[Elarson]

Philosophically, a Pro Stock car (not just engine) is designed to squeeze max power out of the given displacement and weight restrictions. They are designed to be just barely strong enough to survive; since extra strength comes at a penalty of weight, windage, etc, etc.

A fuel engine can make boatloads of power so it's design philosophy is totally different.....concentrating on making it as rugged as possible within the given dimensional restraints.

A production engine needs to run troublefree for 150,000+ miles which brings on an entirely different selection of constraints.

I always laugh to myself when the marketing guys talk about a "no-compromise" design. There's NO SUCH THING!! LOL.

Eric

[Elarson]

As a side note, caps waving around isn't necessarily a problem; unless that condition causes the main caps to fail from fatigue or the waving introduces strange bearing wear.

If it's at one particular engine speed and you don't linger there, it may be a non-problem. For instance, if that resonance occurs at 6000 rpm and you're only there for a few milliseconds as you accelerate thru that speed, it may be no big deal. If you're running a circle track engine at 6000 rpm for several hours, it may be a showstopper.

Eric

[Tom Vaught]

Originally Posted by mgarblik

This is an interesting thread even if it has veered off in a few directions. As far as adding a Ford type brace on a Pontiac stock block, I feel there would be little if any benefit. The reason I say this is Pontiac already has the movement of the caps found in SB Fords covered with the dowel pins. I have to agree with Calvin in re-doweling the block with longer pins and a good fit will do more to keep the caps in place than the brace alone. The Ford brace works on the Fords a little by holding the caps more or less together as a unit because they don't have anything to locate them at all other than the little interference where they register at the sides. When the crank loads increase and pushes the crank down, most of the register interference is gone and the fasteners are all that's holding the caps. Putting all 5 caps together with a band-aid brace helps a little. Pontiac's really don't have that problem in my experience, and if they show fretting, then the clamp load is not high enough on the caps and new, better hardware is needed or longer better dowels and a better fit there. If you still have fretting, you need an aftermarket block in my opinion. In summary, I think a brace won't hurt on a Pontiac but it's benefit is certainly questionable. Sounds like a bunch of work for a non-problem if everything else is done right.

I can live with that answer. Thanks Mike

Tom Vaught

[gtofreek]

Originally Posted by Tom Vaught

Call or e-mail Mark at Luhn Performance and he can e-mail you some pics Paul.

That being said, I think you are saying that the factory 6 bolt fasteners needed to be upgraded when the engine had other modifications. We saw no fretting on the caps at 390 HP rated, (closer to 500 actual) during durability testing.

So why put ARP bolts in Pontiac Engines if the factory Pontiac stock bolts are so good at high hp?

Sounds like you are picking and choosing a bit there Paul.

Like I said, the 281 cid Mahovitz engine is able to run 6.05 in the quarter (at least once)
vs our average engines (2 or three of them) running a bit slower with 70% larger engine.

How about a full disclosure of the engine as received parts vs the 650 rear wheel mods.

Know it is possible to make those numbers, the mag guys have made them several times with different superchargers, camshafts, etc. Same basic 6-bolt block though.

Hey Tom, that engine with all the fretting was bone stock. Never been out of the car or taken apart. Don't know how the guy drove it though.

As far as full disclosure of parts goes, no problem. We installed ARP studs, align honed it, put some CP pistons in it, did some head work and installed some VooDoo cams in it.

Not knocking the mod engine Tom, it's actually a pretty good design, just think they should have used bigger bolts in the Romeo block, that's all. Nothing personal.

Yes I install studs in most Pontiac's also. They are just better than bolts. Less wear and tear on the block threads, too.

[gtofreek]

I like to install SB Ford cam dowel pins in the main web of Pontiac blocks. They are much longer than the stock dowels, and protrude though the cap to get full engagement in the cap.

Most stock Pontiac engines I tear down have dowel pins that are so low, they barely stick into the cap. I bet the few fretting cases going on in Pontiac's is due to this. I have found that installing the Ford dowel pins does slightly relocate the cap so align honing is needed afterwards.

