Dyno day, the good and the bad....

I finally made it to the dyno earlier this week. After ballooning a converter two years ago, I took the chance to upgrade some components build a flow bench, port the heads more, you know ....spend more money to make more power. This combination is likely similar to many street performance builds where more time than money is available.

The basics:
`73 464 with iron heads, stage 1 valves and home porting (270 int/175 exh), TA 1.6 roller rockers, 10.05:1 CR w/7.9 DCR, 233/250 SB cam with .538/.536 lift, Weisco 0.038 over dished pistons 0.013" in the hole and .040" gasket, lightened factory rods, Holley 850 DP w/80 jets square, old SP-1 intake with home porting, MT scavenger headers, main studs, TA 7qt. pan.

We broke the cam in with the outer spring and damper only 100# at 1.89" spring height and 255 at 0.55" lift. We then installed the inner springs, at 1.89" got 120# and 332# at .550". Valve tips were a little tall so the springs were shimmed and the rocker was shimmed. I used Brad Penn 30 wt for all dyno pulls.

I was really hoping for 500 HP on this conservative dyno, but after my last dyno 5 years ago (with leaking valves) and making only 440 HP I was not feeling confident about my 500 goal.

I run the motor using a SFI flex plate and 1/2" shims spacers to add the 25# plate to help with strength and to dampen the engine for the pulls. This worked without any problems. We did have to clearance the old dyno frame to clear the headers but the dyno operator/friend did not mind cutting a chunk of his dyno frame to make it work. :TU:

After he asking me if I took my heart pills today, we made the first full pull. Oil pressure looked good; at 2500 steady state we had 40 psi at temperature. After putting the hammer down 8 seconds later we had completed our first pull. During the run I saw 503 HP flash on the computer towards the end, with oil psi. max of 78 psi. The corrected numbers for our first pull was 532.5 @4400 rpms and 509.4 HP @5400 rpm. :beers2: This brought a smile to everyone's face!. Man, I was psyched, even my Chevy friend, who earlier said we were dynoing a motor home motor, was impressed.

Now the bad part
The first run showed we were fat up top so we removed the 80 jets and installed 78 jets in all four corners. This pull was slightly stronger. We thought maybe the motor likes it fat, so we put in 82 jets in but things fell off below the first run. We then changed the timing from ~34 both up and down then back to 34 and the pulls kept going down. We found the voltage was only 11 volts so we fixed that, we also took the valve covers off to check lash, then checked crank endplay....all checked good. We fired it up again and listened closely to the motor, we heard nothing unusual, so we pulled it again. This time we were really down, I'm talking 45 HP. ou:

We pulled the oil filter, cut it open and found what we had suspected, small fragments/specks of bearing material.

Maybe tomorrow I'll start the dis-assembly and evaluation.

I'm looking at the bright side, when I get it right it should perform. Here's a picture obviously before we ran into issues.

I've also attached a .txt file of the first pull. What do you guys think of the numbers? Tunning advice welcome.

I figure I'll be tearing this thing down again and cleaning up everything. I'm guessing I have a main or rod bearing(s) that are toast. I won't be turning this motor up side down until I've got it apart and somewhat cleaned. Time for detective work...I'm open to recommendations on to do order o No:

There you have it the good and the bad.....to be continued....:Comp:

 

Rod and main clearances are critical, critical, and more critical on a BBB. I had to learn that the hard way. I had my rod and mains set @ .002 the 2nd time I rebuilt mine. Do you know what they were @ and did you check them? Might be a cam lobe gone bad too. Good HP/torque #'s though.

 

did you detect any detonation on the pulls,sorry to hear about the damage you were making some good numbers

 

Sorry 4 your problems but those r great #'s once u get it sorted out u will b verry happy with that power hope it goes well 4 u

 

Here are some of the clearances I forgot to include: Rods were 0.002" and mains were 0.0017". Rod side clearance was a little tight and ranged from 0.010" to 0.013", crank endplay a little tight too at 0.004". ARP main studs with 30W was torqued to 130 ft-lbs and ARP rods bolts torqued to 50 ft-lbs (is this low?).

My crank was turned .020/.020, may have to go .030" after inspection.

We did not detect any detionation but the motor does have lots of cylinder pressure, evident by how slow the motor turned over. We eventually put two batteries in series to give it 24 volts. I will likely need a gear reduction starter for hot starts?

 

I think the Mains are too tight. I set mine @.003.

 

I read a thread by JW once that many machine shops do do have the correct size (3.25" ) honing bar tool to insure a 455 Buick mains are round. Here is something to consider when you do the check:


"Tell you the truth, I would be more worried about .0015 than I would be about .003.

