[maloo11]

Can anyone supply compression figures for HC pistons? Im leaning toward head work and webber carb + extractors for best gain out of the 1.3. im not looking for tyre smoking performance, jus resoanable gain over stock

[skyman]

Let me do some research for you on Zuwharrie, I know fastspec2 posted some dyno results. I will see if he has any that include the pistons.

I really think that the pistons would do much better than a header/extractors, I will see if I can find some hard facts for you.

I understand where you are at with these type of decisions. Finding hard data on engine mods is tough. I tried for about a year to get actual numbers for the cams they sell here, and finally got the numbers (lift/duration/overlap)when I bought one. Asking the vendors what kind of a difference a cam made in performance was like asking for pink elephant.

Anyways I get where you are at, you only have a certain amount of money to spend or a budget to stick to, and you want to get the most/best for your money. That can be frustrating when it comes to parts for building engines.

I do know that performance wise, you can gain a lot from porting the intake itself. The intake is one of the biggest power limiting factors with our carbed 1.3's in the states. If you want to port it yourself, I can show you how with pictures, and give you some other tips on getting more out of you intake.

I will post up what I find

[skyman]

Here you go I went and dug out the info, it looks like you would get a C/R of 9.2 to 1, where stock is 8.6 to 1, a fair gain for a simple piston swap.

Here's the source, don't skip page 2 if you are building an engine, some good information there.

For those of you who want to build a 1.6 there is some great info in there too.

All of this research was done by Fastspec2 (thanks a ton!), you may want to search out and read his other posts too, he shared a lot of good engine building information in almost all of his posts.

Link to original thread below quote, and one more to dyno charts for some 1.3's he has built.

Quote:

COMPRESSION RATIO INFORMATION
STOCK 1.3 cylinder head volume = 33cc
Stock 1.3 "dished piston" volume = 3.8cc
1.3 "flat top" piston volume (the valve nothes) = 1.5cc

Stock 1.6 head volume = 32cc
Deck clearance = .010
I checked this on 2 different blocks, its varied a bit, so I averaged them at .010. If anyone wants to check deck at tdc on another stock 1.3 and compare, it would help.

Looking at the information above I finally realized something that I had missed in the passed. The 1.6 cylinder head combustion chamber is the same size, or smaller than the 1.3. In the past, I had always just cut the heads until I ended up with the volume I was looking for. I had never cc's a totally stock 1.6. Interesting yeah? I kinda feel like I missed the boat on that one all this time. So now there is 0 reason really to not run the 1.6 head. The fuel pump is the only thing that could be argued, but its a week one in my opinion.

So compression ratios:
Stock head stock 1.6 head gasket. Factory replacement dished pistons.
stock bore 8.6-1
.030 over pistons= 8.8
.060 pistons = 8.98

Flat top pistons
stock bore 9.1
.030 9.2
.060 9.4

Cutting block down to arrive at 0 deck using the flat top pistons.
stock bore 9.2
.030 9.4
.060 9.6


Cutting .010 from the cylinder head yields about .2's more compression ratio on a stock bore.

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1298 engine
bore 74mm
stroke 75.5
All of these I have seen are useing full floating wrist pins. This meens some of the .040+ pistons will most likely work in the 1590 engines as well.

Pretty much you just need to look through the 1324 section above as these 2 engines are pretty much the same.
The real differnces are in later years when the valve train changed in the cars to a roller aragnement. The roller setup is interchangable as well given that everything from the roller valve train is used.

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Build info
http://bbs.zuwharrie.com/content/topic,88177.0.html
Dyno sheets
http://bbs.zuwharrie.com/content/topic,82730.0.html

[TryHard]

thanks for that info sky man looks like 1.6 head and 1.3 head is good set up