Single Port vs. Dual Port

[AlteWagen]

gearing WILL make a difference in how an engines powerband is applied

66 earlier had 4.37
67-72 had 4.12
73 up had 3.88

different first and 4th gears will make the "pull" feel different. In the later trans the final gear was modified to match the earlier final drive and IS NOT 1000 rpm difference!!

As far as the difference between SP and DP here are my observations (sorry no dyno sheets) in the same car with 437 trans. both had pic 30 and factory manifolds, stock cams

SP
Crisper throttle response
Never had a crack from valve to spark plug hole
Better low to mid rpm "feel"

DP
Soggy low rpm, but better mid rpm "feel"
Often see cracks from seat to plug
Less MPG

I put Kadrons on both and they BOTH woke up!! I will say the SP did stop pulling about 4200rpm where the DP dropped off at 4500. They both reved higher but no feeling of additional power was felt.

For me the SP head with single barrel carbs is a great set up. The DP with single barrel carbs took a bit more to sync and required the balance tube to idle smoothly.

I feel the fact that DP has one runner per valve allows the use of split duration camshafts when running dual double barrel carbs for maximum efficiency.

When running SP heads using dual single barrel carbs will maximize the performance significantly. If going bigger displacement with SP heads I recommend porting to allow more air to flow more freely allowing a more usable powerband

[jamestwo]

I say build the SP, dyno it and report back.
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hEY, lOOK, i'M WRONG HALF THE TIME, AND THE OTHER HALF i'M NOT SURE WHAT THE HECK i'M TALKING ABOUT. MY POST ARE FOR MY OWN ENTERTAINMENT VALUE ONLY.

[chased33]

Apparently, it is pretty difficult to find dyno sheets of this comparison. I guess I was more looking to professional builders who have built and dyno'ed many, many engines to see what the comparison is. (Which, I find it odd that none of the builders who are all over The Samba have made any comments)

I guess I was just looking for a sufficient argument for dropping the SP heads and going for DPs in a street driven vehicle. As of right now I am not convinced it is worth it to spend the extra $ on the DPs for a non-stroked engine. However, I no longer have the single port heads that I was going to use so I might end up with DPs. That is not to say that I am still keeping my eye out for some SPs, but don't want to spend more on them than duals.

If I do end up building the 1915 SP I will most definitely share the results (if I get it dyno'ed). My machine work will be done by Art at ACE, and I do know that he just built a 1915 DP with dual Kads that was dyno tuned so comparisons will be made...
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Chase

1972 Super Beetle (1641 SP)
2009 Trek 7.1 FX (daily driver)

[andk5591]

Art did the DP heads for my 1600 and also did the vac ports on the Kads. Absolutely top notch work. At the minimum get the port match on your heads.......
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D-Dubya Manx clone - 63 Short pan,1914.
Rosie 65 bug - My mostly stock daily driver.
Woodie 69 VW woodie (Hot VWs 7/12).
"John's car" 64 VW woodie - The first ever
Maxine 61 Cal-look bug - Cindy's daily driver.
Max - 73 standard Beetle hearse project - For sale
66 bug project - Real patina & Suby conversion
There's more, but not keeping them...

[grueni]

at art's place the blackline57 guys build the 1621cc 36hp engine with about 85-near 100hp at arround 5500rpm(depends on carb setup)...finished with a record on the salt.

[gothspeed]

[bikesndbugs]

Old thread but I have a 1600 dp currently and have a sp heads and an intake in my garage ive got a baja bug so more torque would be nice. Ive also heard a sp works better with the webber progressive. SO would it be a good idea to swap to the sp heads for more low end?

