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

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Dave81

Dave81

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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?

318 (76) taken out to 390:
Scat cast crank and rods.
ARP everything on the bolts.
Diamond forged pistons (16.7cc).
Eddy RPM 60779 Cylinder heads (standard) c/w felpro 1008 head gaskets.
Hughes Cam - Solid flat tappet - HUG STL4246AS-8 Hughes Engines
I've calculated 9.9:1 SCR at 0 deck Low 8's DCR

Hughes 1.5 Rocker assembly
750 Mech carb (holley or brawler)
Eddy RPM Air Gap Intake
Eddy Fuel pump (mech).
Melling HV oil pump
Milodon sump
Dougs Headers

Thoughts?
 
Not familiar with stroking 318 to 390, what bore and stroke is that?
 
I like it! You can save a few euro's going with a stock oil pan. Those 390 cubes should scream with those components. 65'
 
toolmanmike said:
Power output will have a lot to do with the heads especially with strokers.
Click to expand...

He spec'd. a pretty standard fare set of Eddy's. Prolly get a decent bump on at the top end with a CNC'd set of Trickflow or the like but at probably what... double the cost?
 
74Scooter said:
He spec'd. a pretty standard fare set of Eddy's. Prolly get a decent bump on at the top end with a CNC'd set of Trickflow or the like but at probably what... double the cost?
Click to expand...

Yea, managed to score a set of Eddy heads this side of the water. The exchange rate, shipping and then taxes currently are making the build very expensive. The heads are standard, but I can always have them worked at a later date.

Would love Trickflow heads, but by the time they are on the car I would be at $3k for those alone. Trying to control the cost and I've picked the worst year in history to do it......
 
If you haven't bought all the parts yet you could consider using a 3.58" crank which works out to about 350 cubes. Apparently it gives a better piston/rod angle for more longevity.
This is what I've gone for on my 318 poly stroker (currently mid build).
I don't know if I've made the right decision or not, maybe I should have just gone all in with the 4" crank, but my goal was a reliable cruiser with a bit more power and torque, time will tell.
 
It is pretty easy to 4" stroke a Mopar small block. Kits are available.
 
Dave81 said:
318 (76) taken out to 390:
Scat cast crank and rods.
ARP everything on the bolts.
Diamond forged pistons (16.7cc).
Eddy RPM 60779 Cylinder heads (standard) c/w felpro 1008 head gaskets.
Hughes Cam - Solid flat tappet - HUG STL4246AS-8 Hughes Engines
I've calculated 9.9:1 SCR at 0 deck Low 8's DCR
Click to expand...
HUG STL4246AS-8
SB SLD FLAT TAPPET CAM 242/246 -108ºLSA
.376"/.389" LOBE LIFT
That's a pretty big cam. With alloy heads, it will want a lot of Scr. I wonder if you are using the DCR calculator properly. It needs the advertised numbers, NOT the .050s. Yur gonna need a lot more than 9.9 to get to low 8s Dcr. Alloy heads will easily support 185psi on pumpgas. I have run that on 87E10
Your swept is 799.18cc
Your total chamber at zero-deck is about 63+8.6+16.7=88.3
Your Scr is thus (799.18 +88.3)/88.3= I get 10.05.

But Hughes does not publish the advertised, which is a pita.
so you have to either guess or call them.

If I guess , I will get 288/292/108 and in at +4 I get an Ica of 68*
Now because that cam is a solid, your Ica might change after lashing to say 65* and
Wiki says you are at 236ft elevation.
Plugging those numbers into the Wallace calculator, I get a Dcr of 8.0 @163psi.. That is fine for Iron heads and pumpgas, but with alloys, that is leaving a lot of performance on the table, especially low-rpm torque.
To get to 185psi, will require a change in Scr to ~11/1..
So, I would call Hughes
 
I do not understand why people use DCR...for anything. It assumes in plugging in the cam event that every engine of that size that uses that figure will ingest the same weight of air. Intake design, port flow etc, are going to vary so that a different weight of air will be drawn into the cyl. It is the weight of air that is compressed that will determine the true CR & I do not see how that can be calculated from a static formula that has so many variables.
 
He has a good point Bewy. It’s a PIA to get it working in the head and on the paper. I also have to say that I think the cam is big for the stroker set up. Not without domed pistons. IDK if that’s available for this combination. Also the cylinder head is small for the cubes. Beyond a regular street runner of 370 cubes, that Edelbrock head is limiting. Even at that it is depending on what your doing.

IF it were I doing this, the first step would be to seek a little more compression with this cam or use a smaller one. Port the heads out rod use of the 1.6 rocker, 1-3/4 headers and couple it with a 4.10 gear at a minimum. (3.91’s with the next smaller cam)

I’d also look to put the cam on a 106, not a 110. It’s IMO the 110 will leave the 390 a little soft on the bottom despite its CID.
The cam timing events are key to the power.

@Dave81, I think your combo will perform very much like the BluePrint 408 with the power band shift upwards 500+ RPM.
I suggest the 1-3/4 header (min.), 1.6 rockers and having the cylinder heads well ported. That should release a good 70+hp.
 
I ran the eddies OOTB on a 360 based 410. Managed a 12.4? I had no issues, but I have heard that the guides can be tight on them if they are new. Also the springs that come on them are barely good enough for the advertised lift number from Edelbrock. Add a quick ramp and you can get some instability. I have been running a 4” cast Scat crank with the 360 journals. I shift at 6400 and cross the stripe a 6700. That crank owes me NOTHING, but at this point I’m a little scared to chase more power. I’m at 425 at the crank according to the calculators. For me the cost difference from cast to forged is not big enough to to buy a cast crank. (Your side of the world could be very different)Especially if you plan on spinning it. Plus I know no matter what I going to hammer on anything I build. My Scat cast crank was checked and balanced to 1/2 gram during a piston change 3-4 years ago. It was still straight after 7-8 years of hammering on it.
 
