23 replies to this topic

[jmetal88]

another point about the 1275 head conversion is it'll cost you more than a full 1275 engine would.

In the words of me "bulls**t". Have you seen the price of a second hand engine lately! You pay £100+ for a pile of crap that needs a rebuild. There's a 1275 head in the for sale bit for £40, I have a machinines who will do the skimming and other work for around £30 (although, he's a bit odd on pricing).

A 1275 for £100 your still going to be paying through the nose to have it rebuilt.

...

There, I vented, I feel better now. Time for bed.

Not to mention if you're in the USA, this might be your cheapest option for a 1275:

http://www.minimania...E/InvDetail.cfm

Edited by jmetal88, 22 July 2009 - 06:29 PM.

[jaydee]

You can always sink valves to avoid that they can hit the block anyway.
By the way pocketing block will improve gasflow and will help to lower down CR, the 940 has a nominal volume of 21,4cc while the CAM4180 is 25,5 cc.

Heres some usefull words about the conversion:
http://www.calverst....40_head_fit.htm

Edited by jaydee, 22 July 2009 - 07:44 PM.

[Cooperman]

How does pocketing the block improve gas flow. I would have thought it does exactly the opposite since the valve perphiery is masked by the proximity of the edge of the pocket.
I still think a 12G295 is the best option. It's a safe mod, requires no machining of the block or lowering of the valve seat datum and is an excellent head.

[Turbo Phil]

Why on earth would you want to sink the valves in the head ? That's just a bodge. It will do absolutely nothing for performance as you'll lose a lot of flow so may lose any benefits of fitting the head in the first place. Either pocket the block properly or fit a 295 !

[Cooperman]

The only reason for sinking the valves is to overcome valve recesson due to not putting in enough lead replacement.
As you say, it's a bodge if used to fit a 940 head onto a 998. But then, a 940 onto a 998 block is all a bodge really!
A 295 is the answer.

[datsun100a]

There is nothing to believe about it, it works tried and tested. pocketing the block is not the answer if you want to do it right, get a 295 head. I did it when I had little money and it worked a treat and blasted other well modified 998s hands down.

[jaydee]

Why on earth would you want to sink the valves in the head ? That's just a bodge. It will do absolutely nothing for performance as you'll lose a lot of flow so may lose any benefits of fitting the head in the first place. Either pocket the block properly or fit a 295 !

Yes, personally i'm totally agree with you. I was just giving this option only cause the last time i said that you need to pocket the block to fit a 940 to a 998 unit, i was attacked and been told that was only a waste of time and the only thing needed was to sink the valves about 4 thou..thats it.

[jaydee]

The only reason for sinking the valves is to overcome valve recesson due to not putting in enough lead replacement.
As you say, it's a bodge if used to fit a 940 head onto a 998. But then, a 940 onto a 998 block is all a bodge really!
A 295 is the answer.

Yes, i think there was a misunderstanding on my post, i wasnt saying that fitting a 940 its the best for a 998.
The 295 has the better shape properly designed for the small bore engine. Fitting a 940 its just a bodge to have bigger valves.

[Nightrain]

Heres some usefull words about the conversion:
http://www.calverst....40_head_fit.htm

Edited to save the mods the hassle

Edited by Nightrain, 22 July 2009 - 11:34 PM.