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Baja Forums -:- AzBaja.com Members -:- Projects and Builds -:- looking for tourque
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looking for tourque
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CoachBock
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Post Post subject: looking for tourque
Posted: Tue Oct 16, 2012 08:00 PM
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Getting ready to build my sons, 1641 single port, and wanted to get a little more torque out of it. Thinking about shaving the heads, to boost the compression ratio. Not sure how much to go, thinking about .040, is that to much or to little. Thoughts and opinion's would be useful.


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Post Post subject: looking for tourque
Posted: Wed Oct 17, 2012 03:24 AM
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I would need deck higth and head cc numbers to tell you how much you could safely take out. You might consider getting some dual port heads and a better carb for more power or change the cam to a 110 or something like that.

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Post Post subject: looking for tourque
Posted: Wed Oct 17, 2012 03:24 AM
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I would need deck higth and head cc numbers to tell you how much you could safely take out. You might consider getting some dual port heads and a better carb for more power or change the cam to a 110 or something like that.


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Post Post subject: Re: looking for tourque
Posted: Wed Oct 17, 2012 11:07 AM
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You need to calculate compression you don't want to be buying race gas.
CB cheater cam is going to give you more torque. The Engle W 100 would be a good choice with a Zenith carb and a bit of home made head work. An FK 41 would also be nice.

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Post Post subject: Re: looking for tourque
Posted: Wed Oct 17, 2012 11:07 AM
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Double post Sad


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Post Post subject: Re: looking for tourque
Posted: Wed Oct 17, 2012 11:08 AM
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Darn triple post


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Post Post subject: looking for tourque
Posted: Wed Oct 17, 2012 01:57 PM
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Cb cheater cam, little port work, id say stay around 8 to 1. maybe some 1.25 ratio rockers (if you port the heads), A good svda distributor and Zenith (Great carb) or maybe a 36mm dellorto with empi sp end castings.


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Post Post subject: looking for tourque
Posted: Wed Oct 17, 2012 05:38 PM
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If you want more torque from a VW, which is good for general purpose off-road use, porting the heads is not gonna do that for you. That will improve high-rpm wide-open throttle though, which would be good for sand dunes.

I recommend staying away form rowdy cams too. The Engle 100 or 110 is about as big of a cam as I would go for. Likewise, bigger ratio rockers are again good for dunes, not so good for general offroad.

Keep the carburetion on the smaller side too as that will provide low-down grunt.

I used to know a guy who ran a 2110 stroker engine (more stroke increase than bore, but I don't remember what the specific combo was to get there, maybe 82 x 90.5?) with a stock cam, single port heads and a pretty stock Solex 30-PICT-1 carb. He went places that other guys with screamin' 2332 engine's with dual webers and big cams couldn't get their cars to. And he just chugged along and smiled about his good gas mileage. He never seemed to break his stock gearbox either. But to each his own.


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Post Post subject: Re: looking for tourque
Posted: Wed Oct 17, 2012 08:05 PM
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I should say when I said port in this case it is just cleaning things up a bit smooth out a few tight turns. Port volume needs to stay as close to stock as possible. Like stated it is all about bottom end. Most stock suspension vehicles are going to driven from idle to 2500 rpms. Now if you want to get adventurous build a 76x 85.5 about 1750 CC. You can find a cheap stroker 76 mm crank for under $200. That and the cheater cam should really shine.

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Post Post subject: looking for tourque
Posted: Wed Oct 17, 2012 10:31 PM
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I somewhat disagree, porting can help everywhere, if done correctly most people just go and hog out the port and that will hurt performance thinking bigger is better.

Basically the short side of the pocket need a good radius, If you are replacing guides, you can open up the area where the "guide boss" is, this making the pocket larger, doing this will allow more of the valve to be used. Slightly opening up the port (couple cfm on the top) entrance, will help some. You can add CCs to the port and still pick up FPS. You just need to work the port where it needed. Along the same point, lots of people say adding larger valves hurt low end, but if done right , you can pick up low end torque and horsepower. If you cut the intake to a 30 degree, add a 39mm intake valve, you will really pick up flow in the .350 and under. This also allows you to get rid of the crap that is in the pocket since you can open up the throat some more. Also allowing more material to get a nice short side.
For example I just finished up a set of 350 SBC heads, intake flowed 203 at .500 and had FPS (velocity) of 219, and an intake volume of 158cc. After some mild port work described above, Flow went to 239 at .500 FPS went to 255! and the port volume is now 170CCs. Having a flow bench help to determine what helps and doesn't.

