Packard Forum Index » V-8 (1955-56)

I was talking to a Buick guy who builds engines and breaths it today and I told him all what I know about the Packard V8.
I told him about the 5 inch from center, high nickel and how I've read people taking them up to 400 and possibilities of 500 cubes. He immediately started talking in math only a engine builder could understand but hes a true friend and was patient with me to the point I learned so much in that conversation about the basics in engine building.

Here are 2 question he told me to post.

1. How many cubes has anyone took this V8 Up to in the past?

2.what is the safest one can over bore, and what is the wall thickness in the cylinders.

I wrote notes as fast as I could will trying to process aswell so please acknowledge I might say some wrong things below but I tried hard to give you guys what he was saying....


He pondered with putting a 472/500 Cadillac crank in it. Having the rod journals taken down to 2 1/2 inch, grind off diameter of Cadillac crank 2/3 at the machine shop and having the
packard block bored to 2/3 too.

He also pondered getting the Cadillac heads to be mounted on the Packard block. Making them flow better... the Cadillac had a 4.3 stroke.

Using undersize Chevy bearings for extra stroke.

Continued...
He did not know if the mains on the Packard would line up with the mains of the Cadillac crank so I would love to know that answer.

He said something about taking it to 4.25 x 4.25 stroked out.


I have a Cadillac 472 at home with a spun rod at home.

Well that's all for now.
I hope we can get some answers for anybody who likes going fast.
Thanks, Ronnie

Enthusiasm is good, but so are facts:
1. The Packard block and heads are NOT a high-nickel alloy.
2. The Cadillac crank cannot be made to fit the Packard block, because it uses a center thrust bearing; but it's a cast crank in any case.
3. The Cadillac heads cannot be made to fit the Packard block. The head bolt pattern is completely different.
4. Most 374" blocks can be bored to 4.250" and we just bored one to 4.270" for 401".
5. The very rare Packard V8 forged crankshafts can be welded and ground to 4", but the longest I've personally done is 3.875" for 427". Long strokes with stock rods hit the bottom of the cylinder bores.
6. Aftermarket rods are so inexpensive it's not cost effective to use stock rods in a race build, especially a stroker which needs the extra clearance of rods with cap screws.
7. To build a high-performance Packard with custom machine work, forged pistons, custom rods, stroker crank, roller cam, et al, figure $10,000, minimum.

jack vines

Jack is the source for Packard V8 performance. I would listen to what he has to say.

Hope you are good Jack.

FWIW, the Packard V8 top end also needs all new parts:
1. The long, heavy 3/8" stem valves aren't suitable for higher RPM. They have to be replaced with custom 11/32" or 8mm stem valves.
2. The valve springs are not strong enough. They have to be replaced with custom springs.
3. The valve spring retainers on earlier engines were too soft and would let the keeper pull through, dropping the valve into the piston. Again, custom retainers.
4. The Packard cam profile is great for a smooth idle and low speed torque. For maximum power, a custom camshaft more lift and duration is necessary.

Then, there's the oiling system. I've learned to modify the OEM pump to work satisfactorily, by it's actually less expensive to convert to the Oldsmobile oil pump and pickup.

jack vines

I am curious about the lower end. I seem to recall some older threads where people have said the lower end and webs are small or a bit weak for large HP engine mods. With some of the large engines that seem to be the racing choices having 4 bolt main caps I was thinking there might be some truth to the lower end being a bit weak.

Jack thanks for your answers and tips, much appreciated.

And your right I am enthusiastic about going fast just for the sake of being fast. I want badly to keep the clipper a Packard powered car and I want it to be quick, street quick not track quick. But ti be truthful I wouldn't mind having a track star.

What are any old threads on v8 modifications, power adders, and performance here guys?

Howard thanks for adding constructive content. Wasn't the studes v8 have a stouter bottom end.

Does anyone have a crank out that can take a picture of it next to a tape measure?

Quote:Yes, the Packard main webs are not strong enough for extreme horsepower builds. I tap the main bolt holes with a bottoming tap and install ARP main studs. This, plus a good balance job is all that can be done.

Quote:Yes, all Studebaker V8 crankshafts are forged. Unless turbocharged, the Stude V8 can't make enough horsepower to hurt the bottom end.

Quote: One might understand your interest in the Cadillac crank but it ain't happening. As I said earlier, the Cadillac V8 uses a center thrust bearing and the Packard V8 uses a rear thrust bearing. The Cadillac main bearings are 3.25" and the Packard V8 are 2.50". Cadillac engineers knew they needed all that big diameter for the crankshaft to be strong enough for the 4.30" stroke. Turn it down to 2.5" and it would not be long for this world.

Bottom line - the Packard V8 is an interesting antique. It's never going to be as powerful or as durable as later, more perfected designs. All we're racing for is "fastest antique". If there were a racing class requiring blocks and heads with 1955 casting dates, we'd probably win that one.

jack vines