250 Log on 200

[xrwagon]

Good idea bad idea? Have been offered a head, has been ported, double valve springs, hogged out for Holley, decked 0.020 thou, hardened seats etc. Not sure if it will need more decking to suit my 200 to bump up compression. Also have another 2V head in the wings.

 

[xrwagon]

I just read chambers are the same size, hope that applys to Aussie heads

 

[170-3tree]

If it's fitted for a two barrel and in good shape, it's good to go I would suggest taking .020-.030 of still, as you said to optimize the compression. However I believe the 2v head will do better if you can obtain it.

Anything Australia specific, I cannot help, but I can't remember seeing any differences thru here.

 

[xctasy]

viewtopic.php?f=1&t=71290&p=547170#p547170

Measure for sure first, but its not often a 250 log or 2v 250 head is shaved that much, since the stock 250 2V had a huge 9.3 :1 compression ratio for 97 RON/MON leaded super. Stock was 58 to 62 cc, nominal 60 cc, with a special kidney/heart shaped box head. Nirvana! So shaving till you get a 52 cc chamber is fine. In most cases, 50 thou will get you 52 cc. A total shave from stock to 90 thou is a 46 cc chamber. 120 thou is risky, but it gives about 40 cc or so.


The compression ratio stock for an Aussie 200 in an XR is about 9.2:1, with a 61 cc head. 45 thou composite gasket, 16 thou piston sort fall, 5.5 cc piston dish was stock, I think

Stock 250 1v/2v , 61 cc will make 9.24:1
52 cc will make 10.54:1
46 cc will make 11.66:1
40 cc will make 13.07:1

See viewtopic.php?f=3&t=71291

 

[xrwagon]

thanks mate, i am hoping by Monday i will have two heads, one 250 2V and the heavily modified 250 log.