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408 stroker build educate me
#310880
05/07/09 11:34 AM
05/07/09 11:34 AM
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Joined: Aug 2003
Posts: 2,682
Clinton Twp. Michigan
coronet1966d
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Clinton Twp. Michigan
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im looking to build a 400-450hp small block. i currently have a 360 with roughly 325-375hp but it has dangerously low oil pressure and in need of a rebuild ive aquired a set of "street" ported iron magnum heads and 1.6 roller rockers id like to run on pump gas and im already at 10.2:1 with my open chamber smog heads so in order to keep 360CI id need to buy different pistons anyway so.. My real question is: what economy stroker kits are a good value and can handle 450hp without worry? ive seen scat and eagle make kits anywhere from $950 to about $1500 they just about all come with I beam rods and cast cranks with forged pistons im not going to spray the motor i drive the truck alot so it has to be durable would it be smart to add a forged crank or a waste of money? should i stud the lower end and heads or is that also overkill? any tips would be helpfull i want to do it right once rather than go cheap and have it bite me but im also not made of money thanks in advance! 
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Re: 408 stroker build educate me
[Re: coronet1966d]
#310881
05/07/09 12:00 PM
05/07/09 12:00 PM
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Joined: Jan 2003
Posts: 16,123
Grand Haven, MI
patrick
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unless you plan on seriously turning the wick up later, cast crank should be fine. if you're planning on line boring it anyway, I'd probably switch to main studs. if not, I'd just go ARP bolts.
how radical of a cam do you plan on running? I'd probably look at the diamond forged dished pistons...the KB forged dishes are another option.
1976 Spinnaker White Plymouth Duster, /6 A833OD
1986 Silver/Twilight Blue Chrysler 5th Ave HotRod **SOLD!***
2011 Toxic Orange Dodge Charger R/T
2017 Grand Cherokee Overland
2014 Jeep Cherokee Latitude (holy crap, my daughter is driving)
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Re: 408 stroker build educate me
[Re: coronet1966d]
#310883
05/07/09 12:13 PM
05/07/09 12:13 PM
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Joined: Feb 2003
Posts: 12,675
Columbia, CT
moper
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I dont build a 4" engine without studding the mains. For a heavy truck, I'd recommend it. The cast cranks are fine. But you'll need it internally balanced for the flywheel, and it should be done that way anyway. So be prepared for the extra cost. IMO, the Magnums can't move enough air, and to get them to, you need to spend. I'd run a set of RPMs and get the weight bonus too. IMO, the cam's too small for a 4" stroke engine. Look for something over 245°@.050. That size is where i would start, and it won't make much for power beyond 5K (because it's small). Also plan on a large carb. I start with a wet flow rated Holley 870.
Well, art is art, isn't it? Still, on the other hand, water is water! And east is east and west is west and if you take cranberries and stew them like applesauce they taste much more like prunes than rhubarb does. Now, uh... Now you tell me what you know.
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Re: 408 stroker build educate me
[Re: 69Cuda340S]
#310885
05/07/09 12:36 PM
05/07/09 12:36 PM
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Joined: Jan 2003
Posts: 16,123
Grand Haven, MI
patrick
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since it's in a truck, I'd build it for a 0-5000 or 0-5500RPM motor. given the smallish cross section of the mag heads, I wouldn't expect them to support much above that in a 408 anyway. if they have springs on them that will support them, I'd probably look at something in the 224-230@.050 duration and about .320" lobe lift max. MP .474" lift cam, comp magnum 270, comp magnum 280, comp XE268, summit SUM-K50062, lunati 07401 Would all be good choices. the wider the LSA, the better the idle quality (good for a sleeper), and it will sacrafice a little midrange peak torque for a flatter torque curve that won't lay over on the top end as fast. for price and specs, I'd probably choose the summit cam listed. remember, lift will be 1.0666 times the value listed for an LA cam due to magnum rocker ratio. I'd open up the pushrod pinch on the heads as much as you're comfortable with if it hasn't been done already. I don't see why it HAS to be internally balanced, I'd probably balance it externally to 360 specs, especially if you already have a 360 flywheel. Don (B3W5422) over on the race board ran years on an 360-balanced 416 in a 3400 lb duster running 10.7's, I'd think it'd live in an application making 100 less HP and not being revved to 7k. if your truck is still drivable and you want to minimize downtime, you might want to consider picking up a 360 mag shortblock to build up. then you get a cheap hydraulic roller cam option. get it reground at bullet cams and reusing the hydraulic roller lifters, you have an engine that will be more reliable with todays low zinc oils.
