408 Stroker Motor Build

Discussion in 'Classic Mustang Specific Tech' started by Gailahan, Sep 16, 2006.


  1. Gailahan

    Gailahan Member

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    I am building a 351w engine stroked to 408 for my 65 coupe and I'm looking for some input. With the stroking, I'm thinking the revs will be limited to about 6200 to 6500 rpm max if I am correct. I'm looking at AFR heads, specifically the 185cc or 205cc models. I think that the powerband might be too narrow, especially on the street, with the 205cc heads because they are specced for 3500 to 8000 rpms, whereas the 185s are for 1500 to 6500 rpm. I am also looking at the Edelbrock Performer RPM Airgap manifold which are also rated for 1500 to 6500 rpm. I might possibly add forced induction later on down the road so I want to plan accordingly. Is the AFR 185cc and Performer RPM Air Gap combo not up to par for my 408 stroker motor? I plan to use the car mainly for street use, but I also would like to do autocross racing. I'm planning on 500 to 600 na horsepower. My main worry is that the 3500 to 8000 rpm heads and intake will creat a powerband that is too narrow, and not very streetable (3500 to 6500 as opposed to 1500 to 6500.) You guys are pretty smart, do you have any suggestions?
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  2. 5.0ina66

    5.0ina66 Member

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    In a perfect world, I'd run AFR 205s with a 750cfm carb, 11:1 and a mild single plane intake (like the excellerator) and a custom solid cam, looking at 531hp right there. Otherwise same with PerfRPM @ 500hp. Cammed right, it'll run on 89 octane, have lots of lowend, and rev to 6500rpm. Only real downside to strokers is you cant rev them quite as high, but you oght to get enough Rs out of it for the street. Stroking tends to trade massive torque for a little RPMs, not create a narrow powerband.
    HTH
    --Kyle
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  3. Gailahan

    Gailahan Member

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    I'm not saying that the stroking will create a narrow power band (*I'll fix my first post to be more clear*), I'm saying that the heads and intake will. The AFR 205cc heads are 3500 to 8000rpm heads. If my motor will only go to 6500 max rpm, my powerband would be 3500 to 6500 with 205cc as opposed to 1500 to 6500 with AFR 185cc heads. I could be wrong and it may not be a problem at all, I'm just hoping to get some advice / words of wisdom.
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  4. dennis112

    dennis112 Active Member

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    You might want to consider that the advertised RPM levels for both the heads and the intake are for a 351ci engine. A 408 will need to move much more air to get to the same upper RPM's as a near stock 351.

    Not sure about the heads, after some studying on other sites, the RPM and Stealth dual planes "start" to sign off at about 5800rpm on the larger engines. I am not saying the RPM won't take you to 6500 with a 408, I am saying that a Vic Jr. would probably make you happier when you run hard.

    When trying to reach 500-600hp with a 408, most builders would opt for the 205 heads as the 408 will have sufficient enough torque to ensure good daily driveablility, assuming the correct cam is chosen. If you are going to run a manual tranny, that is the way I would go. The 205's will also have room to grow should you get the bug for more speed--basically spending your money only once and future proofing. If you are planning on building only the one motor and it can meet all your goals, the 185's might work well for you--but remember that power is addictive and you will probably want more no matter what you build!

    Intakes, on the otherhand are fairly cheap and you could conceivably try both a dual plane and a single plan to see which you like better. My switch from a Stealth to a Vic Jr. was barely noticeable. I can light the tires up (see sig) in first and second gear by nailing it at any speed from idle up to my 6400 red line, and yet I can still cruise through town at 1500rpm in 4th gear without downshifting or surging.
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  5. GoinBroke

    GoinBroke New Member

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    Music to my ears Dennis. I am hoping to drop my stroker in maybe two weeks. I can not wait for the torque!
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  6. Gailahan

