piston/cylinder recommendations for turbo 79 3.0 SC engine

[iamchappy]

I am contemplating a rebuild because of a oil pump failure. the engine is a 79 CIS SC 3.0 that is turbocharged in my 914 and I would like to run 12 to 14lbs of boost.
What would you recommend for new pistons and cylinders. Or any other suggestions I should consider.

I have another post showing the turbo install in my post- my first rebuild - with your support.

[cnavarro]

At the low level of boost you want to run, a 98mm big bore kit with some 7.5:1 pistons would be excellent or even a machine in 100mm big bore kit, both of which would give you lots more low end torque and top end power.

Charles Navarro
LN Engineering
http://www.LNengineering.com
Aircooled Precision Performance

[iamchappy]

My goal is for a reliable street car laying down 350 up to 400hp from the CIS 3.0 SC engine. I ran the car last Summer and Fall at 9lbs with the stock engine and compression using a 911 SC - CSV 7th injector for enrichment off of a pressure switch and a msd btm boost retard ignition system. The car ran great with rich A/R numbers in this form. Over the winter I added a 1080 CFM Spearco intercooler and was looking to turn the boost up to 12 to 14lbs but the oil pump failure ended the test before I started and I was only able to drive the car around for about an hour before the mishap while breaking in the car after the Winter lay over.
Talk about Bummer huh.
Anyway I hope you guys can steer me in the right direction as to what needs to be done, I wont be racing the car and I am not out to build a monster engine or have the fastest car on the road, just one that will garner a little respect.

[cnavarro]

A safe and well spent upgrade indeed would then be a 98mm big bore kit. A bored out 3.2 cylinder from 95 to 98 and then replated and match honed to a set of new JEs would be a good starting point. Also have a turbo guy like Turbowerks go over your heads. If budget allows, a set of Nickies would give you an added margin of safety for more boost at a later date. If any money is to be spent, it's well worth it there. New heads studs would be a good investment as well- Supertec or ARP, both are excellent pieces.

As long as your fuel system can deliver enough fuel and flow enough air, 400HP should be no problem- aim for a bar of boost. I'm not sure how far you want to go, but an upgrade to programmable EFI would give you added tunability, but I know it can be a big pill to swallow when the CIS is working just fine. :-)

Charles Navarro
LN Engineering
http://www.LNengineering.com
Aircooled Precision Performance

[iamchappy]

Thanks Charles for the info. What price differance would I be looking at between the Nickies and a bore and replate job. It seems to me thats were the money should be spent if its within reason.

What type work do you think is needed on my heads, again I am not out to squeeze every little bit of horsepower I can out of it. I just want to keep everything together.

[cnavarro]

On the headwork, you might want to make a post on c2turbo.com, since all they live and breath are turbos :-)
If your existing cylinders are the style w/o a sealing ring, then they can be stripped and replated, and in that case, you're looking at somewhere around $1000. The Nickies, no matter how you cut it, will be over twice that, but you could for the same price do a 100mm conversion and up the boost to the 1 bar you are looking for, or with the 98s, have a piece that can handle gobs of boost. Again c2turbo.com would be a great place to ask about this stuff.

Charles Navarro
LN Engineering
http://www.LNengineering.com
Aircooled Precision Performance

[iamchappy]

How much more displacement can my stock CIS handle in regards to everyday driving, will it be able to compensate.
I can effectively throw all the fuel I want at it on boost, but will regular driving be ok and what about ignition.

[cnavarro]

You have a few options. With the single plug setup, a unit like the J and s safeguard (there is one for sale in the classifieds) with some time taken for adjustment and placement of the sensor. This will automatically retard the timing on each individual cylinder if pre-ignition or knock is detected. Twin plug would be a great thing, something like an electromotive distributorless ignition. It probably would be good if Henry could chime in, since I know he's done some big cis engines, as have some of the other members here. 400 horsepower sounds reasonable to me to ask of the CIS setup?

