Ivan
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| posted on 16/8/10 at 07:59 AM |
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Chev 350 Engine rebuild - WTD??
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
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wilkingj
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| posted on 16/8/10 at 09:47 AM |
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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.
1. The point of a journey is not to arrive.
2. Never take life seriously. Nobody gets out alive anyway.
Best Regards
Geoff
http://www.v8viento.co.uk
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Ivan
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| posted on 16/8/10 at 10:56 AM |
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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.
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v8kid
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| posted on 16/8/10 at 11:41 AM |
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10.5 seems a bit low I'm running 11.5 on pump fuel and it's OK
You'd be surprised how quickly the sales people at B&Q try and assist you after ignoring you for the past 15 minutes when you try and start a
chainsaw
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snapper
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| posted on 16/8/10 at 12:28 PM |
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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 eat to survive
I drink to forget
I breath to pi55 my ex wife off (and now my ex partner)
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bitsilly
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| posted on 16/8/10 at 03:36 PM |
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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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bitsilly
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| posted on 16/8/10 at 03:38 PM |
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Thats 420 british hp, or around 960 US hp.
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Ivan
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| posted on 16/8/10 at 04:37 PM |
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quote:
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.
I will reuse the original heads and the current cam that's a good street cam that see's me getting 13.5 sec 1/4 mile times with very
unsuitable tyres. In fact I beat many potentialy much faster Cobras because I could control wheel spin better than them but traction was still and is
still a problem. One just can't get suitable 15"X 275X60 tyres in SA.
Head is standard with 3 angle valve job and home ported. Brakes are adequate for the 4 or 5 laps at a time that I do before cooling off myself and the
car. The turbo would cost a lot less than new heads that I would really like a lot but just can't justify cost wise.
The stroker kit will be the Eagle balanced kit and it's just a matter of choosing piston , flat top or dished. I am going this way because I
don't trust my conrods any more at nearly 45 years old with original bolts that were a rattling good fit when I installed them 20 years ago 
and the cost of new conrods and pistons is not much less than a full stroker kit hence the decision to go 383 inch.
When I approach 6500 revs I am starting to wait for the bang so it's spoiling my fun.
I would not contemplate supercharging because of cost , weight and too much early torque unless I went for a centrifugal supercharger, in which case I
would prefer a Turbo which has lot less efficiency cost at low rev cruising and is cheaper and easier to get here in SA.
[Edited on 16/8/10 by Ivan]
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Rod Ends
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 posted on 16/8/10 at 06:49 PM |
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You need David Vizard's book of low-budget Chevy V8
builds
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