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Thread: My 68 Homemade Turbo Slant6 Dart

  1. #21
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    Re: My 68 Homemade Turbo Slant6 Dart

    Time to drill the intake manifold and add injectors? That's what I always thought the turbo slant 6 guys did.

  2. #22
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    Re: My 68 Homemade Turbo Slant6 Dart

    I think I have a theory as to what can be the issue here - I recently changed the "boost" gauge to a "boost/vacuum" style and notice i only get 10 inches of vacuum under idle. I tried adjusting the bleeds, and it's still 10. From what I can see this usually means a small vacuum leak, or valve timing is off. I'm thinking the latter as i have recently rebuilt the carb now, and made dead sure there were no leaks during reassembly. I also rejetted and built a BRPV, and boost referenced the BRPV cavity.

    I looked up some info on slantsix.org and it seems timing chains slacking out is a common issue, and I'd think at 47 years old (even with only 100k miles on it) I may have a slacked chain and have the wrong timing all-together. Oreilly's had a new entire set (chain/sprocket/ gear) for $25. I'm thinking it's worthwhile to replace anyway and then see if the degree is still right on the cam. It could be slightly off.

    Right now i have 2 1/4" exhaust leaving the engine manifold, and leaving the turbo it turns into 2 1/2.

    Needing more timing is a big possibility, I'm just looking at it like Vigo says where I'm wondering why it doesn't work better as-is. My whole setup is almost a blatant copy of about 4 other builds that work really really well with worse quality parts in some cases. The timing and everything else is identical to those, so why not as good? This is another reason why I'm considering no matter how i set the timing on the distributor I believe it's off in general, or walking around so to speak.

    I gave it a good go in 1st gear and i can get it to rev over 4k RPM just fine, it just doesn't seem to make any more power there. I don't disagree that there should be more timing in general, I'm just concerned as to why if everyone else runs 18 total, why mine doesn't seem to run right with just 18. It could be that I'm running low boost in which case like Ondonti says I can get away with more timing (which makes sense) most of the builds i see people are pushing about 14psi - which seems to be the general number. SOme are 20, but most are 14.

    I'm also guessing based on this info that the vacuum advance is pulling off just fine. One other thing is just a couple days ago, I was driving the car on the freeway, but really "driving it" if you know what I mean. I stayed in boost longer than I ever had a need to before, and after about 30 seconds at high RPM and 8psi, the AFR went from 11.8 to 16 very slowly, so I let off, and drove under vacuum home. This prompted me to rejet and build the BRPV, because obviously the regular power valve wasn't working under boost conditions and the jets obviously couldn't keep up over time. I believe having the power valve function on boost now, should help add fuel if the car stays in boost. The fuel pump is more than capable of keeping up, and the regulator is working just fine - it increases 1:1 as it should. And sorry Ondonti I don't really have a good map of how the timing goes throughout the RPM range. I am doing all of this in my driveway at an appartment, and do not really have an extensive tool set for checking things. I have an 80s snap-on timing light that can count backwards to guess timing, but the mark as far as everyone on slantsix.org is concerned "doesn't always mean 0" and with a sloppy chain, it will walk - which it seems to be doing. I didn't really get a good baseline either of how it ran under n/a operation because it ran good and got decent mileage, so I left it alone - there was really no reason to check after that for me.

    - - - Updated - - -

    Quote Originally Posted by Shadowv4l View Post
    Time to drill the intake manifold and add injectors? That's what I always thought the turbo slant 6 guys did.
    Some do - yes, but I don't have the knowledge really to build an electronic injection system. I read up for about a year on turbo stuff before I thought i could accomplish the turbo setup, and went for it. I am thinking of pursuing EFI, with a COP design for spark, but that is in the future when I can afford it. Right now the car drives me to work every day so huge downtime is not in the books. Once I can put it to the side as a purely fun car I'll probably do that, then bring it back as my daily driver anyway. It's just hard to go buy parts for something if you have the car taken apart and undriveable.

  3. #23
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    Re: My 68 Homemade Turbo Slant6 Dart

    I think your setup looks a little too pretty to have some of these worn out parts :P Would also be nice if you could pressurize your exhaust and see how the valves behave

    While I did not directly say it, I am questioning what the timing is stock, what you are trying to time things at, and MAYBE what is really happening with the timing.

    I have run my Junkyard with 10 degrees pulled across the map and it lost a lot of power but still seemed to run fine. I ran my Spirit with base timing accidentally set below zero and it was terrible :X

    Your exhaust is small but its not killing power as drastically as you are suffering. Yes it would be a good mod to go 3" but 3" can handle 750hp (triple your goal) and at that point it definitely hurts.

