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Single port or Twin Port?
Jo Mama - November 30th, 2002 at 01:22 PM

I'm going to buy a 69 bettle off my mechanic which has a bored-out 1835cc engine running off a dual throat weber, feeding single port heads. When I asked him about the single port heads he replied that they give more low end torque and that twin ports give more high end torque. Is he lying to me? Anyone know?

Thanks,

Nick.

56astro - November 30th, 2002 at 02:19 PM

In simple terms he is right.

It depends on what you want from your car whether the SP motor is what you're after. There are some very experienced people on this forum who will be able to give you some really good info on this.

Grey 57 - November 30th, 2002 at 05:25 PM

Jo Mama , I have single ports head on my 1600 and was told the same thing. I would like to know if this is true too.

Bizarre - November 30th, 2002 at 08:45 PM

might be out of my depth here but .......

Single port IS better. Once you go past stock you can get bigger carbs that feed dual ports, carb per cylinder and that is good. But in a stock situation i have read a lots of builders prefer single port. I think the dual port has benefits up high (5k+ revs) but you need the other bits (carbs etc) to get the benefits.

Che Castro - December 1st, 2002 at 01:23 AM

yeah single port is less prone to cracking, then again a twin port head wont crack if u dont overheat it all the time. they apparently do give more low end at the expense of top end. however 1835 means 92mm pistons and cylinders, these are usually the thinwall ones that have a bad reputation for wearing out real quick

Single port heads are more expensive new by about $50.

geodon - December 1st, 2002 at 05:40 AM

I've got a TP in my '60 KG & a SP in my '60 SC ute. I prefer the the SP for its lovely low down torque but the TP has the potential for for higher revs & thus more power. You pay for it though- it's a noisy bugger cf the the SP. (both 1600's)

[Edited on 30-11-2002 by geodon]

KruizinKombi - December 4th, 2002 at 04:14 PM

I agree, I prefer single ports for stock motors, for drivability and reliability. :)

I think though that with an 1835 with dual throat Weber than you may be better off with twin-port heads, but there's probably not a lot in it. Try porting the single port heads. :)

70AutoStik - December 5th, 2002 at 01:10 AM

Hey, Kruizin; yet another intelligent reply. I agree that the stock SP produces more torque at lower revs; but with the larger displacement (a configuration I don't believe in,) the loss would be negligible - but, with the right manifold (and someone who knows how to set up a single IDF) dual port would yield a significant amount of useable power. The costs do, however, add up (heads, end pieces, manifold, boots, clamps, cylinder tin.)

But, for a stock 1600 - SP rules!