964 engine upgrade to 3.8L spec
 

Hi,
I'd like advice re a partial rebuild I plan to do on a late eurospec 964 engine which is in in good running condition.
I sourced at a good price some barely used 102 mm JE 12.5 to 1 CR pistons and 102mm Mahle slip fit barrels
The engine will be used for fast street I need it to be usable in traffic and tick over ok.
My plan is not to open the case but to replace the rod bearings and up-rate the rod bolts.
I intend to overhaul the top end while it is off but I don't particularly want to spend money on porting and bigger valves .
I am happy to upgrade the cams.
I know that the ideal combo is mahle/mahle or JE/Nickies but hopefully this combo will be ok?
So my questions;
Is this comp ratio ok for street? Am I right that slightly more aggressive cams will have the effect of reducing the dynamic CR .
What cam profile would you recommend ? I have looked at Dougherty and web cams.
I did read comments by some people that the angles around the valve seats on JE pistons are a little sharp and that rounding them off a little can improve airflow(and it would slightly reduce CR) .Is that a good idea ?
Any other advice would be of help.
Some relevant details;
Engine is going in a 1971 car with upgraded suspension and brakes.
It will have a Patrick conversion with a lightweight fly wheel and single pulley.
B B heat exchangers and a free flowing muffler with no cat.Steve Wong chip.
Petrol (gas) in the UK is standard 93 ron but I intend to use the premium 97 grade.
Hope I've not gone on too much.
Thanks.
Martin

1. Rod bolts, just FYI, the right way to do this is to have your rod big ends re-bored once you get your new bolts fit. You may want to condition the bolts (tighten to spec torque and loosen, at least 3 cycles) before you send to the machine shop. You are looking for consistent stretch once you get to the torque spec. Ideally you would measure the stretch each cycle until you are getting a consistent elongation value. Then you can say the fastener is "conditioned".

2. I'm no expert on CR, but a true 12.5 CR sounds too high for 97, I think you will need race gas

3. Talk to cam grinder. He will have questions for you, based on your answers, he will recommend a cam grind for you. Being that you are not replacing your rods, i believe your rev limit will be about stock + 500 rpm. So that fairly constrains where your power band will be, but still need to define overlap, duration, and lift

Martin, may be worth giving Richard Chamberlain a call, he's up nr. Huntingdon....what he doesn't know probably isn't worth knowing.

CTR Developments

...although please don't distract him until he's finished mine and Jonathan's (JBL930) work, there's a good chap ;) :D

Thanks,
I'll speak to him.
Martin

Hi Guys,
anyone have an opinion on this?
thanks Martin