[Tom Vaught]

Stuck all of your comments together Eric so I could respond in one post.

Originally Posted by Elarson

I confess I don't know which other engines are register-only vs. dowel pinned caps. When the engine is on a power stroke, the crank is pushing down on the center of the main cap and deflecting it downward. Is the deflection .001", .010" or something else? Depends on the power level and the stiffness of the cap.
But to understand how a main caps wants to behave under power, try this little experiment. Hold your hand up with your thumb and index finger forming a "V" to simulate a main cap. Now push down on the little tendon that bridges between those 2 fingers and watch your 2 fingertips retract toward each other. That's what your main caps are doing. If the caps have register-only configuration and not enough clamp load, they're moving in and out on every power stroke and there's your mechanism for fretting.
Splayed outer bolts are way better for resisting this retracting motion than vertical outer bolts and they also send the load into the stronger outer wall of the block. Cross-bolting helps in the same way.
Fore/aft waving of the caps isn't a loading issue in the traditional sense. Look at a journal bearing. Except for the #4 thrust bearing, none of them are taking any fore/aft loads. The waving of the caps is a natural frequency that corresponds to the engine running speed (resonance). The cure for that is a stiffer cap in the fore/aft direction (or a girdle that stiffens it) to raise the cap's natural frequency above the engine operating range.
Philosophically, a Pro Stock car (not just engine) is designed to squeeze max power out of the given displacement and weight restrictions. They are designed to be just barely strong enough to survive; since extra strength comes at a penalty of weight, windage, etc, etc.

A fuel engine can make boatloads of power so it's design philosophy is totally different.....concentrating on making it as rugged as possible within the given dimensional restraints.

A production engine needs to run trouble free for 150,000+ miles which brings on an entirely different selection of constraints.

I always laugh to myself when the marketing guys talk about a "no-compromise" design. There's NO SUCH THING!! LOL.
As a side note, caps waving around isn't necessarily a problem; unless that condition causes the main caps to fail from fatigue or the waving introduces strange bearing wear.

If it's at one particular engine speed and you don't linger there, it may be a non-problem. For instance, if that resonance occurs at 6000 rpm and you're only there for a few milliseconds as you accelerate thru that speed, it may be no big deal. If you're running a circle track engine at 6000 rpm for several hours, it may be a showstopper.

Eric

Marty P put Splayed Steel Main Caps on his 67 400 block for a reason. It worked at his power level for several years. The webs were stronger (without the 4 bolt drilling) among other items mentioned in other threads.

Ford Engines are designed for a given power level. In some ways like the Pro Stock Engine in the comment above. The system was designed to live at 390 HP for 150,000
miles. I am sure that John Mahovitz was not running stock production main cap fasteners in his 281 cid 6.05 et Turbo drag car, I am confident that GTOFREEK's main cap fastener change was a proper thing to do. (Along with the other mods) Especially at 650 RWHP power levels.

Mark at Luhn Performance HAD aftermarket ARP fasteners in his Boosted 455 block and it was properly line honed, machined, etc BEFORE the dyno testing. The caps still fretted. Possibly longer precision fit cap dowels would have helped. The main caps I believe were stock 455 2 bolt main caps. Given that the engine made 863 HP at only 5300 rpm and was not pulled higher. The Vortech Supercharger was rated at a max of 820 HP and the Luhn engine made 43 MORE hp vs the Vortech rating says the engine was not screwed up.

The cap fretting was severe, I saw the pictures. It makes you think that a stiffer cap (or different cap design) is almost mandatory on a 455 type engine at 850+ HP.

I also agree that the Aftermarket Blocks are a great thing. Having a recessed register at the pan rails possibly gives the splayed caps something to consistently "lock" against when torqued.

Thanks for the posts, Mike, Eric, and Paul.

Tom Vaught

[Half-Inch Stud]

Originally Posted by Elarson

...register-only vs. dowel pinned caps. When...register-only...fretting.
Splayed outer bolts...
Cross-bolting...
Fore/aft waving... of the caps...
I love this stuff.

