You already have them and are ported then yes makes sense to use them.
But to me starting with the best heads you can within reason makes the most sense.
It will allow hp goals to be reached with smaller cams.
318 MAX fuel economy builds?
- Thread starter gagembassett
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But to me starting with the best heads you can within reason makes the most sense.
It will allow hp goals to be reached with smaller cams.
I don't have any HP goals. This is a temporary engine to get me by while I build something bigger and get my frame tied ect. I understand the bigger port and I have a set of J heads sitting here. But I don't have fuel injection to squirt the fuel down the port so I'm hypothesizing that a smaller more efficient port would move air faster and atomize my fuel more efficiently at low RPM. I have used Rhoads lifters for 40 years to tame street cams but this is only my second attempt to use them as a VVT system at low rpm for mileage on a mild street cam. The other time is my current 273 with a 220 at .050 cam. So far it's working well considering I have a rich carb. I'll address that soon. Let's approach this from another angle. If I get a set of 920's to flow similar to J heads stock how will the smaller ports negatively affect my performance from a mileage stand point?
Those look very nice and yes happy. I don't need 400 hp. Just good mileage and a lil power when needed. Who on here is willing and capable of doing a set of 920's like this for a guy? What size valves did you use? And who has a clean set of these for sale to build upon? I can always slap a set of J heads on later and I'll have a great set of 920's for some ones 318 or?
So I do have the new Rhoads lifters that require adj rocker. I have 273 rockers on my 273 and plan to use them on the 360 build. I am thinking of having them bushed and indexed to 1.55 or 1.6. I have 3 extra sets and figured having one set done to 1.6 and bushed would be cool and maybe beneficial. I see there are a couple guys on here that can do that.
My car weighs 3800 with me in it. 3.55 gears and an A-500 OD transmission. It really is a test of a theory I have as far as the 920 heads go. Like I told 273. If they don't work I can swap heads and someone will want a nice set of 920's.
I had a '82 5th Avenue about 20 years ago that had lean burn and a 2bbl I rebuilt. 25 mpg on the highway was easy.
Dan the man
Well-Known Member
Another example of the mileage is going backwards on the newer vehicle's. Everyone knows that the 5th Avenue had zero aerodynamics.
Well you kind of do you got a head and cam range picked out which will make certain amount of hp in a narrow ish range.
No I don't think it will negatively affect gas mileage a may have a slight increase don't know if it would be noticeable amount though eg 1-2 mpg increase.
My point is say you end up making 300-325hp, right now your comparing ported 920 to stock J's by why not port the J's which will need less cam to make the 300-325hp which to me be more streetable and better on gas since a cam has greater effect on mileage or with same cam you'd have more power with similar mileage.
But since this a temp engine and you already got a decent set of 920 I see nothing wrong with you going that way. Plus I feel mileage is hard to gain but easily lost, so as long you don't do anything to overly kill fuel mileage these builds should come out with similar results give or take a few mpg.
I would be careful using Rhoads lifters with a mild economy cam. It could be counterproductive because it reduces valve lift at the lower rpms, where economy is made. Every engine has a 'sweet spot' where everything melds for best efficiency & you are seeking the highest efficiency from the fuel used.
I only compared the two heads because I see they can get the same flow. But I believe the smaller port will dramatically improve atomization at 1500 rpm. I may be wrong and this is the test. But if they flow the same or similar at full lift and 25% faster than with the J heads at low rpm I'm hypothesizing better mileage and low rpm torque. 200 cfm on the intake at .450 to .500 would be plenty and I see they can get near 225. If my car was FI I would go with the J head. But beings as I require the air speed to carry the fuel into the cylinder I'm hoping these work better for my application. I picked the cam based on the ability to use Rhoads lifters and get the cam near a factory 2 barrel cam below 1500 rpm and close to a 340 mag cam fully pumped up. So in essence I'll be running a factory 360 2 barrel cam for the first 1800 rpm. This along with the small ports I'm hoping create a MPG friendly engine that has more than a 360 2 barrel engine when needed. Not trying to out run a 340 hp or anything pumped up. YET!!
That's why I want to use a 215 to 220 at .050 cam. It's a nice street cam that becomes an economy cam below 1800 rpm with Rhoads lifters.
Actually I'm looking for a set of 920 heads to do this project. I want to leave this engine intact as it's a great running little engine with less than 5000 on it. But I'm willing to spend a few bucks to test my thoughts and build a set of 920's for the project. Maybe I take it to the dyno then install my factory 1.88 J heads stock nice valve job and compare the difference in MPG and power.
Your thinking is sound, I don't know if you'll see a major gain in mpg but definitely can't hurt if the choice is ported 920 vs stock j, with same flow but better velocity, i'd pick 920 to.
Thank you. I'm learning more about the quench and the KB raised dish pistons along with the closed chamber of the 920's puts me at .040 on the Diamond pistons calculator. I'm hoping this allows me to run 9.5 compression and reduce knocking allowing me to get more timing for better MPG. Time will tell.
That would an interesting test.
The math I did was me using a .027 gasket. I can't find those .010 shim gaskets like that one.
A few nos ones floating around but pretty much unobtainable
Going with that 220@050 cam was something along the lines that I am also considering and it’s a Howard’s Hyd grind I’m looking at with the use of standard Rhoads lifters in my 5.9 back by a 727 & a 9-1/4 w/3.55’s on 245/60/15’s. The Rhodes will only be on the intake. The cam is on a 108 LSA. Stall is 2500.
