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| guess of horsepower gain if .... https://slantsix.org/forum/viewtopic.php?t=42900 |
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| Author: | SCOTT EVIL [ Wed Dec 15, 2010 5:16 pm ] |
| Post subject: | guess of horsepower gain if .... |
My 1968 Dart Slant is completly stock. Advertised horsepower is 145. If we keep that as the beginning base measurement, how much more horsepower for each of the modifications below: Offenhauser dual single barrel carb manifold. Maybe an increase of 10 hp? And then from the base engine, I will later machine the offenhauser dual manifold to adapt 2 two barrel carbs. Maybe an increase of 15 hp above the original 145? I understand that there are more and better intake systems out there but just want to play with this first. Thank guys and Happy Holidays ! |
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| Author: | brian72valiant [ Wed Dec 15, 2010 7:43 pm ] |
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ive been doing alot of research about this / building power on a slant - and it seems like there are some realley good ways about doing so - the dual single barrel intakes sound fun if you can get the linkage right and make it work with the kick down cable for the tranny if your using an automatic. exhaust is going to have to be looked at - as well as a set of dutra duals, I would imagine would be the "best" way to add a dual system. dual 2" exhaust pipes are recomended for the dutra duals all the way back to your choice of muffler but internal work on the engine will probably bring it all together. doing single things at a time might not yeild much until you have the valves redone and port match everything - deburr everything and just port work a little to help flow. cam / decking the block for compression ext... will all add up to a really powerful slant in the end... but from what I gather from reading around on the subject - it all needs to be done to achieve the desired effect. going piece by piece about it might not help until the end when its all done edit - I have been looking about this for my car also because - its a show car - not in the sense of a trailor queen - but its got fancy paint - and id like to be able to hot rod around in it some. and be realley proud to show off my engine bay at the shows it attends. my car actually is no slouch already. its stock 225 and single barrel / auto from 72 actually has some go to it off the line and getts up to speed nicely so there is no complaints - but at the same time id like to improve what I already have at the same time re building possibly a new 225 block to the hot rod specifications and when its done - just swap it in. the only thing id like to not do is - multiple carbs - and I want to keep single exaust. so im going to have 2.25" exaust pipe made for my viechle with a standard turbo muffler for a nice quieter sound... my tire size I run are 255/80/13 wich I believe is quite smaller than the stock spec tire for my car - so by using a smaller diamater tire - I have effectively changed my rear end gear ratio to something higher.... how much im not shure - but I can tell that this has helped me off the line a bit. what it has not helped with is highway speed - as im now croozing 55 mph at about 2200 rpm vs the stock size tire i believe would be a bit less rpm / fuel consumption from the engine... ive also been doing alot of reading in the section of efi / tbi here to see how guys are using electronic fuel metering to help. I also know that the "vintage hotroder" guys have developed some 1 barrel carb look alikes that are actually throttle boddies with fuel injectors for efi setup - but look like old style 1brls. usualy see them setup as a 6 pack on a retro chevy or something - but us slant sixers are pretty creative so im shrue some one will adopt them sooner or later. |
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| Author: | wjajr [ Thu Dec 16, 2010 6:50 am ] |
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The published HP & Torque from the sixties were measured at the fly wheel with no accessories attached to an engine. By today’s measurement methods these engines would yield numbers closer to 100 HP, less than most modern four cylinder engines make… A compression increase, gasket matching & mild porting, exhaust enlargement, and distributer recurve will generate more power per dollar when upgrading a stock engine. Larger cams & carburetors won’t yield much until compression and engine breathing has been improved. The next step up would be Super Six, possibly over sized valves, a cam upgrade, and duel exhaust (headers, or Dutra’s) into a “Y†pipe. Next would be drive train changes, suspension up grades, and tire & wheel changes. It never ends, making a perfect example of “Mission Creepâ€â€¦ Check out Aggressive Ted’s engine build for torque & mileage. Dream Department: Also take a look [url=http://flag.blackened.net/mopar/] here[/url], and [url=http://slantsix.org/articles/Josh_Carb_Article.htm] here[/url], and [url=http://slantsix.org/articles/Slant%20Six%20Racing%20Manual.pdf] here[/url]. |
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| Author: | Aggressive Ted [ Thu Dec 16, 2010 10:50 am ] |
