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billshotrod

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I am building a 318 for my 72 Dart it was fresh so i am not changing the internals but i recentley got a set of magnum heads off a 360 which was blown up. I have a lunati voodoo Duration @ .050 IN/EX: 213/220;Lift IN/EX: .454"/.475";LSA / ICL: 112/108. I was wondering if the rpm airgap would be a good intake for this combination. I was also wonder what type of carburetor to use. i was looking at the 650 edelbrock thunder or maybe a holley of the same cfm. It is going to be a 4sp car with 4.10s.
 
i think they said more CFM for a stick but im not sure. and i have the AIR GAP becasue i heard beside the M-1 its a really good intake but since you have magnum heads like me you have to get the correct AIR GAP or a CROSSWIND which is the lower cost version but the same thing
 
billshotrod said:
I am building a 318 for my 72 Dart it was fresh so i am not changing the internals but i recentley got a set of magnum heads off a 360 which was blown up. I have a lunati voodoo Duration @ .050 IN/EX: 213/220;Lift IN/EX: .454"/.475";LSA / ICL: 112/108. I was wondering if the rpm airgap would be a good intake for this combination. I was also wonder what type of carburetor to use. i was looking at the 650 edelbrock thunder or maybe a holley of the same cfm. It is going to be a 4sp car with 4.10s.
Click to expand...

Bill, that would be a very good intake to use. That cam starts making power right about exactly with the intake. The 650 cfm carb is again an excellent choice. The maker/style is a user choice for carbs. Ethier will do well. I like Carter sytle carbs alot. Both are easy enuff to tune up.

Beware of the new lift.

.454 /1.5 X 1.6 = .484
.475/ 1.5 X 1.6 = .506

Check for valve bind & clearance as well as piston clearance.


you have magnum heads like me you have to get the correct AIR GAP or a CROSSWIND which is the lower cost version but the same thing
Click to expand...
The crosswinds intake is not exactly the same, very closely copied, but does offer dual bolt patterns for ethier head. Otherwise, your choice is ethier a new Magnum style intake or drilling the heads to accept a "LA" intake or drilling the intake to accept going on to the Magnum heads.
Magnum attaching hardware goes straight up and down where the LA's are angled.
 
How would i go about checking for valve spring bind. And if bind happens how would i go about fixing it?
 
ya i wish i could drill my AIR GAP but i dont beileve there is enough room to drill the intake
 
DB15, start searching the net for the mod.
bill, you can have a shop do it or your going to have to get into the head and start turning the engine around with a feeler gauage
 
i did. if its the mod your talking bout. he retired the jig to drill the heads but if its not what mod?
 
That would be it, however, a good machine shop can do it for you. Check the heads for cracks before proceeding.
 
at .500 lift you will need a better valve spring, I dont know what is available for the Magnum head though. Mopar Performance has a few available, They require different locks and retainers.

And Speaking of retainers you have to check your guide to retainer clearance. It gets real tight at just over .500" lift.
 
The stock Magnum head spring setup is good to .525

Anything larger causes problems with the retainer clearance.

With the Magnum heads you get a 1.6 ratio rocker setup rather than the customary 1.5 ratio rocker.

Take the lift number, divide by 1.5, then multiply by 1.6 to get you effective lift measurement. The advertised lift figures are based on a 1.5 ratio.

For example: Cam lift is .470... divided by 1.5 = .31333, then multiply by 1.6.
Your effective lift number is now .501333
 
As for how much horsepower you would be looking at will vary depending on compression ratio and cam selection.

This article http://www.moparmusclemagazine.com/techarticles/mopp_0409_318_engine_build/index.html

tells you how to build a bolt together 318 that will make 400hp with no machining or use of special parts.

However, the cam, carb and intake setup make it a top end monster... not really too street friendly. So it depends on what you are wanting your car to do and what type driving are you planning on doing with it.

I am working on a 318 build that is similar, however, I am going to use a cam grind to work better on the street... either a comp cams XE262 or XE268. I will also use a dual plane intake rather than the single plane they used in the article. Instead of a 750cfm carb, I am opting for a 600cfm unit.

