Type IV Heads

[914Hugh]

I am about to rebuild a 914 2.0 motor.

I have read in Tom Wilson's book about the differences in the 914 2.0 heads and the type IV VW heads, namely the valve size, the different intake studs, and the plug angle.

As long as carbs were used, it seems as if I could use the type IV bus head for the 914 2.0 engine. Does anyone have an idea at what difference I would be dealing with in terms of performance?

The reason I ask is bc new 2.0 914 heads are going for $900 a piece.

Any suggestions?

[ViolentBlue]

it depends a lot if you're planning on reworking them for larger valve size, if you are the type4 heads will work as nicely as the 914, but for stock bolt up application its better to spend the extra cash and buy the 914 heads. also consider using euro 2.0 pistons for a little higher compression to get that extra performance

VB

[914Hugh]

Based on your comment, sounds like extra work to use the 2.0 VW head and some loss of performance. I guess this just doesn't fit with my expectations of "the common man's porsche". In the 914's defense, it has been cheap for me to maintain over the last 10 years.

Nonetheless, with two new heads and a new set of pistons and cylinders, I am really starting to approach the cost of a chevy conversion (without the added bonus of chevy horsepower).

Any arguements for sticking with the 2.0 other than I will not be a 'pure' vw/porsche hybrid?

[ViolentBlue]

I always wondered how a 944 turbo engine would perform in a 914. theres plenty of low milage ones for sale out there for a reasonable price.
I'm all for swapping for performance, but I wouldn't taint a nice piece of german engeneering with american power.
just my opinion

VB

[Patrick]

If you're rebuilding a 914 2.0 and already have a set of heads, just have them rebuilt. There's no need to buy new ones at $900 each as long as your old ones aren't too far gone. Even at a worse case scenario with your heads needing new seats, some welding to fix cracks, etc. a qualified machine shop should be able to have your heads as good as new. By the way, bus 2.0 heads have smaller valves than 914 1.7's. If you want to go cheaper than 914 2.0's, I would look at the 914 1.8 heads. They're within 1 or 2 mm on both the intake and exhaust sizes and are cheap to buy valves for (unlike the 914 2.0 exhaust).

[914Hugh]

Thanks for your input. If this car wasn't my daily driver, I would probably have an idea of the condition of the heads right now, thus ending speculation. I know my mechanic was trying to prepare me for the worst, but his insistance on new parts has lead me to question his judgement Equally frustrating is that other than blowing out a quart of oil a week my engine is running great (it has just had the mothballs taken out of it after a four year ciesta in my parents garage (yes, I have tried to get the rings to re-seat, but I had this problem before I put the car to sleep).

I am planning on taking the heads out myself and finding a good machine shop that will give me a fair evaluation (if I have to buy new heads, then that is what I need to do).

As far as the potential for using the 1.8 heads, Tom Wilson's book says that the valve sizes for the 1.8 are 41mmX34mm, and also states the 2.0 valves as the same size. I guess this is an error based on the sizes that are in the Pelican catolog (2.0 is 42X36). I guess I would also have figure out different sheet metal and intake manifold. Hopefully I won't get this far though.

I will post an update to let anybody interested know what happens. This bulletin board has been an invaluable resource for helping me out!

[vw911]

2.0L 914 heads are 42x36. You can use T4 heads rework them and get the performance you are looking for. 914 heads cost so much because they have sodium filled valves in them and the construction of the heads. You can put 44x40, 46x42, or 48x44 valves in your car ported and polished on T4 heads and get the performance.

[914Hugh]

I think the Porsche purists would come back with the arguement about the angle of the spark plug in using the regular typeIV. (Notice I didnt post this topic in the 914 forum (I really respect Porsche design in general, but I also appreciate the progress of other cars as well. There are limits of what I respect though. For example, was the 914 really built to be driven in the heat that I live in (FL). I digress.) Nonetheless, I was reading in an engine book (American) the other day, and they said that it was the location of the plug and not the angle that made the difference (I myself do not have enough exprtise to know who is right).

Also from my reading, it sounds like a bad idea not to use the sodium filled exhaust valves, given the heat that these engines have to deal with. Any more opinions?

Lastly, going to the standard type IV head, you would also have to deal with the 3-bolt to 4-bolt intake manifold change. Since the buses also had FI, I assume it wouldnt be hard to find them.

[914Hugh]

PS. The price for the heads that I was quoted by several shops was only for the bare heads!

[RonM]

The spark plug is relocated to provide for better flame travel upon ignition of the charge. If the plug is in such a location that it is shrouded by valves,combustion chamber shape or piston crown shape, you get less than complete combustion (poor flame front travel). This is a serious matter in racing engines where you are trying to produce maximum HP. On a street prodified engine, you probably wouldn't notice the difference.

Larger valves are to overcome poor cylinder filling and/or increase volumetic effeciency. If a stock engine operates at 60-70% volumetric effeciency, addition of larger valves may increase it a few percentage points. A full on racing engine will approach, maybe exceed 95% volumetric effeciency BUT this includes modifications to the intake system and exhaust system. To get the greatest benefit out of any change, requires the entire system to be considered.

You also have to consider the shape of the back side of the valve head, stem diameter, valve guide shape and how they are placed in the combustion chamber(shrouding by cylinder walls, combustion chamber walls, etc)- Got a Flow Bench? You can make all the changes you want, but unless you have the equipment to measure increase you won't know if the change did any good. Generally, you butt isn't a good testing device (very subjective).

Take the heads, with the intake manifolds, to a competent head porter and let him do the "magic". It'll cost bucks, but you'll get the greatest benefit (and keep the American Economy green). The greatest horsepower gains in any engine begin at the air cleaner and end at the end of the exhaust pipe. All must be integrated to gain the most.

[AirJose]

Hi: I might be opening a new can of worms here but I am building a 66 912 project w/type 1 VW engine, I have most of the parts for a 1641 or 1776 engine, has anyone done it? any suggestions? thanks.

[SteveStromberg]

I can sell you 2.0, 3 bolt heads with valves for $300.00each outright.Steve 818 508 0582