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300 RW Horsepower from a 308?

Discussion in 'Technical Q&A' started by maurice70, Sep 16, 2004.

  1. maurice70

    maurice70 F1 Rookie

    Jan 25, 2004
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    maurice T
    I know that this topic has come up before but was wondering if it is possible to achieve 300 rear wheel h/p from a carbed 2V 308 normally aspirated engine?My brother was talking to a guy who said he owned a worked 308gt4 that produced 300 H/P at the rear wheels.He didn't ask what work was done as my brother is not that mechanically inclined but what could be done to get this power?
     
  2. mk e

    mk e F1 World Champ

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    Possible? yes. But to do it you'd need to spin the engine to 8500 or 9000, port the snot out of the heads, monster carbs and run cams that make P6s seem mild. It won't idle at all below 1500 and won't be drivable below 3000. Basically you'd be building a drag motor. 250rwhp is a much more realistic goal. My guess is you rbother was talking to someone who was "estimating" his rwhp.

    If you are thinking about more than 250rwhp, you should be thinking about boost from a turbo or supercharger. On a QV, I got 304 rwhp at 10 psi using an eaton roots type supercharger. I have since replace it with a screw type supercharger, added an intercooler and am getting 425rwhp....with no magor internal changes and no change in the car drivability unless you count needed to be careful when you open the throttle because in 1st or 2nd gear the tires just start spinning if you open it too far.
     
  3. snj5

    snj5 F1 World Champ

    Feb 22, 2003
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    Yes, there are many threads on the topic available. The Carobu article published in Forza talks about 308 available hp specifically. Just so you know, 300 hp at the rear wheels is about 360+ at the flywheel, or 117 or so hp/liter. That's pretty difficult on just 2 valves with normal aspiration, although easy with a super/turbocharger. Even to get 300 hp at the flywheel, it would definitely require aggressive cams and higher compression that may sacrifice some drivability. Remember back in the 2 cam days, 100 hp per liter was the goal for racing cars (e.g. GTO).
    One of the best normally aspirated hop-ups example on the board is pma1010's 308 with the factory P-6 comp cams with 42 DCNF carbs. For forced induction, M ke's supercharged 500hp 308 is exceptionally well crafted as well. I think to search these two well respected posters would be a great start.
    hth
    best
    rt

    edit - dang - Mark beat my post by moments!
     
  4. maurice70

    maurice70 F1 Rookie

    Jan 25, 2004
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    Thanks Mark.I hope to meet this guy and find out what he has under the bonnet,boot,err engine lid.When I do I will post more info.Yes I have been following all your threads about your car.You are like a guru for 308s.I told my brother how you said that you could only take off in 1st gear if you want to go slow and that if you wanted to take off fast you needed to use 2nd.He was quite amazed!I think its more like 300 at the flywheel but I still want to know what he has done
     
  5. mk e

    mk e F1 World Champ

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    Please do, if you find out anything.

    A harley xr750 (dirt track motor) has almost exactly the same bore/stroke as a 308 and is 2v. They make 85-95 rwhp. So multiply by 4 gives you 340-380rwhp at 3 liter. But the do it mine had .580" lift cams and 270 degrees duration@.050" lift, so maybe 320 total duration, 12.5:1 CR. The intakes flowed 148 cfm at 12 inches of water, tuned open exhaust, and 106 octane fuel. I just don't see how a street engine could come close to that and I'm pretty sure you can't put those cams in or flows through the heads no matter how hard you try.
     
  6. pma1010

    pma1010 F1 Rookie

    Jul 21, 2002
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    Some "data":
    - the LFSC Michelotto 308, a 2v car, produces, I am told, 342 BHP (crank). I believe this is P6,40 mm carbs, high CR and lots of head work [I believe Michelotto started with the 208 heads due to the smaller exhaust valves and then enlarged and flowed the intakes;
    - Bill Pound, a respected tuner, indicated a 2v with 13mm cam lift and big durations would run 340+ BHP a 4v, 380.

    All the above track only (the Michelotto car is tube framed).

