4 replies to this topic

[MiniCarJack]

Hi all, I'm currently in the middle of swapping out the tired 1275 engine in my Mk1, and replacing it with a much livelier engine which should put out around 100hp (fingers crossed). I mistakenly assumed I already had an LCB manifold fitted along with my single-box RC40 system, but after removing the exhaust system yesterday it turns out it's a "freeflow" manifold rather than an LCB.

 

I'm wondering whether I should bother replacing the manifold and potentially the exhaust system with a new one - engine spec of the new motor is as follows...

 

- Pre-A+ 1275 block from a 1979 1275GT, overbored to 1330cc

- 12g940 big valve head, rebuilt and ported by JW Engines w/ unleaded conversion

- Omega pistons and rings

- Swiftune SW8 camshaft with new lightweight followers and MED push rods

- Minisport 1.5 Roller Rockers

- Swiftune CSI electronic distributor

- MED Duplex adjustable timing gear with DSN billet timing cover

- MED harmonic balancer pulley

- MED lightened and balanced pre-verto clutch and flywheel assembly

 

I'll be running this setup with twin HS4 carbs, fitted with stub stacks and a RamAir foam filter.

 

Given this should be quite a revvy motor and I'll probably be driving it in quite a "spirited" manner (albeit still on the road), would I get any benefit of swapping out my freeflow manifold for an LCB instead? Also worth mentioning is that my current exhaust system is 1.75" diameter, so basically a standard single box RC40 setup.

[nicklouse]

The exhaust is fine.  I would go for an LCB. like the maniflow medium bore but I would lose the rockers.

[MiniCarJack]

The exhaust is fine.  I would go for an LCB. like the maniflow medium bore but I would lose the rockers.

 

Thanks for the advice. Curious to know why you'd switch out the 1.5 rockers which are currently fitted? 

[nicklouse]

 

The exhaust is fine.  I would go for an LCB. like the maniflow medium bore but I would lose the rockers.

 

Thanks for the advice. Curious to know why you'd switch out the 1.5 rockers which are currently fitted? 

 

They may give you a little more power at the top end but at the cost of drivability through the reduction of lower rpm torque. Also not a make I would fit. If you do fit them remember to check the rocker position and shim according. And check for coil bind and machine head if needed.

[cal844]

Personally I'd use the free flow for more torque.