455 Olds And RPMS!!!!!

[Stv Euro]

I have a Tahiti jet with a Berkely A2 impeller with a strong built 455 Olds. The engine has a custom Mondello cam cut heads, intake, exhaust, and bal. I still can only turn that engine 4800-4900. Has ANYBODY been able to turn an olds any higher? The chevy boys say they are turning the same impeller 6000 with mild built crate engines.

[Stv Euro]

The hull is a Tahiti hull. Weight I do not know.
CAM:
(JM-28-29) 0.544 0.544 292°/300° 248° 258° 108° 3200-6800
In lift Ex lift adv dur in ex lobe RPM
.050 Range
Jet Boat/
Bracket/Pro
Drag Racing

The cam was degreed in "straight up". The head have had all the stress taken out. Behind the valves and all the way out the exhaust and even has the zinc poured in the heads to help keep the heat out of the intake. The valves are the BIG valves thats all I know on that. The compression is 185-190. The intake is a Torker 455 Eldebrock. The fuel is 9-10 lbs run by a Holley pump and the carb is a 850 double pumper Holley with man secondaries. The jets that I run are 80's in the front and 88's in the back with a big pop out valve. I have an HEI for fire because points act so crazy around water with 8mm wires. The exhaust is no problem 5"-6" bells lets it flow free with water only on the tips with the water cooled logs doing the rest. The engine just run into a wall at 4700-4800 on 93 oct. I ran 108 and only gained maybe 150 rpms. That no a lot of gain for $3.75 a gal!!
I love this stuff so thanks for looking at this and get back when you can.
Do you have any 455 parts left? EX: Intakes things like that.

[typhoon]

I read an article in Car Craft or similar a few years ago about the Olds motors...they are torque monsters, and really wil not rev past about 5200-5500 without a lot of pieces of metal flying about in an uncontained manner. Apparently, it has a lot to do with the sheer size of the crank, bearing diameters, rod weights etc.
I will try and dig up the magazine, and scan it..not promising anything, as it could be anywhere here..lots of boxes! The name Mondello comes to mind as one of the Olds gurus...how is it I can remember lots of engine stuff, but forget what to buy when grocery shopping???

Regards, Andrew.

[RayH]

Go to www.liquidaddiction.net/impeller.html you'll find an Impeller Chart. For an A2 Impeller to turn at 4800 RPM's you need 420 hp. To turn the same Impeller at 5000 RPM's you need about 480 hp.

[Stv Euro]

It is so hard to believe that my motor does not have any more HP than that. It has had everything done to it. My old motor had been in the boat for ten years. Compression was down to nothing and it would turn 4800. Now the compression is in the upper 180s and will turn 4900.

Let me ask another question. When the motor is out how hard should the impeller shaft be to turn by hand? When the motor was being rebuilt I reached down to turn the shaft and I could not. I then put on a glove and put both hands around it and could move it very little with a lot of effort? Is this normal?

My motor was built by a guy that had his on the Dyno at 500hp and he built mine even stronger. So I don't know what to do. NOS 75-125 hp I know that may help but I don't know how much. Maybe I will have to accept it as a water pounding jet boat and not a flat out race boat. It will sit there and idle with the best of them.

Thanks

[Capt.Insane-o]

Stock olds heads suck. A modified set of Edelbrocks work much better. Getting the rotating assembly right is necesssary too.

[halveb]

With respect to Olds motors (if you haven't already done this) install a set of restrictors in the motor. I have heard that the Olds motor was famous for sucking all the oil out of the pan and there is a restrictor package that helps keep the oil where it should be. Sorry I don't have any other information on the restrictors other than most jetters who run Olds put them in. Unfortunately it requires a tear down to do but is a cheap fix if you're already in the motor.

[RayH]

You should be able to turn your jet by hand fairly easy. You won't be able spin it but it should turn with one and pretty easy. As for the Olds 455 and the A2 impeller; if the motor was Dyno'd at 500+ hp, you should be turning about 5100+ RPM's. Has your Jet been rebuilt lately? If so, check the oil in your bowl, and check that your Thrust Bearing is not to tight (at the shaft entering your pump, nuts/bolts on either side). The Oiling problem with the Olds is due to poor return to the pan. At 5000 RPM you'll start running into this problem. The quick fix is restricted push-rods. In either case, check your Jet.........

[Stv Euro]

My pump was rebuilt 2 years ago with little time on it. If the thrust bearing is to tight how or can I loosen it up? Is that the fiber washers? Sorry to get confused but I have not looked at it at all this year. But warm weather is on the way!!:D :D

[RayH]

Go to www.cpperformance.com/TechTips/bjd-manual.htm you'll find good troubleshooting information and drawings on your pump. Also general maintenance.

[Shaun Barcelow]

This post has been inactive for a while but I'll throw in my two cents... My father has a mid 70's Checkmate with a W30 Olds 455. He's in the process of (slowly) replacing the stringers and transom, so it's been a few years since it's been on the water. That engine would turn about 5,200 RPM's at WOT, but the boat has a "YJ" Jacuzzi pump. A Berkeley dealer tried to convince me that the impeller was shot because it was turning too many revs. (It's not; that engine has turned 5,200 as long as I can remember.) Anyway, the Berkeley, being a high pressure pump, takes a lot more HP to turn high RPM's than a low-pressure Jacuzzi pump.