Eric

Powerstroke; Rod pushes on center of Rod journal, waay offset from Main center (60-73 deg * Stroke/2). So some force is Main Cap sideload while other is down. For Even Rods, the Odd Rod throw may be accelerating up to (worth 5000-9000 lbs force upward) for Even rods at 90 ATDC. For Odd rods, the Even Rod may be adding to the downward force. I don't know for sure but further lokksy may reveal a desire to "Girdle-up" one siderail of the Main more than the otherside.

Since we're not seeing the CYL bottoms crack-propagating away from the MainWebs, Rather we see Main Webs splitting, the Force diagram should reduce/simplify to the Rod Journal Push against the crank Mains. I'm back to the 2 LOCAL Main Bolts and them 2 Dowel Pins. Dowel pins take the loads WHEN they are: tightslip fit & Large enough.

--->LONG 2-Bolt Mains bolts with nuts in the Lifter valley?

Seems pointless for PMD to have scalloped the CYL bores so deep into the Main Webs HUH. Piston skirts never ride there.

Cure for Fore/Aft Waving is a stiffer Crank: Large Main Journals for more Rod/Main overlap, go Billet, or both. Tighter bore spacing too in theory but that is not our Performance direction huh.

[Half-Inch Stud]

Originally Posted by Tom Vaught

...Mark at Luhn Performance HAD aftermarket ARP fasteners in his Boosted 455 block and it was properly line honed, machined, etc BEFORE the dyno testing. The caps still fretted. Possibly longer precision fit cap dowels would have helped. The main caps I believe were stock 455 2 bolt main caps. Given that the engine made 863 HP at only 5300 rpm and was not pulled higher. The Vortech Supercharger was rated at a max of 820 HP and the Luhn engine made 43 MORE hp vs the Vortech rating says the engine was not screwed up.

The cap fretting was severe, I saw the pictures. It makes you think that a stiffer cap (or different cap design) is almost mandatory on a 455 type engine at 850+ HP.
Tom Vaught

Makes me think there was a Fastener problem. (line-honed assures to me that larger& longer match-drilled dowels were prego).

[Tom Vaught]

I personally think Mark might have used some counterfeit ARP Main Studs.
His ARP studs did not have the hex on the end IF I remember correctly.

Mark can confirm.

Tom Vaught

see post on moparts web site: http://board.moparts.org/ubbthreads/...ge=0&fpart=all

"I Could not achieve a repeatable Torque Value on the Main Studs when Assembling a World Aluminum Block, then 1 Main Stud snapped in half !!
Some had seemed to be "stretching" excessively @ 100ft/lbs just prior to this ?
Upon removal and further inspection, I THEN noticed, that although the Nuts had "ARP" on them, the Main Stud Ends themselves DID NOT ?
Fooled me up until then !

A subsequent Phonecall to ARP, confirms ARP Studs do indeed have "ARP" on the ends.

I Removed the suspected "Chinese" studs, and found they were "stretched" visually thinner in areas on the threads, from the Rec'd 100ft/lb Torque applied.
Mic readings indicated many had indeed shrunk by .030" in Diameter at their weakest threaded points, and were also about to break !"

[gtofreek]

Originally Posted by Tom Vaught

I personally think Mark might have used some counterfeit ARP Main Studs.
His ARP studs did not have the hex on the end IF I remember correctly.

Mark can confirm.

Tom Vaught

see post on moparts web site: http://board.moparts.org/ubbthreads/...ge=0&fpart=all

"I Could not achieve a repeatable Torque Value on the Main Studs when Assembling a World Aluminum Block, then 1 Main Stud snapped in half !!
Some had seemed to be "stretching" excessively @ 100ft/lbs just prior to this ?
Upon removal and further inspection, I THEN noticed, that although the Nuts had "ARP" on them, the Main Stud Ends themselves DID NOT ?
Fooled me up until then !

