L Series Block Brace

[sweetleaf]

Naytaa hyvalta, Missa pain suomea sa asut?

[Raami]

Naytaa hyvalta, Missa pain suomea sa asut?

 

Kiitos kiitos. Minä asun Kalajoella.

 

(means: Thank you thank you. I live in Kalajoki.)

[lammbn]

sorry, i think you mis-understood what i meant. so i drew a picture, i know that always helps me. i hope this is an accurate depiction of what you have got going on. but before i begin i appologize for such a long post, i tend to look at everything through the eyes of a mechanical engineer. please bear with me.

 

so the red arrow is showing the force of the brace that i was talking about. if this is pulling up on the main bearing cap like that it will skew your torque readings when you are tightening them down. this would make them loose fitting and possibly cause them to pull away from the block a little. but that is all it would take to cause the crank to move around inside the bore. especially at the higher RPMs you are designing this to run at.

 

idealy what you would want is to have it pushing down on the mains so that it is alway pressing them into their slots. but to do this you you have to add more washers to flex the brace out and have it push down.

 

but that brings me to another area of concern. you are building this to help dampen vibrations within the block. those washers can move relative to eachother so i would be worried about the shear stress being put on those bolts right at the top of the mains cap and the bottom of those washers. correct me if this isn't really a problem.

 

i think that the best option would be a solid plate that was welded to the brace that bridges that gap instead of the washers, slightly thicker than what is needed so that it will exert force down on the cap. Then instead of running one bolt through the whole thing i would use a stud, preferably high grade, and use nuts on top of the mains to torque them down. then enough of the stud coming out beyond that to use another nut to secure the brace to the mains. you would have to mill or drill a pocket out on the bottom of the plate to clear the nut holding the cap. like this.

 

sorry for such a long explination. but i dont want to see you to ruin your engine after putting so much work into it. i hope i didn't rock the boat too much.

[Tony D]

No, never been to Finland, but grew up in the U.P. of Michigan listening to Karl Pellenpaa every Sunday Morning on "Finland Calling", a local show out of Marquette done entirely in Finnish for all those from the old country that emigrated to work locally in the mines. Lots of "Maki's" Keskamaki, Millimaki, Marjomaki...hell just plain old Maki as well. We had Eino and Toivo, and all sorts of 'old country' names. You don't expect American kids to have names like Toivo, or Orlo Olaf..... LOL

 

The U.P., from what I could tell, was very similar to Finland in the Birch Trees, and of course, EVERYBODY had a sauna at 'The Camp'. I grew up on the 'bottom seat', while all the 'old men with no hair' sat on the top seats in the Sauna, whipping each other with freshly-cut evergreen switches. Ahhhh, whip it up and get that pine oil into your pores, then open the door and dash out into -40 weather and roll around in the snow to 'seal the smell in'... Man, now you got me all misty-eyed about my youth! LOL "I digress"

 

Sorry for veering off topic. Back to the regularly scheduled programming...

[Six_Shooter]

The plate welded to the bottom (top?) of the brace is not necessary, but the studs are.

 

If you look at "stud girdles" for 302/351W (Ford engines), you will see that studs are used, and the girdle is placed in such a way that there is a seperate nut that holds the girdle to the studs. I haven't seen a 302/351 girdle that attaches to the pan rail however. The attachmnet to the pan rail, just makes the need spacer or stud nut thickness to be more accurate. Also the oilpump pick up should be lowered by the same amount as the thickness of the girdle, so that it is the same distance from the bottom of the pan, to keep from being uncovered. Probably not a big problem, but something that should be considered.

[Raami]

Why do you think that brace would be pulling those mains loose?

The reason I will put 10.5mm washers and not 10mm washers is that then there will be little gap between block and brace in the outer bolts. (oilpan bolts)

So when I torgue those oilpan bolts, there will be little flex on the brace and it will be pushing even more to the mains.

My engine won't be running so high RPMs. Or atleast not so high as Tony but I will have turbo on it.

 

It's good that this topic is alive and everybody are saying what they think of it.

 

lammbn: You didn't rock the boat too much.

[BRAAP]

…

 

but that brings me to another area of concern. you are building this to help dampen vibrations within the block. those washers can move relative to eachother so i would be worried about the shear stress being put on those bolts right at the top of the mains cap and the bottom of those washers. correct me if this isn't really a problem.

….

.

