23 replies to this topic

[mozzo1]

i want more power from my little 1000 cc and cant afford to bye 1275 engine at the moment so was wundering if it is worth just putting a 1275 head on for now untill i can afford to swap the whole engine and box . so wanted to know is the power difference noticable or should i just wait untill i can afford to do a complete transfer

[Turbo Phil]

You'll need to pocket the block to allow clearance for the valves, so ideally the engine needs to be removed & stripped. It can be done in situ, but it's far from ideal.
If the rest of the engine is standard you'll be much better off fitting a 12g295 {998 Cooper head}.

Edited by Turbo Phil, 20 July 2009 - 03:43 PM.

[Cooperman]

You'll need to pocket the block to allow clearance for the valves, so ideally the engine needs to be removed & stripped. It can be done in situ, but it's far from ideal.
If the rest of the engine is standard you'll be much better off fitting a 12g295 {998 Cooper head}.

Agree absolutely, a 12G295 is the best head for a 998, especially if it is mildly gas-flowed as well.
It saves stripping and machining the block and it's easy to skim a bit off as necessary to get the correct compression ratio.
You will always need to skim a 295 head as the original 998 Cooper from which the head came had 'D-Top' pistons to get the comp ratio up.

[Turbo Phil]

Agreed, but it's also important to check it hasn't already been skimmed, as it's probably rarer to find an unskimmed one now.

[Nightrain]

As above 295 all the way, another point about the 1275 head conversion is it'll cost you more than a full 1275 engine would. Unless you can do all the work yourself.

[mozzo1]

I"LL WAIT TILL I CAN GET A WHOLE 1275 ENGINE AND BOX AS SOUNDS LIKE A LOAD OF GREAF THAT I KNOW NOTHING ABOUT BUT THANKS FOR POINTING ME IN THE RIGHT DIRECTION GUYS

[Big_Adam]

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.

[Nightrain]

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.

LMFAO, Right so you've done it ? Or at least bodged it ...... I got a 67000 miles GTA engine for 150 quid a few months ago. To do the job properly you need to strip the engine and take the block to your machinist, he pockets the block after skimming it to make sure it's flat. Iirc there's a water way that needs blocking as well. As the blocks stripped it'd be daft not to install new cam bearing. So there's a least 200 quid new oil pump again it'd be daft not too 25 quid. Gasket set another 25 quid, are you gonna use the old bearings ? I wouldn't so thats another 100 quid !

Of course you could just take the head off and set about it with die grinder, then swill it off and stick the 1275 head on........that'll give miles and miles of trouble free motoring NOT !

[Big_Adam]

LMFAO, Right so you've done it ? Or at least bodged it

In process of.

...... I got a 67000 miles GTA engine for 150 quid a few months ago.

Crap, why do I never find these deals.

To do the job properly you need to strip the engine and take the block to your machinist, he pockets the block after skimming it to make sure it's flat. Iirc there's a water way that needs blocking as well. As the blocks stripped it'd be daft not to install new cam bearing. So there's a least 200 quid new oil pump again it'd be daft not too 25 quid. Gasket set another 25 quid, are you gonna use the old bearings ? I wouldn't so thats another 100 quid !

Of course you could just take the head off and set about it with die grinder, then swill it off and stick the 1275 head on........that'll give miles and miles of trouble free motoring NOT !

Sleep and my logic don't work well together.

Okay, you're right. I'm a berk. I'll be sulking in the corner if you need me.

[datsun100a]

Why do you need to pocket the block??

[Big_Adam]

Why do you need to pocket the block??

If not the valve smash into the block.

Which is bad.

[datsun100a]

First i've heard of that with a standard set up. done it twice over the years with no problems.

[Big_Adam]

Well I'm on a roll of being wrong here.

[Turbo Phil]

First i've heard of that with a standard set up. done it twice over the years with no problems.

It is possible to get away without pocketing the block if you retain the standard cam, but the valves run so close to the block face at full lift, the merest hint of valve bounce & you're in trouble.
I wouldn't advise it. If you're going to fit the 940 head you may as well do the job properly and pocket the block, besides you're going to want to fit a decent cam while you're at it.

[Cooperman]

I'm with Nightrain here.
It is believed that you can fit a 12G940 head to a 998 without pocketing the block so long as you stick with a standard cam and the head has not been skimmed too much (if at all). I build quite a lot of engines and it's not something I would do or have ever done. To me it's asking for a major engine blow-up. With a 12G940 on a 998 block there would be a tiny clearance between valve head and block deck at full lift. Er, no thanks.
But then, to buy a 2nd hand high-mileage unknown history 1275 motor and just stick it straight in is also not advised. The best thing to do is to get a cheap 1275 lump and then re-build it properly (or pay someone to re-build it).