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#154913 - 11/22/08 11:47 AM 318 small block build recomendations
gtx6970 Offline
I Live Here

Registered: 06/28/03
Posts: 16357
Loc: Land of Booze and Horses
Short version of the story is I have a local customer wanting to upgrade the engine compartment of his 1971 Challenger convertible.
It s a 318 now and he's not opposed to upgrading to a big block ( prefer not to ) BUT, if it stays small block then the OE trans and various other brackets, hardware, etc can be re-used.
So my thoughts are upgrade the top half and valve train to something to flow a bit better , convert to a 4 barrel, better heads, better /dual exhaust.

Only real requirement is to remain/keep somthing of a stock outward appearence. So aftermkt heads and headers are already out of the question. The overall idea is to build something of a 'what if' kind of restoration. It's a 71 challenger convertible with Air and keeping the A/C would be a bonus but not a detrement if it goes away.

He had talked about installing a hemi, But I think this would be more for eye candy than anything else. Plus added costs to do a correct conversion may be to much. I personally would prefer to stay small block and build the insides to make a nice driver and KEEP the air.

Ideas much appreciated.

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#154914 - 11/22/08 12:26 PM Re: 318 small block build recomendations [Re: gtx6970]
Neil Offline
I Live Here

Registered: 01/19/03
Posts: 10979
Loc: Eagle, Idaho
Magnum heads

Raise the compression ratio

Roller cam - not a necessity, but if the money is available...

4" crank - would really run nice, but I wouldn't bother making the engine larger with 318 exhaust manifolds.

Start with a 318 magnum core engine to begin with????


Edited by Neil (11/22/08 12:27 PM)
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#154915 - 11/22/08 12:57 PM Re: 318 small block build recomendations [Re: gtx6970]
68Bullit Offline
mopar

Registered: 03/30/08
Posts: 566
Loc: Western NC
If He isn't opposed to going big block but would rather keep the obvious brackets, etc, then go with a 360 and paint it 318 red or whatever color it's supposed to be. Still would need headers though. With a 318 or 360, gotta have the headers


Edited by 68Bullit (11/22/08 01:03 PM)

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#154916 - 11/22/08 12:58 PM Re: 318 small block build recomendations [Re: 68Bullit]
Anonymous
Unregistered


Quote:

If He isn't opposed to going big block but would rather keep the obvious brackets, etc, then go with a 360 painted 318 red or whatever color it's supposed to be. Still would need headers though. With a 318 or 360, gotta have the headers




This. Truth is, you'll pretty much always get more power for the money if you just build a 360 and drop it in.

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#154917 - 11/22/08 05:50 PM Re: 318 small block build recomendations
tpabayflyer Offline
pro stock

Registered: 01/20/03
Posts: 1546
Loc: Tampa, FL go bucs/rays!!
rebuild the 318 on the cheap with a cast 4" crank... 390 cubes and mild upgrades will yield minimum 400HP easily and all the accessories,trans,etc will work..... Why everybody is so against that I can't understand... My 390 1983 Cordoba 3.73 gear is quite a bit faster than my old 'Cuda 360 with 3.91 gear.a 360 is nice but a 390 is better! TBF

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#154918 - 11/23/08 12:54 AM Re: 318 small block build recomendations [Re: tpabayflyer]
Anonymous
Unregistered


Don't know your budget, but my version of cheap is $1000 or less, so if you go with a 4" crank, pistons would be required, and a basic stroker kit would run you $1500+. Then cost of machine work if needed for an overbore. You could find a 360 from a wrecking yard for $350 or cheaper, freshen it up with rings, bearings, gaskets, to bring you to $500. You would also need a 360 torque converter because the balance is different, so $50-$350 depending on what you want, stock from wrecking yard or basic aftermarket.

If you wanted to stay with the 318, 1992-newer magnum heads can gain you 50hp just by bolting them on, but require a different intake, shorter pushrods, newer style lifters (great time for a mild cam kit, 260-280 degree range, about .470 lift) and 10 bolt valvecovers (which wont look stock.) The magnum valvetrain has an increased rocker ratio of 1.6:1, which turns a .474" lift cam into .506, which is about the max the stock magnum springs can handle anyway. These heads are a closed chamber design, which would raise a stock compression ratio of about 8.2 to 8.8, or somewhere close to that.

