462 build, help with static and dynamic compression

I 100% agree! You keep citing the diamond piston page and I've read it like three times in the last week, LOL! If I lunch my bottom end I'm tempted to get a short block or rotating assembly from JW. Between you and Edourd my jaw stays on the floor. I got two cars with 455's, the Centurion get's all the left overs from Skylark upgrades, lol.

 

Larry brings some good points to this conversion. You have made a great choice in head and cam combination.
This combination should produce over 500 hp and can rev to 6000 rpm.
However with the heavy pistons and the stock rod combination you could run into trouble.

On a stock set of rods the machining is inconsistent and there are weak areas all over the place as illustrated in previous post #15
It sometimes takes 2 to 3 sets of rods the find 8 that are suitable. This includes magnafluxing to find cracks that have developed over the years.
A stock set of rods are over 40 years old and have been through millions of cycles of compressing and stretching which fatigues the metal so even after all the inspecting and testing a rod may still develop a fracture later on and fail.

It is not reasonable in my mind to risk thousands of dollars invested in the engine over one piece that is marginal.
That is one of the guide lines we use in the shop.

Just as a side note. The reason why a person can use horsepower as a connecting rod limit is because horsepower is a function of torque and rpm so in most BBB cases it takes over 5500 rpm to make over 500 hp.

Paul

 

I agree about the RPM being more of a concern than the HP. You all make very valid points. Looks like I'll have to wait till I get the heads and get everything measured then get the blocked decked.

 

We ran a 13:1 462 with stock rods and ARP bolts for two points seasons in the mid 90's. It was driven to the track each weekend and saw 6400 RPM before each shift. It had forged JE pistons, Gessler iron heads and a TA 608 cam. We saw another 10th in the quarter at 6700 RPM that finally frightened us away from the stock rods. The stockers were replaced with Oliver rods at that point and are still around here somewhere. I would not let anyone sell you that aftermarket rods are a necessity.

Cheryl

 

Cheryl

Thanks for your input. You were one of the lucky ones. There have been others not so lucky.

Aftermarket rods are not a necessity.

It is a matter of being willing to take a chance with your engine over a single rod that may be marginal.
We have racers locally that have gone through multiple engines because they continue to shortcut.
One of our customer's competitors just lost his 9th engine last week.

Out of 3 racers in our class last weekend, we were the only ones left by Sunday. So we ran both heats on Sunday solo.
Leave it to luck?
I don't think so!!

The decision here may be to use the factory rod and there may never be a problem and that would be great.
Or the only possible weak link in this project could be replaced and never have to worry.
Then there would be plenty of margin for head porting or any other upgrade later on.


Paul

 

I agree Cheryl..

From strictly a durability standpoint I would certainly not stand on a soap box and say that you cannot use stock rods in a build like this, for street and mild strip use.

But that's not where the rubber meets the road, so to speak.

Let's look where he is at now.. TRW's with stock rods..

It would be normal that he went thru about 2 sets of rods to get 8 good ones. You will typically pitch at least 4-6 in a set, just with a visual inspection.. the hole in the pin end is way off to one side on a lot of them.. The other 2-4 rods will get pitched when they try to resize them.

When put together stock, the rod bolts did not dowel the cap.. so the cap could move side to side. Factory did not care, they just bolted the rod together, and bored the hole. But now, we try and put a set of ARP rod bolts in, that dowel the cap.. and often, that will leave the cap offset on the rod body.. the only way to fix that is cut a whole bunch off the rod and cap, and hone it back to size.

Then you end up with short rods.. I just put together a TRW/stock rod deal, with customer supplied parts. It was done professionally, but probably without the benefit of having several sets of rods to pick thru.. there is not a rod that is the same length in that motor.. they vary up to .005. End of the world?.. nah.. like I said, I just put it together for a customer. But that was a "good" stock rod motor. I have seen them come thru here, with rods that are .020+ different in length.

That becomes more of a problem.

And now you have to balance these rods... trust me, there is the reason the factory just threw them together, "close enough" to not vibrate at low rpm. If they really had to precisely balance every 455 rod.. they would still be building early 70's engines, because I am here to tell you, it takes forever. Without excess material to take off either end, but a weight "pad" about 3/4 of the way down the rod, balancing a set is a real pain.. you always seem to get one that is way off. We have all seen the butcher balance jobs on stock Buick rods.