    I'd guess you can get to 300 or so with some effort and expense and keep it reliable. After that, IMO, the real gain is through shedding 500 lbs +

    How are Kermit or is it Nick getting on with the 4 litre conversion?

    Oh, and you can put a v12 in a 308 if you get really crazy. It's been done. Motor is lighter than the 8 cyl too...

    Philip
     
  7. mk e

    mk e F1 World Champ

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    That sounds about right and in line with other engines. I didn't realize 13mm (.511") lift would fit, that helps a lot. On the XR, the heads didn't flow anymore at .580 than at .450, but the extra lift was needed to get ramps steep enough without bouncing the valve on the nose of the cam. Just thinking about for a minute I guess with overhead cam (the XR is pushrod) the valves are less prone to bounce, so you could cut down the total lift and still be fine. But 340 crank still won't make 300rwhp, I guess the 308 is 17 or 18% loss, so that's about 280rwhp. On the XR I used a 41.5mm venturi because I couldn't bore them out any more than that and they were still the main restriction. The header tubes1.62", for about 8", then 1.75" .
     
  8. pma1010

    pma1010 F1 Rookie

    Jul 21, 2002
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    Mark,
    FYI, the 1974 308 GT4 LM (NART) car had a 36mm venturi and an exhaust with three components: a tapered 38mm-> 40mm header (2:1), followed by 40mm -> 42mm taper 2:1 collector and a megaphone (42 -> 80mm) for each bank.

    I am no expert with exhausts, but I thought you generally built 4:2:1 exhausts for greater torque and 4:1 for greater top end. Maybe I have it backwards, because the LM car would clearly be designed for flat out running.

    Bill (Pound) believed the "restriction" with the 308s was the size of the exhaust valves and ports -- they were too big.

    By the way, I think a streetable 308 with 320 - 340 BHP and a decent torque curve would be a highly attractive car.

    Philip
     
  9. lromanosky

    lromanosky Rookie
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    Aug 27, 2004
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    I've got a friend who has got the Ferrari Bug (from me) and is talking about buying a 79 308 with a "Le Mans" conversion with a claimed 350hp. Also, some suspension work. Anybody know anything about this "Kit" supposedly offered by dealers and "approved" by Ferrari?

    My advise was to be extremely careful as the car has 50,000km on it, and the engine work was done when the car was new. I figure a 25 year old Italian engine pushing 115hp/L with 50,000km is not going to last much longer...

    However, he claims that although it has a high idle, it is tractable, doesn't smoke, and is very fast.

    Is it possible that what he is talking about is a replication (sort of) of the NART 308 GT4 engine?

    I don't recall any 308's in Le Mans, am I wrong?

    Regards, Lawrence.
     
  10. mk e

    mk e F1 World Champ

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    Just ask for a PPI with a leakdown test and and include a dyno run, it's only about $100-$150 and he'll know what it is he's buying. Even I wouldn't touch a car with a modified engine unless I had a parts list or a dyno sheet. It is much easier to screw it up than it is to make it better. I've never heard of a dealer Le Mans convertion, that doesn't mean there wasn't one, but it seems unlikely the dealers where building race engines. Also 79 was the start od polution stuff, I'm not sure they could mod the engine, maybe. I think it probably had a set of cams installed, maybe P6 which are the La Mans cams I guess. [/quote]
     
  11. mk e

    mk e F1 World Champ

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    I think you are right on the exhaust, but if the exhaust ports are too big, a little more restriction in the exhasut system may actually help. That could be the answer. I have overported exhaust ports to get the flow up through the street muffler. That might be what ferrari did too. I did a set of 911 heads and the exhaust required a lot of welding to make them flow right.

    I am sure that a 308 (particularly a QV or better yet 3.2QV) could have 320-340hp in street trim. But it is a lot of work and you'd probably have to lose your beloved carbs. On a high power 2.7 liter 911 they cost about 25 hp over EFI. On my XR, 38mm cars cost 12hp (12x4=48hp for a 308) over the 41.5mm. Bigger is better for flow, but you lose control of the mixture at low rpm, that is where EFI comes in, you can run as big a throttle body as one want without giving up anything down low.
     
