1.6 Gti Specs, Piston To Deck Height, Gaskets, Cr, Etc....

[djvu205 1]

hi all, have been doing some searching but cant seem to find what i need.i am trying to calculate the amount i need to remove off my cyl head to obtain 10.5:1 CR.

have found some calcs online but they all need different info. can anyone help with specs?

 

my motor is a xu5ja with a b6d head from series a 2 uk spec 205. from what i know and have been told, it should already have flat top pistons and be the high compression big valve head?

 

i also have an si head which will probley be the donor for re build and understand they are the same?

 

apparently the b6d head with std 1.6 bottom end should be 9.8:1

and the si head im unsure of?

 

can anybody answer the following questions for either si or 1.6 gti?

 

1. what is the piston to deck height?

2. what is the best head gasket to use for a hi comp rebuild and how thick would it be

also what is the bore dia in the gaskets?

3. are the pistons dead flat? or dished?

4. what is the cc's of the head chambers i was working on 34cc but then found somewhere that they are 32cc.

 

i can and will be pulling engine down soon and can probley measure and calc all this stuff but would like to know in advance so i can get a bit of a plan going and accumulate the required bits and pieces.

 

cam is on its way and i have gone for a stage 3 newmans grind nothing to big at this stage. all help greatly appreciated

[welshpug 1,661]

the pistons wont be flat topped, flat topped were the low comp and 405 SRI XU9 engines

 

they will have a dish that looks the same as a 1.9 gti piston but a smaller volume, can't remember if they rise flush with the deck.

 

32cc is correct IIRC for the B6d and D6B heads.

 

standard gasket will suffice, they are 1.4mm I believe, and afaik 83.5mm bore.

 

check that the PH3 cam doesn't have too much lift for the springs.

 

 

the Si engine is a new one on me TBH, I don't know what it is as we never had Si badged cars here, I guess it must be an XU5M SPI engine? that may well have flat topped pistons which would save machining your head heavily, they have larger chambers in the head and shorter valves if they are close to the other engines.

Edited July 10, 2010 by welshpug

[djvu205 1]

the pistons wont be flat topped, flat topped were the low comp and 405 SRI XU9 engines

 

they will have a dish that looks the same as a 1.9 gti piston but a smaller volume, can't remember if they rise flush with the deck.

 

32cc is correct IIRC for the B6d and D6B heads.

 

standard gasket will suffice, they are 1.4mm I believe, and afaik 83.5mm bore.

 

check that the PH3 cam doesn't have too much lift for the springs.

 

 

the Si engine is a new one on me TBH, I don't know what it is as we never had Si badged cars here, I guess it must be an XU5M SPI engine? that may well have flat topped pistons which would save machining your head heavily, they have larger chambers in the head and shorter valves if they are close to the other engines.

 

thanks welshpug. i didnt think about you guys not having the si model there. yes it is the xu5m eng. i think i read somewhere there are 8.7:1 in std form? i worked out i would need to cut about 60 thou (1.5mm) off to bring it up to about 10.8:1.

if i use my d6b or b6d (i get this mixed up alot) head, about 20 thou (.5mm) will bring it up to about 10.5:1

but all this was based on zero piston dish and zero piston to deck height i just changed gasket thickness to get the formula to calculate either 9.8 or 8.7 initially then altered gasket height again to determine how much would need to be cut off head to obtain required CR. i guess if the formula is kept consistant that it should show me the gain in CR by skimming the head? still it would be better to confirm everything is right instead of guessing. does this sound fair?

 

so gasket specs i have, but i probley should obtain more info, to do it correctly?

1. piston to deck height?

2. piston dish volume?

 

 

as far as springs go i will probley run double valve springs from a datsun L series apparently they fit? but does anyone know how do you determined the rate of them?

i have heard you can over spring the valves?

 

thanks again welshpug for the speedy reply.