A subsequent Phonecall to ARP, confirms ARP Studs do indeed have "ARP" on the ends.

I Removed the suspected "Chinese" studs, and found they were "stretched" visually thinner in areas on the threads, from the Rec'd 100ft/lb Torque applied.
Mic readings indicated many had indeed shrunk by .030" in Diameter at their weakest threaded points, and were also about to break !"

The older ARP studs did not have the hex. That is a new thing, probably the last 10 years or so. Also, the hex in ARP studs has no peeled down metal at the bottom of it. Just a clean hex pocket. Not sure how they do that. And yes, both studs and nuts should say ARP on them.

[Tom Vaught]

He might have had the studs on the shelf for years, (;>)
Thanks Paul.

Will have to ask him when he bought the studs. Engine was tested about 3-4 years ago.

Tom Vaught

[RAIV55]

Tom, In the past I've run into NEW ARP head stud sets for the BBC that didn't have their stamp on the ends. The ones in particular are the longer studs for the exhaust ports like what's used on Dart/Brodix heads.

[Tom Vaught]

There was a post in a recent magazine where the arp people said the ARP had better be on their parts.

[Real] Real ARP-made fasteners are specifically marked “ARP” and usually with the alloy as well. Knock-offs so far have been “blank” or stamped with a generic alloy such as “8740” or “2000.”

Read more: http://w5.www.hotrod.com/feature_sto...#ixzz2he1BxG00


Tom Vaught

[mgarblik]

It is possible to have genuine ARP studs, nuts, washers without any markings. I think you are safe if you buy from a reputable vendor and buy ARP fasteners made in the past 5-7 years because they should be marked. I have some that are older without the broached hex in the stud end and no markings on the nuts, bolts, washers and so forth. It used to be if it was in an ARP box all was well but that was before the Chinese decided to destroy the performance aftermarket just like they have the regular car parts business. It's scary out there!

[Steve Barcak]

Originally Posted by mgarblik

This is an interesting thread even if it has veered off in a few directions. As far as adding a Ford type brace on a Pontiac stock block, I feel there would be little if any benefit. The reason I say this is Pontiac already has the movement of the caps found in SB Fords covered with the dowel pins. I have to agree with Calvin in re-doweling the block with longer pins and a good fit will do more to keep the caps in place than the brace alone. The Ford brace works on the Fords a little by holding the caps more or less together as a unit because they don't have anything to locate them at all other than the little interference where they register at the sides. When the crank loads increase and pushes the crank down, most of the register interference is gone and the fasteners are all that's holding the caps. Putting all 5 caps together with a band-aid brace helps a little. Pontiac's really don't have that problem in my experience, and if they show fretting, then the clamp load is not high enough on the caps and new, better hardware is needed or longer better dowels and a better fit there. If you still have fretting, you need an aftermarket block in my opinion. In summary, I think a brace won't hurt on a Pontiac but it's benefit is certainly questionable. Sounds like a bunch of work for a non-problem if everything else is done right.

I'll disagree with you Mike, esp for a Fuel motor. You need all the reinforcement you can get. We'll see how well your IAII holds up after some more real hard passes. Perhaps you will change your opinion with time . I would guess 95% of your exp is with gasoline and n2o? What you say would be true for something like that set up but, that combo is a cake walk on parts compared to blown fuel. At least 1 blown alky IAII has come apart at the mains. We'll see how your deal handles a 14-71 with high percentages as you are set up for. Do not get me wrong, I certainly hope your deal does hold up. I just have my doubts as to lower end durability on your set up.

Moral of the story- Build it at strong as you can.
The one piece lower end deal discussed is pretty but has to be a bitch to service between rounds. Obviously not intended for fuel application.

Over 15 years ago, closer to 20, I designed and had built 3 of these modular 6 bolt main lower ends for my 389s and 577. They have met and exceeeded all expectations for durability and serviceability. To date, have not seen a lower end stronger/tougher and more more proven than these, regardless of engine type let alone for a Pontiac, in a blown nitro or alky combo ( the 2 most stressful). All 5 mains are tied together and each cap removable to check bearings easily between rounds if needed.