    Gailahan Member

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    Thanks for the help Dennis, the 205cc heads would probably be my best bet as I may run forced induction later on, and I don't want my engine signing off at 5800rpm. I am planning on running either a TKO 600RR tranny or a T56, which will allow me to run a pretty radical mechanical roller cam. As far as the manifold, I may run a Torker II or a Victor series, I'm not sure yet. I really wish I could see a dyno chart on a 408 stroker motor running 205cc AFR heads with a few different intakes.
    #6
  7. bnickel

    bnickel Founding Member

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    for a street car i'd stick with the dual plane, the RPM air gap would be fine for a driver and even some mils road racing and definitely fine for the occasional drag strip blast as well. now, when you go with a power adder like blower or turbo you may want to go with a single plane intake or if you decide to hit the track a lot more often. my biggest worry is that with a stroker, afr 205's and a single plane intake that the car will be less streetable than what you want right now and it will get relegated to occasional use only, even for the street. for now i'd stick with a good dual plane intake and a smallish cam even with the 205's, once you upgrade to the blower you'll likely need to change cams and intakes anyway, so for now stick to the lower end of the equation.

    quick question, what compression ratio are planning to end up with? don't go too high or you'll kill it quickly once you add forced induction later on. shoot for about 9.0-9.5:1 max and even then you'll have to keep the boost fairly low, under 8 pounds.
    #7
  8. Maxamil

    Maxamil Founding Member

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    I have a 418 Stroker and am running the Edelbrock Vic Jr. Heads (equivelent to AFR 205's) great powerband to 6500 RPM. I am also using a Perf. RPM air gap intake man. I was going to go vic jr but after talking to my engine builder we decided the dual plane manifold was better for my application (mailnly stop light racing). I also am runing a milder cam H284 comp cams i think w/ a speed demon 750 carb. FYI Expect 500+ HP. Build a bulletproof tranney/readend setup your gonna need it. =)
    #8
  9. dennis112

    dennis112 Active Member

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    A 408 with 205's and a single plane certainly doesn't even come close to being dead for street driveability, if the right cam is installed. I do agree that a small cam works great with free flowing heads and would be best in a mostly street machine. To much cam will kill driveability and is much worse than using the wrong intake or heads.

    Small cam with big heads equals good torque and a wide power band.

    I run what is considered a "small" cam for such a big engine.

    I base the following driveability "opinion" on me having a somewhat similar combo as Gailahan. He will have a light car (possibly lighter car than mine) 15 more cubes, plus a manual tranny with a good choice of gears.

    Although I have 210 ported Vic Jr. copycat heads (big ports-2.055/1.60 valves), and a Vic Jr intake, my 393 car is very streetable. As a matter of fact it borders on docile riding through town. Downshifts from 4th are not really needed to cruise at 35mph or even 25 for that matter. I can take my family out in the car and enjoy a smooth leisurely cruise through town without needing to run up the RPM. Stop light to stoplight does not require me to rev the engine any more than I would my Olds 88. It will pull in 4th from as low as 1500rpm without a bog or ping. Anyone who can drive a stick (wife, son, grandpa) could easily drive this car, as long as they keep the pedal off the floorboards.
    :D

    With that said, I agree that a dual plane may fit Gailahan's driving style better than a single plane, but my point is that not using a dual plane does not automatically lead to intense driveability problems. In my opinion, he can't really go wrong with either choice. If his car is his daily driver, the dual plane might be more to his liking, although the differences will be small. With a little consideration of the build (the reason he is posting here), a single plane can also help him meet his goals.
    #9
  10. 69gmachine

    69gmachine Member

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    My 408 w/AFR 205s is reasonably streetable, but if it was a daily driver it would probably get to be a pain. Parts list is in my sig below. I never intended it to be a daily driver though, and there are several things that I could have done if street manners were a priority.

    1) I used a Torker II single plane intake. It was port matched to the heads but it has small runners, so by itself I don't think this was much of a factor. I'm sure a Stealth or RPM manifold would give me more streetable manners though.

    2) I used an aluminum flywheel. A 408 has so much torqure I felt I could get by with it. The bottom end is a little soft, and I have to rev to around 1800 to leave a stoplight. If I'm not careful, it's easy to squeel the tires.

