318>390 Stroker.......Your thoughts

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Dave81 said:
I run it on UK 99Ron fuel which is different to US rating. Think my fuel is above US 91.
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I've been over this gas thing with a few of UK guys.
As far as I/we can tell, the gas is pretty much the same, the ratings are just arrived at from a different calculation. Check it out.
Here in Canada, they add the two ratings and divide by 2 to get the average. They call it
(R+M)/2
>Rumble in post 15 makes some very strong points. I agree with his points that argue for raising the pressure; which,he addresses well.
If your short block is already assembled and the cam is in your possession, I get that you are sorta between a rock and a hard place.
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My story;
>With alloy heads, I have not been able to find detonation, even at up to 195psi, on our 87E10, which everyone loves to avoid. My 367 now has well over 100,000 miles on it, has never run on anything other than 87E10, and has never pumped less than ~180psi on my gauge, Which the Wallace predicted to be 177psi.(sorta pointing to the accuracy of the calculator, IMO)
>Both times that I have called Hughes, they have recommended one of their cams that I felt was one or more sizes too big for my combo. I have always been happy with the smaller cams I chose, in fact, the happiest my engine has been, is with a cam that wasn't even on their radar.
>The biggest cam that I have run was the Mopar 292/292/108hydro, which IIRC was about [email protected] .. I only ran it for one summer, because it very quickly became obvious that it was just too big for my application. I ran that cam in my Eddie-headed 367/A833/3.55s, at 11.3Scr. It did not like those 3.55s one bit. And I did not want to run more gear.
>I replaced that cam with a Hughes HE2430AL which is 223/230, and I measured it at 270/276/110 advertized. This combo made a freight train of torque, but obviously lost some peak power. However, with 3.55s, I only pass thru the power peak once, on the way to the speed-limit, and the tires were always on fire the whole way. So for me, I lost no street-performance, gained a huge increase in low-rpm performance, and the driveability and gas-mileage increased dramatically.
With the 292 cam, had made the common mistake of chasing a power number.
>I would still to this day, have been happy to drive that little Hughes cam, except in the Fourth year it dropped lobes right after an oil-change, due to the loss of zinc. I replaced it with next-bigger cam, the Hughes HE3037AL, also a hydro, but now 276/286/110.. I have had to live with that cam-choice since 2004, cuz it just won't die. Yes it makes more power, but I cannot feel it on the street, cuz at WOT, the 295BFGs just never stop spinning. With 3.55s, 6000 is 71mph in Second, and 7000 is 82 mph. Well it would be if the tires weren't spinning. Both of these cams used to bust the tires loose at 45 to 50 mph, with just a stomp on the go-pedal; 50 with 3.55s is ~4200 rpm in Second gear with the A833.
What I haven't mentioned is that with each of these cams, I adjusted the Scr to maintain about 180psi CCP.
>The point of my story is this: Don't let chasing a power number, ruin your street-fun. On the street, with spinning tires, 300 hp is IMO, just as much fun as 350/400; and the bottom-end is invariably more fun. Crank up the pressure and let the power be whatever it will be.
>"If your short block is already assembled and the cam is in your possession, I get that you are sorta between a rock and a hard place"
But If it was mine to do, I would shelf that cam, and install whatever it takes to get the pressure up to 180 or more. Those Eddies are gonna stretch your usable rpm band out to 6500Plus in the lower gears, and even tho the power will be down, the tires will be on fire, so yur never gonna know it. You won't perceive a power-deficit until the engine has to buck wind, sometime after maybe 80 mph. With a Mopar auto, and 3.55s, 80mph will be around 5600 @10% slip, and she still has more Second gear left in her.
>People say I put too much emphasis on pressure.
Maybe that's true IDK, but my chit boogies pretty good. My Street 367/A833/3.55s Barracuda went 93mph in the Eighth@3457 pounds with that stinking 230* cam, and 180psi. I only ever completed the one run, so IDK, it mighta had more in it.
I'm never going back to 155/160 psi.............
> with an automatic; Your other option is a hi-stall TC to get your rpm out of the soft zone, on the starting line; and smarter guys than me have already mentioned that. I'm not a fan of hi-stalls on the street. I mean the speed limits are 30 to 50 mph, and 65 on the hiway, so this is one or two gears for the bulk of the time. And even with a soft bottom end, yur only in it for at most one second! So why sacrifice the rest of your driving experience, especially when hi- pressure cures most of the problem. If the tires spin, the hi-stall, for take-off, is a waste. With a 4" arm, and decent pressure, I doubt you will need a hi-stall. Altho, I like the way my 2800 feels (different combo), it makes me smile every time it winds up.
Anyway, Rumble is snoring, so ...............
Happy HotRodding

EDIT
BTW, these are my thoughts
 
AJ, it seems that you rarely consider that some folks have performance goals and driving styles that are unlike your own. Some of us like to take our street cars to the drag strip and we also have sticky tires/slicks for that purpose. Your thing seems to mainly be spinning tires and accelerating up to 65 mph. Maybe the OP wants to run 11s or something in the 1/4 and couldn't care less what gear he needs for best acceleration from 30 to 55(or whatever) mph on the street. I can't relate to the idea of building a performance vehicle and then never track testing. Without actual testing, it's all speculation and "seat of the pants". Someone telling me that their car runs good without knowing the numbers really tells me nothing but their own perception.
 