 

The sheer loads of the washers, even if they are loose, shouldn't affect the bolt/stud. Over time maybe they could rub through the bolt/stud, but unlikely as they are being clamped and by design, when the perimeter bolts are tightened, this brace is slightly preloading that clamping force.

 

…

i think that the best option would be a solid plate that was welded to the brace that bridges that gap instead of the washers, slightly thicker than what is needed so that it will exert force down on the cap. Then instead of running one bolt through the whole thing i would use a stud, preferably high grade, and use nuts on top of the mains to torque them down. then enough of the stud coming out beyond that to use another nut to secure the brace to the mains. you would have to mill or drill a pocket out on the bottom of the plate to clear the nut holding the cap. like this.

 

.

 

Interesting. I could see that approach having a bit more benefit by isolating the clamping loads for the main caps and the girdle individually. Good thinking. To make that concept a reality would also mean having to machine the tops of the front 6 main caps, (rear main cap wouldn’t need this). With main caps bolted in the block, the block then on the mill table, machine the flat on the top of the caps to the exact same depth below the pan rail. Then those plates that are welded to the girdle (that sit atop the main caps themselves) all need to be the exact same thickness, (depth below the girdle perimeter after being welded to the girdle).

Doable? Yes. Beneficial? In theory looks like it adds a tad more cap stability. Worth the extra fab/machining and time? Maybe not in this application, but for the mega RPM Bonneville racers, I’d put forth that extra effort.

 

This plate in its original design, as Raami has implemented it here, should help keep the main caps themselves from flexing fore and aft in the block, and to a lesser degree, side to side, (there is not much in way of the main caps trying to escape the block vertically so no real need to add vertical support) and also makes the block overall, more rigid, there by allowing the crank main-line to remain truer, especially in heavily loaded conditions such high RPM. For Raami's application, his brace/girdle should add some rigidity to the main line and block structure, full filling its intended purpose with little to no drawbacks, other than an extra gasket surface to seal.

[Six_Shooter]

In the 302/351 applications I cited earlier, the main caps were also machined, but not attached to the block. They were just cleranced, so that the girdle did NOT touch the main cap. The girdle applying pressure to the main cap would or could cause deformation of the main cap and cause the bearing surface to become oval as opposed to round (this could be a benefit, but that's a whole 'nother discussion). The other problem is it became real difficult to ensure that when the girdle was torqued down, the torque reading was coming from the nut tightening, instead of the girdle being pressed against the bottom of the main cap, causing inaccurate torque readings (loose) and after a few heat cycles, the nut could loosen off and allow the main to walk, negating any benefit of the girdle.

 

I'm also not sure I would want to place any pressure on the main cap, by way of clamp from the oil pan rail, for a couple reasons, the gasket will effect the clamping force, at time of assembly and also through heat cycles. The expansion and contraction of the girdle/brace over the linear path of the part (side to side accross the pan rails, that included for and aft), and will change the clamping force due to this. The change is probably minimal, but the effect is there, think leverage. The open spaces, that are machined, help control the expansion and contraction, but it still exists.

 

I haven't seen too many girdles that tie into the pan rails, most just support the mains and help control them "walking" under high stress. The girdles I do see tied into the block have usually been crossbolted, and are usually part of the main cap. I don't recall the engine off hand, but it is a straight 6 that I have seen this way, actually a few of them, also a few 4 cylinders. I thought it was a rather interesting design, all main caps tied together, and then crossbolted on the side of the main itself.

 

The real need for a girdle is to keep the mains from walking for and aft, all other ways are usually taken care of, or at least have minimal movement side to side or vertically. The domestic engines I usually work on, have small recess on either side that are an interferance fit, to help hold the main side to side. There's nothing really holding them for and aft though, which seems to cause the most problems where main caps are concerned.

 

I have thought about making a different girdle that didn't tie into the main studs/bolts, but attached to the main caps themselves via new drilled and tapped holes. The only problem I see with this is a new failure (weak) point.

[lammbn]

Thank you guys for your input.

 

Braap: i agree totally that this setup would be completly un-nessesary in 95% of applications out there. But seeing as how i am a hobby machinist/fabricator and a Junior in my bachelors degree for Mechanical engineering i know that i tend to over-engineer things. and thanks for clarifying that the shear stress was not an issue with the washers (i'm not sure if you italicized sheer because i spelled it wrong but i could have sworn that spelling meant see-through. but who would have guessed that english would be an engineer's worst subject. )

[Raami]

Now that brace is ready and installed.

I have bad pics of it. Engine also has LD28-rods, wiseco forged pistons and metalheadgasket.