318 MPG and HP

-
D

Dakota_Don

Well-Known Member
Joined
Mar 19, 2008
Messages
200
Reaction score
1
Hello, I have a 68 dart 4door with the original 318 that has the orginal flat top pistons, if i swap the original heads with a pair of 89 360 heads,(i have them) approx how much would i have to mill them to keep MY cr the same, or even bring it up? These heads are about 70ccs. I may even concider magnum heads.. Would the 270H comp cam be ok? ( I have it)or is there a better choice.

I would like to install a TQ carb,(i have one) and 360 manifolds or headers. I am running a 904 and have an A500 to swap it with. I have 3;23 gears now and i think these will be ok for my use.

Oh do you know if i can use Dakota shorty headers or block hugger headers on a dart?

I am building for mostly MPG what are your opinions? And NO i do NOT want to drive an econo box, I love driving my dart everyday.. The ole girl even gets a
thumbs.gif
once in a while.. whens the last time you gave a thumbs up to an econo box..
down.gif


Thanks Don
 
If you want MPG I would keep the stock small port and valve heads. The stock heads will support around 300 HP. You can get 100 HP over stock 318 without changing heads. Comp 270H might be a bit large for intended purpose, I like 3.23 gears but you might want to go higher depending on how much highway driving you do.http://www.moparmusclemagazine.com/techarticles/engine/mopp_0312_318_long_block_bolt_ons/index.html My set up runs a .30 over 318 with 340 cam and valve springs, old streetmaster intake and 600 holley. Manifolds and full 2 1/4 exhaust. Currently running 2.76 gears this has delivered a best of 23 MPG and 20 is easy to get if there is any highway driving involved. Much more power then stock revs to 5600+ easy. I do plan to go to 3.23 gears once I get my 8 3/4 in but I am sure my MPG will drop some.
 
Heres my deal.

'74 Duster w/ a '79 - 318 stock with bolt ons and a cam. 904 & 3.21 gears, 225/70/14's. Top to bottom, the bolt on's are;

MP Unsilenced air cleaner
Carter 625, have used a Holley 600 cfm 4160 model as well.
Edelbrock, LD4B
Hooker headers into a Jegs 2-1/2 exhaust system
Crane Cams 272/284 - .454/.480 lift on a 112
(Duration @ .050 is 216 - 228)
Orange box ignition
Electric fan

This combo get's me 17 MPG Hwy. and very low 15's at the 1/4 @ 89 mph.
(I know theres a 14 second run in there somewhere! LOL)

What would work better for this set up?

2-1/4 exhaust pipe for better velocity getting it all out.
MSD or equal ignition

Your overdrive tranny is a excellent idea since this will reduce the 3.23 gear ratio down to a 2.2287 feel final drive ratio. You may need to be at speeed some in order to effectivly use this.


I think a cam more in line with what I have is more suiteable to what your trying to do.

Look at a XE Comp cams grind for this. They have a very comparable one.

Use the full length headers and a small primary T-Q.
 
OH, I forgot to add. At the track, the car was largely untuned on a cold Oct. day. I est. this engine to be able to run the upper 14's with time and a better tune. This should bring the power somewhere around the 275 HP mark.

This is my guestimate. I made this guess based on the factors, car weight and 1/4 mile trips, not the mag article.

Also, I forgot to mention that the factory iron intake is a good choice on a few fronts. Cheap, on hand, able to deliver the power and there is little in the way of a port mismatch. It exisits, but it is small potatos.

The use of the factory intake with a T-Q is a beauty match. But you'll need to get that T-Q dialed in right. I made mention of useing the small T-Q over a larger one. It's in the primary size. The big T-Q primarys measure 1.50 in size while the smaller one is 1.38.

The smaller primary size is a bennifit to enhanced driveabilty (Higher primary velocity) and possibly an edge in mileage if properly tuned.
 
rumblefish360 said:
Heres my deal.

