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Regrinding 308 cams - anyone B.T.D.T.?

Discussion in '308/328' started by dave80gtsi, Nov 28, 2005.

  1. dave80gtsi

    dave80gtsi Formula 3
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    Nov 3, 2003
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    Dave Meredith
    Greeting to all - I am toying with the idea of having my OEM cams (2V Injected) reground so to provide for higher lift, especially the intakes.

    Anyone ever tried this, and lived to tell about it later?

    Would appreciate feedback accordingly.

    Thanks and Cheers - DM
     
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  3. Newman

    Newman F1 World Champ
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    Dec 26, 2001
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    Rufus on this site has done just that and is pleased with the results. Injected cars are finiky though, go to far past stock and the fuel distributor plate will have a fit and the car will run like crapola. Carbs on the other hand are receptive to more radical profiles. 2 choices would be Elgin cams or Web cams. Web charges $1340USD to weld, straighten and regrind to any spec you desire for the set of four.
     
  4. don_xvi

    don_xvi F1 Rookie

    Nov 1, 2003
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    Check out a few searches on Elgin and Web cams, a few users have had some of this done with varying results. Web cams seems to have a good rep.
     
  5. Matt Morgan, "Kermit"

    Matt Morgan, "Kermit" Formula Junior

    Nov 12, 2003
    405
    Ferndale, WA
    I would highly recommend Web Cam. Laurie is quite knowledgable, and the quality is great. Russ Turner had some troubles with Dema Elgin's shop, and I'm not sure if it ever got straightened out, FWIW.
    A bit more lift certainly isn't going to cause troubles, but to much duration, which causes low manifold pressure at idle is going to give you an opurtunity to learn a lot about tuning the K-jetronic, the hard way.
    While the distributor's air plate is going to give some reaction, the biggest trouble is the Control Pressure Regulator (usually refered to as the WUR, or warm up regulator). It has two other functions. One being an altitude compensation circuit, which is fed from a line before the throttle plate in the throttle body, and the second is an enrichment circuit, fed after the throttle plate. There is where the problem begins. A low vacuum in the plenum is read as a partly open throttle, and extra fuel is automatically added to eliminate any bogging, much like a power valve in a carburator. Cams with too much duration, and the low vacuum they are known for will give the wrong signal to the regulator, causing a rich idle that just can't seem to be adjusted. Keep the cams around carb cam specs, with a lift around.375" and you should do OK.
    Dial them in around 30 BTDC and 30ATDC instead of stock carb settings, and you will get a good power band, with more top end
    HTH
    Kermit
     
  6. dave80gtsi

    dave80gtsi Formula 3
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    Nov 3, 2003
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    Dave Meredith
    Guys - Thanks for the insightful comments thus far.

    My intent here was to simply add a bit of a power increase to the otherwise maligned "low power" 2V injected motors via a simple cam grind. I don't have the specific details in front of me, but I'd guess that maybe I could coax about 1 mm greater lift out of a given lobe by having the backside ground, and then reshimming the valve tappets to close up the resulting gap.

    I don't anticipate intentionally changing the camshaft timing, since I too have heard tales of how the F.I. system goes all wonky with radical cams. But a slight bit of lift increase, especially on the intake lobes I would think, would be OK and worth the effort?

    Cheers - DM
     
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  8. Newman

    Newman F1 World Champ
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    Reducing the almost non-existant base circle on the cam probably isnt a good idea if at all possible. Shim availablity is the issue if you do that and its sort of a half cocked way to do it. Bottom line is $1340 from WEB for the four regardless of the grind or profile and its a lot of money and time to road test it after and go "yeah, I think its a little faster" because that will be the extent of the gain.
     
  9. mk e

    mk e F1 World Champ

    Oct 31, 2003
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    In my mind the cams would be the second stop. The 1st thing to do is a carb or EFI conversion. That will get you about a 10% hp bump by itself and may be enough for you. If it's not enough, then regrind the cams to any spec you wish without fear of CIS problems. Going Carbs or EFI and P6 spec cans will get you to about 260hp, a full 30% over stock. Just lift alone on the cams, I'd doubt you'll see 5% gain....of couse the stock cams work pretty well with a turbo or blower :)
     
  10. Matt Morgan, "Kermit"

    Matt Morgan, "Kermit" Formula Junior

    Nov 12, 2003
    405
    Ferndale, WA
    Newman is quite correct there It is in reality just a few thou differance in the base circe diameter and the cam itself. Not nearly enought to mess with. I have seen it done another way. Leave the intake alone, so there isn't the mixture problem, and have Laurie do a cam for the exhaust only. No K-Jetronic problems then! when ya speak to her, ask for the same grind I got for a 2 valve injected. .375" lift, smoooooth idle, and you know there is something there! part # 01-991
    HTH
    Kermit
     