I did want to also use the A-500. This may come to pass later as the tails act has no provisions for a OE floor shifter.
My car weighs in about the same. You and I are in the mists of testing the same idea. But I have a ‘00 - 5.9.
So is my ‘18 Ram 1500 but i average 20+ on the Hwy and have done the best of 23.7. The aerodynamics of the Ram are a brick and it’s a heavy brick!
I agree. The Howard’s cam I’m looking at is aided with the Magnums 1.6 rocker. I have the math on paper somewhere. So I went with the approximate math Rhodes suggests is happening. Even with the reduction in lift, it gets some back with the 1.6 ratio. Just in the territory of the head needing a really good valve job for best effect.
Personally, I think @Dmopower is onto something and will find out before I do since our builds are a little similar. As I wrote early in this post, my ‘79 Magnum has a floor shift I want to keep and the trans tail or mid section has no provisions for brackets to let the linkage work. I do t want to butcher the floor shifting brackets out for an aftermarket shifter.
Honestly, I’d rather put in a manual transmission.
Dan the man
Well-Known Member
What's the part number of the Howard's cam that you are going to use? I had 3 different dodge truck's, a 1971, 1989, 1998, all 318's, 2 wheel drive regular cab truck's and all were gas hogs. I think that the best they ever got was maybe 15 highway. I wouldn't have another dodge truck
Are you ditching the roller cam in the 5.9 then to run the Rhoads? I see they make roller lifters for ford but I have not seen any Mopar roller Rhoads.
@Dan the man
This cam;
Howards Cams 711451-08 Howards Cams Hydraulic Flat Tappet Camshafts | Summit Racing
It has a .506 lift with a 1.5 rocker. Recalculate it with the Magnum heads rocker of 1.6 which equals .539 (-733333333)
Rhodes lists a reduction of .010 - .020. (.529 - .519)
& a cut in duration of 10 - 15 degrees @050 that is restored @ approximately 3500 rpm. They claim an increase of 1-2 inches of vacuum.
So this is why and Dmopower are looking at these lifters. Today, you can call it what Dmopower said, a poor man’s VVT. I’ve done this in the past, used these lifters in this thought process. Just not with ported heads looking for mileage. But his thoughts, IMO, have merit. Now he’ll find out if it works for him.
Normally I had much larger cams and power brakes to contend with, so, these lifters got the nod.
Rhoades also has other lifters that are able to reduce the duration @050 a little bit more and there are other features you can get with them as well.
Check’em out!
Rhoads Lifters
This cam;
Howards Cams 711451-08 Howards Cams Hydraulic Flat Tappet Camshafts | Summit Racing
It has a .506 lift with a 1.5 rocker. Recalculate it with the Magnum heads rocker of 1.6 which equals .539 (-733333333)
Rhodes lists a reduction of .010 - .020. (.529 - .519)
& a cut in duration of 10 - 15 degrees @050 that is restored @ approximately 3500 rpm. They claim an increase of 1-2 inches of vacuum.
So this is why and Dmopower are looking at these lifters. Today, you can call it what Dmopower said, a poor man’s VVT. I’ve done this in the past, used these lifters in this thought process. Just not with ported heads looking for mileage. But his thoughts, IMO, have merit. Now he’ll find out if it works for him.
Normally I had much larger cams and power brakes to contend with, so, these lifters got the nod.
Rhoades also has other lifters that are able to reduce the duration @050 a little bit more and there are other features you can get with them as well.
Check’em out!
Rhoads Lifters
That is the thought process. But this build is on hold until the car is up and running again. I have to do an exhaust.
Rhoades does have MoPar roller lifters. Click below and scroll down to the second to last on the left for V8 applications, all the way down on the right is a listing for the 239-6 cylinder as well. The listing stops at the year 2000.
Maybe I’ll find a roller cam that meets my spec? IDK?
Product Listing - V-Max_Flat_Tappets
The ‘00 - 5.9 Magnum in my Magnum
(There’s a joke in there somewhere right?????)
My double Magnum…. Magnum squared????
It is currently equipped with a 750 AFB, RPM intake, Hooker Super Comp headers at 1-3/4, Chrome box ignition & a trap door air cleaner. It just needs a cam and some head work.
As I said….. if I can get the A-500 in there….
Then I’m done powerwise.
If the Rhoades only cut 10*’s of duration, then it’ll put around on approximately a 210@050 intake duration. If the valve only gets shorted .010, that’s fine. The valve work and bowl blending are more than enough.
This mind set is trying to create a flexable cruiser and flyer. I really like driving this car.
(There’s a joke in there somewhere right?????)
My double Magnum…. Magnum squared????
It is currently equipped with a 750 AFB, RPM intake, Hooker Super Comp headers at 1-3/4, Chrome box ignition & a trap door air cleaner. It just needs a cam and some head work.
As I said….. if I can get the A-500 in there….
Then I’m done powerwise.
If the Rhoades only cut 10*’s of duration, then it’ll put around on approximately a 210@050 intake duration. If the valve only gets shorted .010, that’s fine. The valve work and bowl blending are more than enough.
This mind set is trying to create a flexable cruiser and flyer. I really like driving this car.
I would be all over those roller lifters for that 5.9. I had no idea they had them for Mopar and I just bought a new set of vmax last summer. I can see that you def have an advantage on me in the friction area. I just gave away a good 5.9 mag engine to a buddy. lol You are using the magnum heads I take it?
Dan the man
Well-Known Member
Thanks for the info, I'll check them out
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