[Boolean]

Single port heads are worse than double port heads everywhere in the range. But they are much worse at higher rpms, so they may feel torquier than DP's, which they are not.
Want torque? Or rather, a lot of bottom end power? - Use DP heads, big capacity, and a stockish cam.
Havent tried a progressive with SP heads.
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I strive for perfection. Excellence will not be tolerated!
Build thread here:
http://www.thesamba.com/vw/forum/viewtopic.php?t=529379

[Bob Brugge]

Anyone that claims they can go over 77 MPH with a STOCK SP engine is lying. Straight up! Just take their advice right out of the mix. I can barely reach 83MPH in my 70 std bug with all stock 1600 except for the 87mm jugs.
Any engine will benefit from more air flow, whether it is through carburation, valve size, or cam lift.
I would guess that no one has bothered to put a larger than stock sp on a dyno. I think you are beating a dead horse.
Apples to apples? Get a set of both heads, try them out, sell the ones you don't use.
Easy peasy
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Keep on Dubbin'!

[AlteWagen]

[modok]

[bikesndbugs]

[Alstrup]

Line bored AS case.
Good used stock crank.
215 mm Flywheel, stock weight
Stock 215 mm clutch. All balanced.
Silverline main Bearings
Mahle rod & cam bearings
CB Unitech rods. 550 gr.
26 mm Shadek oil pump w. full flow system. Stock late model oil cooling + a thermostatic controlled steel cooler from a 34 hp engine, located between the struts under the car.
CB Thin line oil sump. 1,3 qrt.
Engle W100 cam installed on 106 ILC.
CB lightweight lifters.
90,5 mm Mahle cylinderset.
Sgl port cylinderheads, ported, chambers altered to a compact wedge style. Stock valve size. Intake flow 120 CFM at 0,500” and 25”. 9-1 CR.
Manton push rods.
Bolted CB rocker shafts w. 1,25/1,1 rockers.
34 mm PDSIT dual carbs from an early 1700 bus engine. Modified. CB sgl port manifolds w. 20 mm extensions to get more plenum area and also get a better intake length. 60 mm home made intake stacks, bus type hex bar linkage, modifiead to fit in a type 1 set up. When we were done they flowed 115 CFM @ 25” hooked to the heads.
Bosch 205 SVDA distributor from a type 4 bus engine, rebuilt and altered curve to fit the type 1 engine.
Older Scat 30 hp fan housing with doghouse and venturi ring, and large fan.
Stock heater boxes. Bugpack 1 3/8” header with twin Citroen BX 16 mufflers, exiting at the center of the car, giving a slight 356ish exhaust look.
https://www.thesamba.com/vw/gallery/pix/1194909.jpg

Recently built a 2007 cc. std plus sgl port for a split bus. Owner is currently sorting out some electrical issues. But when that is done it will hit the rolls. goal, 85 hp @ 4300 and 175 Nm torque.

If you build a larger than stock displacement engine, that can breathe better than stock too, with stock sgl port heads versus the same engine with dual port heads the latter WILL outperform the sgl port any day.
apart from that it is almost like comparing apples to oranges, because you are looking at two different engine behaviures.

T

[atticus finch]

[Alstrup]

Two words, forget it. The 30 mm will be so restrictive that - shall we say - reasonable power below approx 3000 rpm is what you will get

[atticus finch]

[andk5591]

Agree - with that displacement and that size carb, you will be starved at higher RPMs, but maybe you dont care....This is something that you can measure though...We did that on a dyno with dual 40mm on a 1955 to make sure I wasnt restricted and I wasnt.

There is more to this subject than I know. But I do know that smaller intake helps at lower RPMs and larger is better at higher. This is one of the reason dual planes are popular on street V8s and such. But do more research - this stuff isnt rocket science and has been sorted out decades ago.
_________________
D-Dubya Manx clone - 63 Short pan,1914.
Rosie 65 bug - My mostly stock daily driver.
Woodie 69 VW woodie (Hot VWs 7/12).
"John's car" 64 VW woodie - The first ever
Maxine 61 Cal-look bug - Cindy's daily driver.
Max - 73 standard Beetle hearse project - For sale
66 bug project - Real patina & Suby conversion
There's more, but not keeping them...

[Zundfolge1432]

Try this build a 1600 single port and use 1300 heads with smaller valves, yes you'll cut them to fit the larger jugs.

[Lingwendil]

[67jason]