Rebuilding 78 SC to 3.0 RSR
 

I have a 78 SC motor, I want to rebuild it to an RSR spec.

RSR cams springs
10.5:1 CR je or RSR pistons
1 5/8 headers
2in/out muffler
40mm webers


Now the Andersen Book says that the RSR 95mm pistons do not work too good with the 78 sc head, (can't get a good CR) due to the head size.

If I use JE 10.5:1 pistons will I have the same issue with CR or will a JE piston inwith my 78 heads be 10.5:1.

My other question is webers I have a set of 40mm with 36mm venturis, these will be rebuilt to RSR spec, id the 36mm venturi too big for 3.0 RSR?

cheers

Matt

Matt

I built a very similar motor from a '78 SC for my RSR clone.

It's a 3 liter twin plug with Mahle 10.5 RSR P's and C's, DC-60 cams, 1 3/4 " headers and 46mm PMO's. The heads do have to be cut down to reduce the combustion chamber volume to get the CR up to 10.5. You'll also have to run twin plug unless your using race gas only.

Here's more info:

http://forums.pelicanparts.com/porsche-911-technical-forum/246563-another-rsr-clone-project-dyno-day.html?highlight=dyno+day

http://forums.pelicanparts.com/uploa...1222335422.jpg

Nice motor Tom,

I would prefer to not change the deck height, if possible would I have to do this with the JE's?

my mechanic thinks I can run 10.5:1 on a single plug with 98 octaine gas OK

Matt

You control the deck ht with the cylinder base gasket thickness. The combustion chamber volume along with the piston dome volume will set the CR. You can use JE's but I'd be careful about single plug with the high dome pistons and 10.5 CR. Twin plug has many other benefits.

See this from Rennsport Systems:

http://www.rennsportsystems.com/2a.html

Wow...what's the name of that color orange? Is that Signal...tangerine?
Stunning

Signal Orange

http://forums.pelicanparts.com/uploa...1222379615.jpg