'74 Duster w/ a '79 - 318 stock with bolt ons and a cam. 904 & 3.21 gears, 225/70/14's. Top to bottom, the bolt on's are;

MP Unsilenced air cleaner
Carter 625, have used a Holley 600 cfm 4160 model as well.
Edelbrock, LD4B
Hooker headers into a Jegs 2-1/2 exhaust system
Crane Cams 272/284 - .454/.480 lift on a 112
(Duration @ .050 is 216 - 228)
Orange box ignition
Electric fan

This combo get's me 17 MPG Hwy. and very low 15's at the 1/4 @ 89 mph.
(I know theres a 14 second run in there somewhere! LOL)

What would work better for this set up?

2-1/4 exhaust pipe for better velocity getting it all out.
MSD or equal ignition

Your overdrive tranny is a excellent idea since this will reduce the 3.23 gear ratio down to a 2.2287 feel final drive ratio. You may need to be at speeed some in order to effectivly use this.


I think a cam more in line with what I have is more suiteable to what your trying to do.

Look at a XE Comp cams grind for this. They have a very comparable one.

Use the full length headers and a small primary T-Q.
Click to expand...

I don't want to sound like an RV cam guy, but wouldn't that give the guy some decent mileage? Also, not trying to divert this thread but how far above an RV grind is the cam in your 318? I'm very interested in maybe experimenting on mine and putting in a different cam.
 
LJS30 said:
I don't want to sound like an RV cam guy, but wouldn't that give the guy some decent mileage? Also, not trying to divert this thread but how far above an RV grind is the cam in your 318? I'm very interested in maybe experimenting on mine and putting in a different cam.
Click to expand...

This Crane I have is mello in idle by choice. Thus the 112 C-line. On a 110 C-line, it'll have a performance chop to the idle as the whole Comp Cams line up does.

A mello idle or wider C-line doesn't automaticly give a engine/car more/better mileage.

The term "RV cam" is a generic term used to describe a mello cam operating in a lower power band that is still yet larger than stock. However, if you take a look at stock cams, the stock 318 cam is the smallest followed by the 360 cam followed by the automatic 340 cam with the manual cam for the 340 (1968 cam) being the biggest IIRC.

Seeing that theres is 20*'s difference in cam size from small to large and also in displacement, what exactly is a RV cam? In what engine? For what purpose? It's all realitive and also relaitive with the size of the engine.
The bigger the engine, the larger the cam.

Heres food for thought. My cam in MOD's , Mikel Becks race only Duster ran low 12's. Hows that for ya? It ran very 15's with just simple bolts on in my Duster with A/C, P/S, P/B and slightly more than 1/2 tank of gas. (I'm 180 lbs.)
All in a low compresion ('79) 318, 904, 3.21 gears.
( http://www.forabodiesonly.com/mopar/showthread.php?t=10508 )

You should choose a cam that has a operating RPM band in which you'll be driving in and with a lift not exceeding the flow abilty's of your head. This is why, with your description in mind, I pointed at the Comp Cam for your build. Crane is no longer in biz and the mello idle charter of the cm doesn't fit your description of what you want to do with the engine and have it sound like.

IF your wondering any further, the best bet is to call up a cam grinder and ask for there opinon and see what they recomend. Also note the tech's name. Then call on a different day and talk to a different tech and get a different answer.

Since your set up is very much lke mine, you can expect good drive manors, good passing power, decent mileage, more with the O.D. trans, and the 110 centerlne will give a nice chop in the idle. Your cars weight will be a factor in it's 1/4 mile times as well as your state of tune. But you can expect similar results to mine.

If you get this in tune, the whole package, I beileve you'll see high 14's at the strip.

Experimenting with cams is the only way I learned how and what was right and wrong and how they acted. Which parts worked well and which ones didn't. Back when I was younger....LOL, and richer.... I would go through 3 or 4 cams a year just to see how they acted, worked, performed and ran.

I've learned a few things the hard way this way, but it was fun....and expensive to fix sometimes. But learn I did.
 
sorry.. but the only way your gonna get decent milage without the lobes looking like a broomstick is with a roller cam.

Hello, I have a 68 dart 4door with the original 318 that has the orginal flat top pistons, if i swap the original heads with a pair of 89 360 heads,(i have them) approx how much would i have to mill them to keep MY cr the same, or even bring it up? These heads are about 70ccs. I may even concider magnum heads.. Would the 270H comp cam be ok? ( I have it)or is there a better choice.
Click to expand...
1989 360 heads on a 318? thats a BAD combo. '302' or magnums would be better.