Ratio rocker DO help if the head will flow well into the lift range of the cam It wont help much bellow 2000 to 2500 but will help a lot in the midrange. If your head stalls at .400 lift then no real point in adding ratio rockers, but if your heads flow to .450 then why not use the flow potential of the heads. The higher lift will add some higher rpm power, but its area under the curve that it really shines. A cheater cam only has .398 lift with 1.1 ratio rockers, figure you lose .004 through lash and probably another .008 through pushrod deflection, your not talking about a very big cam. Adding 1.25 rockers will take you to .448 minus the above pretty much in the sweet spot of mildly ported vw heads. I've found duration of the cam effects rpm range of the most. then Lobe centerline, then lobe separation, then lift. And lift only changes rpm through the flow pattern of the head. If the head will flow well into the lift range, you will pick up power everywhere. Heck 1.25 ratio rockers seem to work well with the stock cam, if you aren't looking at going aftermarket cam.


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Post Post subject: Re: looking for tourque
Posted: Sat Oct 20, 2012 09:30 PM
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perrib wrote:
I should say when I said port in this case it is just cleaning things up a bit smooth out a few tight turns. Port volume needs to stay as close to stock as possible. Like stated it is all about bottom end. Most stock suspension vehicles are going to driven from idle to 2500 rpms. Now if you want to get adventurous build a 76x 85.5 about 1750 CC. You can find a cheap stroker 76 mm crank for under $200. That and the cheater cam should really shine.

madman74 wrote:

I somewhat disagree, porting can help everywhere, if done correctly most people just go and hog out the port and that will hurt performance thinking bigger is better.

Basically the short side of the pocket need a good radius, If you are replacing guides, you can open up the area where the "guide boss" is, this making the pocket larger, doing this will allow more of the valve to be used. Slightly opening up the port (couple cfm on the top) entrance, will help some. You can add CCs to the port and still pick up FPS. You just need to work the port where it needed. Along the same point, lots of people say adding larger valves hurt low end, but if done right , you can pick up low end torque and horsepower. If you cut the intake to a 30 degree, add a 39mm intake valve, you will really pick up flow in the .350 and under. This also allows you to get rid of the crap that is in the pocket since you can open up the throat some more. Also allowing more material to get a nice short side.
For example I just finished up a set of 350 SBC heads, intake flowed 203 at .500 and had FPS (velocity) of 219, and an intake volume of 158cc. After some mild port work described above, Flow went to 239 at .500 FPS went to 255! and the port volume is now 170CCs. Having a flow bench help to determine what helps and doesn't.

Ratio rocker DO help if the head will flow well into the lift range of the cam It wont help much bellow 2000 to 2500 but will help a lot in the midrange. If your head stalls at .400 lift then no real point in adding ratio rockers, but if your heads flow to .450 then why not use the flow potential of the heads. The higher lift will add some higher rpm power, but its area under the curve that it really shines. A cheater cam only has .398 lift with 1.1 ratio rockers, figure you lose .004 through lash and probably another .008 through pushrod deflection, your not talking about a very big cam. Adding 1.25 rockers will take you to .448 minus the above pretty much in the sweet spot of mildly ported vw heads. I've found duration of the cam effects rpm range of the most. then Lobe centerline, then lobe separation, then lift. And lift only changes rpm through the flow pattern of the head. If the head will flow well into the lift range, you will pick up power everywhere. Heck 1.25 ratio rockers seem to work well with the stock cam, if you aren't looking at going aftermarket cam.