1976 Spinnaker White Plymouth Duster, /6 A833OD
1986 Silver/Twilight Blue Chrysler 5th Ave HotRod **SOLD!***
2011 Toxic Orange Dodge Charger R/T
2017 Grand Cherokee Overland
2014 Jeep Cherokee Latitude (holy crap, my daughter is driving)
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Re: 408 stroker build educate me
[Re: patrick]
#310888
05/07/09 01:14 PM
05/07/09 01:14 PM
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Joined: Oct 2003
Posts: 7,506
Az
Crizila
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Az
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For your application, I like the "drop in" kits sold by Hughes, Scat, Mancini, etc. They make life easy by including everything you would need ( crank, rods, pistons, bearings, rings, balance if you want, in one nice package. For your needs, cast crank, hyper pistons, and eagle I beams would be fine. A few years back I ran a 408 with this package, your heads ( bowl ported 2.02 - 1.60 ), big Hydraulic - 246 @.050,.606-.614 lift & 108 LSA, Victor Jr and 750 Demon. Pushed my 4100lb turd to low 12's @110plus. Only thing you might want to ease up on would be the cam, especially if you will be doing a lot of street driving. I'd keep the LSA around 110. 12's should be no problem.
Fastest 300
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Re: 408 stroker build educate me
[Re: coronet1966d]
#310889
05/07/09 01:47 PM
05/07/09 01:47 PM
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Joined: Jan 2003
Posts: 16,123
Grand Haven, MI
patrick
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Quote:
id love a magnum lower end but i already have the engine in my truck and i have another 360 block in my garage. and it seems like the magnums pull a premium. are the rotating assembleys the same between La and magnum?
id like to keep the iron magnum heads i already have as eddys would ad another $1500 to the cost of the build.
i currently have a holley 750 double pumper could i use that on the stroker or would i need the bigger carb like preveously mentioned?
for a street truck, you might be giving up a little due to carb size, but I'd say it'd be fine...moper had good advice, but I'd say his advice is geared more towards a race application, not a daily driver/street app.... it'll probably need to be re-jetted.
rotating assy's are similar. crank is the same. mags have slightly lighter rods, hypereutectic pistons with a smaller dish, and metric ring pack, which changes the balance factor. the biggie is the lifter bores are taller and there's bosses in the valley to accomodate the retention pieces for the OEM roller lifters and the lifters themselves. they're ~.75" taller than flat tappet lifters.
and I call shenanigans on the 600+ HP/tq on a chassis dyno with an eddie headed 408. you need a MAX EFFORT solid roller cammed eddie headed stroker to get much above 600 FLYWHEEL HP on an engine dyno. are you sure you weren't in 4 low, or a lower gear where the torque multiplication wasn't factored into the dyno numbers? sounds like it to me. it's incredibly hard to get much more than 1.2-1.4 flywheel torque per CID.
Last edited by patrick; 05/07/09 01:54 PM.
1976 Spinnaker White Plymouth Duster, /6 A833OD
1986 Silver/Twilight Blue Chrysler 5th Ave HotRod **SOLD!***
2011 Toxic Orange Dodge Charger R/T
2017 Grand Cherokee Overland
2014 Jeep Cherokee Latitude (holy crap, my daughter is driving)
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Re: 408 stroker build educate me
[Re: RDJ]
#310891
05/07/09 03:37 PM
05/07/09 03:37 PM
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Joined: Aug 2004
Posts: 3,335
MARYLAND
69Cuda340S
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MARYLAND
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Quote:
One thing I noticed looking at the stroker kits, the SCAT rods are a better grade of steel than the Eagle rods.
