Engine building, Looking for suggestions... Options

[Hine62]

I've read "a lot" about the type 4, but still have some questions. My father worked on these engines when they where new, so he's teaching me how. I'm looking to build an type 4 engine with these parameters:

1.8l case
96mm cylinders
78mm crank

Some questions:
1. If the stroke of the crank is increased, how does this affect the cylinders?

Are the cylinders shimmed to the new stroke?
Does someone make "78mm" cylinders"?
Are the pistons/rods shorter/longer to make up the difference?

2. Should I look for a 2.0l case? From what I've read the cylinders fit in the 1.8L case. Are there any other benefits to the 2.0L case?

3. If I decide on 103mm cylinders, where should I send the case? (It will need to be machined for the crank anyway. Unless I decide to take a grinder to it (IMG:style_emoticons/default/biggrin.gif) )

4. There are a lot of 'kits' to buy. Should I go with a kit or buy the parts separately? One advantage is kits come with gaskets, etc...

I have more questions, but this will get me started. Thanks

[02loftsmoor]

http://aapistons.com/engine-calculator

try this link to AA Pistions

[Dave_Darling]

Some questions:
1. If the stroke of the crank is increased, how does this affect the cylinders?

Are the cylinders shimmed to the new stroke?
Does someone make "78mm" cylinders"?
Are the pistons/rods shorter/longer to make up the difference?

The cylinders don't care. The pistons, however, might care a lot. It depends on the rod length and the wrist pin height. Your best bet is to get a set of parts that is known to work together...

The case will care a lot. 78mm is quite an increase from the original 66mm. To fit that, you have to do some clearance work inside the case. You also will have to go with a reduced base-circle cam, because one of the rods will hit a cam lobe otherwise. Even with that, it can be very close and you may still require some work (or at least checking) to make sure this doesn't happen.

2. Should I look for a 2.0l case? From what I've read the cylinders fit in the 1.8L case. Are there any other benefits to the 2.0L case?

There are no effective differences between the cases. Especially where it comes to fitting longer-throw cranks, or larger cylinders. The spigots where the cylinders go are the same size for all three stock 914-4 motors. The only real differences are:
- Early 1.7s did not have any provision for the windage tray
- Later 2.0s (and 1.8s?) did not have the secondary oil control piston

3. If I decide on 103mm cylinders, where should I send the case? (It will need to be machined for the crank anyway. Unless I decide to take a grinder to it (IMG:style_emoticons/default/biggrin.gif) )

Dunno--maybe FAT Performance in Orange CA? 103s are not that hard to do on their own, but they are not known for being very durable. They don't shed heat that well, and they often don't start out particularly round or straight...

4. There are a lot of 'kits' to buy. Should I go with a kit or buy the parts separately? One advantage is kits come with gaskets, etc...

The easiest thing is to get a set of parts that are known to work together. That said, some vendors are more reputable than others. It's usually best to go with those that have a good track record.

--DD

[Hine62]

Thanks Dave!

Could you explain the reduced base-circle cam? I assume the cam doesn't open the valve as far, but must keep the valve open longer to compensate lack of height. There is also the option to go with chevy or vw journals which would change the thickness of the rod end.

[colingreene]

I just finished building what you are talking about doing.
The reduced base circle cam just has a smaller circle to clear the rotating assembly.
how it works is the base circle is smaller but the lift from base to peak is still the same.
thats what counts.
As far as clearing the inside of the case it depends largely on the rods you choose to run.
Pm me if you have more questions.

[malcolm2]

66mm and 71mm were the stock cranks. 93mm was the stock piston diameter. plug them into the calculator link. 71mm crank with the 96mm pistons gets you a 2056 cc displacement.

From what I have read, folks like to use a 1.7 Liter case. I think they were a bit beefier. I believe any upgrade to a 1.7 case will require some clearancing to allow the rods to clear. The bigger crank has smaller journals to help account for some of the distance difference.

Then you need to consider your heads and valve openings and push rod lengths. I'm sure your Dad told you about the Carb cam or Fuel Injected cam.

Have Fun, take your time. I tried to buy high quality parts for my engine and just get it driveable. I did not worry too much about how the car looked. That's when the real fun begins. (IMG:style_emoticons/default/driving.gif)

I bought all my internals from TYPE4STORE.com. My stuff did not come with gaskets. A gasket kit will be around $50, sold by engine size.

[Dave_Darling]

Could you explain the reduced base-circle cam?

A cam is basically a circle with a bump on it. The lifter (or follower) will ride along the circle, and then get pushed outward by the bump, then ride along the back side of the bump to the circle again.

The circle is the "base circle". So a reduced base-circle cam (-shaft) is made with a smaller circle. The bump is still the same, so the amount of lift and duration can be the same, but the piece takes up physically less space. That allows for more room for the rods and rod bolts.

It also means there is less surface total for the cam, which may speed up wear. It also means that the lifters have to stick out of their bores a little further, which I think also leads to them rocking in the bores slightly, which also increases wear.

--DD

[rhodyguy]

what they said.

[bdstone914]

A good starting point is to decide how much you have to spend. You can easily top 10 K with a big engine. Select components that work together to make a good engine for your use.

[Hine62]

Thanks again everyone.

[ChrisFoley]

I can do the crankcase work here.