I'm looking for an engine recipe.

[liquidrush]

I'd like all the power to be from off idle to about 4 or 4500. If it's possible it'd be nice to do everything as bolt on. In other words not a bunch of machine work outside of the regular stuff like align bore. I'd like to be able to hang a set of cylinders and pistons on, buy a crank and rods, a camshaft and use stock type dual port heads. Or am I being too wishful.

[toddb_67]

One popular build is the 1800cc "no machining combo" using a 74mm crank (biggest crank that fits into a stock VW case without clearancing) and 88mm thick wall pistons/cylinders that fit in a stock case opening but uses a head opened for 90.5mm pistons/cylinders (the cylinder walls are actually thicker than stock). Great alternative to a stock 1600cc rebuild and gives you a little more power.
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1974 Karmann Ghia- current project, 1967cc engine. https://www.thesamba.com/vw/forum/viewtopic.php?t=775207
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[Brian_e]

You need to figure out how much power you want, then design the engine around that. Wanting idle to 4500rpm power, and easy to assemble, but no HP target sounds like a bone stock 1600cc build to me.

Brian
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[Zundfolge1432]

Actually if you go back to main page look at top FAQ and stickies you find dozens of possibilities
https://www.thesamba.com/vw/forum/viewtopic.php?t=536400

[liquidrush]

Right now I have a pretty much stock 1600 that I rebuilt a year or so ago, it's in a buggy, it runs good but lacks power in 4th gear, especially on hills. At 50 mph in 4th the rpms are around 2500. Most of the driving I do is back road or gravel road and I rarely see 60mph but on hilly roads I can't maintain steady speed. I recently installed dual carbs which helped power but I'm still lacking that power on hills. It made enough power to cause slippage on the180mm clutch so I replaced it with a 200 and cured that issue. I'm thinking if I added some CC's and some HP it'd help out.

[vwracerdave]

Part of your lack of power in 4th gear may be gearing. What transaxle do you have? what size rear tires?
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2017 Street Comp Champion - Thunder Valley Raceway Park - Noble, OK
2010 Sportsman ET Champion - Mid-America Dragway - Arkansas City, KS
1997 Sportsman ET Champion - Thunder Valley Raceway Park - Noble ,OK
Featured in Dec. 2001 HOT VW's Magazine page 63

Watch my racing video's http://www.youtube.com/user/okvwracer/videos

[liquidrush]

67 swing axle. We've talked about this before here, I think the general consensus was that I have tall rear tires but not excessively tall for my setup. Goodyear Wrangler 235 75 15s

[Brian_e]

Big heavy tires kill power BAD.

Have the gearing reworked so the peak torque is right near your cruising speed. Right now you are probably way below the peak torque.

A bigger engine will help, but it will also be way below its peak torque.

Brian
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[sled]

according to the math, if you have a stock 67 trans with those tires, you're only turning around 2150 rpms at 50. Thats far too low for an otherwise stock engine. Dual carbs do not really add any power to stock engines at lower rpms. They may add some up top.


regardless of engine, I would address your gearing first. Once you gave that optimized, a larger more powerful engine would definitely be more fun.
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drive your split.

[GMendoza]

Displacement = torque
torque and RPM determine horsepower.

Since you want to keep RPM low, increasing displacement is the way to go to add HP.

If you are OK having a case line-bored, machining your case and heads for larger cylinders should be no problem.

For your goals, a 1914cc with 94mm pistons, stock crank, cheater /small cam, stock 043 heads would be very easy to build, drive like stock and have much more torque.

[cbeck]

235 in the buggy world doesn't seem all that big. That is what is on the front. I vote close ratio 3+4 in the trans. I did a 4.375 rp, 1.46 3rd, and 0.93 4th. If I had a do over, 4th would be steeper. 3rd pulled almost as hard as 2nd.