One of my favorite drag motors was a 430 I had. With a set of stock rods and super-light Jahns pistons, that sucker would get rpm like no 455 would, with the same budget in the build. I ran that for many years, with 6600 rpm seen regularly in the traps.

In the spring of 1996 at 2nd points race at BIR, number 4 rod finally let go.. not on the big end, at 6600 rpm, but at 5400 rpm, right off the starting line. Broke my heart to loose those superlight, and irreplaceable, Jahns pistons.

So they do break, and not always in the lights.

But back to Collin's motor here..

So now, hopefully he has went thru all that pain on the rods.. and has come up with a decent set, not one that varies greatly in length, nor has a couple rods with really thin small ends.. but let's assume he has.

Now we have to deal with the pistons.. CC size?.. Put the numbers 23 thru 27 on the dart board, and throw a dart.. because that is possibly the best way to know what dish volume of a set of current TRW's will have,out of the box. Seems the QC in India, where they are made now, is not what is was in the ol USA.. I have seen, and heard stories of that L2353F piston coming out of the box between 23 and 28 CC. The same time that CC article came out, with the 27.8 CC pistons, I had a new set sitting on the shelf, in a box.. I measured one.. it was 24cc. So I called TA and talked to Mike, to question him on them.. he said "yup, we see that piston all over the place these days.. those were that big".

So any of us sitting here speculating on his SCR and DCR, as was stated, are just wasting our time. There is simply no way to know without measuring. That's no way to "plan" an engine combo. I rarely get surprised with volume stuff anymore. Although I did just see a set of STG 2 SE heads that came out of the box at 62cc. That's unusual, and left me holding a grinder for an extended length of time..

These pistons vary up to .002 in diameter and up to 6grams in weight, within a set of 8.. I used to laugh when I saw the factory supplied sticker on the box that said "matched set"... ya, right..

Now this is not that big a deal, unless your living on the planet here with the rest of us..

Stuff happens, it just does.

Having a known piston size (and thus a known and consistent bore size) in an engine is a good thing.. case in point.. about 2 years ago, I sent a nice STG 2 470, 580 HP motor to a customer in NJ. A couple weeks later, he calls me back, asking about pistons.. seems he dropped a wing nut into his brand new motor. No big deal, he got ahold of the correct replacement pistons, dropped them in, and just ran 123mph in a high ten pass in his GS here a couple weeks ago.

No problem just dust out the hole with a hone, and drop the new replacement piston in.. because quality pistons (JE, SRP, Diamond, ect) are all the same size and weight. But with these? Well, we hope our replacement piston is not 5 grams light, and .002 smaller than the original set.. not a lot you can do in that case, but live with it.

So let's assume he has navigated thru all these minefields now..

Now he is sitting there, with a motor with the slugs .050 or so below the deck. This is a bigger problem than the "intellectual" problems of different length rods, and size and weight pistons.. We have to deal with this one, if we are hoping to build a good solid shortblock for performance.

When he first posted here, I was just watching.. and when he was actually considering putting the motor together at .050 in the hole, I was standing on my chair, yelling at the computer screen... "Don't do it".... somebody has to tell him not to put it together with the pistons in the hole that far.

Not only poor flame travel and performance results, but it will ping like the dickens. Reduce your dcr threshold a full point, to stay away from detonation, and you will be safe. I have personally seen motors with .040 on the deck, with an SCR in the low nines and DCR in the low 7's, be a ping machine. Consider the stock motors... not a one of them was close to being actually 10-1 statically, but with a small cam and a ton of deck clearance, the were ping factories on pump fuel, unless you pulled the timing way back, and turned them into a pig.

So we need to cut the deck off, never run more than .010.. zero is better.

But, now a new problem arises.. after paying $300 to $400 to whack a ton off the deck (usually more than .025 is a double charge at the machine shop) the intake manifold no longer fits. So now we take the brand new Alum heads, and cut them to fit the intake.. or cut the brand new intake.. and build a motor that no other "out of the box" intake will fit.. pick your poision..

Not to mention let's add more money to take assembled heads apart, cut them, clean them, and set them back up. So now we have at best $100 (if we are fitting just bare castings) to maybe $250 if we have to take them all apart and go thru all that trouble..

