80_cutlass

A few weeks ago I detailed for ya'll the drama surrounding my mismarked crank and the machine shop made it right....they swapped the correct bearings for me for the 350 crank.

But I got to thinkin' and decided to use the 403 crank in the 403. So, it ended up ground 20/20 and I got it back on Friday. So, this pm I put together the rotating assembly and its just waiting to be finished. Next weekend I should be able to knock it the rest of the way out and start the process of stabbing it into my 84 Cutlass.

I used the KB405 pistons and I am pretty stoked about getting it going.

sb

88 coupe

You did balance it didn't you?

Norm

80_cutlass

Well, no. The whole reason I went back with the 403 crank, rather than using the 350 crank that started the whole fiasco, was to avoid the balancing issue.

Am I building a time bomb?

I have put together many an engine with varying degrees of hot rodding and only balanced one.....?

captjim

I am going to guess that the KBs are heavier than the stock pistons. Balancing is $175 +/-, it is just silly not to do it, IMO. Money well spent.

80_cutlass

Well, call me silly, then.

Built many slant sixes, small mopars and a handful of big mopars. Never balanced a crank, save one 318 that I balanced the crank, matched the rods and the pistons to .01 grams. Couldn't tell a bit of difference between that 318 and any of the others I built. Built a couple of chevys. Never balanced a crank. Built a couple of Fords....never balanced those. I never had a problem with them shaking out my fillings.....? Had them in everthing from Jeeps to boats.

Visually the KBs would appear lighter. Less skirt. But they do have more meat between the rings. Oh well. They are installed and the old ones have already been recycled. No chance to get the mass on them.

If this one goes boom, I'm done with Olds...I'll go back to mopars.


sb

cutlassefi

[quote=80_cutlass;203246]Well, call me silly, then.

Built many slant sixes, small mopars and a handful of big mopars. Never balanced a crank, save one 318 that I balanced the crank, matched the rods and the pistons to .01 grams. Couldn't tell a bit of difference between that 318 and any of the others I built. Built a couple of chevys. Never balanced a crank. Built a couple of Fords....never balanced those. I never had a problem with them shaking out my fillings.....? Had them in everthing from Jeeps to boats.

Visually the KBs would appear lighter. Less skirt. But they do have more meat between the rings. Oh well. They are installed and the old ones have already been recycled. No chance to get the mass on them.

If this one goes boom, I'm done with Olds...I'll go back to mopars.



Great logic, blame it on the engine not the builder. Make sense to me!

80_cutlass

[quote=cutlassefi;203284]Not particularly illogical. It would indicate an inherent issue with the engine, as the builder is the same, however the engine that is built is different.

Turned many of those engines above at high RPM for 1/4 mile times and cross country driving and flying around in boats. Some with stock pistons and some with KB pistons (for the record the balanced 318 was with stock parts and was in a 1986 2WD Jeep Cherokee) without throwing parts out of them and/or shaking like an unbalanced washing machine.

So, if this 403 does those things, I guess I can just be one more person who "can't build" an Oldsmobile. I can live with that. Is this what I can expect when I finish this build if the crank is not balanced? Really?

The admission price to play in the Oldsmobile arena (as far as engine hotrodding goes) is out of reason. I enjoy being the oddball. That's what got me hooked into Mopars. The cheapness and ready availability of G-bodies is what got me into Olds. The incredible inflation in Mopar car prices helped in this, as well. (For example: $1800 for a non-running Duster /6 with no title???)

The fact that I can't stand everyone sticking a Chevy into every car on earth convinced me to stick an OLDS motor in my G. However, if every time I mess with one I need to balance the crank....its just getting to the point where I may as well spend the extra money on the car rather than the build of the motor.

Just so the question doesn't come up:

best times in the 1/4 mile
low 12's 74 Dart with a 360 4.10 rear
slant six high 14s 65 B'cuda 3.55 open rear

boat was a 305 chevy that we turned 4700rpms all day at times.

big mopars were in a Coronet in college (no times)/4WD ramcharger.

The cars that I did get times on were full body/interior. The Bcuda was driven as a daily driver and to and from the track.

Admittedly, not earth shattering, but they didn't "go boom" either. Sold all of those to friends except the ramcharger and coronet. The other motors I have built have been for friends or for money or I just sold the car to go to the next project. A fault, I admit.

So, before you throw me under the bus, understand where I am coming from and my background. I guess it comes to this - is the balance of the 403 going to be THAT bad without balancing the crank? And will this cause it to go boom? My fault? Maybe. But that has not been an issue on the other motors I've built. You tell me why not.

sb

captjim

The short answer IMHO is that you happen to choose the worst platform for a performance build. Yes, big inches in a small block. But, large bore = heavy pistons slinging around in a windowed block with VERY thin cylinder walls. Add to that Siamsed cylinders (prone to overheating and detonation) and thin bore spacing. It is just not a great recipe for high rpm or high power. It was perfect for it's intended purpose, a "bridge" between the 455 and 350 for the big land yachts. It has been proven to be a reliable street engine.

80_cutlass

I am not building a high RPM, high horsepower motor here. It will be cammed to make peak power about 4000-4500 rpm. Peak torque should be right around 2000 rpm.

Again, is this engine going to grenade when other similar builds I have done with other makes have held up really well? If it does, just because I did not balance the crank, then yes I will blame the engine not the builder.

sb

cutlassefi

Are you converting this 403 to a diesel?

80_cutlass

LOL! No, I am just going by the CamQuest info from the Comp Cams info. With the grind I ended up with it shows peak torque @ 2000 rpm and staying pretty flat all the way to ~4000, but the graph is small and difficult to read. The text does say peak torque @ 2000.

*Now that I am home, it says 439.7 ft/lb (I thought it was lb/ft) of torque @ 2000. Peak hp @4000 of 306.

Is this contrary to what you have seen?

sb

cutlassefi

What's the grind? You may have a fairly flat curve but it won't "peak" at 2000, my guess is more like 3800 or so unless it's something other than what I think it is.

Hope it all works out.

80_cutlass

It is definitly not peaky like a mountain....more flat like a mesa on the graph. The grind is the 260H, I believe. I will have to check when I get home. I do remember the duration is 218/218 and the lift is 456/456. I do not recall the other stats, but will post them here when I get to the house.



sb

olds 307 and 403

The KB pistons are similar in weight to stock pistons. On a low rpm engine, you should be fine. I used a 307 crank to do an ultra cheap 403 build, my crank was really worn. No machine work on mine, has seen 5000+ rpm. You should have done it while the over bore and other work was being done. Some don't like Comp Cams, high duration and low lift.