ABY to SMF part number

[bobby singh]

Hi everyone - I tried to search this before posting but could not find a clear answer.
Background
I'm building a spare high power engine and want to get the bottom end all balanced etc
My car currently has a 3b smf with a 707 clutch which off course I can not use in the new engine as I want to balance the lot and keep my car on the road.

I need help to id a 3b smf

Looking on ebay I found https://www.ebay.co.uk/itm/224945504...YAAOSw1bNiXS0L
This flywheel has a part number of 034105271C and according to the description is the same for 3b & 7a - is that true?

Forum search bought up 3b part number as 034 105 270AA or 034 105 271J

Thanks in advance
Bobby

[rxl]

that is a 7a one. buy aftermarket one.

[bobby singh]

that is a 7a one. buy aftermarket one.

Thanks for reply - does 7a one also work on aby?
Aftermarket - I have considered that but they are x 3 the price and not sure if the advantage is justified

[rxl]

would work but has its issues

[bobby singh]

would work but has its issues

Can you expand on the issues?

[_ShurikeN]

I've heard rumors that 7A flywheel pin position is a few grads shifted from one on 3B/ABY flywheel. Did not check myself.

It can be essential on stock motronic, not an issue with aftermarket engine management.

[pfi]

Compared my 7A with my 3B, can't see any pin difference but 7A is ~1kg heavier.
You also may use any other 5-pot flywheel but then it needs to be machined and of course have inserted the trigger-pin at proper position
Another alternative may be 3B aftermarket ALU flywheel

[rxl]

its not what i would put on upgraded engine. your downgrading it. trigger issues are possible, weight, mashining costs that are the downside of it.

[pfi]

its not what i would put on upgraded engine. your downgrading it. trigger issues are possible, weight, mashining costs that are the downside of it.

what is what You wouldn't put on upgraded engine ?

[rxl]

your ebay link. just my opinion.

[pfi]

The eBay looks like a 7A, reasonable priced.
What You want to put on depends on what You want to achieve ...

My FW's :
- NF : 10.5 kg (milled)
- 3B : 10.7 kg
- 7A : 11.5 kg
- 3B Alu : 5.1 kg
- AAN SM Alu : 5.5 kg

personally I'd liked ~8kg, mby try to machine more of my NF to see if it's possible ...

my 7A :
7a-03.jpg

the part# can't be trusted, it's probably a "raw" number of the FW before machining to specific engine, think there's a thread regarding this on the forum some place ...

https://www.s2forum.com/forum/techni...in#post1234372
.

[bobby singh]

wow thanks for the information guys yes the engine will have a EFR 83 so maybe best to stick with a light weight item.
Its only a weekend toy but having light flywheel could help in getting those rev's up

[pfi]

If "fast" rev's up is Your goal, go for aftermarket Alu FW ...

[bobby singh]

Well I want easy rev'ing haha
I'm using a diesel crank to make 2.5l so anything to help

[pfi]

2.5 crank in 2.2/2.3 block or in 2.5 block ?

IMHO a stroker is more for torque than fast rev's ...