At .0015 we had better be sure the mains are round, and the crank is straight. A crank slightly tweeked could wipe the oil film right off a bearing, leading to failure.

I would at miniumum take it apart, and install the crank without the rear seal (unless it's neoprene) and then see how it spins with just light oil on the bearings. It should turn easily with your fingers, and be nice and smooth.


Neither of these clearance figures are what causes bearing failure in freshly built big blocks Buicks. The main difference you will see is idle oil pressure.. if you have a stock 70 cover, then I would bet your going to be running 20-50 if the clearances are around .003. No big deal tho.. being tight requires that everything is machine to a higher level of accuracy, as you simply have less clearance to play with.

If your willing to go farther for piece of mind, take it apart and take it to a machine shop of your choice, and stand there and watch him measure the main housings, for out of round and size.. Out of round mains is what kills BBB rebuilds.

Then install the bearings, torque it up and read the size again. Write it down, measure the crank, and do the math. That's your real clearance. Repeat the process with the rods.

Or cross your fingers and run it....

JW"


http://www.v8buick.com/showthread.php?t=153038&highlight=main+clearances

 

Craig look at post #14 in the thread linked below in which JW says it all about insuring the quality of the potential machine shop work when going with close main clearances:


"...Line hone (or Line bore) the motor.. and be very wary of who does this for you.. every machinist can line hone a BBC, with it's rather small main diameter. But the BBB has those wonderful 3 1/4 inch mains, and doing those with a hone, and keeping the housing sizes within .0002, and round, takes a machinist who has experience and the right equipment to do it correctly. Mine has a honing bar just for that diameter main, and I gave him a reject block to "break in" his new stones just recently..."

http://www.v8buick.com/showthread.php?t=49981&highlight=tool+size+machine+mains+round

 

In my case .003 to 0035 clearance on the mains and rods got me a melted front cam bearing and spun #7 rod bearing....I had the rods and mains all set at .002 and the 455 now has 20 lbs of pressure at hot idle and 65 lbs at 60 MPH with 10w30....its been about 7 years since I rebuilt it and it runs great.

 

lets us now what you find when you get it apart

 

Thanks for the read Jim!

I will not be tearing this one down until I take a quick cranking compression reading. The standard battery at the dyno had problems turning the motor over. I went with the smaller of the two cams choices so I bet I'm in the range of 180 to 200 cranking compression. My IVC is 68 with 10.05:1 CR.

Are there other ways of identifying detionation if you can't hear it ....during an the engine dyno pull? I am tempted to run a 3" piple from the header out the port hole at the dyno next time, so I can hear better!

I'll have to run by the speed shop this week, they have my bellhousing, before I can crank the motor over. I'll likely do it without plugs. Oh, wait a minuet, i can do this since the starter bolts to the block, duh.

I corrected my spring pressure in my first post (332# @ .550" lift)

 

The cranking problem you are describing tells me either the crank is binding or the pistons but i think its the crank due to the tight clearances.At 200 cranking comp. it would still crank easy heck your stock starter should crank it easy with 250-275

 

That's way too tight on the Mains Craig.

 

X2 on that. Man, I had to make some dyno headers when we did my engine !! They came out nice though and clear the dyno frame. I had some issues with guide clearences, to tight, had to replace a valve and have the machinist re-do the guides. Back to the main clearences, I believe most guys, including myself, set them at the high side of .002, say .0025-.0030. Here's why, especially on a turned crank, I don't think they ever get "trued" so you end up with some runout or out of round. Hence, if the bearing is to tight it actually wears out a spot on the bearing were the high spot is so you might not hear a knock but you'll see bearing material in the oil. Mine dynoed out at 495 horse and 515 lb. of torque, uncorrected numbers. Hope this helps. Phil

 

After realizing the battery had issues turning the motor over (after first start-up) we turned the motor by hand and saw no issues. We did this again later after the power fell off, but it was not obvious even then (this was with the plugs in).

The mains were spec.'ed at 0.002, but when I used the plasti-gauge I got 0.0017. I know plasti gauge is not the most accurate way but I'm sure it was in the ball park.

The mains were line honed with the studs installed, but I do not have a spec sheet from the shop that did them. I tried measuring them with telescoping gauges after getting the motor back some time ago and know these type gauges are not as accurate or repeatable as other more expensive equipment.

