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Mondial 3.2 ported/polished head/big valve/big cam/header upgrade

Discussion in 'Technical Q&A' started by snj5, Mar 29, 2007.

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  1. snj5

    snj5 F1 World Champ

    Feb 22, 2003
    10,213
    San Antonio
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    Russ Turner
    #76 snj5, Aug 4, 2007
  2. snj5

    snj5 F1 World Champ

    Feb 22, 2003
    10,213
    San Antonio
    Full Name:
    Russ Turner
    #77 snj5, Aug 10, 2007
    Last edited by a moderator: Sep 7, 2017
  3. Verell

    Verell F1 Veteran
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    May 5, 2001
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    Verell Boaen
    #78 Verell, Nov 1, 2007
    Hello Russ,
    I'm involved with a project to convert a 2Vi engine to carbs & also increase hp. Supercharging is out of the question as the engine needs to be refreshed anyway. Any help you could give with the following questions would be appreciated:

    How did you specify the pistons to ensure they were made with adequate clearance for the valves at high RPM?

    Were things like conn. rod stretch & journals moving slightly off-center factored into the piston design?

    I keep coming across statements that all 308s are under compression because the piston tops are 0.055 or so below where they should be. Have you determined that this is indeed the case?

    Can the 2Vi ignition system be kept & used, or does it have to be replaced with a modern system?

    mk e, Russ: Any word from Vic on increasing the flow on 2V heads?
     
  4. mk e

    mk e F1 World Champ

    Oct 31, 2003
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    #79 mk e, Nov 1, 2007
    IMO, the stock system can be used, it's not the best, but it's ok.

    No work on 2v flow. I'll should have a flow bench in a couple weeks, so if there is a scrap head out there, I'd be happy to see what can be done.

    I think I could make a rubber mold of the stock port and cast a practice head in plaster too.....I'm thinking of giving that a try for the TR heads if I can't find a scrap one.
     
  5. etip

    etip Formula 3

    Apr 4, 2004
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    Eric
    #80 etip, Nov 1, 2007
    Verell,
    I too am rebuilding my 2v. I am having Weisco do a set of 10:1 pistons for me. I gave them the specs; cc the heads, bore desired (20 over), stroke, CR, cyc volume at TDC, etc. When I expressed concern about the valve pockets she said they make them deeper and factor the depth in with the CR.
    Might not be the best verbage, but I hope that helps.
    etip
     
  6. snj5

    snj5 F1 World Champ

    Feb 22, 2003
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    #81 snj5, Nov 1, 2007
    Verell
    concur w/ etip; we gave the head cc volume, bore, stroke, cyl vol@ tdc and valve diameters. We used JE for a set of 10.5:1 as shown. As per many people, the max on street gas and by Norwood's experence is about 11:1; I am on travel right now, but **THINK** that Kermit at one time had posted the numbers for the stock head, especially in relation to valve lift. Check the older performance camshaft thread of a couple of years ago, I think. While folks had issues w/ Kermit, his data was quite good and he had some good results - especially with Randy Mdamba's car. Something makes me think he got the heads well into the 90s - stock qv flow levels - with a good port job. Certainly Randy's 2v car generated QV hp proven on the dyno with those numbers. He also had a bump in compression to around 10 or 11 as well with incredible results.

    I also remember for sure that in the case of the 2 valve, that flow continued to increase up to .500 lift on the stock 2v where the qv was done at .350

    One thing that surprised me is that while my engine ran ok, it was getting close to a valve job upon inspection - I'm told a good multi angle valve job - even if just on the intakes makes a noticible difference.

    I have also heard that stock compressions were always lower than advertised when measured, even before FChat on Flist. I also some how remember that this supposition was based on cylinder pressure measurements and not on calculated static compression. We did not measure ours unfortunately.
    As to ignition,the stock is ok but if it were me, there is NO QUESTION that I would immediately upgrade to the Superformance electronic single distributor - a straight simple bolt-on with computer controled firing that looks like a stock unit; simple and reliable and laptop interface adjustable.

    I think with a good set of carbs and heads you will get 260 - 280+ solid reliable hp, but more importantly the torque curve will be fat and left shifted (like me now that I am retired :) ) and you will feel the power and response much earlier thanks to increased low rpm flows. and if you are converting to carbs from Kjet, the engine response as the accel jets kick in as compared to the Kjet barn door will make it feel like even more.

    Will try to find Kermit's numbers when I get home if you don't find them. Looking forward to your results.

    best
    rt

    I'll look when I get home
     
  7. luckydynes

    luckydynes F1 Rookie

    Jan 25, 2004
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    pit bull
    #82 luckydynes, Nov 1, 2007
    Double check your piston to valve clearance if you're running new cams . .. if you checked it with stock pistons and have an accurate way to measure and compare new ones . . . fine.

    I've had 2 sets of pistons which had incorrect pocket depths even though I made blue prints with dim from pin center line.

    If using stock cams you can compare the pocket depth to stock pistons . . . this is not an "easy" measurement but you really want to double check it some how . .. you really want to measure from pin center line since other features like valve pocket diameters and compression height might be different making measurement from piston top difficult.

    Stock pistons/valve pockets with stock cams have a bunch of piston to valve clearance . . . just double check they go that deep. Manufacturer made things right and I'm not posting to beat on them . .. just making sure you guys realize this is an important feature to double check!!!


    Sean
     
  8. mk e

    mk e F1 World Champ

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    #83 mk e, Nov 2, 2007
    The super easy way to get the pistons right and to the CR you want is just order then through a shop like Norwood or Carobu who already have piston designs worked out. I don't even think it's more expensive because they get dealer pricing at the piston maker and you will get list pricing either way. Just a though.

    One thing to keep in mind that hasn't been mentioned is that is you are planning head work, it's too early or order pistons. When the heads are re-done, the valve seats will be re-cut and that will drop the valve into the chamber and change the chamber CCs. If porting is going to be done, there may be some cutting in the chamber that will change the ccs. And if valve are being replaced with non-oem, that will most likely change the ccs. So do the heads first, then order your pistons.
     
  9. Verell

    Verell F1 Veteran
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    May 5, 2001
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    #84 Verell, Nov 3, 2007
    Thanks guys, this is starting to make sense to me.

    Probably means I just haven't figured out what the next level of issues are. ;)
     
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