Yeah, OK guys. I'm not totally opposed to porting, but so very many just flat ASSyou-me that means hog it out big. The guy said he's looking for "more torque". In a mild engine which doesn't get revved to the redline all the time, too smooth of an intake port can lead to the fuel dropping out of the airstream. Big carbs and big ports contribute to that. A little texture in there from the casting process can contribute to surface turbulence in the port to keep the mixture moving around and the fuel in suspension. Bad thing at wide open throttle, high rpm. But good at low rpm, part throttle I've seen so many offroad cars fall flat on their face after getting nothing other than porting...And the guys never seem to understand why. Like Perry says, unless the chassis and suspension is there to handle high speed and that is how it's gonna be used, most porting and bigger cams and big carbs are wasted in a Baja or even in most buggies.


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Post Post subject: Re: looking for tourque
Posted: Sun Oct 21, 2012 07:44 PM
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In a mild engine which doesn't get revved to the redline all the time, too smooth of an intake port can lead to the fuel dropping out of the airstream.

You are wrong. Ever heard of " boundary layer " ? Look it up

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Post Post subject: looking for tourque
Posted: Sun Oct 21, 2012 09:30 PM
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OK...I'll bite.

At one point in my career, I was a student of aeronautical engineering , including aerodynamics. YES I've heard of boundary layer. But...There's always more to be learned.

So I DID look it up on Google search:
One of the very 1st items which showed up was this article:

It tells of how boundary layer flow causes fuel to precipitate out of the air stream onto the surface of a smooth port and how that results in a waste of fuel and reduced power and why it is better to have a rougher surface inside of a port as I was saying.

As with any subject, there are going to be differences of opinion. So with that basic premise in my mind, I'm not going to tell you that you're absolutely unequivocally wrong and foolish. But the article cited above supports my views on this subject.


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Post Post subject: looking for tourque
Posted: Mon Oct 22, 2012 08:38 AM
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The article above is still talking about porting the heads, and seeing an improvement, in all around power.


Polishing is different than porting. Polishing the intake runners is a no no (exhaust and combustion chamber are different or direct injection EFI). A 40 grit cartridge roll leaves enough texture in the walls to not have to worry about fuel separation. Also the flow bench don't lie, if the FPS goes up its going to be a more responsive port. Think of it this way. A 1"dia 45 deg angle is going to flow more and have a higher velocity than a 1"dia 90 deg angle. And why is this? turbulence in the port! Porting doesn't mean that you have to hog out the port, porting can mean that you are trying to take control of how the air and fuel get to the combustion chamber. Smoothest flowing with the least turbulence and, allows more use of the valve. And this can pick up flow in the low valve lift ranges, thus boosting power from idle on up!!!

If an engine falls flat on its face just because of porting, then somebody doesn't know what the heck they are doing with a grinder! Or somebody doesn't know how to build the engine, or tune to take advantage of the extra flow. Now too big of port(volume), is bad, too big of cam is bad, too low of compression is bad, too big of carbs is bad, too low of velocity is bad, too much head flow (cfm) no such thing. Another nice thing about a higher flowing port, is you can use a High lift, lower duration cam and make more power than a longer duration cam in a lower flowing head.

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Post Post subject: looking for tourque
Posted: Tue Oct 23, 2012 11:10 PM
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madman74 wrote:
If an engine falls flat on its face just because of porting, then somebody doesn't know what the heck they are doing with a grinder! Or somebody doesn't know how to build the engine, or tune to take advantage of the extra flow.

OkMadman...now you're talking...and we're agreeing.

I just encounter SO many people around motorsports who ASS - U - Me (and if one is going to assume - I demand they leave "me" out of it!) that "porting" automatically includes polishing and only look at the maximum horsepower number that comes out of a dyno pull. Life isn't all about a drag race.

Desert and mountain offroading (as opposed to sand dunes or mud-bogging) in particular require a broad power band that a drag-race oriented sort of build isn't gonna work well for. There are good reasons why from 1975 to the 2013 season superchargers have been banned from offroad racing and the all-time winningest engine combo is a VW Type 1 2180 with relatively stock dual port heads and a single Zenith 32NDIX carb. There are a lot of engine combos that make more hp, but it took nearly 30 years to make any of them consistent winners. And those still cost more$$. And lots of times, even against modern alternatives, I've watched 80hp VW 1600s with a stock 30PICT-1 carb, un-touched ports and VW-based suspension with 10 and 12" travel cars beat 700hp/28" travel cars for overall wins.


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