Charles Navarro
LN Engineering
http://www.LNengineering.com
Aircooled Precision Performance

[iamchappy]

I guess I shouldn't get hung up on numbers really, around 300 is plenty fun in a 914. I may have been close to that running 9lbs. so I thought with an intercooler and 1 bar of boost I could see 50 to 75 or 100 on top of that.
Anymore than that, my 901 tranny with LSD will definitely be stressed and compromised. As it is sort of a daily driver street car, reliability is a big concern.

[sammyg2]

For the money you are thinking of spending you could probably buy a low mileage 3.3 liter 930 engine for it.
A little turbo work and aftermarket intercooler would put you well over the 350 hp mark with no hassles with the CIS, reliability, or smog (if that applies up there).

[iamchappy]

Well Sammy, Ive got the new turbo and intercooler, money I dont have right now. I have been thinking I might pick up a nice used 3.0 to get the car back on the road again. And then work on the Improving and rebuilding other engine at a later date.
The performance with a stock 3.0 engine turbocharged was fine with me, a few more pounds over 9 is what I was planning on running through the intercooler and was going to be the end of it.
Now with the pump shot and having to tear it all apart it opens up options and places I wasn't thinking about going.
I got Wayne's book today and will start to scratch my head as to what I am going to do. If I start taking the rebuilding project on who knows were it could lead, just like my other projects they seem to be leading me somewhere.
In the end I will probably have a pretty scary 914.(It was already getting kinda scary)
I know there are a few things that need to be changed with the turbo engine, Im not sure what they where, flywheel, fuel pumps?
But that might be a good way of going also.

[strokher racing]

What compression is the engine right now?

Eric Hood

[iamchappy]

8-5.1 stock compression for 79 sc 3.0
K27 7200 turbo
Spearco 1080 cfm intercooler
Using a MSD btm boost retard ignition
7th injector for enrichment fired by a hobbs switch
Tial wastegate 38mm
Tial bov 50mm
turbo x boost controller
Never had any predetenation at 9lbs always ran rich on boost with enrichment injector when used without the intercooler.

[WERK I]

iamchappy,
Maybe you have already thought of this, but turbocharged applications really require forged pistons. The standard 3.0 SC offerings were cast I believe.
Did you do custom headers for the engine or use 3.0 turbo heat exchangers? The Tial 38mm wastegate is really on the edge, in terms how much HP it can handle. In the standard configuration or the aftermarket(B&B or GHL), most tuners are recommending 46mm WG to handle 400+ HP.

[iamchappy]

That is the purpose of this thread, I was aware that the stock cis pistons were vulnerable on turbo charged applications, could I reuse the cylinders and purchase pistons that would be more boost friendly, hp numbers are not that important to me as this is a street car and is pretty damn fast for a 914 with the boost set at 9lbs. The 901 transmission with Quaffe LSD has short gears in it so you can imagine I have my hands full as it is. Over the Winter I added the intercooler and was out to see how the engine handled 12lbs to 14lbs of boost. The car rarely will see any prolonged boost, mostly short bursts while entering the highway and a blast now and then when the coast is clear.

[iamchappy]

The intercooler has two 7" fans pulling fresh air from a duct fashioned into the rear spoiler, and exits out the bottom through and around Stainless steel ducting and heat shielding from the muffler.

[cnavarro]

You could keep the stock bore, strip and replate, then fit a set of 95mm JEs, which would most definately be on the conservative side.

Charles Navarro
LN Engineering
http://www.LNengineering.com
Aircooled Precision Performance

[iamchappy]

Charles, if I can manage it I will spring for your 95's or 98's, Time and money will determine what direction I will go, so far ive not spared any expense in assembling the right parts for the project but a rebuild this soon wasn't in the plan.

[air-cool-me]

i want to see where this goes! i have a turbo 79SC motor that is on its last legs....

i plan on using aftermarket injection.

and i dont have a ton of $$

[iamchappy]

I have the engine stripped down to the long block, I will procede further.

( i want to see where this goes! )

Nick, so do I!