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  #1  
Old 03-31-2006, 07:28 PM
72 340Dusta' 72 340Dusta' is offline
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Help! 408 Stroker Build

I'm planning to build a 408 stroker using a 72 360 block, 4" stroker crank,and stock 360 heads. I want this motor to put out 450-500 ponies and my price range is around $4000. I already have a 74 318 that is pretty stout and I plan to use alot of stuff from it(intake,carb,ignition,etc.) what is the best combo for making big power for this motor? CAM? PISTONS? RODS? VALVES? Any advice would be appreciated going into a 72 340 Duster-4spd.-8 3/4 w/3.91 gears.
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  #2  
Old 03-31-2006, 07:43 PM
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Quote:
Originally Posted by 72 340Dusta'
I'm planning to build a 408 stroker using a 72 360 block, 4" stroker crank,and stock 360 heads. I want this motor to put out 450-500 ponies and my price range is around $4000.
Good Luck. Do you have hook-ups to discount performance parts and can you do the assembly and machine work yourself? You do have a good block (pre-74).
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  #3  
Old 03-31-2006, 08:35 PM
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72Challenger 72Challenger is offline
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In any engine build, the cam is key to the characteristics the finished engine will have. The other pieces need to be matched to the cam in order to realize the full potential. You don't mention how this engine will be used, but since you state 450-500 HP, it doesn't sound like an all-out race engine. Since it'll have a 4" stroke, and probably be running on the street, plan on limiting it to 6000 RPM. Based on that, you want peak power to happen in the high 5000 RPM range. This would dictate a cam with approximately 235 degrees duration at .050" lift.

Pistons don't need to be forged, but I always like them that way. Others like the hypereutectics. Choice of material doesn't affect power, but does affect things like clearances. Are you buying a 408 kit? If so, pistons will be included so the decision will be made for you. If you're piecing this together yourself pistons should be chosen to give you about a 9-9.5 compression ratio to match the cam. That's actually on the low side for a 408, since the longer stroke increases swept volume which in turn increases CR. This will also depend on the combustion chamber size, which brings us to the cylinder heads.

Your choice of head will make it difficult (probably impossible) to reach your power goal. Stock 360 heads just won't flow enough air to make that power. You will need to plan on some porting work being done. You'll need at least 220 CFM on the intake side, even more would be better. Stock 360 heads with the 1.88" valves will flow at best about 190 CFM. Plan on opening up the intake seats to 2.02". Better would be to just buy a set of aftermarket aluminum heads. Your budget will allow this.

You plan on using the induction system from a 318, what are you using now? 318 ports are smaller than 360 ports, so a proper 318 intake will be too small for a 360 head. Same goes for the carb. Perfect for your intended build would be an Edelbrock Performer RPM, with a 750 CFM carb.

I'm not trying to discourage you, your goals are very reasonable and fairly easy to obtain. You just need to plan properly to attain them.
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Old 03-31-2006, 08:47 PM
72 340Dusta' 72 340Dusta' is offline
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the car will is a street machine, mainly weekends and the occasional trip down the strip to spank one of my buddies.

I was already planning to port the stock 360 heads and install 2.02/1.60 valves That will free up some money instead of the aluminum heads. The intake is an Edlebrock Streetmaster(old school). A Holley 650 DP sits on top of it. Would these be ok or I was thinking tunnel ram with two 650 Holleys(I have a spare on the shelf) Also I'm runnig 1 5/8 hedman hedders and 2 1/2 pipes with Flowmasters. How about the stock rods? will they handle 500HP or should I upgrade?
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Old 03-31-2006, 08:47 PM
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Quote:
Originally Posted by 72Challenger
pistons should be chosen to give you about a 9-9.5 compression ratio to match the cam. That's actually on the low side for a 408, since the longer stroke increases swept volume which in turn increases CR. This will also depend on the combustion chamber size, which brings us to the cylinder heads.
With alum. heads isntead of iron heads, would you recommend 10-10.5 CR pistons? Or stick with the 9-9.5?
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  #6  
Old 03-31-2006, 08:48 PM
ace26 ace26 is offline
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Your build is almost exactly what i'm doing.I have a 72 360 block at the machine shop now getting bored,decked and line honed for the main studs.I'm using the eagle 4" forged crank and H beams and ross -21cc dished stroker pistons along with a pair of edelbrock magnum aluminum heads and airgap manifold,should end up with around 10 to 10.5 to 1 static compression,not sure about cam yet either a decent sized solid or the like hyd somewhere in the 450 ish HP range and a 100 shot somewhere down the line.Going into a 73 318 duster,i have a 8 3/4 rear and springs to replace the 7 1/4 that's in it and my brother has a built 904 with the low gearset he's gonna let me use.
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Old 03-31-2006, 08:51 PM
72 340Dusta' 72 340Dusta' is offline
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Did you buy a stroker kit or are you piecing this together? Would 5.9 Magnum heads be better than the iron heads? Are you going with four bolt main caps?
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  #8  
Old 03-31-2006, 09:03 PM
ace26 ace26 is offline
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I've just been getting the parts as i can afford them been saving and getting stuff for the past year and a half or so i was going to do a supercharged buildup at first but my brother talked me out of it,probly a good thing!I wanted the eddy magnum heads because of the 58CC chamber with a decent portjob on them i think they flow around 260 to 270 at .500.On the main caps i was thinking about the 4 bolt conversion but my brother said for what i was going to do with the car it was a waist of $$$ and not necessary,I try to listen to him since he knows alot more about this stuff than me.
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Old 03-31-2006, 09:14 PM
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Quote:
Originally Posted by ace26
compression,not sure about cam yet either a decent sized solid or the like hyd
Why would you want solid with a 450hp build?