    I have never done it but if you were on the dyno again, I would take a timing light. I would assume that you can mimic full WOT conditions in neutral, I won't try to remember too well how your carb and timing works as you keep changing it. I have struggled in the past with commanded timing vs actual timing. My megasquirt did not lie to me but because of how I set things up I couldn't actually achieve certain timing numbers that I commanded. It would be pretty cool to see this car running Megasquirt but I know that takes out a lot of the slant 6 fun. Ghetto tuning is pretty frustrating. You probably don't know but I spent a lot of time with ghetto added fueling and a stock N/A ECU for timing. Ive run 24 pounds of boost on a stock motor with stock n/a timing on E70+Methanol as well as 26 pounds of boost on a built shortblock, 8 degrees more timing than n/a stock, 91 octane + Methanol. At least with a carb'd chevy or ford etc, you have more control over the timing options. Lack of timing control is why I gave up pushing the envelope. I always hit a brick wall where I didn't want to put anymore octane or methanol into the motor to keep upping power.

    I also don't compare boost numbers straight across. 10psi on a bad tune from a huge turbo is worse than 10psi on a bad tune on a small turbo. That is simply because your power level will be higher...unless the turbo is so much bigger that your torque numbers at peak suffer (which is a good thing for the motor surviving).
    Last edited by Ondonti; 12-08-2014 at 03:34 PM.
    Brent GREAT DEPRESSION RACING 1992 Duster 3.0T The Junkyard - MS II, OEM 10:1 -[I] Old - 11.5@125 22psi $90 [U]Stock[/U] 3.0 Junk Motor - 1 bar MAP [/I] 1994 Spirit 3.0T - 11.5@120 20 psi - Daily :eyebrows: Holset He351 -FT600 - 393whp 457ft/lb @18psi 1994 Spirit 3.0T a670 - He341, stock fuel, BEGI. Wife's into kid's project. 1990 Lebaron Coupe 2.2 TI/II non IC, a413 1990 Spirit 3.0 E.S. 41TE -- 1993 Spirit 3.0 E.S. 41TE -- 1994 Duster 3.0 A543 1981 Starlet KP61 Potential driver -- 1981 Starlet KP61 Parts -- 1983 Starlet KP61 Drag 2005 Durango Hemi Limited -- 1998 Dodge 12v 47re. AFC mods, No plate, Mack plug, Boost elbow -- 2011 Dodge 6.7 G56

  4. #24
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    Re: My 68 Homemade Turbo Slant6 Dart

    Well, with an absolutely "stock" slant 6 the timing should be 0 initial while idling, and 32 advanced at "All in" with no vac advance hooked up with a 1 barrel Holley Carburetor. On that setup I went to 6 advanced just because it ran better.

    When you move to the two barrel, like i did - it varies, but the Weber liked 12 degrees initial at idle and 32 all in with the vacuum advance off and that worked great.

    This two barrel 350 is a little smaller than the Weber in CFM, but more adept to tuning and has more information out there for blowing through modifications. The timing currently is 8 degrees advance initial, and 18 "All in" with vac advance disconnected, with the vac advance connected it gets a lot higher on vacuum, but under boost - it is 18. I have not been able to get a good number with the vac advance as I'd have to place the car under load to see the transistion and it's hard to hold a timing light on a car that starts a 1 tire fire when you brake stall it. Like you said, it'd be good to bring one to a dyno and check. I'm sure they wouldn't mind.

    One thing I have made a breakthrough with is fuel delivery - having changed the power valve to operate on boost rather than vacuum, I get a much more steady fuel reading when transferring into boost - I still need to increase the jets I think, as there is a big noticable gap from where the jets can maintaint - to the power valve turning on. Just as I'd be able to hook up the electronic distributor I have in a couple days - there is going to be a good rainstorm so that's out till at least the weekend unfortunately. That distributor has the stock timing curve still there, and the volvo unit. It has one port for vacuum, and one for boost (push/pull) So I don't necessarily have to start out with a boost reference to it - and it will still function. We'll see what happens then I guess.

  5. #25
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    Re: My 68 Homemade Turbo Slant6 Dart

    i think 350 cfm even under boost is too small of a carb look to a 5oocfm 2bl holley of better a 4bl under 600 cfm as for the stock timing chain i bet it"s got over a 1" of slop if original and the cam would be close to round too

  6. #26
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    Re: My 68 Homemade Turbo Slant6 Dart

    Quote Originally Posted by bakes View Post
    i think 350 cfm even under boost is too small of a carb look to a 5oocfm 2bl holley of better a 4bl under 600 cfm as for the stock timing chain i bet it"s got over a 1" of slop if original and the cam would be close to round too
    Cam wear, interesting point!

    What octane fuel were you running 32 all in with? If it was 87 and then you went to 92 octane, you should be able to run a few psi of boost on 32 "all in." If you were on the ragged edge when running 32 then you might only want to run the first 2 psi boost on full timing. If you already were on 92 octane without turbo, timing has to start dropping right away. I think I usually had lazy timing at 0 psi boost so that timing would move into the efficient yet safe zone as boost came on. Thats what happens when you have no boost retard. The new distributor sounds kinda interesting. What does it actually do to retard timing and how much change can it make?
    If the combustion chamber is really detonation prone then that would force you to have to pull more timing with boost. I would hope to get away with 1 degree per psi or less. For comparison sake, the SRT-4 maps pull between .5 and 1 degree per psi of boost depending on the boost level.