I would like to install a TQ carb,(i have one) and 360 manifolds or headers. I am running a 904 and have an A500 to swap it with. I have 3;23 gears now and i think these will be ok for my use.
Click to expand...
TQ is good. headers are good (less weight). with a A500 i'd use at least 3.55's so your not into the pedal too much.

Oh do you know if i can use Dakota shorty headers or block hugger headers on a dart?
Click to expand...
nope. steering column and k-member are in the way.

I am building for mostly MPG what are your opinions? And NO i do NOT want to drive an econo box, I love driving my dart everyday.. The ole girl even gets a
thumbs.gif
once in a while.. whens the last time you gave a thumbs up to an econo box..
down.gif
Click to expand...
its great that your car gets the old thumbs up. IMO if your lookin for decent milage and economy (haha),
get a late 318 mpi engine (not the throttle body version). decent power and economy.
 
RV cams have next to no lift or right at about 'example'.420 with tiny @.050 like 206* but can have an advertised duration of around anywhere from 250's to 290's with 114cl's and such. just a vague bit of info for you, I'm no rv cam wizard.
 
rumblefish360 said:
This Crane I have is mello in idle by choice. Thus the 112 C-line. On a 110 C-line, it'll have a performance chop to the idle as the whole Comp Cams line up does.

A mello idle or wider C-line doesn't automaticly give a engine/car more/better mileage.

The term "RV cam" is a generic term used to describe a mello cam operating in a lower power band that is still yet larger than stock. However, if you take a look at stock cams, the stock 318 cam is the smallest followed by the 360 cam followed by the automatic 340 cam with the manual cam for the 340 (1968 cam) being the biggest IIRC.

Seeing that theres is 20*'s difference in cam size from small to large and also in displacement, what exactly is a RV cam? In what engine? For what purpose? It's all realitive and also relaitive with the size of the engine.
The bigger the engine, the larger the cam.

Heres food for thought. My cam in MOD's , Mikel Becks race only Duster ran low 12's. Hows that for ya? It ran very 15's with just simple bolts on in my Duster with A/C, P/S, P/B and slightly more than 1/2 tank of gas. (I'm 180 lbs.)
All in a low compresion ('79) 318, 904, 3.21 gears.
( http://www.forabodiesonly.com/mopar/showthread.php?t=10508 )

You should choose a cam that has a operating RPM band in which you'll be driving in and with a lift not exceeding the flow abilty's of your head. This is why, with your description in mind, I pointed at the Comp Cam for your build. Crane is no longer in biz and the mello idle charter of the cm doesn't fit your description of what you want to do with the engine and have it sound like.

IF your wondering any further, the best bet is to call up a cam grinder and ask for there opinon and see what they recomend. Also note the tech's name. Then call on a different day and talk to a different tech and get a different answer.

Since your set up is very much lke mine, you can expect good drive manors, good passing power, decent mileage, more with the O.D. trans, and the 110 centerlne will give a nice chop in the idle. Your cars weight will be a factor in it's 1/4 mile times as well as your state of tune. But you can expect similar results to mine.

If you get this in tune, the whole package, I beileve you'll see high 14's at the strip.

Experimenting with cams is the only way I learned how and what was right and wrong and how they acted. Which parts worked well and which ones didn't. Back when I was younger....LOL, and richer.... I would go through 3 or 4 cams a year just to see how they acted, worked, performed and ran.

I've learned a few things the hard way this way, but it was fun....and expensive to fix sometimes. But learn I did.
Click to expand...

Cool, very cool explanation.
 
thanks a lot of good info,

I have the 68 .040 318 short block ready to go. with floating pins,steel crank and old trw flat tops.

it has the 270H cam..but I can change it.


I will get a set of magnums 318 or 360 or does it matter.what yr?

i will use the smaller TQ i have.

I will get a smaller cam 252-260ish range.

I will try magnum exhaust or shorty dakota headers

I will also try for 9.0 to 9,5 CR if posible and good quench if posible.

