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Discussion Starter #1
I’ve heard a story in regard to a 3.3L cam in a 4.1 block giving greater lift and or duration. Does anyone know wether this is justifiable for power or a myth and wether it can cause problems?

It all came from a drunken conversation between mates in regards to the 3.3L motor being tweaked a little in order to provide greater power in compensation for its capacity? I don’t know wether this is a load or for real.

I’ve also heard that because the bore remains the same, the 3.3L pistons can be used along with using a 3.3L head to raise the compression. Obviously the crank and rods will remain 4.1 spec however I was wondering if this combo may cause problems? ie height of pistons plus stroke length equalling a really expensive bang! I have a 3.3 unleaded head and I also want it to replace my poor old 4.1 leaded head. Any thoughts on flow restriction (3.3 vs 4.1)???

I figure that because I have a rebuild coming up and a 3.3L spare motor, it could be a very cheap means of obtaining that extra power.

Any input would be fantastic as well as any info on specifications of the 3.3 and 4.1 litre. (stock cam lift and duration, stroke combos, valve specs etc.)

Thanks.

Mick
 

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Even if the 3.3L cam was larger it would still be puny by performance standards.

I would just use a 4.1L ACL RACE kit, they are very good quality and generally up the compression anyway.
 

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Hi,

I would keep the rods out of your 3.3 litre and use them in a 4.1 block using the 250 crank. This gives you a better bore/rod ratio which lets the old 250 rev better and stops side loading on the bores, you need a special piston from acl and i cant remember the part number but it wont be hard to find.

Cheers

Simon
 

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Discussion Starter #4
Thanks guys,

Well the crunch has come and I decided that a new cam is on the cards. Ive heard various reports on the specs of different manufacturers however at this stage I want to conserve the cost of a rebuild using stock parts. Ill put it on the back burner a while I think.

I also heard that the heads were exactly the same from the 3.3 to 4.1. Ive finally decided to pull the heads of both motors and check this theory. Aparently it was only the carby, crank, rods and pistons that changed however I still seek varifycation on this.

Can anyone help????

Once again, Thanks
 
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