RSR Engine Rebuild thinking

[txhokie4life]

I picked up a '75 RSR Replica. The deal was right so I jumped on it.
It will replace my 924S Chumps car as my DE and then as my skills increase maybe
PCA Club Racing.

In the interim -- my 924S will satisfy my W2W desires.

I realize I'm skiing over my tips here car wise, and moving into an
opperating budget that I prefer to keep on the lower end of things.

I've got about 6 months track time with a handful of DEs and a couple
of stints wheel to wheel racing road courses.

I have some Porsche engine experience, but this is my first air cooled,
and I have a partner mechanic that knows his way around air cooled
engines, but not a modified race engine.

The RSR engine was in pieces and Im playing CSI with out the credentials.

But lets assume all is good -- or at least I'll start with the components I have.

Known --
964 Case,
964 Crank,
Clewett Pulley,
Carilla Rods (haven't measured them yet)
Mehle Cylinder Liners, 100mm
Ross domed pistons, 100mm
993 Heads, look to be ported, twin plug, not sure of valve sizes yet
964 Cam Housing (I haven't pulled the cams yet)
TWM Throttle Body and Fuel Injectors

Motec M48

Also Known,
I've got more car then my driving ability at the moment :-)

What I've been told: (take all with a grain of salt)
This was a 12.8:1 CR engine
Failure might have been stretched or improperly torqued head studs leading
to piston slap.
Rumored 400+ HP

Desires:
Keep cost down - both short and long term.
Keep things reliable
Run in PCA DE's and maybe dabble in PCA Club Racing as my skills improve.

My game plan at the moment is to just mic everything out -- make sure all mechanicals are good and then put it all back together replacing bearings,
header/rod bolts, gaskets et al. Leaving the setup as is.

Then either biting the bullet on AV gas, or detuning to run on pump gas.

Then detune somewhat across the board to put HP in the mid 300's.

How much HP will we lose making it safe to run on pump gas (I'll probably
more than happy with that).

As my skills increase and I can actually utilize the HP, I then can ratchet
up the tuning to get more out of the engine/pay for AV gas as is desired.

I've done a lot of reading about detonation and knock sensors.
I don't need to play on that knife's edge.

thoughts?

thanks,

Mike

[Steve@Rennsport]

Mike,

Interesting project,......

A couple of thoughts,.............

1) Don't use Avgas. The octane formula isn't valid for race engines, its volatility and RVP isn't good for sea level operation and it has too much lead in it. Use race gas as runs MUCH better in every way.

2) Engine longevity depends on three things: compression ratio, operating RPM, and quality of assembly. There are a LOT of details involved when asking a motor to remain reliable if 8K RPM is desired. If the engine needs to last a few years, be conservative about CR and max RPM.

Done right, you'll have a good time and learn something, too.

[txhokie4life]

Thank you, Steve.

yes quite a project indeed.

Hope to be up and running by the fall.

If I stay with the components as is -- I'm stuck with the CR.

However, I do plan to limit the RPMs -- no reason to abuse the engine.
7-7.5k should be plenty.

Hope to do the assembly correctly :-) At least commit to upgrading the head studs, replacing the rod bolts, and looking into racing rod bearings.

looking forward to the learning -- hope to keep the tuition manageable :-)

mike

[winders]

Where is the engine designed to make power? If it is setup to rev to 8000 RPM and you limit it to 7000 RPM, you could be giving up a lot of power and driveability. You might need to a different cam setup....

Scott

[Steve@Rennsport]

Originally Posted by txhokie4life

Thank you, Steve.

yes quite a project indeed.

Hope to be up and running by the fall.

If I stay with the components as is -- I'm stuck with the CR.

However, I do plan to limit the RPMs -- no reason to abuse the engine.
7-7.5k should be plenty.

Hope to do the assembly correctly :-) At least commit to upgrading the head studs, replacing the rod bolts, and looking into racing rod bearings.

looking forward to the learning -- hope to keep the tuition manageable :-)

mike

I'm no fan of Ross pistons so thats something I would consider changing. Get the CR down and engine life is really extended.

3.8 RSR cams are conservative (as far as race cams go) and make decent power from 4K to 8K. You can run them to 7200-7500 and once again, extend engine life between rebuilds. If you have something custom, I'd find out what they are.

RSR head studs are already excellent, replace the SPS rod bolts (that what Carillo uses) when they are stretched beyond spec, and use a good aftermarket rod bearing such as JW Racing ones.

[txhokie4life]

Did a quick search on JW Racing Bearings -- but it did not come up fruitful.

Have a pointer to a source.

thank you,

Mike

[MBruns]

Thats Jerry Woods
Mike Bruns

[txhokie4life]

Originally Posted by MBruns

Thats Jerry Woods
Mike Bruns

Thanks..... for the next guy reading the thread...Smart Racing Bearings

http://www.smartracingproducts.com/catalog/engine.htm

[txhokie4life]

Originally Posted by Steve@Rennsport

I'm no fan of Ross pistons so thats something I would consider changing. Get the CR down and engine life is really extended.

Anything in particular I should be concerned about with these pistons aside from the large CR?

I'm not trying to make huge HP. I'm trying to most economically get the car back on the track and keep it there.

I realize that having an RSR replica and being economical might sound like an oxymoron, but it is the world that I am trying to live with.

3.8 RSR cams are conservative (as far as race cams go) and make decent power from 4K to 8K. You can run them to 7200-7500 and once again, extend engine life between rebuilds. If you have something custom, I'd find out what they are.

RSR head studs are already excellent, replace the SPS rod bolts (that what Carillo uses) when they are stretched beyond spec, and use a good aftermarket rod bearing such as JW Racing ones.

I'm not sure there are any real RSR parts in this engine (still TBD). I believe
this was a cobbled together engine design by SpeedWerks. A good engine,
but a hybrid of many models and 3rd party parts.

I plan to replace the rings, head bolts, rod bolts, and I like the idea of the JW bearings (although pricey).

For components, I'm torn between just working with what I have vs
the expense of replacing non-wear parts and risking non-compatability.

still learning (and always will be),

Mike

[Ollies930]

Recommend reading up on retuning for e85. That way compression ratio will not need to be altered and fuel is readily available and cheap. Might even pick up a couple hp.
Just need to make sure injectors and fuel pump are up to the task (approx 50% increase in flow).

[txhokie4life]

I like the idea Ollies930.

I just did some quick reading up.

I'll have to see if the fuel system is up for it -- but I suspect it is.

thanks,

Mike

[txhokie4life]

Circling back.

I had the CSI folks figure out what happened to the original engine (piston slap and melted heads)

In the interim I rebuilt the top end of a street 3.6 and have been running that for a few years on 93.

I'm looking at building up the original 3.8 -- but since the pistons are toast, I'm re-considering the E85 and looking to see what is the maximum CR I should consider.

This will be a strictly track engine -- running at places like COTA and TWS (or its replacement) and maybe MSR-Cresson.

Also the link to the Smart Racing Bearings is NLA -- so I'm on the search again for bearing solutions.

thanks,

mike