    3) The biggest factor I believe in making my car a little edgy is the cam. The LSA is 112 with the specs below. I have a slightly smaller cam I'm planning to swap in. It has .556i @ 224 and .566e @ 232 on a 108 LSA.

    4) The 1 3/4" headers and 3" exhaust are definetly overkill. If I had it to do over I would use a 2 1/2" system. When I build a dedicated track car I'll swap this over and put a 2 1/2" X-pipe on this car.

    All of these combined does make it a bit racy, but it's still reasonably streetable. I think the 205s were meant for a 408, and it can be made as mild as you want, and still have a ton of grunt.
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  11. Gailahan

    Gailahan Member

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    This car isn't going to be a daily driver, just a fun car that will blow away my buddy's LS1 Camaro =). I want it to be a "race-car" that is streetable enough to go for a nice cruise around town or to a local car show yet powerful enough for a few runs at the drag strip, along with some autocross racing.
    I'm thinking about running 9:1 compression just in case I ever decide to run a power adder. The low compression will also let me use lower octane fuel.
    So, here is what I think I might go with as of now:
    My 408 Stroker Motor
    351w Late Model Roller Block Bored .030 over
    Eagle 4340 Forged Stroker Crank- Internally Balanced
    Eagle 4340 Forged H-Beam Rods
    Forged pistons that will allow around 9:1 compression
    AFR 205cc Heads
    Not sure on Intake yet???
    Edelbrock 750cfm carburetor
    Roller Cam--Need Help Here Also.
    1.6 Roller Rockers

    I was thinking of running a Comp Cams Mechanical Roller Camshaft, but I could definitely use some help choosing the right cam. I'll probably use an aluminum flywheel so I can rev a little higher. I'm running a heidts mustang II front suspension with QA1 coil-overs, and I'm planning on doing some surgery on the rear suspension as well (Maybe 4 Bar or 3-Link setup). I have a 9 inch rear built with 3.50 gears and moser 31 spline axles. I'm planning on running a TKO 600RR or T56 but will probably go with the TKO 600RR because I don't know if the extra gear is really worth it for the added cost. So that's where I'm at.
    #11
  12. dennis112

    dennis112 Active Member

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    Sounds like a nice build.

    I caution you on the use of an aluminum flywheel on the street. They work best in a car that weighs less than 3000lbs. The driving characteristics is more race car like and they are less forgiving when you start from a dead stop and when shifting to other gears due to the lost momentum that a normal "heavy" flywheel offers. The daily driveability will suffer. Do some research and then decide if you really need one.

    Just not something I would consider in a primarily street crusier. . . . .
    #12
  13. Rookie71

    Rookie71 Member

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    MM&FF did a recent 408 buildup using 205 heads. They ran it in EFI configuration and also as a carburated motor. I think 520-550hp is what they were getting
    #13
  14. bnickel

    bnickel Founding Member

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    this statement seems to be a bit contrary to your first post, or maybe you just didn't state all of your intended goals in the first post. anyway, if this is really what you want out of the car then a single plane intake like a victor JR. would be fine. i also would reconsider the aluminum flywheel even for a mildy streetable car, especially with a healthy cam and single plane intake as the engine will be more "peaky". i still think that you'd be better off for now with a high rise dual plane like a stealth, performer rpm, stealth air strike, or performer rpm air gap and a smallish cam until you go with the power adder. the combo will be more streetable and still be a great performer at the track. as is said earlier you will likely need to change cams when you add the power adder and possibly the intake as well. that said you can still go ahead and run a single plane intake now as the 408 will have plenty of low end torque but the dual plane will still have slightly better street manners.
    #14
  15. 70vert

    70vert New Member

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    heh, I'm learning a lot here.

    I went with the AL flywheel as well thinking the same thing - 408w is coming later, 302-2v original right now. I can drive the 302 with the AL flywheel fine around town, but I do lose RPM between shifts. (TKO600) It's a little bit of a bummer to hear about you having to rev to leave a stoplight with the 408. Bet it's fun on gravel or in rain starting from a dead stop :D If I take it to San Francisco I bet I'll have fun on the hills.:rolleyes:

    I'm glad I just decided on a 2.5" Magnaflow kit. I don't think I'll ever need anything bigger.

