R2 Heads Really Needed?

[mfg]

I’ve mentioned this before, but am still wondering about the necessity of changing cylinder heads when converting an R1 Avanti engine to Avanti R2 specs.

Is 10 or 10.25 to 1 compression ratio really too high when the added boost of a Paxton supercharger is put into the mix?

I realize Studebaker decided a compression reduction to 9 to 1 was, for  warranty issues, a prudent move. However, in my eyes the bottom end of a Studebaker V8 is so robust that 10 to 1 plus a Paxton seems like child’s play!

Continuing thoughts on this subject are welcome!! 🙂

 

[Gunslinger]

While I’m no expert at it…it’s more than just the additional compression ratio…the compression actually increases exponentially…maybe logarithmically…not sure the correct term…engine rpm’s increase multiplied by the pulley ratio. Modern engines with blowers and turbos have waste gates to keep the engines from blowing up…I don’t believe the Stude engine has any.  The potential of detonation is very real.

While I might be very wrong on the engineering of it…too much compression is very hard on the engine.  I’ve heard of R1 engines having a blower installed but I would imagine they’re not driven very hard.  Studebaker engines…while very strong…have to be warranted and having engines blowing up due to overstressing would be very expensive for Studebaker plus the bad publicity.

As it was…Studebaker sold the R3 engines without a warranty.  

[ronmanfredi]

I turbo charged my first engine in 1978, a Datsun 620 pickup with a 2 Liter 4-cylinder engine.  It was all a custom/experimental job with 2 stages of water injection, and ignition retard through the use of a pressure switch and second set of magnetic pick-up coils in the distributor.  Back then, it was easy to get 98 octane gas, which I ran.  Right out of the gate, the ring lands collapsed on the pistons at about 8 PSI of boost.  So, I went with forged pistons, lowered the compression ratio from 10 to 8 PSI and O-ringed the block.  Once the engine was broken in, I continued to increase the boost by raising the turbo blow off valve pressure until the limit was hit, 28 PSI.  The engine, which by now had been rebuilt a couple of times, continued to run without further problems.  For the next year or so, the only reoccurring problem was the nut on the transmission output shaft behind 5th gear would eventually get loose due to the power and I'd loose 5th gear.  (The turbo was a Nissan race car turbo of the day)

The 2 Liter Datsun engine had a 5 main bearing crank which was basically a Z Car crank cut down for a 4 cylinder.  As an educated auto tech at the Datsun dealer for about 12 years, we never really had many problems with the engines lower end, unless the owner let the vehicle run out of oil.  But the pistons, that was a different story.  Over the next decade, I continued to work in conjunction with a couple of other specialty shops developing sellable turbo kits for several models of Datsun cars.  The one thing that we always insisted on, was lowering the compression.  Not for the lower end, but for the pistons.

[Dwight FitzSimons]

A stock R1 engine is prone to detonation (pinging).  I'm no expert, but I assume that the first thing detonation damages is the rings; it breaks them.  Adding the boost of a blower would increase the fuel octane required to prevent detonation.

Of course, the timing is different on an R2 than an R1.  I assume that, if one were to add a blower to an R1, then the R2 timing should be used (both initial & distributor).

I have also thought of adding a Paxton to my R1 engine.  No more than I would drive the car the extra cost of racing gas might be worth it.  If I were caught somewhere without availability of racing gas I would drive it easy home & refill with racing gas before driving the car hard.

[mfg]

So, I take from the above insightful replies that, for an R1 converted to R2 specs… without a cylinder head change… Improved (forged) pistons, and aviation type gasoline are the safe play! (If engine is to be run hard)

[Dwight FitzSimons]

6 hours ago, mfg said:

So, I take from the above insightful replies that, for an R1 converted to R2 specs… without a cylinder head change… Improved (forged) pistons, and aviation type gasoline are the safe play! (If engine is to be run hard)

Non-expert here, but, yes.  If we assume that Studebaker chose the compression ratios correctly for the R1 & R2 engines, then adding a supercharger would increase the "effective" compression ratio by 1.25 points ( R1 has 10.25:1, R2 has 9:1).  So, adding a blower to an R1 would increase its effective C.R. from 10.25:1 to 11.5:1.  An 11.5 C.R. is pretty high, I assume too high for 93 octane fuel, unless one drove the car very easy.

(I realize that my reasoning isn't exactly correct, but isn't too far off.)

[Mark63Avanti]

16 hours ago, Dwight FitzSimons said:

A stock R1 engine is prone to detonation (pinging).  I'm no expert, but I assume that the first thing detonation damages is the rings; it breaks them.  Adding the boost of a blower would increase the fuel octane required to prevent detonation.

Of course, the timing is different on an R2 than an R1.  I assume that, if one were to add a blower to an R1, then the R2 timing should be used (both initial & distributor).

I have also thought of adding a Paxton to my R1 engine.  No more than I would drive the car the extra cost of racing gas might be worth it.  If I were caught somewhere without availability of racing gas I would drive it easy home & refill with racing gas before driving the car hard.

That's interesting that the R1 engine was prone to pinging since that Avanti didn't come with a "use premium fuel" label on the gas cap.

[64StudebakerAvanti]

AFAIK, Avanti R1s did have a sticker on the gas cap stating premium fuel only. I have what appears to be original caps with the sticker.  The sticker is available from our Studebaker vendors

[64StudebakerAvanti]

Some of these may be available:

https://www.hotrod.com/features/ping-fighters-october-1981-982-1152-65-1

I have one on the shelf that I inherited from a failed twin S/C project.

 

[64StudebakerAvanti]

Ed, you could also review comments to your post a year ago.

https://aoai.org/forums/topic/44438-r2-heads-a-necessity/

 

 

 

[64StudebakerAvanti]

in  case anyone is interested, this is the device I have on the shelf:

http://www.jandssafeguard.com/NewUniversal/UniversalVersion.html