    I would think that a 350cfm carb will move a lot more air under boost just like n/a throttlebodies can be very small on turbo cars but need to be massive on n/a cars.
    Brent GREAT DEPRESSION RACING 1992 Duster 3.0T The Junkyard - MS II, OEM 10:1 -[I] Old - 11.5@125 22psi $90 [U]Stock[/U] 3.0 Junk Motor - 1 bar MAP [/I] 1994 Spirit 3.0T - 11.5@120 20 psi - Daily :eyebrows: Holset He351 -FT600 - 393whp 457ft/lb @18psi 1994 Spirit 3.0T a670 - He341, stock fuel, BEGI. Wife's into kid's project. 1990 Lebaron Coupe 2.2 TI/II non IC, a413 1990 Spirit 3.0 E.S. 41TE -- 1993 Spirit 3.0 E.S. 41TE -- 1994 Duster 3.0 A543 1981 Starlet KP61 Potential driver -- 1981 Starlet KP61 Parts -- 1983 Starlet KP61 Drag 2005 Durango Hemi Limited -- 1998 Dodge 12v 47re. AFC mods, No plate, Mack plug, Boost elbow -- 2011 Dodge 6.7 G56

  7. #27
    Moderator Turbo Mopar Staff Force Fed Mopar's Avatar
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    Re: My 68 Homemade Turbo Slant6 Dart

    I would just bump the timing 2 degrees and see how it does
    Rob M.
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  8. #28
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    Re: My 68 Homemade Turbo Slant6 Dart

    I too believe 350 is plenty, because if you look at it mathematically, it only takes 325 cfm to turn a 225 cubic inch motor @ 5,000 RPM if the volumetric efficiency "were" 80%. 500 is just adding another power valve and jets that i have to play with - while it does add another "stage" that would be nice, I'd like to dial in this carb first. Once I get the timing chain and oil pump off, I'll take a look at the cam if I can. Hopefully it is not rounded like Bakes is saying.

    Maybe I am misinterpreting it - the car does not run bad - and is very nice - but I feel it should make more power under the current setup based on other stock builds which also use 350 carbs.

    Ondonti I was running 87 stock after I got hardened valve seats installed so that it would be possible - before that I ran premium just to prolong the life of those - which ultimately failed 6 months into owning the car and dropped two exhaust valves (the car still ran on 4 but really slow) - to prompt an entire head rebuild. That was probably the best deal around - $270 got the whole thing redone - new valves, seats, springs, hot tanked, painted, resurfaced, new push rods - etc.

    As for the new distributor - on the top plate, on a normal distributor - it pulls and moves the plate over and advances, then gets let go to the 0 position. On this one, the groove was enlarged by the previous owner, so the plate can move forward and back and uses a combination of the volvo plate and arm so the pow connects. This move with the 240t distributor has been talked about on occasion with slant6s but I've not seen one used yet. The plate moves in either direction with a connecting rod to the diaphragm. On a stock mopar one, it only pulls with the vacuum. The swap itself is done a lot of times on Volkswagons and some other Turbo cars - not a whole lot of experimentation with slant 6's though. AS far as i know the original owner never actually used it - he just had plans to. I finished assembling it as it was still a bunch of parts when I got it and am thinking it could work nicely.

    This is the 1982 240t Volvo Unit in Entirety:






    And the Mopar Stock Electronic Ignition 6 cylinder Distributor:



    And this is my distributor:








    I feel like it is ready to use, but I don't have any information on how far the timing will back off under boost or how it reacts to anything - and would only be able to tell if I installed it on a Dyno.

    ForcefedMopar - I am not against doing that. I can do that till it pings and see where it gets me.

    But Ondonti - I like what you're saying about setting timing to come in in stages. What would i have to do to work that out? I have a MSD 6aln ready to go - but what would need to be run off of it? I feel if I did it that way, I could just divert the current distributor to its normal governing plate and curve, and then retard it electronically with that. I'm assuming there's possibly an MSD compatible unit for it? ANd if so how/ and how well does it work?

  9. #29
    Moderator Turbo Mopar Staff Vigo's Avatar
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    Re: My 68 Homemade Turbo Slant6 Dart

    but I feel it should make more power under the current setup based on other stock builds which also use 350 carbs.
    I think you're right about that. Even if the thing didn't make a lot of horsepower, i would think a low-rpm-biased 225ci engine with 8 psi should be making well over 300lb ft of torque, even over 350.

    Dont push the red button.You hear me?

  10. #30
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    Re: My 68 Homemade Turbo Slant6 Dart

    Hmmm still think 350 cfm is to small as per carbs from back then from personal experience they really didn't flow what they were rated at when put on flow bench bet if would be closer to 275 cfm

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