Well; from Post #1;
Dave81 said:
Hey Guys,
So last month i started the long and costly process of upgrading the engine. Being in the UK getting a 360 is near impossible to find and will cost ££££. So i've always liked the idea of taking the 318 out to 390.
Luckily i knew of a decent standard bore block locally, so picked that up to allow me to keep the car Dart on the road over the next 6 months (Aiming for on the road next spring).
Spent quite a bit of time researching what I wanted, so will post below my combo. Just a bit of fun.....What do you think this combo will produce HP and TQ?
Thoughts?
Click to expand...

Well;
since we're not in the Racer's Forum,
but in the SBM forum,
a subdivision of Mopar Technical,
and I have thoughts .............
And besides;
OP can shut me down at any time,
but he has not ................
So thanks for your thoughts ............
 
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Do not know about the UK, but here in Oz, the octane ratings are about 3-4 points higher than equivalent US fuel. 91 here is about the same as 87 US.
 
Thanks guys. I'm happy to read anyone's thoughts and thank the guys that take the time to put down long constructive answers.
The aim was always something that would be circa 400HP and mid 400sTQ. Ideally wanted the car to run in the low 12s but be streetable. Understand you may have to compromise on some stuff and I would drop HP for TQ as that part of the power band is where It will realistically be driven most of the time.

Engine hasn't even been to the shop yet for work. No point until I have most of the parts to allow it to be completed. I have the heads, crank and rods. Pistons, cam and the rest of the rotating assembly is on back order.....waiting game.
 
More thoughts;
Low 12s with SuperStock suspension is 377hp@3300pounds.
With street suspension, expect at least a half a second slower, so 12.5s; is that low 12s enough for you?
The trapspeed associated with that ET, is about 112mph, which direct gear with an automatic, will require, at 10% slip, a rear gear of 4.30s; for 112=6300; which is with 88" rollout tires =28s.
6300 thru the traps will require the powerpeak to be around 6000
at 390 cubes, that will require a heckuva cam, too much for street I think.
4.10 would make it 6000 and a powerpeak at around 5700, but the tires will need to be bigger, say 90" that's still a pretty big for street cam. 90inches is a 28.65 tire, rounds to 29", for 112=5322@zero-slip, perhaps 5850 on the tach @10% slip, and a powerpeak at say 5500. That's doable on the street, with a cam around [email protected] in the 390.
The 250* cam would require a lot of cylinder pressure in the 390, to not be sluggish at low-rpm, so yur probably looking at the usual, hi-stall bandaid. And, of course, those 4.10s are Not gonna be hiway friendly. Well, that 292 cam is none too street friendly, either
Of course the whole thing depends on a raceweight of 3300#. Allowing 200 for the dressed driver, that makes for a car weight of 3100........ which is a bit of problem, if you want to keep it as a streeter.

So then, perhaps a review of your application is in order.

Obviously, the engine has to stay.
From your avatar, Ima guessing you have an early 70s Dart at 111wb or hopefully a 2dr Scamp @108wb. Those Scamps come in at around 3100 without power steering, so that is why I used 3100. And that has to stay.
The 4.10s kindof have to stay.
and the hi-stall has to stay.
But to make it streetable, yur gonna need a modest stall and an overdrive, and I don't know about you but I'll never run a 250* cam again on the street; been there/done that.
So that just leaves the transmission.
If the auto has to stay, then I would make it an A500 lock-up.
With it's slightly lower gear ratios, this would allow a lesser stall, and the 4.10s become 2.83s in .69overdrive.
And finally, I would swap out that theoretical 292hydro-cam for a solid lifter with say 228*@.050 after lashing.
Of course the power will be down some, so the MPH will drop. Say she comes in at 106mph; that is a requirement of 303hp, which is cake for the 390. But the ET has fallen to 12.9. Is that enough for you?
Since the mph has fallen to 106, you might think that you no longer require the 4.10s. But that is not correct. Your power-peak has fallen about the same percentage as the speed, namely 5%, so the rear gear also has to stay.

Ok now, This is NOT a recipe of what AJ thinks you should do.
This is just a study of what you might expect your future to look like when you try to marry a "street car" to a "race car". In this endeavor, you really need a big tame engine and or a lightweight chassis. ell, 390 is already pretty big.

