How do you guys know all this stuff? I'm trying to get all this information to sink in and it's overwhelming! I guess it takes a lot of hands on experience. I need to take an aprenticeship with a person who specializes in the both type of VW heads. I guess I can do that after I retire. Got 10 more years to go (25 years gov. service) to retire at 49 and still be young enough to learn machine work and cylinder heads as a trade.
Louie
1.7l 914 heads
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Plastermaster
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Re: 1.7 exhaust port mods.
What happens if you decrease the length of the strait shot beneath the valve? Turbulance?HAM Inc wrote:. Anything else decreases the length of the straight shot beneath the valve before the turn and is to be avoided like Mad Cow decease.
A more involved trick is to reproduce the 2.0l port beneath the 1.8l (34mm) valve. This is trickier, requires experience and doesn't make much sense for the smaller displacement, budget engine. Hope that helps.
Len
Ron
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Chris181Westy
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HAM INC. Would these heads be worth putting $$$ into for a larger displacement engine. Can they accept bigger than the 1.8 or stock valves, seats, and bore? Are they worth having intake port work done to them?
I found a pair for $100 and I am thinking of getting them for my Sandrail, which will be driven off-road, therefore I am not concerned with street driving. Since they are much cheaper than buying some 2.0L cores I was thinking I would have some work done to them, if it is worth it?
I found a pair for $100 and I am thinking of getting them for my Sandrail, which will be driven off-road, therefore I am not concerned with street driving. Since they are much cheaper than buying some 2.0L cores I was thinking I would have some work done to them, if it is worth it?
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MASSIVE TYPE IV
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GDRBO
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HAM Inc
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1.7l 'Q' vs. 'S'
Chris you got me on this one. I can't recall coming across a 1.7l 'S' head. I went upstairs to check my core bank but I don't have any 1.7l 'S' heads. I am familiar with the 'J', 'Q' and the 022.101.372. Some 1.8l heads are 021.101.371 S. Sorry I couldn't help. Now I'm going to have to find one of these 'S' heads. If anyone out there has one, I'll pay shipping if you'll let me borrow it for an exam.
Len
Len
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HAM Inc
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port shape
A couple of people had questions regarding port shape, specifically why the straight distance beneath the valve is critical. The answer here has to do with flow around the valve. The first thing that has to be understood is that the valve has but one function, which is to seal the combustion chamber during compression and expansion cycles. The rest of the time it is in the way, which is why bigger valves alone don't improve flow. The flow around the valve, regardless of direction, forms a cone before and after the valve. Anything that disrupts this cone has a devastating effect on mixture quality and velocity. Physical characteristics that disrupt the cone can be; closely shrouded combustion chamber walls, the cylinder wall itself, or below the valve a port that pulls away from the cone (as happens when the short side of the port is opened-up). The straight shot below the valve is critical in keeping the cone formed until the charge (sometimes refered to as a slug) has merged back to its natural tear shape. This straight shot should always be as long as possible, with a half inch being the accepted minimum ideal, but more is better. THE FIRST PRIORITY IN PORT SHAPING IS TO CREATE A PORT THAT ALLOWS FOR A FULLY FORMED CONE. Hope this answers your questions.
Len
Len
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Guest
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HAM Inc
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Head selection
I'm going to address two questions, Chris181Westy's & GDRBO's. First everyone knows that as box-stock heads go the 2.0l 914 head is superior by a country mile. That said, given enough money, time (see money) and know-how the 'Q' can be trained to do any of the tricks the 2.0l head can perform. But this just isn't practical for most enthusiast. If the engine won't be used in competition I feel it's almost pointless to get concerned with some of the details I see enthusiast get hung-up on.
This goes double for the sandrail guys. Rails tend to be very light and by nature responsive and fun even with modest power plants. If you're not competing I think the 'Q' heads are an excellent choice as is. Not sure what you want out of your buggy, but if you just want to have some fun on the weekends I wouldn't concern myself with a lot of mods. Up the valve spring pressure a little to safe guard against over revving, but you could get by with a stock head on a good fresh engine with a little cam. The buggies light weight will make up for a lot of the stock heads limitations. And if you still want more power you can always pull the heads and kick it up a notch later on. It's easy on a rail.
As for GDBRO's question I don't have much experience with turbocharged engines. Based on the fact that you have destroked I would guess your goal is high RPM's. If you intend to turn a lot of revs by all means start with a 2.0l head, and I'd want 44mm x 38mm or 40mm valves. The dilemma here is if this is a street engine then you'll be faced with turbo lag. I'm going to take a poke in the dark, but here goes.