Have Fun!!
JJ


Edit: 1971 318s had higher compression to start with, 9.0 I think, so the end result may be 9.5-9.7, and the higher compression pistons may be close to hitting the valves in the .510" neighborhood, don't know for sure. And don't bother putting 360 heads on the 318. They do flow better, but have bigger combustion chambers, which will lower the compression ratio, nearly cancelling out any improvements from increased flow.

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#154919 - 11/23/08 01:28 AM Re: 318 small block build recomendations [Re: tpabayflyer]
Moparmal Offline


Registered: 01/19/03
Posts: 3882
Loc: Melbourne.....Oz-land
Quote:

rebuild the 318 on the cheap with a cast 4" crank... 390 cubes and mild upgrades will yield minimum 400HP easily and all the accessories,trans,etc will work..... Why everybody is so against that I can't understand... My 390 1983 Cordoba 3.73 gear is quite a bit faster than my old 'Cuda 360 with 3.91 gear.a 360 is nice but a 390 is better! TBF




Tpa - Fantastic to hear someon who's gone down the 318/390 path.

Did you find your gas mileage changed much from the 360 to the 390?
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#154920 - 11/23/08 07:37 AM Re: 318 small block build recomendations [Re: Moparmal]
Supercuda Offline
Proud owner of a small weasel

Registered: 09/04/07
Posts: 7362
Loc: West Texas
Basic 318 upgrade.

better cam, small 4bbl carb, good exhaust.

Anything more is ridiculous on a 318.

You want more cubes, don't fool with stroking a 318, you are just turd polishing. Might as well stroke a 360, about the same cost, more cubes, better bore sizing, better choice all around and a virtual bolt in for a 318, a couple of minor issues to deal with.
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#154921 - 11/23/08 07:39 AM Re: 318 small block build recomendations [Re: Supercuda]
terzmo Offline
top fuel

Registered: 03/12/05
Posts: 1790
stroke that 318 and embarrass alot of people...I'd stay with a 340 rather than a 360 if changing blocks....better block for the year

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#154922 - 11/23/08 07:56 AM Re: 318 small block build recomendations [Re: gtx6970]
RapidRobert Offline
Circle Track

Registered: 11/20/03
Posts: 26035
Loc: Lincoln Nebraska
I'm assuming that it's a running/driving car right now. I would build a 360(same size/all brackets fit) w magnum heads(looks stock) proper piston/head gasket selection to get .035-.040 quench with a CR in the 10's(gives you max efficiency/power) & 68-70 340 HP ex manifolds(you said no headers). mag neads have 318 sized ports so bear that in mind as you select an intake manifold(sb street dominators work well 60-75$). When it's ready to go drop it in & there's less down time & the customer is out the door(& happy) quicker.
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#154923 - 11/23/08 09:17 AM Re: 318 small block build recomendations [Re: RapidRobert]
HotRodDave Online   content
master

Registered: 01/29/05
Posts: 8104
Loc: Kalispell Mt.
360 motor mount brackets are different, they can be made to work but are not drop in.

Magnum heads do NOT have 318 ports, they are pretty close to 360 size but way better. You can use old LA valve covers, not perfect fit but you can get them to seal and all 5 LA bolt holes line up. Most aplications I have fooled with putting magnum heads on you have to fool with the altenator to get it to fit mag heads because the heads are slightly longer and the back of the altenator can hit the head. Thease differances asside I highly recomend magnum heads.

The street dominator has great fuel distribution but that is where the performance ends for it, it has very low flow witch should make good tq but the runners are very short and the plenum is big so it is really mis matched within it self.
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#154924 - 11/23/08 11:15 AM Re: 318 small block build recomendations [Re: Supercuda]
tpabayflyer Offline
pro stock

Registered: 01/20/03
Posts: 1546
Loc: Tampa, FL go bucs/rays!!
Quote:

Basic 318 upgrade.

better cam, small 4bbl carb, good exhaust.

Anything more is ridiculous on a 318.

You want more cubes, don't fool with stroking a 318, you are just turd polishing. Might as well stroke a 360, about the same cost, more cubes, better bore sizing, better choice all around and a virtual bolt in for a 318, a couple of minor issues to deal with.




Well... turdly 318's are avialable usually for free..... a 360 block gives you 408 cubes which is 18 more than the 318 stroked to 390. For any given combo assuming you make 1 hp per cube or a little more you are looking at about 20-25HP less. Does that make it a turd? Is a chevy 383 stroker a turd??? SBC 350's stroked to 383 are probably about the most common stroker combo on the planet and Chevy guys love them. Yet the Mopar crowd seems to turn up their nose at a 390? I just don't get it.

