Bhp variances on American V8s
Bhp variances on American V8s
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Mario149

Original Poster:

7,789 posts

208 months

Monday 21st June 2010
quotequote all
I've posted this here in the hopes that more people will see it....the Yank Motors section looked a little quiet - tempting the mods I know wink

Okay, for the last couple of days I've been googling AC Cobra replicas etc as a kind of fantasy car garage thing, especially because they're pretty much the polar opposite of my daily drive.

I found this website that supplies engines amongst other things, and was wondering what exactly the differences were that make what appears to be the same engine more or less powerful? I'm mechanically savvy, but have never worked on an engine or anything so I was wondering if people in the know could explain to be why one 5.7 litre block can produce 250bhp or 350bhp....what are the company changing? You can goe fairly nuts with the technical terms, don't worry, I'll look them up if necessary!

TIA

PS: hypothetically, what would be the advantages of having alloy as opposed to iron heads?

Edited to fix url...

Edited by Mario149 on Tuesday 22 June 09:09

LuS1fer

43,526 posts

275 months

Monday 21st June 2010
quotequote all
In general, camshafts which dicate how long valves open for to let fuel in and the size of the carburettor assuming the valves can swallow enough fuel and burn it.

Alloy heads are much lighter and probably easier to cast.

davepoth

29,395 posts

229 months

Monday 21st June 2010
quotequote all
Alloy heads also dissipate heat much better than iron, which lowers the combustion chamber temperature, allowing a denser fuel-air mixture to go into the engine, meaning more power.

aeropilot

40,784 posts

257 months

Monday 21st June 2010
quotequote all
Mario149 said:
I was wondering if people in the know could explain to be why one 5.7 litre block can produce 250bhp or 350bhp....what are the company changing?
The 350 cube small block Chevy can range from 250hp to 700odd depending on internal component spec...... crank, rods, pistons, heads, cam, intake manifolds, carbs or injection, headers.... and that's without adding forced induction to the mix.

During the past 50 odd years, there has literally been an almost infinate range and supply of speed equipment for the fabled 'mouse' motor.


Mario149

Original Poster:

7,789 posts

208 months

Tuesday 22nd June 2010
quotequote all
Thanks for the replies all smile I'm sensing that they must be quite a lot of fun - barn door engineering that you can easily work on at home. Can def see myself owning something like that in Dax 427 form at some point in the future biggrin

300bhp/ton

41,030 posts

220 months

Tuesday 22nd June 2010
quotequote all
Mario149 said:
I've posted this here in the hopes that more people will see it....the Yank Motors section looked a little quiet - tempting the mods I know wink

Okay, for the last couple of days I've been googling AC Cobra replicas etc as a kind of fantasy car garage thing, especially because they're pretty much the polar opposite of my daily drive.

I found this website that supplies engines amongst other things, and was wondering what exactly the differences were that make what appears to be the same engine more or less powerful? I'm mechanically savvy, but have never worked on an engine or anything so I was wondering if people in the know could explain to be why one 5.7 litre block can produce 250bhp or 350bhp....what are the company changing? You can goe fairly nuts with the technical terms, don't worry, I'll look them up if necessary!

TIA

PS: hypothetically, what would be the advantages of having alloy as opposed to iron heads?

Edited to fix url...

Edited by Mario149 on Tuesday 22 June 09:09
There are lots of reasons for HP differences.

The biggest is marketing, as in the more HP you want, they more they'll charge you for it.

As to how the HP is made can vary. The SBC (small block Chevy) has undergone many guises over the years and different "generations" of engine. Yet within each generation there are a number of different displacements and specs.

In the 70's many engines suffered very low CR, restrictive heads and mil cams. Which added up to truly pony levels of HP. In the aftermarket all of these can be rectified. So sensible CR levels, good ported and flowing heads, higher lift cams, lighter rotating assemblies, better induction and carburetors.

The current LS generation SBC's are undeniably the best, with alloy blocks and superb power levels.

snotrag

15,686 posts

241 months

Tuesday 22nd June 2010
quotequote all
OP - FYI theres a Cobra Replica buyers guide in this months PPC, hurry though cos the new one is out this week.

Mario149

Original Poster:

7,789 posts

208 months

Tuesday 22nd June 2010
quotequote all
snotrag said:
OP - FYI theres a Cobra Replica buyers guide in this months PPC, hurry though cos the new one is out this week.
[ignorance]
what's PPC?!
[/ignorance]

snotrag

15,686 posts

241 months

Tuesday 22nd June 2010
quotequote all
Practical performance car magazine - its brilliant!

mat205125

17,790 posts

243 months

Tuesday 22nd June 2010
quotequote all
Aren't there reams and reams of literature on small block tuning?

Is there a particularly good DIY book that could be recommended to the OP? I've not yank-boat-anchor excperience myself, however was thinking along the lines of the Vizard Mini book

300bhp/ton

41,030 posts

220 months

Tuesday 22nd June 2010
quotequote all
mat205125 said:
Aren't there reams and reams of literature on small block tuning?

Is there a particularly good DIY book that could be recommended to the OP? I've not yank-boat-anchor excperience myself, however was thinking along the lines of the Vizard Mini book
Yep there's loads and loads of stuff. Too much probably.