AJ/FormS said:
HUG STL4246AS-8
SB SLD FLAT TAPPET CAM 242/246 -108ºLSA
.376"/.389" LOBE LIFT
That's a pretty big cam. With alloy heads, it will want a lot of Scr. I wonder if you are using the DCR calculator properly. It needs the advertised numbers, NOT the .050s. Yur gonna need a lot more than 9.9 to get to low 8s Dcr. Alloy heads will easily support 185psi on pumpgas. I have run that on 87E10
Your swept is 799.18cc
Your total chamber at zero-deck is about 63+8.6+16.7=88.3
Your Scr is thus (799.18 +88.3)/88.3= I get 10.05.

But Hughes does not publish the advertised, which is a pita.
so you have to either guess or call them.

If I guess , I will get 288/292/108 and in at +4 I get an Ica of 68*
Now because that cam is a solid, your Ica might change after lashing to say 65* and
Wiki says you are at 236ft elevation.
Plugging those numbers into the Wallace calculator, I get a Dcr of 8.0 @163psi.. That is fine for Iron heads and pumpgas, but with alloys, that is leaving a lot of performance on the table, especially low-rpm torque.
To get to 185psi, will require a change in Scr to ~11/1..
So, I would call Hughes
Click to expand...
I've emailed and spoken to Hughes. Based on the combo it was this or the next cam the 4650. My concern was as the number goes up so does the lift and the Eddy heads I believe have max lift at .575.

I had a full rotating assembly offered to me but passed on the Icon pistons. Piston choice at this size is poor. It's either 23cc, 16.7cc (these) or around 4cc as with the icons offered.
That calculated my SCR at 11.5:1. Nothing in-between to get me mid 10s.

I run it on UK 99Ron fuel which is different to US rating. Think my fuel is above US 91.

Appreciate the input. This is the exact reason I've asked.
 
rumblefish360 said:
He has a good point Bewy. It’s a PIA to get it working in the head and on the paper. I also have to say that I think the cam is big for the stroker set up. Not without domed pistons. IDK if that’s available for this combination. Also the cylinder head is small for the cubes. Beyond a regular street runner of 370 cubes, that Edelbrock head is limiting. Even at that it is depending on what your doing.

IF it were I doing this, the first step would be to seek a little more compression with this cam or use a smaller one. Port the heads out rod use of the 1.6 rocker, 1-3/4 headers and couple it with a 4.10 gear at a minimum. (3.91’s with the next smaller cam)

I’d also look to put the cam on a 106, not a 110. It’s IMO the 110 will leave the 390 a little soft on the bottom despite its CID.
The cam timing events are key to the power.

@Dave81, I think your combo will perform very much like the BluePrint 408 with the power band shift upwards 500+ RPM.
I suggest the 1-3/4 header (min.), 1.6 rockers and having the cylinder heads well ported. That should release a good 70+hp.
Click to expand...

Thanks.
The heads may well get machined at a later date. I already have them and they are better than any stock head available in the UK. Cost is the killer here and I've already blown the budget due to exchange rate and parts cost hikes due to availability etc.
 
furrystump said:
I ran the eddies OOTB on a 360 based 410. Managed a 12.4? I had no issues, but I have heard that the guides can be tight on them if they are new. Also the springs that come on them are barely good enough for the advertised lift number from Edelbrock. Add a quick ramp and you can get some instability. I have been running a 4” cast Scat crank with the 360 journals. I shift at 6400 and cross the stripe a 6700. That crank owes me NOTHING, but at this point I’m a little scared to chase more power. I’m at 425 at the crank according to the calculators. For me the cost difference from cast to forged is not big enough to to buy a cast crank. (Your side of the world could be very different)Especially if you plan on spinning it. Plus I know no matter what I going to hammer on anything I build. My Scat cast crank was checked and balanced to 1/2 gram during a piston change 3-4 years ago. It was still straight after 7-8 years of hammering on it.
Click to expand...

I've already allowed the cost to purchase the springs to match the cam from hughes. The Eddy ones won't make it onto the engine.
 
74Scooter said:
Re-reviewing your list... plans for a windage tray?
Click to expand...

Not sure on windage tray or scraper at the moment. Still looking into it. Some of the racers over here taht ive spoken to are not that keen on windage and prefer the scraper system.
 
Dave81 said:
Not sure on windage tray or scraper at the moment. Still looking into it. Some of the racers over here taht ive spoken to are not that keen on windage and prefer the scraper system.
Click to expand...

As long as you have something to keep the oil under control in the pan at rev's... think you'd be fine either way.

FYI. Mancini sells a nice set of rockers made and guaranteed by Harland Sharp at a substantial discount over what it looks you will pay for the Hughes rockers. I just installed a set. I had to touch mine up a bit as they were tight on the shaft.. but well worth the investment IMHO.

Mancini Racing Aluminum Roller Rocker Arm Kit
 
Dave81 said:
Not sure on windage tray or scraper at the moment. Still looking into it. Some of the racers over here taht ive spoken to are not that keen on windage and prefer the scraper system.
Click to expand...
So both. Get the rockers made for the Edelbrock heads.
 
Dave81 said:
Not sure on windage tray or scraper at the moment. Still looking into it. Some of the racers over here taht ive spoken to are not that keen on windage and prefer the scraper system.
Click to expand...

My engine builder built a custom scraper when he did my shortblock. Claimed it was worth 5-7 horsepower, for 120 bucks, I thought it was worth having him do it
 
While some balk @ a 5-7hp worth, the oil control and having it live longer instead of being beat up by the crank shortening its life is a big plus.

$120? Heck ya!
 
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