lb ft peak torque at 3500 RPM, with over 90% available from idle to 5000 RPM will probably feel stronger than a 475HP motor but with 450 lb-ft peak at 5000 RPM and only 70% of peak torque available off idle and 90% not available until 3000 RPM...

Posted By: MR_P_BODY

Re: 318 to 390? - 10/09/12 03:02 PM

Lets see here... your gonna buy a stroke kit... that
part is a wash... why not buy a 360 block and get the
added cubes... that would cost about 200 buck more..
cubes are great for the street........ JMO

Posted By: justinp61

Re: 318 to 390? - 10/09/12 03:52 PM

Quote:

Lets see here... your gonna buy a stroke kit... that
part is a wash... why not buy a 360 block and get the
added cubes... that would cost about 200 buck more..
cubes are great for the street........ JMO

Pick up a later roller cam 360 block, everything else costs the same. Plus the larger bore of a 360 will help unshroud the intake valves.

Posted By: Triple Threat

Re: 318 to 390? - 10/09/12 04:01 PM

Quote:

Quote:

Lets see here... your gonna buy a stroke kit... that
part is a wash... why not buy a 360 block and get the
added cubes... that would cost about 200 buck more..
cubes are great for the street........ JMO

Pick up a later roller cam 360 block, everything else costs the same. Plus the larger bore of a 360 will help unshroud the intake valves.

And I owned a pretty stout 318-390" stroker. The same package with a 360-408" engine probably would have been worth another 20-30lb ft of torque at no added cost. 360 blocks aren't that hard to come by.

Posted By: HotRodDave

Re: 318 to 390? - 10/09/12 04:21 PM

Quote:

Quote:

Quote:

Lets see here... your gonna buy a stroke kit... that
part is a wash... why not buy a 360 block and get the
added cubes... that would cost about 200 buck more..
cubes are great for the street........ JMO

Pick up a later roller cam 360 block, everything else costs the same. Plus the larger bore of a 360 will help unshroud the intake valves.

And I owned a pretty stout 318-390" stroker. The same package with a 360-408" engine probably would have been worth another 20-30lb ft of torque at no added cost. 360 blocks aren't that hard to come by.

30lbs from 16 cubes

not to mention bigger bearings robbing power

due to the SB good valve position they do not see much more flow (a little but not significant) from a 3.91 bore to a 4 inch bore, that is only gonna give you .045 more clearance on one little section of the valve, a very small notch on the bore would do the same thing for free.

And 360 roller LA blocks are hard to find being only a couple years in very low selling rigs that were not always optioned with 360s. If you are willing to use magnum heads (you should) then finding roller blocks is real easy.

Any differance in a 318 stroker and 408 stroker is minimal, especially when you start looking for a roller block or even any block at all that is not free.

Posted By: 2734bbl

Re: 318 to 390? - 10/09/12 09:26 PM

I dont know Wade personally but I have seen this car and it certianly doesnt give you the impression it runs that fast.

https://board.moparts.org/ubbthreads/show...rue#Post6507721

Posted By: Mad Dart

Re: 318 to 390? - 10/09/12 11:18 PM

Quote:

You might want to think that over carefully..

https://board.moparts.org/ubbthreads/show...rue#Post7384092

This was a 318/390..

Chris..

Unfortunately when a part fails like this it takes out the whole enchilada. This has nothing to do with the 318/390 build at all. I had the same thing happen to a hot 340 I had at 7200 RPM, Was not quite as bad but it did drop a valve, took out a cylinder, broke a pistion fkd up the head, annihilated a Rod. I could only find balled up pieces in the pan and all over the inside of the engine, intake etc. This can happen to any engine when a Valve lets go. I put a 410 Stroker in it and when I fired it off I had quite a few pieces come flying out the exhaust that were stuck in the mufflers.

Posted By: Tinmans21

Re: 318 to 390? - 10/10/12 02:49 AM

Idk if this makes a diffrence but the 318 actually came out of a 83 pickup. The motor is on a stand atm. Does anything change with that motor? It really sounds like its a matter of opinion or choice with the 318 vs 360 arguement. I'm going to stick with the 318 an stroke it to a 390 an bore the block .40 over. I'm going to stick with the 318 cuz i have a 383 block sitting soooo buying a 360 would just mean another motor sitting until I can sell it. I may plan on using nitrous for track use only permitting that the motor will handle it. The car will have a A833 for sure an a 8 3/4 axle for sure. Im new to this so any advice is appreciated. I am going to lighten the car as much as possible since it will see the track but i need to keep in mind it will also be a friday night cruiser. Thanks for all the input!!

Posted By: DusterDave

Re: 318 to 390? - 10/10/12 03:16 AM

Quote:

Idk if this makes a diffrence but the 318 actually came out of a 83 pickup. The motor is on a stand atm. Does anything change with that motor? It really sounds like its a matter of opinion or choice with the 318 vs 360 arguement. I'm going to stick with the 318 an stroke it to a 390 an bore the block .40 over. I'm going to stick with the 318 cuz i have a 383 block sitting soooo buying a 360 would just mean another motor sitting until I can sell it. I may plan on using nitrous for track use only permitting that the motor will handle it. The car will have a A833 for sure an a 8 3/4 axle for sure. Im new to this so any advice is appreciated. I am going to lighten the car as much as possible since it will see the track but i need to keep in mind it will also be a friday night cruiser. Thanks for all the input!!