You mentioned that you would prefer torque over power. That is a wise choice. But on the street, getting a street tire that fits in the factory tubs, to stick, with anything over a 318 engine is already a challenge. The point is that it is easy, with anything bigger than say a small-cam 340, to blow the tires off, with just about any rear street-gear. So when you show up, with a hi-stall 390 and 4.10s, the tires don't stand a chance. Your Scamp is not an 80,000 pound Kenworth,lol; it will be all too easy to have too much torque, and you just can never hit the go-pedal at full power, in that configuration.
So what's the answer?
IDK
I thought I knew.
I had a hi-pressure 367 with a 223/230/110 cam, but with a clutch, and the 3650 pound raceweight street-car has 3.55s, and she went [email protected] right out of the gate with no tuning; spinning thru two gears and part of the third, with street tires. That's nuts. I installed a double overdrive in it, which took the 3.55s down to 1.97; and 65 was 1600rpm. And I took the 750DP off it and installed a lean-calibrated 600VS on it with the Secondaries disconnected. I installed a dash-mounted, dial-back, timing module, so I could give the engine the timing it wanted.
On a certain day-trip, in 2004, she returned 32 mpgs.
For it's trapspeed and raceweight, the Wallace Calculator predicted 330horsepower. but the torque at 195psi CCP was outrageous. I didn't care that it was "slow", cuz it was just so much fun.
That cam died, so I replaced it with the next bigger cam (230/237/110) from the same supplier. Simultaneously I reduced the pressure to 180psi. This combo, in the Eighth, went 93mph @7.92 @3457 raceweight, translating to over 400hp, which translates to an unverified 11.98@115mph/SS suspension/in the quarter.
But the low-speed/low rpm torque fell off quite a bit, and the fuel economy went away. No big deal, the car has a clutch, right? lol.
So IDK anymore.
Your 390 is 6% bigger than my 367 and at 3300pounds your car would be 10% lighter than mine, at 3650 in street trim.
But you know, I have a GVod, which I often use as a splitter. The day I went to the 1/8th track, I was at 3457pounds, and I used 4 gear ratios, to hit that number. The road-gears were 10.97-8.56-6.82-5.32; and 93 was 6160 on a powerpeak somewhere between 5100 and 5300, with that 230* cam. BTW; That 5.32 is Second-over.
So then, these are my thoughts, maybe you can take away something from them.
I liked the 223* cam way better.
 
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I've often thought about doing a 318>390 build for one of 2 vehicles I have
An 80 volare is one, an 83 d250 is the other (my son actually has the truck) he pulled the original 318 out of the truck cleaned it up and painted it, it's going into something else.
These would be built differently between the car and the truck, being as how the car is lighter and the truck would be used like one. Neither would be raced
 
Thanks AJ.

Car had and all new rear end three years ago. Ive worked from the back forwards with the basis of that 390 as a power plant. When this was done I went for the SS springs (002/003 from memory).

I will look at the cam selection again.

Edit. 72 Dart by the way.
 
Dave81 said:
Thanks AJ.

Car had and all new rear end three years ago. Ive worked from the back forwards with the basis of that 390 as a power plant. When this was done I went for the SS springs (002/003 from memory).

I will look at the cam selection again.

Edit. 72 Dart by the way.
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I went 9.80’s on 002/003 leafs for years with a very small tire(28 by 10) car was deadly, wasn’t cut or minitubbed( 70 Duster) 3350 with driver.
Those springs are more than capable of supporting plenty of power
 
volaredon said:
I've often thought about doing a 318>390 build for one of 2 vehicles I have
An 80 volare is one, an 83 d250 is the other (my son actually has the truck) he pulled the original 318 out of the truck cleaned it up and painted it, it's going into something else.
These would be built differently between the car and the truck, being as how the car is lighter and the truck would be used like one. Neither would be raced
Click to expand...

I've read many threads in here and most shout 'go for a 360'. They are rare in the UK and if you find one very expensive to procure. So that's not an option for me. Guy I know paid £3000 just for a block, no heads etc.
Biggest issue is piston choices for the 318/390. Trying to get the comp ratio you want is very hard.

My options are 9.9:1 SCR or 11.5:1 with what I can find.
Shame as ideally I want mid 10s.

Always wanted to keep the 318 as a base, but wanted something to kick me in the back when I romp on it. Cubic inches was my choice to do both.
 
Dave81 said:
I've read many threads in here and most shout 'go for a 360'. They are rare in the UK and if you find one very expensive to procure. So that's not an option for me. Guy I know paid £3000 just for a block, no heads etc.
Biggest issue is piston choices for the 318/390. Trying to get the comp ratio you want is very hard.

My options are 9.9:1 SCR or 11.5:1 with what I can find.
Shame as ideally I want mid 10s.

