420 and 450 cams - early head

[dunclentdr1]

I’m am currently running 420 cams in a 1680 cc twin cam - this gives me c145bhp which is good for hill climbs but I would like a little more!

I am considering fitting 450 cams which I gather will require longer springs. It is an early head.

My questions are:-

- does anyone have experience or advice with 450 cams - Is a c10bhp improvement realistic?
- are any other changes required apart from longer springs?
- any concerns about running 450s in an early head?

Thanks
David

[rgh0]

I’m am currently running 420 cams in a 1680 cc twin cam - this gives me c145bhp which is good for hill climbs but I would like a little more!

I am considering fitting 450 cams which I gather will require longer springs. It is an early head.

My questions are:-

- does anyone have experience or advice with 450 cams - Is a c10bhp improvement realistic?
- are any other changes required apart from longer springs?
- any concerns about running 450s in an early head?

Thanks
David

By early head do you mean the head with the half moon projections into the spark plug well. The smaller intakes on these heads make them less responsive to tuning but otherwise you should be able to fit higher lift cams and you will get more power. The end outcome will depend on the rest of the engine. The valves will need replacing with longer ones as well as the springs and you may also need to replace the cam followers also to get the right spring install heights and an acceptable shim thickness. There are multiple ways to achieve this setup so try to buy parts that you or someone knowledgeable knows will work together. You will also need to check valve to piston clearance on overlap

cheers
Rohan

[Verve]

Hi David ,

My S3 26R style Elan has a later Q450 head , which ironically , I am thinking of detuning to Q420 spec` as the car is used purely for the road ... it behaves beautifully & has the correct QED Red Race Springs etc ., ... it`s only done road running in mileage .... maybe I should sell the complete head as it is ?

Cheers ,

Paul .