The '83 318 block is different than the older 318 blocks. The decks are weaker, and susceptible to cracking between the coolant hole and the nearest head bolt hole. I know this, because I was going to use a 1983 318 block to build a 390, and that block had a total of 10 cracks on both decks. They weren't discovered until after several machining operations. Here is a pic of what my engine builder found. Two differences you can see are the head bolt holes going through the deck, and larger coolant holes, both of which weaken the deck. On the older blocks, the head bolt holes are blind and the coolant holes are smaller.

I'm not saying your block WILL have these cracks, all I am suggesting is that you have those decks carefully examined before sinking money into machine work on that particular block. Also, have your machinist check for twist in the block. Seems the '83 blocks in general are on the weak side, which proved to be the case with mine. It was twisted pretty bad. Although my machinist informed me that the cracks could be fixed, I decided to cut my losses and start over with a beefier 1970 318 block that was available to me.

Posted By: patrick

Re: 318 to 390? - 10/10/12 04:44 PM

'83 block is a non-roller block. personally, that's the big advantage of building a 318 based stroker over a 360, it's MUCH easier to find a roller cam block for cheap

Posted By: Performance Only

Re: 318 to 390? - 10/10/12 05:16 PM

Quote:

I'm going to stick with the 318 an stroke it to a 390 an bore the block .40 over.

My advice would be to bore it the least amount you can get away with, especially in a stroker application and your talking about spraying nitrous too. I've sonic checked a lot of blocks over the years, and 318's (among others) are not known for having thick cylinder walls.

Posted By: dizuster

Re: 318 to 390? - 10/10/12 09:54 PM

My point about the 360 vs. 390 was purely cost related. You could get a running magnum 360 cheap. All of the rebuild parts are a wash between the two (gaskets, machining, etc�)

My opinion is that you can buy a 360 magnum motor for the price of a cast 318 stroker crank. So call that a wash dollar for dollar.

But if you're on a budget, I'd MUCH rather have a 360" with a 360 magnum head, then a 390" with a '83 318 smog head any day of the week.

It was more then just the cubic inch difference. Just depends how much money you want to spend�

Posted By: Moparmal

Re: 318 to 390? - 10/11/12 05:14 AM

The OP mentioned using 360 heads at the start -

I agree that if you don't have the heads for a 392 - then its a different $ equation.

Posted By: patrick

Re: 318 to 390? - 10/11/12 06:21 PM

Quote:

My point about the 360 vs. 390 was purely cost related. You could get a running magnum 360 cheap. All of the rebuild parts are a wash between the two (gaskets, machining, etc�)

My opinion is that you can buy a 360 magnum motor for the price of a cast 318 stroker crank. So call that a wash dollar for dollar.

But if you're on a budget, I'd MUCH rather have a 360" with a 360 magnum head, then a 390" with a '83 318 smog head any day of the week.

It was more then just the cubic inch difference. Just depends how much money you want to spend�

you can? here core 360 mags go for over $500, and runners are in the $800-1k range, even if they're over 120k miles...318 mags go for about 1/2 what the 360's do...

but yes, I'd much rather have a mag 360 and give up 30CID than a 390 stroker choked with LA 318 heads.

Posted By: Tinmans21

Re: 318 to 390? - 10/11/12 10:09 PM

Oh trust me i would never use the smog 318 heads on the 390 stroker. lol. Those heads would kill the motor. Im doing more research on the 383 big block i have. its a 68 with closed chamber heads. Stock cam no intake atm. The 318 may just go in so i can drive the car at least then work the 383. It would b nice to have 500hp to the wheels on a streetable car but im not sure if its possible. just more research must be done.

Posted By: gregsdart

Re: 318 to 390? - 10/11/12 11:04 PM

If you don't open the hood the big block will make it a real sleeper. A LOT more cubic inches stroked, and stock heads with big valves and a little bowl work can flow enough to go over 500 hp. Probably with a hydraulic cam if you like.

Posted By: dizuster

Re: 318 to 390? - 10/14/12 09:39 PM

Quote:

you can? here core 360 mags go for over $500, and runners are in the $800-1k range, even if they're over 120k miles...318 mags go for about 1/2 what the 360's do...

Yup really... well based on my 15 seconds of searching anyway...

http://detroit.craigslist.org/wyn/pts/3337858380.html

Listed at $300 obo.

Posted By: patrick

Re: 318 to 390? - 10/15/12 12:13 PM

Quote:

Quote:

you can? here core 360 mags go for over $500, and runners are in the $800-1k range, even if they're over 120k miles...318 mags go for about 1/2 what the 360's do...

Yup really... well based on my 15 seconds of searching anyway...

http://detroit.craigslist.org/wyn/pts/3337858380.html

Listed at $300 obo.

nice price, but that's a 5+ hour round trip for me....

Posted By: OUTLAW MOPAR

Re: 318 to 390? - 12/16/12 03:01 PM

Go 390 stroker they make super impressive motors with correct parts. My darts 390 consists of a '71 318 block scat cast 4" crank scat H rods custom ross 9.5 blower pistons hughes hyd roller retrofit setup. Heads are Indy lax that flow 284 @ .550 w/ 2.02 1.60 and procomp airgap knockoff intake. Also has the awesome PRW. 1.6 Stainless roller rockers. This assembly was worth 457hp @ 6300 and 488 tq @ 4400 at the wheels. My buddy built a 360/414 shortblock same comp, heads, cam, intake, rockers he only bested me w/ 461hp @ 6300 and 490tq @ 4400 at wheels. Great motors but not much more for a ever harder to find '72 360 block which he paid $250 for when '67 to '75 318's are all but free like mine was cast was given by a local bowtie enthusiast. That bowtie boy aint real happy about being patty slapped by his cast away 318 from that rotted out powerwagon he scrapped.