btw: I'm building a 408 now and this things already cost me about 5k and I still need to buy the pushrods and (mech) fuel pump.

and hoses and belts... and break-in and post break-in oil and filters... and other fluids like coolant... And fuel line... And sheet metal for trunk.. and paint for my trunk... and exhaust system components... and..

Last edited by dust : 03-31-2006 at 09:15 PM.
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  #10  
Old 03-31-2006, 10:13 PM
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72Challenger 72Challenger is offline
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You originally said stock 360 heads, but since you plan on porting them and installing the larger valves, you should be okay. Double-check what that will cost vs. new AL heads. When you factor in re-doing the seats, new valves, porting, maybe new valve guides, milling, new springs, retainers, locks and seals, you just may find a pre-assembled set of aftermarket heads are a really good deal. That said, I built my 340 by porting and rebuilding the X heads that I had, but I did all my own machine work, and had access to a flow bench.

This is from the Edelbrock web site:

1974 Edelbrock addresses the needs of its customers, introducing the fuel-efficient Streetmaster manifold series during the world’s gas crisis.

A manifold made over 30 years ago for fuel efficiency is probably not the best choice for a high-performance engine. The 650 carb is borderline for 450 HP, inadequate for 500. You can certainly keep it for now and upgrade later.

Your stock rods can handle your projected power level if you rebuild them and install better bolts. Again, more $$$. A complete rotating assembly, already balanced, can be had for under $2K. You'll likely spend as much piecing together your own components, and certainly spend a lot more time and effort doing so.

dst brings up a good point, with AL heads compression can be increased by 1/2 to a full point. Plus, don't forget the weight savings. On the other hand, iron heads are kinder to head gaskets.

It is real easy to go over budget in this hobby. I sure have. I'll bet everyone else on this board has too. But with careful parts selection and doing as much yourself as possible, you should be close. In all honesty, with a $4K budget, you've got a better chance of success skipping the stroker route and shooting for "only" 400 HP. But if you do that, and you really want the stroker, you'll always have regrets. If you do it "right", but go over budget, well, it's only money, right?

Last edited by 72Challenger : 04-01-2006 at 02:06 AM.
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  #11  
Old 04-01-2006, 10:17 AM
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Quote:
Originally Posted by 72 340Dusta'
I'm planning to build a 408 stroker using a 72 360 block, 4" stroker crank,and stock 360 heads. I want this motor to put out 450-500 ponies and my price range is around $4000. I already have a 74 318 that is pretty stout and I plan to use alot of stuff from it(intake,carb,ignition,etc.) what is the best combo for making big power for this motor? CAM? PISTONS? RODS? VALVES? Any advice would be appreciated going into a 72 340 Duster-4spd.-8 3/4 w/3.91 gears.
The 2 best intakes for the street/strip that are not expensive would be the Edelbrock RPM air gap version or the single plane M-1 MoPar manifold.
For 400+ cubes on the street, you'll need a 750 or greater carb. But the 750 will do you.
Full port the heads with stainless steel valves.
Pistons are on the shelf all over. Your choice. Keep the ratio no greater than 9.5-1. Thats all you need. 9.0-1 engines can make very big power. Don't be fooled by what appears to be a low ratio. Hyper-U's are inexpensive and strong enuff for the task at hand. Gap rings per instructions and do not over advance the timing or run poor gas. This will have the engine pinging and break the pistons.
A basic cam for a 450 + HP level with 3.91 gears could use a MoPar 292/.509 cam.
The best ignition I have ever used is a Jacobs with a standard distributor. Use quick advance springs from MoPar as needed.
I suggest Hooker Super Comp headers or tti's if you foot the bill for best power.
2-1/2 inch exhaust min. 3 inch would be prim. for the upper level HP sought.
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  #12  
Old 04-01-2006, 10:49 PM
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¿Are stock rods ok for this combo? ¿ what think about 340 rods? they are more strong that 36
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'70 Dodge GTX 340 - In Argentina GTX is DODGE and A-body
Solid cam MP 284?/.528", Edelbrock Aluminium Heads, Weiand Single Plane X-CELerator,
Holley 600 double pump, 4 speed manual, 3.54 rearend.
http://www.geocities.com/dodge_gtx
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