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Thread: High torque 408 cam recommendations? M1 4bbl vs AirGap?

  1. #1

    Default High torque 408 cam recommendations? M1 4bbl vs AirGap?

    Jeep weighs 5k lbs with tall gearing. Stuck using a single 3" exhaust with a cat. I'd like to shift at 6k and run a low stall or a really tight higher stall. I always thought the AirGap was too restrictive on a 408 so I instantly dismissed it. Something about it only flowing 250ish cfm and the heads could flow more. But I'm hearing different now and it shows in dynos that it makes great torque. Wondering if the 4bbl M1 is able to make around 540tq before 4500rpm? Narrowing cams to something around 224-230. Something on a wider LSA would be nice for check engine lights and smog.

    From reading up around the web the last year or so you guys seem to know what's what, so I wanted to hear from the folks here first. I'm not 100% on a 408 either, PIE has a vortech kit that looks pretty good and I've got a 212/212 110 .563 cam I could throw in the stock block. If something happened and I lunched the 408 I'd be pissed. Blow a stock 5.9 not so much No idea how a centri would be vs 408 for low end. Thank you!

    This is what I've got:
    IMM Magnum heads
    4bbl M1
    Doug Thorley tri-y 1/58 headers-dual 2.5" Y to single 3"
    26lb 4 hole injectors
    SCT
    1.7 RR's
    58x52mm TB

  2. #2


    krs1r/t's Avatar
    want more inchs STROKE IT

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    You are on the right track
    Chris at pie will get you where you wanna be

    Bad Luck Truck
    Current setup
    429ci W5 heads 700hp N/A 3950lbs
    1/4 mile #'s coming soon

    Old 1/4 numbers below with 408
    Fastest N/A 2010,2011,2014
    477-RWHP ?-RWTQ

    11.244 ET @ 119.71mph N/A
    FOXHOLE RACING
    "If you like me good, if you hate me, even better!"
    Chris

  3. #3

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    Quote Originally Posted by THEhomelessONE View Post
    Jeep weighs 5k lbs with tall gearing. Stuck using a single 3" exhaust with a cat. I'd like to shift at 6k and run a low stall or a really tight higher stall. I always thought the AirGap was too restrictive on a 408 so I instantly dismissed it. Something about it only flowing 250ish cfm and the heads could flow more. But I'm hearing different now and it shows in dynos that it makes great torque. Wondering if the 4bbl M1 is able to make around 540tq before 4500rpm? Narrowing cams to something around 224-230. Something on a wider LSA would be nice for check engine lights and smog.

    From reading up around the web the last year or so you guys seem to know what's what, so I wanted to hear from the folks here first. I'm not 100% on a 408 either, PIE has a vortech kit that looks pretty good and I've got a 212/212 110 .563 cam I could throw in the stock block. If something happened and I lunched the 408 I'd be pissed. Blow a stock 5.9 not so much No idea how a centri would be vs 408 for low end. Thank you!

    This is what I've got:
    IMM Magnum heads
    4bbl M1
    Doug Thorley tri-y 1/58 headers-dual 2.5" Y to single 3"
    26lb 4 hole injectors
    SCT
    1.7 RR's
    58x52mm TB
    Is your .563 cam measured for the 1.7 rockers? First thing I would do is change out your tall gearing if you want low end torque. RPM's come quicker that way and take advantage of cam specs as well. In other words, get to where the cam lives more quickly. That would make the most difference over any manifold. Pain if you have 4wd and your weight points that you do. Still it would give your jeep the biggest kick in the pants for money spent. There is more to manifolds (or heads for that matter) than total cfm.
    Your 4 barrel could substantiate a 408. 224-230 is a good size cam for a 408 streeter imo. If you aren't doing the crank swap yourself, you need to figure another 4-5 grand for the 408.

    You should not be able to lunch a properly built 408 all that easily. Just keep your revs reasonable.
    If you're going blower and want to stay together longer, hone your rings for more space.
    I was just going to plop the cam, heads and intake on my engine. I decided to take the engine out to hone my rings. Doesn't take long at all to pull an engine. Might as well do it right the first time if I go nitrous or blower later on.
    I can do all this stuff myself or else cost would be prohibitive.