  12. snj5

    snj5 F1 World Champ

    Feb 22, 2003
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    Seems to me it's all about flow, and the American cars, especially post smog, were really strangled. The biggest parts of that were head flows, cams and exhaust.
    The 4.0 liter project not withstanding, I think Kermit (www.durable1.com) has worked a lot on head flows; for instance I remember in the 2v cars the flow kept on increasing up through .5 lift where the qvs leveled off after .35. I'm told the 348 heads flow even a lot better than the qv/3.2s. Also in American trim, the 2v and qv are a bit shy on compression, ranging from about 8.8 to 9.2.
    The FI/qv cams are quite duration restricted (to prevent confusing reversion waves to the Kjet airmass plate) compared to the original carb car specs. To compare how far you can go, the stock 308 Euro carb cams ran 260/244 durations with 58* overlap while the 2v P6 comp cams run about 290/288 durations with 92 overlap. Another Ferrari 2v engine, but with 12 cylinders, the 250 GTO almost developed the magic 100 hp/liter, but needed a cam with 294/290 durations.
    As a comparison on the qv's (which need less cam) the stock durations are 244/244 with 26 overlap. The most qv cam for the street I'm told by both Elgin and WEBcam is about 260 degrees. Will let you know soon I hope.

    I find that the idea of adding exhaust restriction being beneficial is interesting - will put on some resonators and see if it helps... :) Anyway, the exhaust matching to the cam characteristics determines flow upstream of the cylinder as well as downstream. The parts are all working together. The early cats and thermal reactors were quite restrictive to allow emmisions control, and opening up the exhaust flow will help. We can argue about if there is too little, but on the street John Law will have interevened before then for noise. Another interesting Ferrari historical note was on the early Ferrari V-8 sports cars (i.e. 268 SP, also with a flat crank), Phil Hill relates in Doug Nye's book "Dino, the little Ferrari" (thanks Carbon and FML) that the race mechanics could change the power band of the V-8 by having 2 sets of exhausts available. A long set for high speed and a short set for torque. Point being, you can tune the powerband by subtle changes in the exhaust.

    As Mark said, while carbs can flow as much air as FI, they can't do as well at Air/Fuel (A/F) mixture accuracy - you typically optimize for a desired power band determined by the cam and accept some slop elsewhere (of course, I like to refer to this as 'personality'). I must say though, Webers are pretty remarkable for what they can do considering how elegantly simple they are. This is also helped by the Ferrari V-8s tolerating a wide range of A/F with not much output variation (in my experience).

    Bottom line is that more flow is what will give you more power. Cams are the central contrbutor to the character of the flow and powerband that can be improved in a non Kjet constrained Ferrari... I also agree with Mark that if all parts were optimized, a qv could produce about 100 hp/liter, maybe more. The modern street Ferraris even exceed that, but they have variable valve timing and inlet length, with 5v per cylinder. I am personally shooting for a DIY reliable and daily streetable 95 to 97 hp/liter figure that is tolerant of pump gas.

    Just my experience here. For my next trick I'll invent ignition advance... :)
    best to all
    rt
     
  13. Matt Morgan, "Kermit"

    Matt Morgan, "Kermit" Formula Junior

    Nov 12, 2003
    405
    Ferndale, WA
    What I'm reading between the lines here is you want 300 HP.
    Haven't we all (OK there are stunning exceptions) wanted another hundred HP at one time or another? But you may want to consider it the following way: To get it withcams, major headwork etc, it is gonna take RPM to make it work. Right? Longevity and internal stresses increase by the SQUARE of the speed, not linear as is commonly misbelieved. Going the naturally aspirated route to get that power means that is the RPM range and engine longevity that comes with the package. Not a good "Bang for the Buck" IMO. A "Time Trials" motor. But then again, with a blower or a turbo, who knows what you have? big lumpy cams are a dead givaway. I'ts a lot more fun blowing them into the weeds with what they A.S.S.U.M.E.D. was a stock 308!
    And BTW, Phillip, I am not the one doing the 4 litre motor, as I am not associated with NFF. I am however skeptically waiting to see some Dyno #'s
    Best Bang for the Buck? HHHMMMMM?????
     