I would like to install an A-500 not to keen on a stick.. but its a posibility.

I will keep the 3:23 which should be good with the OD trans.

the 318 in my dart now runs great, not to much pwr,
I get about 17 MPG now on the HWY, not to good in the city.

I thought about just swaping the heads cam ect to the original engine, but I have this other 68 short block just waiting for a home..

if i stick to my plan do you think its posible to knock down 20 to 22 mpg?

and thanks for the suggestions..

any thoughts??
 
Thanks LJS.

Don, I'm gonna say, if you keep the duration at or less than what I suggested and use a MSD, which IMO, was excellent in getting some more mileage, it is very possible to get close to if not 20. I'm getting 17 now in my Duster and do not have the MSD.

318 and 360 Magnum heads are the same. No difference. I'd just do prep work on stock heads with a larger exhaust valve installed. Small/minor bowl work at most.

Also, if you go to Magnum heads, beside the expense of it all, you'll have to recalulate the lifts and get new springs.
 
rumblefish360 said:
Thanks LJS.

Don, I'm gonna say, if you keep the duration at or less than what I suggested and use a MSD, which IMO, was excellent in getting some more mileage, it is very possible to get close to if not 20. I'm getting 17 now in my Duster and do not have the MSD.

318 and 360 Magnum heads are the same. No difference. I'd just do prep work on stock heads with a larger exhaust valve installed. Small/minor bowl work at most.

Also, if you go to Magnum heads, beside the expense of it all, you'll have to recalulate the lifts and get new springs.
Click to expand...


thanks, since the magnum rockers are 1.6 ratio.. should i use the same cam? or should i go smaller, such as a XH262 comp cam? and i beleive i read some where i can use GM 3.1 valve springs, retainers and keepers
 
If you want to use that cam, XE262H, then use it. However, you will have to recalculate the cam lift and maybe purchase a different set of springs due to the Magnum heads 1.6 rockers.

To recalc. the lift, the math looks like;

lift divided by rocker ratio (1.5) them multiply by the new rocker ratio (1.6)

If you can use GM 3.1 valve spring, that would be news to me, but, I'd go with the cam manufactures recomended valve spring period.
 
rumblefish360 said:
If you want to use that cam, XE262H, then use it. However, you will have to recalculate the cam lift and maybe purchase a different set of springs due to the Magnum heads 1.6 rockers.

To recalc. the lift, the math looks like;

lift divided by rocker ratio (1.5) them multiply by the new rocker ratio (1.6)

If you can use GM 3.1 valve spring, that would be news to me, but, I'd go with the cam manufactures recomended valve spring period.
Click to expand...

If i can find the article i will post it.. they look like the behive springs.. I will do some math, or i will call a cam grinder for a suggestion..
 
rumblefish360 said:
If you can use GM 3.1 valve spring, that would be news to me, but, I'd go with the cam manufactures recomended valve spring period.
Click to expand...

I am currently running the chevy springs and retainers on my magnums. Work great with my comp XE256 cam. The springs are a tight fit but, I have had no issues yet. Its a cheaper alternative.
 
I have a 85 dodge ram with 596 360 heads i bowl ported and cleaned up the runners,removed 40 thou off the bottom and 25 thou off the intake side on the original 318.I am running an ld340 intake with a 1405 600cfm eddy carb,and a mallory 6 ignition with a xe256h comp cam with mp lifters.The truck has a 3.21 gear with a 727 auto trans.I am getting about 15 mpg.the truck is a bit slow out of the hole,but the mid-range and top end are great.The exhaust is only a mandrel bent 2.5in single with a dynomax muffler,this combo works great in the truck.If you mill heads,just use adjustable rockers and custom order pushrods.All im using is the proform's with smithbrothers adjuster's and there pushrods.
 
Interesting moparts thread. Patrick is a good man and knows a wee bit I'd say.

I normally do not go there. It was a nightmare of a baord sometime back to a degree I'll never return there and post. I can only speak volumes of poor to absoulte bad about that board, BUT concead that was awhile ago.

I'll still never return.

Again, Patrick is a good fella and a long time member overthere. I've read volumes of his posts.
 
You must log in or register to reply here.
-

Back
Top