I am in process of planning the rebuild of my Cobra's Chev 350 - Plan to stroke it to 383 cu in and am trying to decide whether to set compression ratio at 9:1 or 10.5:1.
The reason for my quandary is that I am thinking of changing it to Fuel Injection at a later date and then fitting a single oversized Turbo at the front of the motor (plenty of room) feeding 7psi and coming in at around 3500 revs. My thinking is that the car is already severely traction limited and early boost will just make things worse but she could certainly handle the extra power that late boost will give.

Standard the motor should make around 350 hp and boosted around 500 which could be great fun on the track whilst retaining in full its burbling docility at low revs on public roads and not impacting too greatly on the already heavy fuel consumption at revs below 3000 or 120 KPH.
I have plotted the pre and post curves below – so should I go low CR and take a hit in power for something I might never do or go High CR and forget my dreams of turboing the car.

Does anyone think like I do that Turbo lag could be a good thing in these circumstances?


ChevCurves

Are you really sure about 10.5 :1 Compression ration AND and a Turbo?

Usually with a turbo you reduce the compression ration to about 8:1 (ish).

Also with 10.5:1 ratio you will be limited to running on Super unleaded as a minimum.

Personally I would stick with 9:1, without a turbo, and less if Turbo'd.

Have you thought about a Supercharger, less lag, and probably simpler to fit, readily avaiable for the V8.
Also no complex exhaust manifold.

Just my 2d's worth.

thanks for your comment - the 10.5:1 is with no turbo and 9:1 if I decide to go with future turbo option.

9:1 will be fine with a low boost of 7psi but will cost power if turbo never fitted.

10.5 seems a bit low I'm running 11.5 on pump fuel and it's OK

There is some good information if you google DCR.
Cam change will require more compression, ally heads help and can take more compression before Det.
Also a lot of info on squish to prevent Det

I read a few books on the matter before stroking my 350. There are plenty of american books which gives list of parts to go for to achieve various outputs.
Are re-using everything like heads and manifold/cams?
If not you should be able to get 420 bhp easily.
I had my Cobra at a track day a couple of weeks ago and it kept up with another focussed track Cobra with lots of trick bits and a more modern TVR V8, but brakes were rubbish compared to his!
Personally, I would plan not to turbo it, use the money for a few nice internals/cams/heads etc and anything left over use on four pot custom brakes!
I would also have a chat with Mike Huddard of Huddard engines on what internals to buy.
Then I'd supercharge it.

Thats 420 british hp, or around 960 US hp.

quote:

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Originally posted by bitsilly
I read a few books on the matter before stroking my 350. There are plenty of american books which gives list of parts to go for to achieve various outputs.
Are re-using everything like heads and manifold/cams?
If not you should be able to get 420 bhp easily.
I had my Cobra at a track day a couple of weeks ago and it kept up with another focussed track Cobra with lots of trick bits and a more modern TVR V8, but brakes were rubbish compared to his!
Personally, I would plan not to turbo it, use the money for a few nice internals/cams/heads etc and anything left over use on four pot custom brakes!
I would also have a chat with Mike Huddard of Huddard engines on what internals to buy.
Then I'd supercharge it.

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You need David Vizard's book of low-budget Chevy V8 builds