I am going with the KB167 pistons with the Magnum heads. Should produce a bit over 10:1 compression ratio. Figuring that the overall horsepower rating will be dropped to somewhere between 325-350... but it will produce its power in a much lower rpm powerband... good for the street!
 
Just my addition, its interesting to see how well they ran with a 750cfm. I'm running a 318 with a 650cfm Edelbrock Thunder AVS. Very good street carb, turnkey carb. However I think my little mill needs more. I'm running a 13.68 @ only 97mph...doens't quite add up, my top end has always dipped off the first half of the track, im messed with every aspect of the carb, timing, more than enough fuel system, etc. I have a 750cfm Holley 3310 Vac Sec i'll be trying on my setup for more top end. I should be up around 100mph or so I'm guesstimating.

My setup
318 + .030
Stock port j-heads
9.7:1 cr
Performer RPM
650 AVS
Headers
Comp .480/280* dur, factory 1.5 rockers

Best of
87 @ 78mph 1/8th mile
13.68 @ 97mph 1/4 ~3550lbs
 
GoodysGotaCuda said:
Just my addition, its interesting to see how well they ran with a 750cfm. I'm running a 318 with a 650cfm Edelbrock Thunder AVS. Very good street carb, turnkey carb. However I think my little mill needs more. I'm running a 13.68 @ only 97mph...doens't quite add up, my top end has always dipped off the first half of the track, im messed with every aspect of the carb, timing, more than enough fuel system, etc. I have a 750cfm Holley 3310 Vac Sec i'll be trying on my setup for more top end. I should be up around 100mph or so I'm guesstimating.

My setup
318 + .030
Stock port j-heads
9.7:1 cr
Performer RPM
650 AVS
Headers
Comp .480/280* dur, factory 1.5 rockers

Best of
87 @ 78mph 1/8th mile
13.68 @ 97mph 1/4 ~3550lbs
Click to expand...

Whats up Goody, Havent seen you around for a while.

I think an airgap will give you the top end you desire. But you may lose more bottom. Just a thought
 
I dont see there being much of a gain if any going from a regular RPM to an Air Gap.
 
sublimeswinger said:
Whats up Goody, Havent seen you around for a while.

I think an airgap will give you the top end you desire. But you may lose more bottom. Just a thought
Click to expand...


Hey there ,i've been lurkin around. Actually a Performer RPM and an Air-Gap are the same height. I believe the only difference is the open area under the carb and no exhaust cross-over. The runners shoulddd be the same i think.

Next up is the 750 :iconbigg:
 
Hey Goody,

How have you been? That article is a pretty good read. Seems simple enough to do, and price wise it isn't too bad either.

I need to ask you... do you know a guy named Stu Harmon? He is the President of a MOPAR club in the San Francisco bay area.

Did your Dad ever sell his car? I was sorry to hear that he was thinking about selling it.

Take care. Have a great holiday season!
 
TheDemonator said:
Hey Goody,

How have you been? That article is a pretty good read. Seems simple enough to do, and price wise it isn't too bad either.

I need to ask you... do you know a guy named Stu Harmon? He is the President of a MOPAR club in the San Francisco bay area.

Did your Dad ever sell his car? I was sorry to hear that he was thinking about selling it.

Take care. Have a great holiday season!
Click to expand...


Hey there, I've talked to Stu a few times, he hangs out over on moparts a lot. He sent me an alternator about 3 years ago. My dad's decided to keep his car for awhile. We take them out a whole lot these days, well he's got about 2,500mi on it so far which isn't too shabby

Take care yourself, Happy holidays :grommit::iconbigg:
 
AdamR said:
I dont see there being much of a gain if any going from a regular RPM to an Air Gap.
Click to expand...



I agree, same intake just not heated.

I like the headed intakes being up here in Michigan, even in the summer it seems fine. At high rpm's theres not much time for the air to heat up anyhow.
 
Now would a stock 1970 340 intake and 340 hp manifolds give the the 318 in the first post a little more torque than a air gap
 
Bill, I wouldn't do a 340 intake and head combo on that mild 318. Better off with a performer and port teen heads with headers being a plus if desired.
 
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