A 390 can be built very cheap. 4" cranks can be had for $325.00 Cheap Eagle SIR rods for $250.00 KB forged pistons for $395.00...... So the reciprocating assembly can be had for less than $1,000 and a 318 stroker with the Eagle rods will not need to have the expense of having the block clearanced. All this can be internally balanced by drilling the counterweights with no expensive mallory metal like the 360 based combo's.

Yes the 3.940 bore is somewhat smaller but there is no problems running even a 2.02 intake valve at all. My 390 uses EQ magnum style iron heads with 2.02 intake valves and it pulls like a big block. TBF


Attachments
4833616-1983Doba040.jpg (144 downloads)

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#154925 - 11/23/08 11:17 AM Re: 318 small block build recomendations [Re: tpabayflyer]
GoodysGotaCuda Online   work


Registered: 11/23/04
Posts: 22892
Loc: Texas
Quote:

Quote:

Basic 318 upgrade.

better cam, small 4bbl carb, good exhaust.

Anything more is ridiculous on a 318.

You want more cubes, don't fool with stroking a 318, you are just turd polishing. Might as well stroke a 360, about the same cost, more cubes, better bore sizing, better choice all around and a virtual bolt in for a 318, a couple of minor issues to deal with.




Well... turdly 318's are avialable usually for free..... a 360 block gives you 408 cubes which is 18 more than the 318 stroked to 390. For any given combo assuming you make 1 hp per cube or a little more you are looking at about 20-25HP less. Does that make it a turd? Is a chevy 383 stroker a turd??? SBC 350's stroked to 383 are probably about the most common stroker combo on the planet and Chevy guys love them. Yet the Mopar crowd seems to turn up their nose at a 390? I just don't get it.





I agree, not many people complain about the Ford 289, and definitely not the infamous 302. Mopar guys tend to trash the 318 pretty quick.
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#154926 - 11/23/08 11:44 AM Re: 318 small block build recomendations [Re: GoodysGotaCuda]
HotRodDave Online   content
master

Registered: 01/29/05
Posts: 8104
Loc: Kalispell Mt.
Popular hot rodding has a 477 hp 318 in it that looks like it would be sweet motor. Peak HP was at 6500 (may have made more past that but thats as high as the test went). It made 427 lbs tq to boot and it used iron heads

I have been gathering parts for a stroked 340 for my 68 cuda but I have a real nice 318 short block in there now with SCAT I beam rods and KB167 flat tops to make it nice and light, I am thinking about porting some RHS Iron magnum heads I have and throwing them on and running it that way. Mine would probably be a touch less hp because I have a little smaller cam but I have the parts so I might just do it.

PHR says the build is on there site but I can't find it
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I am not causing global warming, I am just trying to hold off a impending Ice Age! 68 cuda 360 notchback SOLD 1996 Ram 2500 5.9 eddy intake EQ heads, mild cam upgrade great tow rig!

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#154927 - 11/23/08 12:37 PM Re: 318 small block build recomendations [Re: tpabayflyer]
Supercuda Offline
Proud owner of a small weasel

Registered: 09/04/07
Posts: 7362
Loc: West Texas
Quote:


Well... turdly 318's are avialable usually for free.....




it's only saving grace

Quote:

a 360 block gives you 408 cubes which is 18 more than the 318 stroked to 390. For any given combo assuming you make 1 hp per cube or a little more you are looking at about 20-25HP less. Does that make it a turd?






yes, your assumptions are off the mark.

Quote:



Is a chevy 383 stroker a turd??? SBC 350's stroked to 383 are probably about the most common stroker combo on the planet and Chevy guys love them.





ah, let's bring the most polished turd on the planet into the conversation. The only reason the Chevy 383 is so "loved" is because the even bigger SBC, the 400, is a larger turd than the 350. YOu'll note the only way the SBC 383 makes any decent power is if you dump most of the OEM parts for aftermarket.

Quote:


Yet the Mopar crowd seems to turn up their nose at a 390? I just don't get it.




probably because ANYTHING you do to a 318 will, I repeat will, show more of an improvement on a 360, including stroking it.

Quote:



A 390 can be built very cheap. 4" cranks can be had for $325.00 Cheap Eagle SIR rods for $250.00 KB forged pistons for $395.00...... So the reciprocating assembly can be had for less than $1,000 and a 318 stroker with the Eagle rods will not need to have the expense of having the block clearanced. All this can be internally balanced by drilling the counterweights with no expensive mallory metal like the 360 based combo's.