 

X3 on the mains cost me a bunch of money twice ant the same shop, the second time around before I put it in the car I had a buick racer/builder pull my engine apart and inspect it. Thank God he did it would have come apart again.
Good Luck
Herb

 

I can save you the trouble..

If your cam is 233/250* @.050 on a lobe center of less than 118* .. then the cranking compression is not too high.

If you have a lobe center on that cam of 118 or more, than it could be an issue.

One thing stands out here to me.. 130# on the mains.. I have heard of main webs breaking at 115 ft lbs of torque.. 110# is the max..

Often times if there is some variation from housing to housing sizes, I will torque them individually to anywhere between 90 and 110 ft lbs, based on how the housings react to the torque.

I will let you guys in on one secret.. I rarely build motors with studs anymore.. have seen several blocks that would not "repeat" a housing size with studs in the mains. In fact, the only blocks I use studs on, are those with a main girlde. And even then, the studs are pulled to 90 ft lbs.

What I mean is this.. you torque up the main, measure the size of the housing with a dial bore gauge, loosen it up, and repeat the process 2 or 3 times. It has to come back to exactly the same size, because that is what your basing your measurments on for the main clearance.

The reason is simple here.. the weak block doesn't always distort the same, and studs pull on the block differently than the bolts do.

Craig.. I feel for ya' man.. I know the pain..

But here is what you have to do.. while a lot of guys get away without the more specialized tools for engine inspection/assembly.. your not one of them.. so you need to buy a dial bore guage set, and learn how to use it.. it's really not that hard, and you seem to be a pretty bright guy.. and not all that expensive, a decent dial bore gauge set, that can be used to measure the main housings, the rod housings (with and without bearings) as well as the engine cylinders, is a couple hundred bucks..

What do I think happened?.. Be willing to bet that it's one of two things.. Either you caught number 4 main and wiped it out on break-in, or the mains are out of round, which bled off all the oil pressure before it got to the rods, and you burned a couple rods out of it.

About six or seven years ago, a fellow board member here sent me an engine that he had built at a local shop.. he "suspected" it was hurt, but wasn't sure.. so we bolted it on the dyno and ran it.. had great oil pressure, but it was hurting itself. Second pull was 10 HP less than the first, with no changes.. after careful inspection, it was noted that the number 4 main housing (with studs) would not pull back to a consistant size.. it varied by almost .0005 in both the vertical dimension, and the out of round. To eliminate the problem, I had the motor line honed again with bolts.. and then saw that the number one housing would "repeat" now, and that motor went on to make over 500 Hp, and is running happily to this day. In that motor, the number 4 main was not hurt, but the clearance was so big at the parting line, it was bleeding the oil pressure off that main, and starved the number 6 and 7 rod bearings, and wiped them out.

I bet Craig has a very similar situation here, especially with 130 ft lbs with studs on the mains, and no idea of a possible out of round condition of the main housings.

And one last thing... always, and I mean always, dyno a motor with race fuel of at least 108 octane. I don't care if it's a "pump gas" motor or not.. The dyno loads the motor a lot more than the car ever will, so detonation becomes more likely. From the sounds of it, and the specs of the engine, I don't suspect detonation here, unless you had some really bad pump gas in that thing.

 

Thanks for the words of wisdom, I need all I can get to get this thing right! :TU:

The cam is indeed 233/250 @ .050 on 112 LSA installed at 108 ICL, which gives the 68 deg ABDC as mentioned above.

I took the plugs out tonight after putting another filled oil filter in place to get a cranking compression measurment, to my surprise it was only ~130 psi. It really did not turn over that great on one of the four cylinders it only turned through one compression stroke before stopping. I got 130 psi typical on the other three which turned over maybe three times.

I took the fan belt off to remove any drag from the alternator or water pump and took a torque reading from the crank (with the plugs still out), to my surprise the gauge went up to it 70 ft-lbs max. to turn it. Much more drag than I expected! I will re-check this once I get it back together for comparison.

Some time ago, I did check the torque to turn the motor before I got the heads and cam in and it took ~24 ft-lbs. This seemed very good with all the pistons/rings in I thought.

When I do tear this thing down I will check the torque level it takes for all the rod and main nuts to break loose. A friend has a dial bore gauge I can use to take measurments, just have to figure out how to assemble and use it. I will check how repeatable the main clearances are once I get this together again. Looks like I'll need some ARP bolts to compare repeatability. I will not chance torquing to 130 ft-lbs again.

I'm trying to learn all I can on what to look for before I tear into it....likely by Wedensday night.

 

Good post Jim,Very good info there.

Good luck getting fixed up Craig.

 

Do you feel the same way about head studs?