Turbocharged engines benefit at low speeds from smaller intake ports, the reason being that the port velocity makes up for the lack of turbo pressure until it "spools-up". The fact that you have destroked means your piston speed will be slower at any given RPM. This becomes significant at lower RPMs, as port velocity mirrors piston speed to a large extent. (This is why I like strokers for street cars) If you intend to drive this vehicle on the street and have any concerns about performance below 2500 RPM's I would consider a 'Q' head and move the plug angle to the 2.0l postion, along with extensive exhaust port work.
Truthfully the best advise I can give you is to consult someone who has knowledge of the whole package ie. cam, heads, induction, exhaust, turbo unit size, pistons, C.R. ratio, deck height. Miss on any of these and at the least you won't be satisfied with performance. At worst you may end up with an expensive pile of junk.
Len
This goes double for the sandrail guys. Rails tend to be very light and by nature responsive and fun even with modest power plants. If you're not competing I think the 'Q' heads are an excellent choice as is. Not sure what you want out of your buggy, but if you just want to have some fun on the weekends I wouldn't concern myself with a lot of mods. Up the valve spring pressure a little to safe guard against over revving, but you could get by with a stock head on a good fresh engine with a little cam. The buggies light weight will make up for a lot of the stock heads limitations. And if you still want more power you can always pull the heads and kick it up a notch later on. It's easy on a rail.
As for GDBRO's question I don't have much experience with turbocharged engines. Based on the fact that you have destroked I would guess your goal is high RPM's. If you intend to turn a lot of revs by all means start with a 2.0l head, and I'd want 44mm x 38mm or 40mm valves. The dilemma here is if this is a street engine then you'll be faced with turbo lag. I'm going to take a poke in the dark, but here goes.
Turbocharged engines benefit at low speeds from smaller intake ports, the reason being that the port velocity makes up for the lack of turbo pressure until it "spools-up". The fact that you have destroked means your piston speed will be slower at any given RPM. This becomes significant at lower RPMs, as port velocity mirrors piston speed to a large extent. (This is why I like strokers for street cars) If you intend to drive this vehicle on the street and have any concerns about performance below 2500 RPM's I would consider a 'Q' head and move the plug angle to the 2.0l postion, along with extensive exhaust port work.
Truthfully the best advise I can give you is to consult someone who has knowledge of the whole package ie. cam, heads, induction, exhaust, turbo unit size, pistons, C.R. ratio, deck height. Miss on any of these and at the least you won't be satisfied with performance. At worst you may end up with an expensive pile of junk.
Len
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GDRBO
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Sorry I didn't mention it but the crank was originally for a limited displacement class. I want to use it as there just is not much market for it. I wasn't/am not looking for high revs though I had thought that was what I would get from that crank choice. In my case the buggy is a fiberglass bodied offroad chase/prerunner and relativly heavy. It will also be street driven and has an automatic trans from a bus. I seriously doubt anyone has or will ever run a package like mine. So any thoughts are greatly appreciated!
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Guest
Len, I really appreciate your perspective on the valves "only" purpose. I always knew the valve was in the way, but never took it as far as you did. In the back of my mind, I still thought of the valve as "letting in" and "letting out", but truth is, its just a nesecary evil in the way of flow. Am I correct in assuming the angles around the perimeter of the valve, as in "3 angle valve job" is critical in creating the cone properly? I always thought it was just for seating purposes.
Thanks
Ron
Thanks
Ron
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HAM Inc
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seat angles
Ron the seat angles are extremely important with regard to the cones shape, as are the valve angles and its shape. Seat work and valve shape is a very precise science, and because of it's importance much research continues to be done by those who can afford it, though there is little new under the sun here.
I like my valves to sit up high in the chamber with sharp, crisp transitions between angles. The importance of this is magnified in race engines with limited lift. Over time as the valve pounds against the seat these transitions become dulled and the cones shape deteriorates. This is one of the reasons race heads are "freshened" regulary, even though leak-down numbers may look good.
Len
I like my valves to sit up high in the chamber with sharp, crisp transitions between angles. The importance of this is magnified in race engines with limited lift. Over time as the valve pounds against the seat these transitions become dulled and the cones shape deteriorates. This is one of the reasons race heads are "freshened" regulary, even though leak-down numbers may look good.
Len
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Plastermaster
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Neat. I would then deduce that lapping valves with lapping compound is not a solution for anything except maybe an old farm tractor or something. I actually had an old tractor that even had a slot on the top of the valves so you could twist it back and forth with a screw driver.
Wouldn't it be better if the valve was placed further from the coumbustion chamber so that there was another port or tube to create a place for the cone to form better before entering the combustion chamber. This would make both sides of the valve sort of symetrical.
Ron
Wouldn't it be better if the valve was placed further from the coumbustion chamber so that there was another port or tube to create a place for the cone to form better before entering the combustion chamber. This would make both sides of the valve sort of symetrical.
Ron