318 low budget build

-
This Bad Demon

This Bad Demon

Well-Known Member
Joined
Jun 5, 2010
Messages
224
Reaction score
12
Location
Nassau The Bahamas
I have a 72 Dodge Demon wit a 318 in it.....The engine is .30 over wit a decent cam..360 heads that have been worked...The engine was built by a guy that drag races out of Petersburg Va. Don't know much more than that....Although when I start it or when I drivin round people think it's a 340....Too bad I don't have the performance....I was lookin to up the level without goin to a 360 only cause the bottom end ain smokin and I have very good oil pressure....I kno that the head to engine combo ain the best....I was lookin to get a set of 302 heads and get them worked...What is the largest but at the same time streetable cam that would work good wit the 318? I want a good lope....I'm not exactly sure if the block been zero deck I think the guy did that for me....Also I was goin to go wit an air gap intake(Holley Street Dominator on it now)....650 Demon carb which is on it now.....What kinda power I may be lookin at? Any help would be preciated....
 
if u stay with the 360 heads ur compression wil be less then 8.5..a big cam will make that thing fall on its face,,ide go no bigger then a stock spec 340 cam,,dual plane intake 600 cfm,,and small tube headers,,,exhaust pipes no bigger then 2 1/4..
 
Most stock 318's, pistons down the hole, with 360 heads have around 7-1..........


Unless your building a boat or a motor for your two ton, it ain't enough compression!

302 heads will get it up to the 8-1 range, and you can run up to maybe a .220-230 .050 cam, depending on the overlap.
 
This Bad Demon said:
I have a 72 Dodge Demon wit a 318 in it.....The engine is .30 over wit a decent cam..360 heads that have been worked...The engine was built by a guy that drag races out of Petersburg Va. Don't know much more than that....Although when I start it or when I drivin round people think it's a 340....Too bad I don't have the performance....I was lookin to up the level without goin to a 360 only cause the bottom end ain smokin and I have very good oil pressure....I kno that the head to engine combo ain the best....I was lookin to get a set of 302 heads and get them worked...What is the largest but at the same time streetable cam that would work good wit the 318? I want a good lope....I'm not exactly sure if the block been zero deck I think the guy did that for me....Also I was goin to go wit an air gap intake(Holley Street Dominator on it now)....650 Demon carb which is on it now.....What kinda power I may be lookin at? Any help would be preciated....
Click to expand...

You stated your not sure if it is zero decked or not......I would suggest doing a compression test. Finding out where that is should give a better idea of what parts might give you better performance.

Rickster
 
How fast do you want to go? What cam/converter and gear do you have now?

I wouldn't run 302's if you want performance- I've ran 302's and 587 360 heads- the 587's run much better when the combo is right, both heads used 1.88/1.60's with the bowls ported and the runners cleaned up.

My old 73 Duster with a 318 and 360 heads was probably making 260-275hp with the MP 2,500 converter and 3.91's I was running 8.6-8.7 in the 1/8 @ 80-81mph. It was just a thrown together combo using was I had laying around- stock 318-4 longblock with a comp xe268, M1 single plane, 600 carb, recurved stock dist and ignition, small headers and 2 1/4" duals. At the time it was my daily driver and got 14-16mpg on my 110 mile daily commute.
 
Put a set of RHS cyl heads on it...that 62 cc chamber will go a long way to improve the perf of your 318...
 
well are we working with what he has or what we wish he had?

I'm not too sure about that demon carb...with your engine combO I'd like to see a vac sec 600 holley.
the idea of using the rpm intake is good.

If you wanna go fast....forget about wether it idles rough or not.

BTW certain changes/things will help this and other things that you think would, won't.

we can tune around the 'less ideal' pieces in this combo.

In the realm of the '360 head department' the performer intake and it's smaller runners will keep the a/f better suspended in the lower rpm range, though it's not the best manifold, it may be for this.
The demon carb...ha ha well they say/advertise that they mix the fuel better/smoother venturis..yadda yadda, but if it was mixed better, you'd use less fuel right? demons use larger jets...and some comparative cfm ratings 'like the 750speed demon' actually have larger venturis than a comparative holley 750, That is garbage....
Barry grant is selling his name, not a superior carburetor...jmo

next, what ignition do you have?
and have played with the curve?
how much total and initial timing are you running?

what's the cranking cylinder pressure?

let us know
 
Okay.....As far as my ignition I have the full Msd system. From the box to the plug wires.....It has 36 degree total timing....The headers are hedman headers dumpin into 2 1/2 pipes.....3:23 gears for now....Thinkin of puttin in 3:91 before I ship the car this way.....Converter it's between a 2500-2800....Cam I'm not sure...Has a slight lope...One guy said it sound like a RV cam...Comes in round 2800 rpm......Demon 650 carb...Bored .30 over.....Nothin too powerful....Not the best off line but will chirp tires an give a decent burnout.....People say it sounds like a 340...My question was about changing the heads from 360 to the 302 cylinder heads....I hear/and feel in the seat that the 360 heads are not the best heads for the 318....I wanted a bit more compression....Don't want it too high...The gas here in The Bahamas is the highest I think 89, although we have the new mercedes and bmw runnin on the gas.....So that's one limit there wit compression....I hear/and read that those heads pose to be a better fit.....What's ya feelings on usin magnum cylinder heads? Also round here the speed limit(legally) is 45 on the "highway"....Alot of stop and go traffic short streets and a heap of stop signs.....I only wanted to keep the shortblock cause it's still a good bottom end....Or give me an example if I get a 360(from the boneyard) and build that what kinda money I lookin at.....
 
IMO, with a cam with a slight lope, the 302 heads will perform better, until, liiiike, say 5K.

But if you already have the 360 heads on it, no reason changing it, you can time it to have more bump off idle.
 
keep the 360 heads, if you can afford it, get taller pistons deck the block and heads, can get thinner gaskets and get some compression back. Look at Engine Masters winter 2006 vol 9 no 4, they built a 415hp 318 with 360 heads on pump gas and kb167 pistons but they stated they had to zero deck for the pistons, and mill the heads to a chamber volume of 60cc and 2.02 valves, good luck
 
im working on a 318 too. i got the factory heads should i have them worked over or go to the pick n pull and look for 340 or 360 heads?
 
roylira said:
im working on a 318 too. i got the factory heads should i have them worked over or go to the pick n pull and look for 340 or 360 heads?
Click to expand...

Are you going with higher compression pistons or??? Need to know rest of combination or goals...
 
You must log in or register to reply here.
-

Back
Top