[Elarson]

More than one way to skin a cat, as they say.....

Your 389 block/6-bolt cap arrangement certainly looks like a great idea.

We are currently not seeing any block or cap distress on the IA2 splayed 4-bolt cap arrangement; even though we are at a higher power output than your dragster. As you say, time will tell if the need develops to do anything more complicated.

Our tuner has 50 years experience with nitro and a natural bias toward Chrysler hemi derivatives. He has gone over our combination with a fine tooth comb.....correctly predicted that our old oiling system wasn't up to the task....and is impressed with the rest of the Pontiac package.

FWIW,
Eric

[mgarblik]

Steve, there have been a little misunderstanding in my post. I was referring to adding a little steel girdle like the original post suggested and the Fords use to help hold their flimsy little engines together. I absolutely feel a deep skirt block that is cross bolted is MUCH STRONGER than any block where the crank and caps are out waving in the wind. That's why all the ALL the professional fuel blocks are made that way. So no argument from me about that. But there is a big difference between what you have done on your block, what Taff did with his and what the Mondello guys have designed as the billet cage compared to bolting a little piece of steel to the main caps. At some point the Pontiac block will fail with the registered caps, splayed bolts and dowel pins. At what horsepower that happens, no one knows yet. It's a safe bet it will be well below the 8000 HP the big show guys make today. We are so far away from ever reaching that power we are banking on never finding out. Without detonation or anything else stupid happening, it looks like 3000 HP is possible with the current set-up. Butler and Dale have been closest and neither has had catastrophic lower end damage that I know of. When it gets to the point that we have to totally redesign the bottom end to keep the crank in it, we will likely choose to go another direction.

[mgarblik]

I just saw the picture of your 6-bolt set-up. Are you sure some LS Chevy spy didn't see that before they produced the LS design? Very similar in concept and execution except the LS has the casting extended for the cross bolts. It looks very strong, stable and easy to service. Much better than just hanging a piece of sheet metal on the caps which was what my previous post was directed toward. If we eventually fail our IA II something like that would be the next logical move short of a billet block with these features built-in. LS engines, which have many marginal features, have a lower end that has proven stable at over 2000 HP. You have a nice set-up there !

[mgarblik]

Chipped tooth: Is this pic the general type of brace you were talking about? If it is, this is the type I think would have minimal if any value on a Pontiac block or any block for that matter. Just a band-aid. The braces like Taff, Barcak, and the Mondello shop are making, tie the caps to the block through the strong part of the block. Tying all 5 caps to the same weak area doesn't gain much other than the possible benefit that Eric mentioned about changing the resonant frequency of the cap assembly.

[BruceWilkie]

Originally Posted by mgarblik

Chipped tooth: Is this pic the general type of brace you were talking about? If it is, this is the type I think would have minimal if any value on a Pontiac block or any block for that matter. Just a band-aid. The braces like Taff, Barcak, and the Mondello shop are making, tie the caps to the block through the strong part of the block. Tying all 5 caps to the same weak area doesn't gain much other than the possible benefit that Eric mentioned about changing the resonant frequency of the cap assembly.

Well put!

Pontiac was exploring the "cage" with the Hemi project... pretty interesting.... some good pics here http://www.wallaceracing.com/hemi-1.html and there is some other interesting things worth lookin at too. They were makin a bunch of power for the time period...

I have mixed feelings on their use of long head bolt right down thru the bearing cap... I've seen engines with headbolts that also clamped the lower case on...but they had at least 4 per cylinder PLUS 4 smaller bolts that only went through head to cylinder wall bosses.... I think it could work on a Pontiac but it would have to be bigger than 1/2" IMO, thats a long span... outer head bolts become cap splay studs... interesting.
Does our stock head bolt pattern conflict with our main cap outer bolt placement and create uneven stresses??? which would be more critical in a stock block.