  14. pma1010

    pma1010 F1 Rookie

    Jul 21, 2002
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    Yes, you can see the reversion through the top of the carbs at dusk when not running the airbox or deck lid. At idle there is so little vacuum (2 - 4 inches) with the P6 cams that the carbs have a tough time in getting the mixture right.

    QV told me about a wickedly quick track only 328 in Europe that was running Weber Alpha FI. I suppose an upgrade would be the TWM TB FI - any idea what would it buy me (torque), Mark?
    Philip
     
  15. F1Ace

    F1Ace F1 Rookie

    Mar 15, 2004
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    Wes
    Has anyone done a blower that we know of? I read a lot on this board about turbos, but is much known of trying the blower route on these cars?

    Best!
    Wes
     
  16. Matt Morgan, "Kermit"

    Matt Morgan, "Kermit" Formula Junior

    Nov 12, 2003
    405
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    I would suggest looking on Mark Eberharts profile, as well as looking thru the archives on his project as it went from the start. You will find no less than one EXCELLENT piece of workmanship, let alone the design difficulties he overcame to get where the car is now. IMO, simply a stunning job! As to turbocharging, search the archives, there is many different ways that it has been done, some very good, and some that are amazing. And of curse some not well thought out.
    Personally when it comes time to do a Turbo, I'd like to look into the VATN type, as they react much like a smaller turbo on low end, and as they adjust the angle of the vanes that direct the exhaust gasses, the top end is tremendous. JMO.
    On a side note, I am just finishing a 4 valve 308 that Frank Capo was kind enough to fit doing a set of cams into his busy schedule for. The clutch is a Quartermaster, super light twin 7" disc unit, and I will tell you that this is the most difficult car to drive on the street as I have ever run across. Ferrari motors are not designed to produce low end torque to begin with. Add big cams, lightend parts and the street drivability SUCKS!!! Once it is rolling, and wound up, it is an animal! No doubt the quickest 308 I have ever been around. But for the street, IMO a poor choice of means to the end result.
     
  17. mk e

    mk e F1 World Champ

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    Philip,
    That is a very hard question. If I remember right, you have stock heads and compression ratio? You would see the most benifit right off idle and up through maybe 2000. I would guess about a 15% increase. From 2000-maybe 5000 or 6000, I would guess the weber would equal the injection as long as it is in tune, but gains could come and go with the weather. From 6000 up I would guess you'd gain maybe 10 hp, more like 25 with ported heads, they tend to be more sensitive. The other thing that makes a big difference in low end torque with big cams is compression. P6 cams want an 11:1 + compression ratio. Adding compression to match the cams, and EFI I think would really amaze you at how snappy the bottom would be. I have seen well match engines make 20% over stock torque from idle right through redline. Big cams don't have to mean nothing down low, but all the parts need to match to do it.
     
  18. mk e

    mk e F1 World Champ

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    Matt,
    Thanks for the kind words.

    I was thinking about a quarter master clutch but was afraid it would be to digital, an on/off thing. I couldn't find anyone who had driven one, so I decided to spend a bit more and go with a tilton instead. Did I make the right chioce or is the quartermaster OK?
     
  19. snj5

    snj5 F1 World Champ

    Feb 22, 2003
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    Kermit
    I assume these are the 260+ duration qv cams that we talked about the timing a few months earlier with EFI (as no Kjet could keep up with that overlap). As I am also looking at 260 cams, do you think my stock flywheel will help drivability enough to use these on the street? Or are thay just too radical? Mine is running so incredibly well now don't want to loose too much torque for top end that will not see heavy use.
    Now would be a good time to know! :)
    It does sound pretty interesting.
    best
    rt
    OBTW - will probably put longer air horns and filters to see what drivability is like. Will also be tweaking the distributor ignition advance tomorrow.
     