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Re: 408 stroker build educate me
[Re: coronet1966d]
#310893
05/07/09 05:00 PM
05/07/09 05:00 PM
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Joined: Feb 2003
Posts: 12,675
Columbia, CT
moper
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That package gets 17mpg in a 3.23 geared 3700lbs car. And runs 109mph..lol. With J style heads that flow about 260. What I see is a truck that drag (or street) races. Not a tow vehicle. Plus, it's a stick. You could balance it to 360 specs, but it's not anything I would do. I don't believe in external balancing anything. Just my opinion, and not much more money. I would not have any kit balanced. There are too many places that simply don't get results that are "good enough" for my tastes. A stick OD in this truck has a deep first gear and doesnt have much more for tires than a car. So really, I do think it would need to make power over 5K. Hypers are not designed for the piston speeds reached in a 4" arm engine that revs beyond 5K. Stock rods with good bolts, sure. But cheap stroker pistons are just another place I dont go.
Well, art is art, isn't it? Still, on the other hand, water is water! And east is east and west is west and if you take cranberries and stew them like applesauce they taste much more like prunes than rhubarb does. Now, uh... Now you tell me what you know.
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Re: 408 stroker build educate me
[Re: moper]
#310894
05/07/09 05:34 PM
05/07/09 05:34 PM
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Joined: Oct 2003
Posts: 7,506
Az
Crizila
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Az
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Quote:
That package gets 17mpg in a 3.23 geared 3700lbs car. And runs 109mph..lol. With J style heads that flow about 260. What I see is a truck that drag (or street) races. Not a tow vehicle. Plus, it's a stick. You could balance it to 360 specs, but it's not anything I would do. I don't believe in external balancing anything. Just my opinion, and not much more money. I would not have any kit balanced. There are too many places that simply don't get results that are "good enough" for my tastes. A stick OD in this truck has a deep first gear and doesnt have much more for tires than a car. So really, I do think it would need to make power over 5K. Hypers are not designed for the piston speeds reached in a 4" arm engine that revs beyond 5K. Stock rods with good bolts, sure. But cheap stroker pistons are just another place I dont go.
The fact is, aftermarket or factory cast/steel cranks and KB Hyper pistons ( I guess that would be a cheap stroker piston ) are good to 4,500 ft/min. With a 4" stroke that equates to 6,750rpm. I spin mine to 6,200 ( with Eagle I-beams ) - many passes with no problems. Bought my kit balanced - internally - no problems - just what I have experienced. 
Fastest 300
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Re: 408 stroker build educate me
[Re: Crizila]
#310895
05/07/09 07:58 PM
05/07/09 07:58 PM
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Joined: Feb 2003
Posts: 12,675
Columbia, CT
moper
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Fact is Cri, you're looking at mean (average speed). Mean speed at 6200 is 4133fps, but peak speed is 6833fps. Peak speed at 5000 rpm is 5510fps. If you build for the average amount of force, you will, on average, have great results 50% of the time  If it's your engine, congrats. When you have someone else paying, they get testy if it breaks.
Well, art is art, isn't it? Still, on the other hand, water is water! And east is east and west is west and if you take cranberries and stew them like applesauce they taste much more like prunes than rhubarb does. Now, uh... Now you tell me what you know.