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My cut in half and rebuild thread
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[GMendoza]

[Mikedrevguy]

Drive it as a 3spd with overdrive.
The combo you have should comfortably cruise at 60 in 3rd gear. (3700rpm?) Even better if you put a CW crank in when you re-did it.
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[oprn]

The tires are the problem in my opinion. You could easily spend $2500 on your upgraded engine and still have the low RPM problem in 4th gear or spend $200 on shorter tires and fix the problem... your choice.

Another option I suppose is a Bus transaxle. That is what I did and with 26" tall rubber about 12" wide on 14" x 8" rims mine is running 4000 RPM at about 60 MPH in 4th gear. All the power I could ever need with a 1600 SP engine for off road trail use.
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[cbeck]

[vwracerdave]

A larger engine will always add torque. The no machine 1800cc engine is a great engine for people on a limited budget and when machining is an obstacle. 74mm crank & 88mm pistons, slightly bigger cam, fluff & buff port job on stock valve heads, and dual carbs would make a fun 80-85 HP engine.

https://www.aircooled.net/1800cc-vw-engine-no-machine-combo/

Engine and gearing must always be discussed together in all performance and off-road vehicles. Your buggy should be lighter than a Bug. It takes a lot of horsepower to turn large heavy rear wheels. Same principal as a heavy/light flywheel on the engine.

Many years ago I switched rear wheels on my drag Bug. I went from a heavy cast aluminum wheel to much lighter Centerlines. With the same rear tires, I ran .3 seconds quicker in the 1/4 mile just because of the lighter wheels.

Many years ago I had a '69 class 11 style Bug with 30" rear tires. It had the same 4.12 R&P and stock gearing you have in your '67 swing axle trans. With a stock 1600cc engine I would run that car flat footed, pedal to the floor, and never go faster than 65 MPH. When I put a 1756cc engine with 80 HP it would max out about 70 MPH on the highway. When I put the 1756cc in my Fiberglass Dune Buggy with 26" rear tires it would do 90 MPH easily.
_________________
2017 Street Comp Champion - Thunder Valley Raceway Park - Noble, OK
2010 Sportsman ET Champion - Mid-America Dragway - Arkansas City, KS
1997 Sportsman ET Champion - Thunder Valley Raceway Park - Noble ,OK
Featured in Dec. 2001 HOT VW's Magazine page 63

Watch my racing video's http://www.youtube.com/user/okvwracer/videos

[liquidrush]

What size tires do you recommend I try?

[vwracerdave]

We can help with the engine details. You'll have much better luck talking about gear ratio's & tire size for a Buggy in the HBB Off-Road Forums.

For a mostly stock engine and stock geared transaxle with a 4.12 R&P, I'd suggest you try stock sized rear tires under 26".

IF you really want to keep those 28" rear tires on an off-road buggy you are gonna need a gear change.
_________________
2017 Street Comp Champion - Thunder Valley Raceway Park - Noble, OK
2010 Sportsman ET Champion - Mid-America Dragway - Arkansas City, KS
1997 Sportsman ET Champion - Thunder Valley Raceway Park - Noble ,OK
Featured in Dec. 2001 HOT VW's Magazine page 63

Watch my racing video's http://www.youtube.com/user/okvwracer/videos

[Danwvw]

Well you would have to come down in tire size which I wouldn't do I would bore and stroke that dual port! Maybe 78mm and 90.5mm Bore. But even that less expensive 74mm X 88mm 1799cc-1800cc upgrade would make a huge difference, just a little cam and look into some kind of better carburation. Dual Carbs perform the best for the money but in the dirt many prefer a single carb.
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[Paul Jr]

I agree with not going smaller on tire size. Especially if you plan a good bit of off road use.
My second thought with that would be if you really want to build it bigger/ better, just bite the bullet and do the machine work for bigger pistons when your having the align bore done.
74 x 94 = 2054 with very minimal clearance if any at all
76 x 94 = 2109 with the right rods means very minimal internal clearencing also.