  11. Nick

    Nick Formula Junior
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    Oct 31, 2003
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    Nick Scianna
    Leave the stock cams alone & just change the engine management; it’s the best performance & drivability upgrade you can do to an injected 2-valve car for the money. If you are on a limited budget, just get rid of the OEM ignition set up & go to an Electromotive XDI ignition & you will see a better performance improvement than just changing the cams if the rest of the engine is still original. Good Luck
     
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  13. snj5

    snj5 F1 World Champ

    Feb 22, 2003
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    dave
    great discussion here. in the end, it's all about flowing the most air and fuel in the right amout to the cylinder. The Bosch Kjet and its cams is the major flow restriction in that engine. As has been said, cams will net you some, but you are still having to suck air through the long Kjet system and around the barn door airmass sensor plate. It has been my experience that the cams and the head in my Ferrari were about matched - i.e. i did my cams but could not take full advantage as I had already max flowed my head with the stock camshafts. It was also my experience that the ignition advance basically is pretty good from the factory at timing the flame front properties in the cylinder - i.e. the most hp on the dyno was reached pretty much on the factory max advance wot curve. Just my experience.

    As most know I went with 40 DCNF Webers and reground intake cams (left the stock exhaust to preserve bottom end) on a Bosch Kjet fuel injected car and got not only a hp increase, but an amazing amount of torque and throttle response. This occured I think because even though I had max flowed my induction tract up high, I was getting more air in sooner at lower rpms shifting more power lower resulting in more torque. Oddly enough, the main reason I went to Webers at all was for reliability and DIY maintenence over the long haul. Same for replacing the Marelli ignition with a reliable easily supported Mallory single distributor set to factory WOT advance - simple, lean, clean and reliable. There are a bazillion threads about my conversions and cams. If you do opt for cams - would DEFINITELY go with Webcam: Great service. Elgin ruined my cores I sent them and never returned them or called or wrote. You be the judge.

    For your car, a 2V, an entire carb set-up from an earlier car should probably just bolt right up, then you just fab the linkage and mount a low pressure pump - that's it. Should take about a weekend to do.

    This is what worked for me. As many have said here, you won't beat the hp of forced induction or the flexibility of FI. Mine does sound pretty dang good... :)

    I will also say you would be amazed at how changing from K-jet opens and cleans up the engine bay and loses weight...

    Good luck - there are some really smart people here who helped me.
     
  14. dan the man

    dan the man Karting

    Nov 5, 2003
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    Alabama
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    Daniel
    Guys,

    I have a December 1979 308 GTS with the carb's. is there a difference in any of the US carb'd cams? Or, are they just advanced and retarded differently? Mine is the 210 hp rated 308, and I would like to believe that is due to the cat's and a cam retardation.

    What is the original lift for my car? I am having trouble with the carb's sputtering, but I plan to keep them. I like the sound, and the simplicity.

    Also, has anybody here built a forced through Super charged or turbo set up for the carb's?

    Dan
     
  15. snj5

    snj5 F1 World Champ

    Feb 22, 2003
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    If you have not seen it, this thread at post # 75 has lift data:
    http://ferrarichat.com/forum/showthread.php?t=2788&page=8

    If you can stand to read the whole thread, there are a lot of points made about the 2v heads and cams although it is primarily about 4 valves.
    Good luck
    rt
     
  16. mk e

    mk e F1 World Champ

    Oct 31, 2003
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    Yes, the cams are different, but I'm pretty sure the early ones (308 not GT4) will fit if you find a set.

    A roots or screw type blower won't work well for a blow-though application, they work best with EFI, but roots will work if as long as the order is carb(s), blower, engine. I've seen that done to a 308 with what looked like a holley carb on top of about a 140ci blower.

    A turbo or centrifugal blower will work as a blow-though set-up, although I don't much like centrifugal SC, if you go that root, I guess paxton is the best. I've never seen a pic of one like this, but it can be done and I have seen it on other engine using weber or delortor carbs...I've seen a lot of old vw bugs that way.

    I'm not sure if the float bowls are exerternally vented or vent inside the carb. If they vent inside, all you need to make is a plenum for the top. If they vent outside, you need to either plumb the vent into your plenum or encase the whole carb inside the plenum, which makes the throttle linkage harder. you will also need a fuel pump and regulator to deal with the boost pressure.
     
  17. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    Jan 11, 2001
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    I have different lift values in my notes for early vs late US carbed 308:

    '73-'77: inlet 8.949 mm; exhaust 8.323 mm (per the 308GT4 WSM)

    '78-'79: inlet 7.7mm; exhaust 7.7 mm

    (and I believe the US 2-valve 308i cams are the same as the '78-'79 US 308 cams)
     
  18. BigTex

    BigTex Seven Time F1 World Champ
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    Dec 6, 2002
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    Bubba
    Steve,

    That matches "conventional wisdom" I have heard.......

    Specs changed with cat converter intro........
     

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