Which will make zero power with 318 heads. Polish away. Cheap crank, cheap rods, hmm, you get what you pay for I guess. BTW, same rods can be used in a 360. BTW, stock 360 pistons weigh less then stock 318 pistons, so why does the 360 need to be externally balanced? The STROKE. If thwe 4" 318 crank has enough weight in the counterweights to allow for internal balance then the 360 4" crank should too. Unless your buying a cheap crank, oh wait.

Quote:



Yes the 3.940 bore is somewhat smaller but there is no problems running even a 2.02 intake valve at all. My 390 uses EQ magnum style iron heads with 2.02 intake valves and it pulls like a big block. TBF




Ever hear of valve shrouding? 2.02 might fit the bore, but the valves are substantially more shrouded in the 318 bore. As for pulling like a big block, ah no. It pulls like a stroked small block. Put it up against a 440, or a 413, or a 426W and you'll see what a big block pulls like.

Point is you can spend money anyway you want but my OPINION is that your wasting it on a 318 unless that is your only option.
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#154928 - 11/23/08 12:39 PM Re: 318 small block build recomendations [Re: GoodysGotaCuda]
Supercuda Offline
Proud owner of a small weasel

Registered: 09/04/07
Posts: 7362
Loc: West Texas
Quote:



I agree, not many people complain about the Ford 289, and definitely not the infamous 302. Mopar guys tend to trash the 318 pretty quick.




Why would that be Goody?

Tell us what engineering difference there is between the 302 and the 318 that makes the 302 a better performance engine?

Do you even know?
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#154929 - 11/23/08 12:57 PM Re: 318 small block build recomendations [Re: Supercuda]
70dart360 Offline


Registered: 01/21/03
Posts: 10968
Loc: Hampton, Ga.
Get a 360 and build it. For what you'd spend to get 400 hp out of a 318, you could build dang near 2 360's with 400 hp. Built a 390 for a buddies dart and had my little 360 in mine. Same gears and everything and I could walk away from him easy in high gear even if he dropped back to 2nd. Dont even wanna know what happened from a dead stop. As far as the 289's and 302's well they came with some compression and would scream with mild mods, a 318 aint gonna happen like that with out decking the block or changing the pistons to get some compression. 383 Chevys are popular cause they were one of the first strokers and used common GM parts. SB 400's are worthless???? Ha, got a 406 in a 69 Nova sitting here in the driveway, all GM except the pistons. Wanna come show me how worthless the 400's are? Them wheels on the wheelie bars aint skinned up for nothing.
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#154930 - 11/23/08 01:23 PM Re: 318 small block build recomendations [Re: 70dart360]
70AARcuda Offline
master

Registered: 01/20/03
Posts: 9187
Loc: las vegas


Ok all you 318 mopeds…you need to park your car and stop wasting fossil fuels and most of all bandwidth..

You should not post questions concerning rebuilding a worthless engine, even though it may be the only thing you have at the time because unlike other people, you might have a wife …kids…mortgage and sometimes like to eat…

You are not allowed to post any further questions concerning your under powered 318, you should use all your resources that you don’t have cause of items listed above and get that 340/360 engine that you dream about every moment of the day and night

Until you have a mighty arsenal of 6 340 blocks…7 360 blocks…6 set of W2 heads…2 set of W5 heads and several set of eddy heads your questions about increasing the performance of a 318 is a waste…

And I always thought hot rodding was about doing what you want to do with what ever you have to do it with….also…being a mopar person is being different….so fire up those 318 and run up the rear end of those you say you cant do it….

Ok…I am done ranting….
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#154931 - 11/23/08 01:25 PM Re: 318 small block build recomendations [Re: Supercuda]
Neil Offline
I Live Here

Registered: 01/19/03
Posts: 10979
Loc: Eagle, Idaho
Quote:

As for pulling like a big block, ah no. It pulls like a stroked small block. Put it up against a 440, or a 413, or a 426W and you'll see what a big block pulls like.






I hope you talking about a modified big block. I don't think a stock B,RB, or Hemi can even run with a reasonably built 4" crank smallblock.
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#154932 - 11/23/08 01:29 PM Re: 318 small block build recomendations [Re: 70AARcuda]
70dart360 Offline


Registered: 01/21/03
Posts: 10968
Loc: Hampton, Ga.
70AAR, all I was saying is that a 360 would be as cheap to do with more power, cause he mentioned keeping the original accesories and stuff. If he's not against installing a big block then the 360 would be the best option and keep the factory "looking" small block under the hood.
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