Always wanted to keep the 318 as a base, but wanted something to kick me in the back when I romp on it. Cubic inches was my choice to do both.
Click to expand...

compression is important, no doubt. That said it certainly isn’t a deal breaker.
Going from 9.9 to 11.5 might be a 4-6% gain due to the extra squeeze. 500 horse motor that’s 20 or 30 horse, not nothing, for sure , but also far from a deal breaker
Could be made up other ways, certainly
 
Dave81 said:
I've read many threads in here and most shout 'go for a 360'. They are rare in the UK and if you find one very expensive to procure. So that's not an option for me. Guy I know paid £3000 just for a block, no heads etc.
Biggest issue is piston choices for the 318/390. Trying to get the comp ratio you want is very hard.

My options are 9.9:1 SCR or 11.5:1 with what I can find.
Shame as ideally I want mid 10s.

Always wanted to keep the 318 as a base, but wanted something to kick me in the back when I romp on it. Cubic inches was my choice to do both.
Click to expand...

Getting from 9.9:1 to mid 10's should not be a stretch... deck the block... shave the heads or a thinner head gasket. Any of the 3 or a combination of them should get you there. I should add if you are stuck in the mud at 9.9:1 you'd likely not notice the difference and you won't have to worry about detonation with that CR.
 
B3422w5 said:
compression is important, no doubt. That said it certainly isn’t a deal breaker.
Going from 9.9 to 11.5 might be a 4-6% gain due to the extra squeeze. 500 horse motor that’s 20 or 30 horse, not nothing, for sure , but also far from a deal breaker
Could be made up other ways, certainly
Click to expand...
Yeah I watched the engine masters episode where they did exactly that. Think it was a 9.7:1 vs 11.2:1 327 chevy stroked to 331. Think it was 20 numbers across the entire graph, just like railroad tracks.

Same time, its not wanting to build a dog of a motor. So trying to match parts for a good combo is my aim.
 
Soooooo, that's what I did 6 years ago. Everyone thought I was crazy to stroke a 1968 318, but it turned out awesome! The machine shop said all the parts I researched and purchased for the build was great. Edlebrock aluminum heads, comp cam with 525 lift/287 duration if I remember. 390 stroker kit, 750 quick fuel carb with manual secondaries no choke. Anyway.. it made 450 hp/490tq. You will not be disappointed.
 
74Scooter said:
Getting from 9.9:1 to mid 10's should not be a stretch... deck the block... shave the heads or a thinner head gasket. Any of the 3 or a combination of them should get you there. I should add if you are stuck in the mud at 9.9:1 you'd likely not notice the difference and you won't have to worry about detonation with that CR.
Click to expand...

That SCR is based on the block being decked to 0.01. Felpro head gasket at 0.039 compressed. Heads are 63cc, though they will be cleaned up and shaved slightly for flat. I've ignored any variance on that.
The car that was running the rotating assembly I've bought was originally 390 built wrong, then ipgraded to a 396 (60 over 318). It did 500 miles before it blew a hole in the wall of cylinder 4. That why I declined the Icons at 11.5:1. I'd estimated that the cylinder pressure and thin walls didn't combine well.
 
CUDACOX said:
Soooooo, that's what I did 6 years ago. Everyone thought I was crazy to stroke a 1968 318, but it turned out awesome! The machine shop said all the parts I researched and purchased for the build was great. Edlebrock aluminum heads, comp cam with 525 lift/287 duration if I remember. 390 stroker kit, 750 quick fuel carb with manual secondaries no choke. Anyway.. it made 450 hp/490tq. You will not be disappointed.
Click to expand...

Thanks buddy.
Exactly what I was looking at for the build. If I got to that HP and TQ figure I would be over the moon.
 
Dave81 said:
Yeah I watched the engine masters episode where they did exactly that. Think it was a 9.7:1 vs 11.2:1 327 chevy stroked to 331. Think it was 20 numbers across the entire graph, just like railroad tracks.

Same time, its not wanting to build a dog of a motor. So trying to match parts for a good combo is my aim.
Click to expand...

I have that show set to DVR... one of the best that has been on IMHO. They do some quality work on the dyno and toss everything at it from exhausts, intakes, air filters, carb spacers, cam's, rockers, heads, etc.. The delta between the different setups in regard to HP and TQ numbers is very helpful in determining what to go after first and what quite seriously is not worth wasting your hard earned smack on. A lot of people get hung up on max numbers and forget many of the other shows out there focus on WOT for racing. Nice to have a show that you can use to help decide what works on a streetable engine.
 
Some 318 blocks have been able to be taken out to 4.00” bore. If your block sonic checks we’ll and you have enough meat in the cylinder bores to run 4.00” bore your piston choice and piston cost will be much better.
 
Should start shipping 360’s over as scrap iron! Make a bundle!!:)
 
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