    I'm watching this thread closely - nice car 69gmachine, let me know how it does on the track! I'd like to take mine to the (straight AND curvy) track once it gets its' 408. (see sig)

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  16. Gailahan

    Gailahan Member

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    You guys are right, the aluminum flywheel probably won't be the best choice if this car is going to be driven on the street at all. I think I'm going to go with this setup:
    351w Late Model Roller Block Bored .030 over
    Eagle 4340 Forged Stroker Crank- Internally Balanced
    Eagle 4340 Forged H-Beam Rods
    Forged pistons that will allow around 9:1 compression
    AFR 205cc Heads
    Edelbrock Victor Jr. Intake
    Edelbrock 750cfm carburetor
    Comp Cams Xtreme Energy XR286R Camshaft
    1.6 Roller Rockers
    There is a real good article on a 408 Stroker Motor <a href="http://airflowresearch.com/articles/article046/A-P1.htm">Here</a> It might be the one that Rookie71 was mentioning above. There is some crazy torque on this engine, single plane intake and 440 lb ft at 2500rpm. They even throw it on a turbocharger.
    #16
  17. 69gmachine

    69gmachine Member

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    The aluminum flywheel allows it to rev like crazy. By itself it would probably be OK, but if you're also going to use a big single plane like the Vic Jr, I'll bet it'll be a handful on the street. On the street, the RPM drop when shifting is barely noticeable, it's only when starting from a dead stop that there is even a hint the flywheel is aluminum. The track is a different story, but I hope that when I learn to drive harder into the turns I won't let the engine drop so far down before shifting in the first place. I have other priorities at the moment, but when I swap in the slightly smaller cam, I'll report back if it made a noticeable improvement in the street manners. Regardless, I think I'll leave the aluminum flywheel in place for now. I've taken over 200 lbs out of the car (most off the front end) with aluminum engine parts, my coil over suspension and R&P steering, so with me in the car it barely tips 3000 lbs. For me, I think I'd try a Stealth DP intake before I replaced the flywheel.
    #17
  18. mustangdave

    mustangdave My rearend needs a stud and two nuts. Founding Member

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    I've seen a couple of dyno tests on similar engines and the RPM Air Gap beat the Victor Jr. on torque and almost equalled the top end h.p., (within 5 h.p.), so it seems a no-brainer to use the air gap unless you are building a race car aimed at getting every last bit of top end h.p.
    That being said, I can't understand why everyone wants to spin their engine to such high r.p.m.'s. Most streetable engines start falling off in h.p. at or shortly after 6,000 r.p.m.'s unless they have a radical cam, so why abuse your engine for little or no gain. 6-6200 is plenty for a wide powerband street engine that will still kick butt at the track. 351 W engines have large mains that weren't really designed for high r.p.m.'s anyway. Hope I didn't offend anyone as there are exceptions to every rule.
    #18
  19. Stangninjak

    Stangninjak Member

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    I have a 351w in my 65 coupe. Since I did not want a cowl, I went with a Wei stealth for a intake. I was not sure, and had heard that a airgap, and vic jr, would not fit under the stock hood on a 351 build for a 65.

    Anyway, I am quite happy with the stealth, and I would say it depends on what your making the car for. The air gap is a excellent piece, and if I was sure it would had fit with no prblems, I would have gotten one :)

    My mods are in my sig, and as soon as I get my RR in, and my Toplader refresh kit done, its to the track !
    #19
  20. Spoofty

    Spoofty New Member

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    Another thing to think about. You said you were looking for 500-600 hp and maybe adding forced induction at a later date. Remember you are using a stock block. They can only handle so much. From what I'v heard late model blocks are only good for about 550 hp. With a main stud girdle and a lifter valley brace you might get away with 650-700. The forced indutoin might be better left for an after market block. You take 600 hp and add forced induction of any kind and your over 800 hp easy as most add around 40%.
    #20

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