E30 325 intake and exhaust manifolds & misc

[tibbs.james 1]

Right

I Am considering an engine swap for my E30 as im after more grunt. So sick of the stock m20b20.

My intention is more power and torque than a M20B20, but also to make minor improvements on the 325's engine torque at the same time.

It would appear it not to be worthwhile to play around with the 2.0 as 2.5 engines are avalible for a lot less effort that working up a M20B20.

So i have a few questions

What is the diffierence between a 320i FL Intake& Exhaust manifold compared to a 325 FL intake manifold & Exhaust manifold

Reason i Ask is do i go for a short block with complete Cylinder Head

or a complete engine. It seems a complete engine is going to be necessary.

From what i understnad a PRE FL or FL block will do just fine.

I know there are different Model Cylinder Heads about, So which model car does it come off.

Or what part number is it ?

Camshaft. A good cond 325 Cam should be ok, but is it going to be worthwhile to do a mild cam regrind now for a little extra go ?

Exhaust manifold a 325 item should be easy to find but i believe FL items are more open and better flowing ?

Compression Ratio's is the FL or PRE FL engine diffierent, I assume 9.0:1 to be correct ?

How does one increase the compression ratio on an M20 donk. When my 2.0 head was rebuilt

i was told the head should not be skimmed to increase compression. Short of new pistons is there anything you can do about it?

Or Perhaps a certain Head/Block combo creates an ideal ratio ?

As far as tuning With an ECU chip the, MAF re tensioned and fuel Press regulator, there is no reason not to achieve a perfect tune ( dyno assisted of course ) using the 320i ECU

Any help of these questions would be greatly appreciated

[tibbs.james 1]

When i mean chip I mean one done specificly for this car, not a trademe or similar item.

[antony 0]

I'll try answer a few, unsure of others:

320i has smaller inlet manifold and throttle body.

731 head is from m20b20, and 885 head is from m20b25.

F/L has a bigger exhaust manifold, cant remember differences off the top of my head. (31mm vs 34mm??? or around there)

Pre F/L has higher compression ratio.

Best combination is everything from a m20b25. ie: block, head, intake, throttle, etc.

[Silver Fox 43]

Afaik, the 320 pre fl hi top pistons and block so you get dissy advance options, with the fl head for better flow. This should give you 9.8:1 compression I believe. Just with these small changes the race series cars are going over 125 hp at the wheels. With cam and chipping, and exhaust freeflow, you should get to 140 or so I would think.

[antony 0]

Still only a 2 litre tho.

[tibbs.james 1]

"Afaik, the 320 pre fl hi top pistons and block so you get dissy advance options, with the fl head for better flow. This should give you 9.8:1 compression I believe. Just with these small changes the race series cars are going over 125 hp at the wheels. With cam and chipping, and exhaust freeflow, you should get to 140 or so I would think."

This is very interesting Dave, as it would be super to make use of my recently reconditoned ( wihin 10,000kms ) cylinder Head FL

Can anybody confrim this - seems like not a bad option really

[Mark Babb 1]

"Afaik, the 320 pre fl hi top pistons and block so you get dissy advance options, with the fl head for better flow. This should give you 9.8:1 compression I believe. Just with these small changes the race series cars are going over 125 hp at the wheels. With cam and chipping, and exhaust freeflow, you should get to 140 or so I would think."

This is very interesting Dave, as it would be super to make use of my recently reconditoned ( wihin 10,000kms ) cylinder Head FL

Can anybody confrim this - seems like not a bad option really

Actually some of the fl 320's also have the 9.8;1 pistons. BMW parts guide lists these pistons as an option for models 88/89/90 too. Just depends which country the engine was intended for and if they have strict emission controls ie Japan etc.

But as Dave says if you fully rebuild your 320 and carry out the permitted mods as per race series cars then anywhere between 115-125 hp could be possible depending which rolling road you use etc.

Can't help thinking it may be a lot less hassle and far cheaper just putting a 325 engine in. They say there is no substitute for cc !!

[tibbs.james 1]

My Car was a jap import, go figure low compression emmission regs ect.

My M20 bottom end is getting a bit tired and needs a set of rings. Before i go and spend $500 getting rings bearings and a hone ( what my father reccomends )

I am going to Ring Pete at Euro Rec just in case he has a FL 2.5 avalible for a good price.

Only you can see my situation where not so long ago I Sunk $600 into doing a head rebuild and I'm getting frustrated thinking I will be in for that all over again.

I know i can probally do a rebuilt bottem end for $ 400

But if I Buy a 2.5

Cost of the engine say $500

Rebuild the Head $600 inc all parts gaskets water pumps cambelts & misc belts

Rebuild Bottem end Say $400 inc rings bearings and gaskets

and say add a larger Dia 325 Exhaust thats probally $250 with a muffer & resonator and some pipe ( cutting welding and fitting myself )

Call it $1700

What an a**hole! Ive got a 300zx engine to build soon and i Would prefer the money to go into that.

Perhaps im being stupid thinking about all this cost to get another 30hp dosn't really seem worth it.

Anybody have 2c to throw in ?

[antony 0]

The money spent on the head is a sunk cost, you'll never get it back and shouldn't let it effect your decision.

I'd just put my money into the 300zx, or put in a m20b25, don't bother trying to mod the m20b20.