  20. Matt Morgan, "Kermit"

    Matt Morgan, "Kermit" Formula Junior

    Nov 12, 2003
    405
    Ferndale, WA
    Mark, you are very welcome. Haveing admired the project for some time, and being a fabricator myself, I can appreciate the tremendous effort to arrive at the quality final design that you have!
    As to the clutch, Stay away from it!!!!!!! While stunningly light (it has been said that the entire package, throwout bearing, pressure plate, twin 7" kevlar faced discs flywheel et al, weights what the stock pressure plate alone does). IMO it does not at all belong on the street. There is no springs in the hubs on the friction discs, which will mean it will eventually be prone to chatter, but the worst is, it has a travel of about 1/4" from just beginning to engage, to full lock up. As the motor stock is not known for low end torque, adding cams didn't improve that, and I'll bet you can imagine the problems trying to start out any where smoothly. The stunnigly quick throttle response it provides due to the loss of rotating inertia is great when under way, but try to imaging that factor complimenting the low pedal movement between ingaged and not, and you can get the pictiure. Just touch the throttle, and the RPM is stunningly quick to rise. Now try to let the pedal out smooth, LOL. I am not embarased to admit that I stalled that car more than any other I have ever driven, especially when everything was fresh. The discs not broken in, the pressure plate, slider and "flywheel", still have fresh machine tooling marks, and it does grab!
    As to the cams, Russ, they are working quite well with the Bosch system, including one of our 70mm TB's. They are the same grind that I sent you specs on, includeing the way I degreed them in, (a tad more top end). In hindsight, I would have set them to the specs that Frank sent, and gotten a bit better low end.
    I have found that relateing to reversion: causeing the low manifold vacuum (9 to 10" HG). That made it a devil to dial in until I figured out that the WUR's enrichment circuit ( the small hose that senses manifold vacuum, and enrichens the mixture upon quick throttle openings) wa reading the low vacuum as the motor needed fuel. I pulled the smal hose off it's port just below the throttle plate, and that setled things down a bunch, allowing me to set the pressures and get a different mixture, as needed. IMO, with well ported heads, and a heavier flywheel, it would be streetable. The output I must admit is stunning! I gotta admit, the first time that I had a bit of pedal on in second, and it come on to the cams startled me! It felt like two Nitrous bottles had just kicked in. That will make it a touchy car unless the roads are dry, clean etc, as it would spin any other way, kinda like Mark's Blower motor.
    And I gotta tell you, the quality of the cams is without peer. I haven't seen machining that smooth and precise outside of the optical industry, right down to the 1mm oil hole on each lobe.
    On a side note, as the idle vacuum was so low, the power brakes sucked, so I developed and tested a cure for that, which will be marketed soon. Anyone who has run large cams on the street knows the power brake issue. It feels the same as the brakes do with the motor shut off, high pedal pressure, and a prayer to stop.
    HTH,
    Kermit
     
  21. snj5

    snj5 F1 World Champ

    Feb 22, 2003
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    Kermit wrote:
    "And I gotta tell you, the quality of the cams is without peer. I haven't seen machining that smooth and precise outside of the optical industry, right down to the 1mm oil hole on each lobe.
    On a side note, as the idle vacuum was so low, the power brakes sucked, so I developed and tested a cure for that, which will be marketed soon. Anyone who has run large cams on the street knows the power brake issue. It feels the same as the brakes do with the motor shut off, high pedal pressure, and a prayer to stop."

    Kermit - many thanks - would love to see a hp/torque graph if you get to dyno the car.

    Well - I've seen the EXTREME quality of Frank Capo's work as I have a set of his cast manifolds on my carb'd 3.2 qv. I'm sold. So how do I get a set of these cams? Sounds like that would get me the rest of the way to my 95 - 97 hp/liter goal.

