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Tue Mar 10, 2015 4:14 pm

I have a 1969 bug and was told it had a 1641cc when i bought it, what is the differance between a 1600 and a 1641cc. I need to replace my heads, what size would I be looking for (single port)

Tue Mar 10, 2015 4:29 pm

A 1641 has "slip in" 87mm pistons/cylinders. The head size should be the same.

Tue Mar 10, 2015 5:56 pm

69mm stroke by 87mm bore. Stock 1600 was 69 by 85.5. Same heads as stock. 87mm pistons just slip in.

Tue Mar 10, 2015 8:17 pm

1641 cc is just the piston/cylinder displacement. When I build my 1641 cc, I swapped out the stock crank for a counterweighted one matched to a lightened 12.5# 8 dowel flywheel, swapped an Engle 110 cam, new heads with larger valves, dual Dellorto carbs and a good flowing exhaust. So devil is in the details. Likewise, a 1914 cc can be a real dog if all other bits are left stock.

Tue Mar 10, 2015 8:45 pm

The difference is a false sense of power.

Tue Mar 10, 2015 8:50 pm

Brian wrote: The difference is a false sense of power.

That's not true...

-jeffrey

Wed Mar 11, 2015 5:38 am

bruce pattison wrote: I have a 1969 bug and was told it had a 1641cc when i bought it, what is the differance between a 1600 and a 1641cc. I need to replace my heads, what size would I be looking for (single port)

Out of interest, what carb are u running? You can put dual port heads on and change the intake manifold if u want. Might even be cheaper/more choice on DP vs SP heads.

Wed Mar 11, 2015 8:51 am

1641.. Thin wall slip in cylinders.

Tend to warp with heat. Don't last nearly as long as 1600.

Tue Mar 17, 2015 2:07 pm

Not to steal the thread but i have a 1600 dp . I bought 87mm slip ins and a 110 cam and was told by the dealer this would make it a 1776cc

Tue Mar 17, 2015 2:15 pm

wcagle33 wrote: Not to steal the thread but i have a 1600 dp . I bought 87mm slip ins and a 110 cam and was told by the dealer this would make it a 1776cc
The dealer's wrong.
http://www.cbperformance.com/v/enginecalc.html

The formula is bore x bore x stroke x .0031416 = 4 cylinder engine displacement.
You can't have a 1776 cc without machining case and heads.

Tue Mar 17, 2015 5:22 pm

Brian wrote: The difference is a false sense of power.

Totally wrong on this Brian. While I am not in favor for any slip ins for longevity. The 87mm are not that bad. You do get an increase in HP cheaply, and if you get a good quality set (rings especially), they can last for many miles. However, I would not go slip in 88s. unless it was for a budget sand rail build. The main concern ( and this is for ANY air cooled engine), is that you do not overheat the engine.

Once the engine temps reach a certain point, the cylinders lose their integrity, and can no longer stay true (think wavy). Then the rings can not compensate for the difference in the cylinder bore, and you get blow by and loss of power. Luckily, if the P&C set is good quality, once the engine has cooled, the cylinders usually return to their normal state.

Learned this info in the late 70s on air cooled dirt bikes. After the 30 minute mark in a moto, the average engine would actually lose around 25% of its HP, because of the expansion differences between the cylinder, pistons and rings. VWs do not lose this much HP due to the different materials used, but it still exists.

Tue Mar 17, 2015 5:49 pm

wcagle33 wrote: Not to steal the thread but i have a 1600 dp . I bought 87mm slip ins and a 110 cam and was told by the dealer this would make it a 1776cc

Ummm, sounds like that new math is tough for that dealer. Unless that nice cam has increased the displacement.

Tue Mar 17, 2015 5:50 pm

Welcome Bruce. Why do you think you need new/replacement cylinder heads?
Bill.

Tue Mar 17, 2015 5:51 pm

I had a 1600 and then a 1641 with the same components. They ran the same, never overheated and lasted a long time. Nothing wrong with them at all, but it's much better to go bigger.

Fri Apr 10, 2015 5:20 am

If you toke a 1500 sp and droped in the 87mm slip ins but left everything else stock would this still be a 1641? And will it all work?

Fri Apr 10, 2015 7:46 am

wcagle33 wrote: If you toke a 1500 sp and droped in the 87mm slip ins but left everything else stock would this still be a 1641? And will it all work? .....yes and yes.

Sat Dec 01, 2018 6:04 pm

wcagle33 wrote: If you toke a 1500 sp and droped in the 87mm slip ins but left everything else stock would this still be a 1641? And will it all work? hi did you build this after ...as i am doing it my self cheers fidh in nz

Sun Dec 02, 2018 7:08 am

My experience with 1641 slip-ins compared to a stock 1585 is about the same as Brians. (I otherwise have stock SP's)

All else being the same, your C/R should go from about 7.5 to 7.9 to 1. The 56cc increase in displacement along with the boost in the C/R will yield about 3-4 more hp around 3000 rpm which I believe is around the torque peak of a stock engine. (about 60mph)

I notice the 1641 difference mostly when I'm climbing a steep hill or bucking a head-wind. It's the difference between climbing a long grade doing 50-55mph instead of 40-45mph in 4th gear.

I have a spare stock 1641 engine I pulled that has over 160,000 miles that had good enough compression to start at -15 deg F. (I replaced it during a pressure plate change - didn't want to push the exhaust valves any further)

Tue Dec 04, 2018 12:31 am

goober wrote: My experience with 1641 slip-ins compared to a stock 1585 is about the same as Brians. (I otherwise have stock SP's)

All else being the same, your C/R should go from about 7.5 to 7.9 to 1. The 56cc increase in displacement along with the boost in the C/R will yield about 3-4 more hp around 3000 rpm which I believe is around the torque peak of a stock engine. (about 60mph)

I notice the 1641 difference mostly when I'm climbing a steep hill or bucking a head-wind. It's the difference between climbing a long grade doing 50-55mph instead of 40-45mph in 4th gear.

I have a spare stock 1641 engine I pulled that has over 160,000 miles that had good enough compression to start at -15 deg F. (I replaced it during a pressure plate change - didn't want to push the exhaust valves any further) hi i am building a 1641 sp what carb are you using i have a 28 and a 30/2 carbs can i use ether if i change the jets if so what size jets would be needed cheers fish in NZ

Tue Dec 04, 2018 1:57 pm

"hi i am building a 1641 sp what carb are you using i have a 28 and a 30/2 carbs can i use ether if i change the jets if so what size jets would be needed cheers fish in NZ"

Hi nz fish

I'm running a H30/31 carb and a stock 205T vacuum only distributor with 28-29 deg max advance (@ about 3000+ rpm). Runs/pulls great. No hesitation anywhere.

I burn regular (87 octane US) when I'm only running around town. Mid-grade (89 octane US) on the highway. Premium (92 octane US) only when I'm laden down on long trips expecting all driving (uncertain) conditions. No problem with knocking or detonation.

As far as your setup, you'll have to wait for someone to chime in who knows more than me about what you have and what will work best. Sounds like what you have should work.