  4. #4

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    Yup .331" lobe for the 1.7's. Builder told me I'd be fine with that lift and duration on a stock bottom end plus what I've been able to find online. Axles/gears done the right way with a dynatrac 44/8.8 and truetracs all around is easily over 7k. If I cut corners and run an open rebuilt hp30/8.8 it's still 3k. I'll eventually go 4.88 on 35's over my 3.73 on 32's but won't be for a while. I'm a basic mechanic so I can throw some stuff together but that's about it. I wouldn't spin the 408 past 6500 ever. The stock 5.9 maybe 7k with a girdle. Thanks for the advice on the rings too! Yeah I'd be driving a corolla if I couldn't do some of this stuff myself lol.

  5. #5

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    Quote Originally Posted by THEhomelessONE View Post
    Yup .331" lobe for the 1.7's. Builder told me I'd be fine with that lift and duration on a stock bottom end plus what I've been able to find online. Axles/gears done the right way with a dynatrac 44/8.8 and truetracs all around is easily over 7k. If I cut corners and run an open rebuilt hp30/8.8 it's still 3k. I'll eventually go 4.88 on 35's over my 3.73 on 32's but won't be for a while. I'm a basic mechanic so I can throw some stuff together but that's about it. I wouldn't spin the 408 past 6500 ever. The stock 5.9 maybe 7k with a girdle. Thanks for the advice on the rings too! Yeah I'd be driving a corolla if I couldn't do some of this stuff myself lol.
    There is only one reason to spin an engine to higher revs and that is because you are producing power at those levels. Higher lifts without duration may be a senseless endeavor for a mostly street driven vehicle. Higher lifts excite the drive train for more low end torque but there is a point of no return. It is not as if you have a cam lift of over .600 or higher or a duration of .230-.240. In your situation, all your hp may be all in at 6000-6200. No sense to spin any higher if that's the case.

    Don't trust what anyone states what you'd be fine with. Unless he sees that your piston to valve clearance suffices with an actual mock up, no one knows for sure what any engine will be fine with. My cam has only a .520 lift but I'm checking the p2v clearance anyway even though the world may say "you'll be fine with that lift". It even has a 112 lsa and set at 108 ctr. Until I measure the lift, who knows what I've been sent. I cannot tell you the cams I've seen that were so out of whack from their cards as to be pathetically incorrect for the engine specs.

  6. #6

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    I was thinking of spinning higher because the gearing advantage. How little hondas can be so quick compared to other 4 cyl cars with similar weight and hp but at a lower rpm. I hate how tall the first few gears are and how short OD is.

    Very true. I'll still check even though I already have the cam and rockers. Thanks for the advice!

  7. #7

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    Quote Originally Posted by THEhomelessONE View Post
    I was thinking of spinning higher because the gearing advantage. How little hondas can be so quick compared to other 4 cyl cars with similar weight and hp but at a lower rpm. I hate how tall the first few gears are and how short OD is.

    Very true. I'll still check even though I already have the cam and rockers. Thanks for the advice!
    That's because those engines were designed to make hp at higher rpms. An F1 Formula car spins to 12,000 rpm with 2.6 liter engines. In this case, revs are making up for lack of cu. ins.
    That's not these engines. Higher rpms beyond what most of these 318/360's are modified with, unless designed to make hp at higher revs, will only lead to valve float or worse. In other words, what is the sense of spinning this engine any higher than 5800-6200 rpms if it is simply done breathing beyond that point? The trick here is to get there as quickly as possible and that is why I offered a gear change as first advice.
    Then there is all the back up to produce higher rpms as it relates to balancing, blue printing, fuel delivery, springs, electronics, castings, etc.,etc.
    Your vehicle is heavy. It needs low end torque. The combination of that along with upper range hp is speaking to an engine much larger than you have or getting more air in artificially.
    Last edited by arro222; 02-15-2018 at 02:43 PM.

  8. #8
    FlyinRyan's Avatar
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    On a 408 in a Jeep I use a 220/230 split from bullet.
    112-114 LSA for boost.
    If 360/365 use 210/220.
    RYAN/TUNED

    Got questions?!? Get the answers ->>> http://www.dakotart.com/forum/showth...estions-thread
    For fastest response please text or email at ryan@frptuning.com ,please no PM's!!!

  9. #9

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    Thanks! Ideally would have a twin screw tvs on the stock 360 but there's no kits available.

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