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I am considering super charging my 425 for my 63 riviera with venolia factory compression pistons what will i have to do to the engine to handle the added pressures? I know the normal stuff like head studs, hhhgirhdleh the mains and the like but this is my first nailhead and don't want to destroy it either.
Thanks in advance
Bret H.
Bret:
That sounds like a fun project. I have also thought of doing the same on my 65 Riviera.
There are a couple things I would consider in your project. that I have found out.
1. Go get a 401 Nailhead for the project and save your factory 425 c.i. engine. From the outside they look the same.
The 425's are getting very hard to find, and if it is original, you don't want to risk tearing it up, as it would really hurt the value of your car assuming it is in pretty good shape to start with and, "Numbers Matching"..
2. You need to get Low Compression Pistons for enough boost to made to make you project worth while. Getting Low Compression forged 401 c.i. Pistons for your project will be a lot cheaper, than with your 425, as the 425 pistons have to be custom made. The 425 Low Compression pistons will be in the range of are about 1k vs. $500 for the 401. (I think)
3. The 401 block is the same block as the 425 with a smaller bore. Since your plan is to add Boost, you will have much stronger cylinder walls with a 401 vs. a 425.
4. Scratch the plans of Super Charging the Nailhead unless:
a) You have enough money to buy a custom, purpose built intake manifold for the engine, or you already have an Antique manifold handy. This is a VERY expensive proposition.
b) If you were planning a centrifugal blower, instead of a Roots Type or Twin Screw, and maintaing anything that utilized your stock brackets, you will have a lot of work in front of you, or $$$ if you couldn't do it yourself.
5. Go with a small rear mounted Turbo Charger.
a) It would leave your engine compartment, virtually stock other than a blow through Hat for the Carburetor.
b) It would do away with all the problems and expenses I mentioned above.
c) A small Turbo Charger, set up correctly, would have almost no turbo lag and come on virtually instantaneously, like a Super Charger. Google, "Rear Mounted Turbo Chargers", and you will find, "THE" company who has the most experience with them. I can't remember their name as I write this.
d) Rear Mount Turbo Chargers keep a Hell of a lot of Heat out from under your hood, thus making a cooler charge of incoming air a lot easier. Do to the Laws of Thermodynamics, when you compress air you will induce a lot of heat into the air as a result. Hot air = More chance of detonation in your cylinder and also reduces the ability for you to take full advantage of the money your going to spend with the right Components. The Rear Mount Systems start at about 3k + for a single Turbo last time I checked.
e) Rear Mount Turbos as a result of their location with help allow the Air charge to cool down. (before you get to an intercooler mounted n the front of the car. Highly recommended for good performance)
6) You stock Cylinder Heads don't flow air worth a damn compared to the heads that were created after 1966. The Nailhead Configuration does not allow for larger valves, and the exhaust ports are painfully small. You would benefit greatly from a good porting job. DON"T do it yourself unless you know what your doing. You will screw up the head and have to go find another, which is getting fairly hard these days. (This will cost about $2k + or Minus $500.)
7) While we are on the subject, the valve train, ie. springs, rockers, cam shaft, lifters, push rods etc. will need to examined completely both physically and by their specifications and either be replaced or modified to work properly with any kind of worth while boost project. (5 psi or higher)
8) You should have the engine, "Purpose Built", by someone who knows what they ARE doing to build the engine to run, "Boosted", and to have anything near something that would be dependable. Port matching, newer better parts, anything you can do to make the engine Stronger, and flow air better through the heads, will make the project more successful.
9) Plan on running headers of some kind. The Exhaust can stand anything you can do to help remove the spent air efficiently and to drive the Turbo(s).
10) Find someone to, "Tune", the Engine Properly. The Turbo Charger System suppliers should be able to help with this. If you don't follow through with this you will ruin the engine.
11) Plan on the Engine Costing 8-$10,000 to be done correctly. More if there are large things I have missed (Which is probably plenty)
I hope this has been helpful, with any luck, others will add to this topic and further the necessary information you will need for the project to be a success. Remember, "Anything worthwhile, is worth doing Right". Don't skimp on anything, and you should have a very cool set up.
You also need to join the, "Buick Nailhead", group on Yahoo. (There might be a couple with similar names, but the Big one is the one I'm speaking about)
There you will find tons of information and guys who know a heck of a lot more than I do on Nailheads. I would not even consider doing this without consulting with them on this, plus they will know all the, "Right", people to get the correct parts and/or the correct skills necessary for your engine.
Please follow up on this, I will be very interested on following your project for my own sometime in the future.
Good Luck,
Ty O'Neal
Nailhead Lover and Student
What type of Supercharger? Roots or one of the centrifugal types like a Paxton?
I thought Hampton Blowers still made intake manifolds for the Roots type.
The stock bottom end is pretty strong. Add some ARP rod bolts and it'll be good for some boost.
Pistons and compression ratio are the biggest concern. Even tho the stock CR is rated at 10.25:1, it's actually closer to 9.8:1. Stock.
If you mill the block and the heads, you can get up to 10.25. That's what the NHRA guys had to do back in the day.
Now a rebuilt stocker with a thicker composition head gasket will be in the low 9's....But for a blower, you will want even less CR....so custom pistons are necessary....and forged ones as well.
I don't believe 401 pistons will cost any less than 425 pistons....they're still over $600 a set. probably closer to $800 now. Ross and Diamond have been recommended.
401 and 425 blocks are NOT the same blocks. But i believe 401 blocks may have thicker cylinder walls.....TT will tell you to sonic check the cylinder walls for thickness, and also to partially fill the water jackets with epoxy/block filler to strengthen the cylinders. Just up to to freeze plugs.....it'll be fine for street use.
So what kind of blower are you planning to install???
Probably 871 or maybe 671 have a couple of both, venolia pistons they have domed and flat forged for both 401 and 425 for under 600.