Where does the rubber meet the road?

Practicality..

Years ago, I knew there was a better way to build these things.. I went thru the hassle above many, many times.. you really want a slap in the face? then fork out $800 for forged aftermarket rods, and $700 for good pistons, (with the wrong deck height) and still be .050+ in the hole. Used to drive me insane. And added a lot of money to these builds that could be avoided, with the correct parts.

This is why the 470 exists. For no other reason than it's simply practical.. good cost effective parts, and by the time you get done building the exact same zero deck motor, with my 470, vs a TRW/stock rod 462, you have spend less than $300 more.. in fact, if your already using an aftermarket oil pan, the increased cost is barely over $100.

Total no brainier. At least if your aware of all your choices, and the above factors, ahead of time..

In this case, inexpensive parts require more machine work, and end up being the same total cost, as starting with higher qaulity stuff, that is designed correct to begin with. My 470 (also availabe from AMP) is the only combo on the market right now that fits that description.

The key was the piston.. Designed to zero with just a .020 deck cut (intake still fits) which is the minimum we have found over the years, to completely clean the deck up. Has the correct dish volume (25cc) for compression control and the correct pin size and compression distance to fit a set of $450 rods, that are as much rod as the vast majority of us will ever need. Easily 3 times stronger and more durable than a stock rod. The only "trick" piece is the .050 offset ground crank, with the throws slightly widened, but that's not rocket science.. just need a competent crank shop.

Having said all of this, I hope that anyone who reads this understands that we build the 470 now for one reason.. it's the best deal for the customer. Not because we are trying to convince folks they can't use stock parts. It's a much more complex issue than that simple line of thinking.

If that TRW piston vanished off the earth here tomorrow, I would not lose a wink of sleep.

Now Collin, don't bum out..there is plenty of successful stock rod/TRW motors out there.. my advice to you is to be sure you have a decent set of rods, an easy check is to drop them in the holes, and check how much your deck height varies. If it's a lot, then you might want to consider questioning the quality of the work done on those rods.

Then get everything measured (head, deck clearance, piston cc) and figure out exactly the specs you need, and cut as much deck off the block as you can, while keeping the compression around 10.5-1, which will work out with that cam. Typically you can zero deck with around a 68 cc combustion chamber, and .040 gasket, and it will work out just fine..

I build dozens of them over the years, until I finally got sick of it, and ponied up 3K to Diamond, so they would build my piston, with my part number, and make it a "shelf stock exclusive" for me. This brought the price in line with other, similar quality pistons.

Best money I have ever spent..


JW

 

Thank You Jim for covering this subject all in one post.
The detailed bits of information are outstanding, awesome, (I can't seem to find the right word) and is greatly appreciated.

It would be a shame to lose this post. Can you sticky this so it will always be available for reference?

Thanks again for sharing your years of experience on this subject.

Paul

 

Fellas, do a search of this very site on stock rods. You will find many accomplished "Buick" racers push stock rods much harder then we did without fail. Maybe you are making it harder then it is or mudding the waters? We only had stock rods in the 80's and early 90s, and they lived in literally thousands of Buick performance engines when addresses correctly. Can any of you honestly give a failure rate for well prepared stock Buick 455 rods, or is it supposed, subjective and/or just salesmanship? Any good automotive machine shop worth its use is going to be able to deal with the issues presented as a matter of common practice. It's not rocket science!

Cheryl

 

Great post Jim!

I just wanted to add to those who like to spin high revs with stock rods:

Please value your life, a rod going at 120 MPH is likely going to send your car into a crash.

Use the best quality rods and pistons you can buy....:TU:

 

I am with Cheryl on this. 26 years and long list of BBB builds and I have never had a stock rod failure, they are a decent rod if care is taken. Chris

 

Cheryl & Chris

Yes, you are right that there wasn't much in the way of reasonable cost options not too long ago but that is not the case now and I respect your views.

I'm looking at a set of factory rods and it is apparent that another set or 2 would be needed just to get enough through visual inspection for measuring and testing to get a final set of 8 rods that I would trust.

At this point do I spend the time and money to have our machinist work through over a dozen rods or
do I spend $385 for a set of H beam 4340 steel rods set up for floating pins that Jim Weise is using in his builds?

