Autech Pulsar GTi

this is how i measure lift @ tdc btw
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Personally I think it would be foolish to use a thicker head gasket just to allow for piston / valve clearance.

Do the job properly...have the pistons notched, or install a set of notched pistons, while still keeping the compression high.

I would want 12:1 compression AT A MINIMUM!!!
 
mera red gti said:
what header you using dale?
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Ive ordered the Mazworx 4-1

DBull said:
Personally I think it would be foolish to use a thicker head gasket just to allow for piston / valve clearance.

Do the job properly...have the pistons notched, or install a set of notched pistons, while still keeping the compression high.

I would want 12:1 compression AT A MINIMUM!!!
Click to expand...

As long as i see a healthy power increase (top end) from the engine, i'll be happy.

Anyways, i buttoned the head down today, so im not changing my mind!

PA230679.jpg
 
I think the 11.1:1 is wasting the potential of the head personally, but if I knew more about this sort of stuff Id have fitted the head to my own car.

Liam.. what?
 
DBull said:
Personally I think it would be foolish to use a thicker head gasket just to allow for piston / valve clearance.

Do the job properly...have the pistons notched, or install a set of notched pistons, while still keeping the compression high.

I would want 12:1 compression AT A MINIMUM!!!
Click to expand...

I disagree now....
11:1 is a happy medium where aggressive ignition timing is still possible, with the compression too high, you have to be conservative. Been told every 3* of ignition timing could cost you 10hp..
I'm GLAD mine's under the 12:1 mark after all the issues Craig's had with higher comp...
Dale if you're stuck because of valve-piston contact, and you can't resolve it, keep in mind what I said about a trade for the C2's (there would be cash your way obviously).
Joe
 
shaggy_master said:
I disagree now....
11:1 is a happy medium where aggressive ignition timing is still possible, with the compression too high, you have to be conservative. Been told every 3* of ignition timing could cost you 10hp..
I'm GLAD mine's under the 12:1 mark after all the issues Craig's had with higher comp...
Dale if you're stuck because of valve-piston contact, and you can't resolve it, keep in mind what I said about a trade for the C2's (there would be cash your way obviously).
Joe
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Thing is bud, I wouldn't be building an engine like that without using a high octane fuel anyways, so ignition timing wouldn't even cross my mind.

I could see why this would be an issue thogh on a daily driven car as fuel costs would be horrendous!

But look at it this way...will you make more power with altering compression or igntion timing?
 
DBull said:
Thing is bud, I wouldn't be building an engine like that without using a high octane fuel anyways, so ignition timing wouldn't even cross my mind.

I could see why this would be an issue thogh on a daily driven car as fuel costs would be horrendous!

But look at it this way...will you make more power with altering compression or igntion timing?
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Well an engine is always built around the fuel anyway..
Dale's most likely gonna be using optimax or similar, not race fuel, so I feel 11:1 will fair him well IMO..
Joe
 
the overlap on his cams means he wont be running 11:1 compression though... a lot of the mixture will be lost while both sets of valves are open... lowering the comp ratio... so on paper it coule be 11:1 but in practice when its running it could be a lot lower, meaning you can fire the ignition forward...

the way i see it... high comp pistons are only a supporting mod for lairy cams... to keep dynamic compression up...
 
RAJackson said:
the overlap on his cams means he wont be running 11:1 compression though... a lot of the mixture will be lost while both sets of valves are open... lowering the comp ratio... so on paper it coule be 11:1 but in practice when its running it could be a lot lower, meaning you can fire the ignition forward...

the way i see it... high comp pistons are only a supporting mod for lairy cams... to keep dynamic compression up...
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+1 mainly from the inlet valve lag (the late closing of that aggressive inlet cam)
 
12:1 would be fine on vpower so not really a big deal and like ross says, allows laryyyy cams to work proper.

i only had problems when i was running 97ron lol, and mine's over 12.5:1. with 99ron and a few litres of xylene at anextra £7 a tank i have aggressive ignition. although if used the car alot that'd work out pricey.

However, i feel all this is pretty irrelevant! lol, Its easy for us to spend dales money for him, but having been in the situation of people giving advice and ideas with your money i feel his pain at being torn. Plus, he's torqued his head down now, he don't wanna start takin it off again, thats my weekly routine :P

good luck as it is dale, i'm sure it'll still be awesome
 
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