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Re: 408 stroker build educate me
[Re: moper]
#310896
05/07/09 08:45 PM
05/07/09 08:45 PM
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Joined: Jan 2003
Posts: 12,861
Gloucester,VA STOP MOVING HERE
RangerDan440
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Gloucester,VA STOP MOVING HERE
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I'm running a fairly mild 408 in my truck with a cast crank, no problem but I would definitely stud the lower end. Ive also heard that Scat has a better reputation than Eagle. Keep the cam around .500 with a mellow duration since its going in a truck. Mine is also a Magnum engine and when I built it, intake options were pretty much limited to the MP M1 so thats what Im running; its great over 4000 rpm but Im lacking the low end punch a stroker should have; Im going with more gear when I go into the rear later and hopefully that will cure it. I believe theres an Performer intake out there now for the Magums and thats what I would recommend for an RV-style cam in a truck. Anyway, the 408 puts my 4400-lb 96 Ram into the mid 13s with 17 mpg (518 trans) so I cant complain. You'll have fun dusting off Mustangs and Hemis. 
68 Valiant 408
69 Charger 318
69 Cougar 351W
70 Torino GT 351C
71 Country Squire 351W
71 Road Runner 440+6
71 Satellite sedan 318
73 Duster 318
73 Challenger 383
77 Grand Prix 455
83 Malibu 9C1 383
84 Delta 88 403
87 Grand National
96 Ram 360
09 Crown Vic
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Re: 408 stroker build educate me
[Re: moper]
#310897
05/07/09 09:09 PM
05/07/09 09:09 PM
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Joined: Oct 2003
Posts: 7,506
Az
Crizila
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Quote:
Fact is Cri, you're looking at mean (average speed). Mean speed at 6200 is 4133fps, but peak speed is 6833fps. Peak speed at 5000 rpm is 5510fps. If you build for the average amount of force, you will, on average, have great results 50% of the time If it's your engine, congrats. When you have someone else paying, they get testy if it breaks.
Fact is Moper Mean speed is best way ( and the norm )for measuring piston strength and durability. At peak speed there is very little stress on the piston, so just measuring at one speed ( especially peak ) tells you very little about piston/rod/crank strength. The big hurter is at TDC / BDC, when the piston is at zero fps and changing directions. Yes, it is my engine, and I have had great results 100% of the time. Anyone who limits their stroker motor to 5K should go to their room!
Fastest 300
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Re: 408 stroker build educate me
[Re: Crizila]
#310898
05/08/09 12:52 AM
05/08/09 12:52 AM
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Joined: Jan 2005
Posts: 12,424
Kalispell Mt.
HotRodDave
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If the cam is a little agressive that you have now, reuse it. It will be a little milder in a 408 than a 360 plus the better heads should make for a good flat tq curve. The 750 would be plenty carb for what your doing.
SCAT stuff is way better than Eagle stuff, better steel better processing better structural engineering, even the SCAT cast cranks have wing shaped counter weights. I know a guy with an eagle cast crank that broke where the pin and crank journals over lap (360 mains to boot!), they machine or cast it with very little material there so it can be balanced internally easier, his motor was a stock mag headed 408 with stock cam ex and all, he just wanted a little more tq when the stock bottem end gave up, plus the eagle rods are inferior material and castings look terible with really bad grain structure that you don't have in the SCAT.
I am not causing global warming, I am just trying to hold off a impending Ice Age!
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Re: 408 stroker build educate me
[Re: HotRodDave]
#310899
05/08/09 04:54 AM
05/08/09 04:54 AM
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Joined: Oct 2003
Posts: 7,506
Az
Crizila
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Actually, this is a very good thread as it pretains to the original question. Since most of us are not metalergy experts, it's a good reason to buy a rotating assembly ( drop in kit ) verses individual pieces. The match work has already been done - by experts we hope. Also with the explosion of stroker kits out there these days, piston speed is also a very relavent topic - no mater how you measure it. If you use the mean way ( mean speed in ft/min X 6 divided by the stroke in inches), this is a good rule of thumb: 1. factory cast cranks = 3750ft/min 2.aftermarket cast / steel cranks = 4500 ft/min. 3. factory forged cranks = 4600 ft/min. 4. budget aftermarket forged cranks = 4800 ft/min. 5. typical race aftermarket cranks = 5500 ft/min. 6. hi dollar custom endurance race cranks = 6000 ft/min. 7. prostock/mountain motors = 7500 ft/min. 8. formula one = 7500 ft/min.
Fastest 300
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