Then I can take advantage of the many sets of .0005" incremental size ranges of rod bearings sitting on the shelf in our shop.

Paul

 

No worries, folks can make their own decisions, and rod failure rate is a very small piece of the puzzle. Certainly not the key factor to consider when laying out a combination.

As long as the information is out there, that's fine with me. Buick enthusiasts are smart, they make good decisions in my experience when presented with all the options and facts.

JW

 

Hi Paul, there is no disrespect intended from this end. I have several sets of factory rods that I have pulled out of engines that are ready to be used. They are a forged rod that left the factory shot peened. Would I use them in a 700 HP engine? no way. Would I use them in a 500-550 hp engine? Yes all day long. I would bet that one of the most used combo's out there are stock rods with heavy Seal power/TRW pistons. Do I have TA Sportsman rods on the shelf? Yes. Will I use JW's piston rod combo? Yes . Don't for get that its $385 for the rods + the cost off getting the rod journals widened. Don't under estimate the factory rods

 

Thank you JW for taking the time to post a detailed response. A big thanks to all of you who have taken the time to post a response and offer your opinions.

JW...I wish I would have read your post before I took the short block apart! I would have checked each slug to see how much the .050 varied cylinder to cylinder to get an idea if the stock rod length varied. I understand what you mean about haveing so much taken off the deck to get zero deck and then possibly the heads/intake IF I were going to use the current stock rod and piston combo I have now.

Exactly what would the BBC rods and your pistons cost?

 

Collin,

The pistons are $749, the rods are $459.

And for sure, if you cut the deck to 10.525 or shorter, you will have to cut the intake or intake side of the heads.. I have done it dozens of times.

Unfortuantely the 470 rod/piston combo is not a "drop in" situation, from where your at. The crank has to be offset ground .050, rebalanced, and the bore has to be opened up to 4.350.

Like I said, check the rods, invest in having them pressed off the pistons.. inspect to see if the pin end hole is in the middle of the rod, and check the length on a comparitor. Might be good to have a different machine shop give you an opinion on them.

If they are good, run 'em, and give the mill a workout.. you won't be the first guy to have to do it, that's for sure..

If they are an issue, or if you want to get around all that decking work, then I would invest in a set of aftermarket H-beam Ponitac Rods. here is a set.. http://www.summitracing.com/parts/ESP-6625PP3D/

They are 6.625 long, or .025+ longer than stock Buick. They require a bit of work to narrow the big end, and have to have the pin end opened up, and your crank may have to be re-balanced, but they will work with your pistons and current crank size/stroke.

Then you won't have to deck so much off the block, won't have to cut the heads to fit the intake, and will end up with a better rod for your combo.

There are plenty of folks running around with that type of combo.

JW

 

x2!

Jim, what is the minimum deck height to run your piston/rod combo? I only measured two cylinders for .030" in the hole (with the .038" JE pistons), and I was good with that incase of future need for a clean up (I still average easily over 10,000 miles/yr on my car). As mentioned earlier in the thread, if I get to the point of needing to re-do the bottom end (like eating the crank or spinning a rod bearing, and the block isn't trashed) I'd seriously be looking at your setup.

 

Thanks. So that's .020" off the "spec" deck height. But I'm guessing as with anything they varied a bit. Hmm, if my math is right and assuming(!) spec deck height originally and correct length rods (for the two I measured) mine "should" be in the neighborhood of 10.555". I guess where my original question comes from is what to do with setups that have already been decked?

 

No worries on that.. for building a 470 from a "current block", we can customize the compression distance of the pistons.. cost is $8 per piston for the change.

I can also change dish volume to account for small head chambers (we did that with Larry) or even make it a flat top, if your building a race motor..

The same basic piston is used for 4.250" 400/430 builds, all the way up to the alum block 555 stuff. We just change the specs appropriately. I technically could do a stock bore 400.. (4.040) and it would fit and work out fine, with the correct rods and offset ground crank.

Doing this deal opened up a lot of block cores (400-430) that used to be overlooked, because it took an expensive set of custom pistons to use them. The motor in my avatar is one such example, it's based off a 430 block.

One of the best things that has come out of this, is that now we have a lot of versatility.. it's no longer "take what is in the catalog or it's a $950+ set of custom pistons".

JW