    On another note - I was worried about low brake vacuum signal until I realized that I didn't even have a brake vacuum line - my car has ABS! The stock Teves unit generates it's own overpressure. Another vacuum line saved! The only vacuum line I have runs the heater valves.


    best
    rt
     
  22. mk e

    mk e F1 World Champ

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    That's what I thougt. Everything I found on the quartermaster web site said race only, which nomally translates as on or off and nothing in between. Then add an ultralight flywheel and it seemed like a nightware in the making on the street, I'm sure it would be great at the track. I went with the tilton 7.25"triple disc carbon-carbon because they claimed it was streetable and I found a couple people who agreed. It is also a very very light weight clutch, but I fitted it to a stock flywheel. I did have to cut an 8" x .1" pocket on the flywheel, so maybe 1 lb lighter than stock I guess, then the clutch is maybe 1/2 a stock clutch and a smaller diameter. So all togehter it's probably 2/3 or 3/4 the stock setups weight. It does have solid discs and is propone to a bit of mild chatter at times, but not bad. I get a little over 1" of pedal travel of slip. I'm pretty happy with it so far...hopefully it lasts.
     
  23. Matt Morgan, "Kermit"

    Matt Morgan, "Kermit" Formula Junior

    Nov 12, 2003
    405
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    Russ, I'll E-mail Frank's secretary and see what I can set up for you. As he is a very busy fellow, Kim is the one to go thru, or you don't get there.
    Did you ever get your heads done? If not, I'd sure take a serious look at it. I'll E-mail you off thread on that topic, and what I can put together with Frank. Be warned, it can take a bit of time to get a set out of them, but as busy as he is with all of the races he attends, it is sure understandable.
    As to "Racker", (the name I gave the car before I fired it up, I'm looking forward to seing the dyno results myself. I think it is reasonable to expect 250HP on the rollers, which is around 300Flywheel HP.
    I wish I knew how to post J-pegs on this board, as I would love to put a shot of one of his cams up for all to see. Computers aren't my strong suit though.
    Back to the topic at hand. As I was going into town on the usual parts run, (which means I come back frustated, as opposed to happily with the pieces,LOL), I was thinking on the drivability issue that I had mentioned.
    IMO, this set up is not very streetable as it is, due to the clutch "diet". While this would improve with a heavier flywheel, the peakiness of the cams as they come on can easily cause a loss of control if the roads are not in perfect condition. I'm sure Mark can relate what it is like to have a bit more pedal on than estimated is wise for the road, and if you are in a corner, " ya smoke 'em, ya spin out" is the reality. Those fortunate enough to have driven an F-40 can testify to what happens even on a track if you are in lower gears,and add too much throttle in a corner. You spin out with the tires smoking. It may sound thrilling but that sudden stop at the end is EXPENSIVE!
    I do not as a usual practice build the naturally aspirated cars up to this level, due to exactly what it now is. Difficult to drive, and possibly dangerous in inexperienced hands.
    And BTW Russ, I was thinking the other day of suggesting that the air horns be reworked to tilt them toward each other a bit, which would help get some better flow with thw air filter settup. Extending them could be done when that is done, as you would have more room. Longer horns will impprove midrange for ya, and may hel with the reversion issues. Just a thought..
    Kermit
     
  24. mk e

    mk e F1 World Champ

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    Russ,

    For what it's worth, the more I think about it, the more I think 9.2:1 compression is pretty low for that much cam. I think you'd want to be in the 10.5-11 range if you want to keep the bottom up where it is now. It will still run and will make more power on top, but you might be a bit disappointed below say 3500 if you don't bump up the compression. I'm sure it will still drive ok, but it won't be a nice smooth curve like it is now, it will look a bit like a mild turbo dyno sheet....I think anyway. I have seem a lot of after market cams come back out of engines over the years and I'm afraid you might be heading that way, but bump the compression up and you should have a setup that will make your face hurt from smiling :)
     
  25. mk e

    mk e F1 World Champ

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    If you've got a good pic of the cams, and then of course the dyno sheet when you get it :) , email it to me and I'll post it for you.
    markeberhadt@comcast.net
     

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