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Scott and Brian, Putting a bigger carb on a SL6 doesn't make a lot difference if everything else is stock. The Super Six (two barrel) made a little difference but not a real big change. I can't say enough about the effects of increasing compression on the SL6. It makes a huge difference! Any where from 9 to 1 to 9.5 to 1 really wakes up the motor and that is leaving everything else near stock. I pulled the EGR, OSAC, timers etc. and made the engine look like and earlier version from the late 60's. Click on the red link below my name to view pictures. Performance upgrades that make a big difference. Compression increase would be my number 1 choice. Second would advancing the cam or having yours reground for more torque and advancing it. Mine is reground to the RV10 specs. Third is re-curving the distributor. Fourth would be going to 2.25" exhaust and bigger freer flowing muffler similar to what they did on trucks and vans. Fifth would be going to electric fan to save some HP. The electric fan has many benefits besides increasing HP. It lets the engine warm up quicker, and reduces heat soak for better mileage. After these upgrades, then carburation changes would make a bigger difference. There are many other changes that help performance too like porting, bigger valves, etc.......the list goes on. Look in the Engine FAQ for engine builds. |
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| Author: | Ron Parker [ Thu Dec 16, 2010 4:59 pm ] |
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Scott what do you want. A street car, a street/strip car or a race car. You can not have all of the above unless you have a lot of money to put into this. And one end will be not practable. Thanks Ron Parker  Bagel Could Not Beat Me If He Had Four Nitrios Bottles Two Bamboozlers And A Partiaege In A Pair Tree |
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| Author: | Brussell [ Thu Dec 16, 2010 11:54 pm ] |
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My two cents, Get compression done. And do some head work. Port and upgrade valves (handy if it's not unleaded compliant). Then carb upgrade and bigger exhaust. (here you will notice a bigger difference than if you did this first to a stock engine) In australia I know all this can be done for around $1500 for all brand new items doing virtually no work yourself. However if you know the right people and are great at junk yards etc and good at wielding you'll get it done for maybe 1000 - 1200 $. Then get a different cam. |
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| Author: | Brussell [ Thu Dec 16, 2010 11:57 pm ] |
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Just to add with the upgrades I mentioned a better ignition is always a good idea. However not sure what is currently in your slant. I changed mine in my 67 and noticed a difference in drive ability, though that could be because the current dizzy was so far gone. |
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| Author: | SCOTT EVIL [ Fri Dec 17, 2010 4:54 pm ] |
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Thank you all, I really dont have a performance goal, I am just going to add this and wondered about the gain. I can take the car to a dyno shop for a baseline before reading. This is just a for fun thing I want to do, not race or max it out attempt Happy Holidays |
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| Author: | 66aCUDA [ Sat Dec 18, 2010 4:37 am ] |
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Scott other than the baseline HP I would think with proper tuning your goals of 10 and 15 would be accurite. Frank |
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| Author: | Sam Powell [ Sat Dec 18, 2010 5:36 am ] |
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Everyone has their own path down the mod lane. Some are equal, and others are not. IWayne is right in saying that until you get each phase of the engine working right you will not see much improvement, but I don't think there is any silver bullet. You kind of do what you have money for, and use what shows up first. If you come accross a good super six set up. There is nothing wrong with putting that on next. Here is what I experienced with mine. 1. The electrical systems on these old cars will really hold it back. Check out the charging system and ignition wiring for volatage drop and replace wire and connectors where you are experiencing voltage drop. 2. The Super Six upgrade will give you another 500 RPM and better economy. Plus the BBD two barrel is more tunable than the one barrel. When I put this on my car years ago it ran out of steam at 4500 rpm instead of 4000. 3. Bigger exhaust is nice, but if you are running a carb, you will want carb heat for cold start drivability. So, don't throw away your carb heat exhaust manifold unless you have some other way of providing heat to it when the carb is cold. 4. Electronic ignitions are more reliable than points, but are not necessarily better, especially if your wiring is such that you are experiencing voltage drops. The old points system was not as sensative to voltage loss as the electronics are. 5. The electric fan is a good addition. You feel this at the higher RPM especially where the mechanical fan blade really starts to drag. I think I went from 4500 RPM to 5K when I put the electric fan on. So the 2bbl and the fan seemed to net another easy 1K of RPM that did not feel like the poor engine was going to sue me for abuse. 5. A distributor recurve will yield more usable HP and better economy. It is not hard to do, but it is hard to test results. And it is hard to fiddle with it, as you must take the distrbutor apart each time you want to make a change. Emsvital has some great charts he has developed for good curves, and Doc has a thread on how to that you can look up. Do a lot of reading here. There is much good advice. Have fun, and keep us in touch with your projects as you get to them. And Ron is right. Y0u can build a good daily driver slant, or a very fast track car. To combine the two is pretty hard to pull off. I think the guys who drive their cars to the track and race them get in the 14's and 15s without too much hassle on the street. That guys who turn in the 12's and 13's that I have seen often tow their cars to the strip. Folks who drive their slants to the track and turn in the 12's and below are the rare exception. Sam |
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