Okay, I am doing a once over again with the 406. it's a dart block, eagle 4340 crank eagle 5.7 rods, Je pistons. Anyways, I initally went over and measured the clearance and it appeared to be right around .060. But upon taking a closer look I found that the rounding edges of the counter weights come much closer to the pistons, closer meaning more like 40 and maybe even 30 thousanths. I have already had everything balanced, and it's all together. I am tempted to just lightly grind at the counterweights a little to get the clearance, while taping and bagging off everything else. Then make the block rinse and gargle :). But this is just annoying me, can forged components stand closer tolorances? I am assuming this is a somewhat common combo. being 3.75 crank, 5.7 rods. why are the clearances so stinking tight??? any imput?

Oh and anyone know of a compact power steering pump with perhaps a underdriven pulley, and remote res?

 

I'd give JE a call. I'm not convinced you have a problem. Rod to block and cam should be .050", as I guess you are aware. But that is where the centrfigal force wants to pull and deform the crank in a rotational direction. When the piston is near the crank, it would take rod compression to cause a collision. I'm not saying that this is OK. But I think it might be.

If *I* had to adjust the clearence, I'd mark and pull the pistons. The aluminum removed from the pistons weighs a lot less than the steel you'd have to remove from the crank. I would have the balance shop weigh the pistons, before and after. Once equallized, I would seek their advice on making up new bob weights and spinning up the crank. On rereading your post, I'm not sure I am fully aware of the amount of metal that would have to come off of the crank. Like I said initially, my first act would to call JE. Second, if necessary, would be the machine shop.

I don't know how compact you really need, but stock C4 pumps pretty much fit your discription. Good luck, and...

RACE ON!!!


[Modified by CFI-EFI, 8:34 AM 10/28/2003]

 

I'll have to give them a call. It really bothers me darnit. I thought I was all set on having it all together, and pretty much did. But then I just started looking again and hmmmmm.. I mean when the pistons are at BDC there is plenty of clearance. But when at the piston is either comming down or just going up the counter weight comes pretty darn close but it's only a small portion of the counter weight "like a half inch" that comes close to the pistons which is only a small part of the piston. I already pulled it all apart, And double checked the clearance between the cam and rods, there is no problem there, as long as the timing is setup. it gets too close if not. I guess if I start taking some off the pistons I am going to have to re balance them. It seems like just a little makes a lot of difference as far as balancing goes. But I would just do that my self this time. I don't want to do this, it feels like I don't have a perfect setup anymore :(. I'll give JE a call tomorrow. See what they say, then go from there. thanks for the suggestion,


[Modified by WashingtonRacer, 7:40 AM 10/30/2003]

 

Your problem is the very short rods! If you put in 6 inch you would have .300 more clearance. My 4 inch stroke 427 with 5.85 rods is also close.:( I wish that it had been ordered with 6 inch also.

 

SHORT???

You're kidding, right? He's building a 406. That's a .030" over 400. The stock engine had 5.565" rods. This is a LONG rod engine for a 400.

Hmmm. I've got 5.85" rods in MY 4.00" stroker. Maybe I'll do a triple check.

WashingtonRacer,
Let us know what JE says.

AHHH! Modifying things, and using parts from different manufacturers, not specifically engineered to be used together. Ain't it FUN??? Good luck, and...

RACE ON!!!


[Modified by CFI-EFI, 11:03 AM 10/30/2003]

 

CFI-EFI an long rod would be 6.125 or 6.250 in a 406 I wouldn't even mess with 5.7 or less when 6 inch rods cost the same amount. All the vendors sell the 6 inch rod piston combos for the 406

 

Everything is relative. I agree with you on the use of longer rods. Especially in the case of strokers, where rod angularity and piston side thrust becomes an issue. But I don't know if it is proper to refer to a stock bore (albet a clean up) and stroke engine, with longer than stock rods, as a "short rod" engine. I have a set of 6.00" rods I aquired in preperation of building MY 406, but I tripped over this 4.00" stroke long block, before I got to ordering the pistons. Good luck, and...

RACE ON!!!

 

I was told that you are ok if you dont have less then 0.020 clearance so you should be ok.

Jay

 

I have a similar problem with my 407 with a SCAT 3.75 crank and SRP piston using 5.7 SCAT H beam rods.

I bought it completely balanced direct from SCAT and the #6 piston will hit the counterweight if you spin the engine over one way and not the other way-it is that close (piston rock). I planned to hit the piston skirt with a dremel and call it good.

You would think a kit would work together...aftermarket parts...:(

 

-----and the piston would stick .300" out the top of the block. Piston pin location changes when rod length changes. Counter balance to piston clearance is by piston design on rod length.

Rod length is relative. The stock 400s came with a 5.565" rod. Anything longer than that would be considered a long rod. Some longer than others.

Heck I work on BIG engines that a 400-6.250 rod could be put in the crank pin bore on the rod. The 6.250 rod seems short to me. :D





[Modified by Dan Plett, 6:43 AM 11/1/2003]

 

I wish I was informed about this as being an issue when deciding between the 6 inch rods and the 5.7. I also heard that the 6 inch rods make better geometery relations, but nothing that would really make a difference. So I focused on the pistons, 6 inch rods need those darn pistons with raised pins. and they have that damm gap on the oil control landing. Personally that worried me, all the keeps the oil control rings from pressing into that gap is a small ring. After seeing my previous engine go to crap and how the oil control rings busted the land in that same area, I wanted something with a little more meat on the lands. So I went witht he 5.7 and standard pin locations. Oh well. I guess I am paying for that decision now. Anyways I am going to be spending the rest of the day today taking a little off each skirt. A local machine shop told me that all they do is take a wire with 45 thousanths thickness and if it all clears, then they don't worry about it. I tried that and most of the pistons pretty much cleared. I decided to just go ahead and take a little off the pistons where the edges touch, then a little off the crank. just a slight amount. I hope that the amount I am taking off will not even effect the balance. the area being effected is going to be around a 1/4 inch, and only 10 thousanths at that.

Oh JE said the same as everyone else. Just start grinding. Not much else I can do. They were shocked that my clearances are so tight though. I guess it's not all that commen in a aftermarket block/ rotating assem combo.

 

It isn't a rod issue. It's a piston problem. See Dan's post, above, again. However much a longer rod you would use, the pin has to be that much higher in the piston. That brings the skirt back down to appox where it was, close to the counter weights.

As for the pins encroaching on the pin bore. I think you could have used the 6.00" rods without that problem. A 6.00" rod on a 3.75" stroke puts the center of the pin, 7.875" above the crankshaft centerline. I have a set of 5.850" rods on a 4.00" crank. That puts my pin at 7.850" above the crank. My pin is only .025" lower than yours, and IT doesn't pass through the ring groove. I would guess, you might have been able to find pistons to clear. But as you said, you've got them, now.

Bummer, about the grinding, but at least you got it straight from the horse's mouth.

I appreciate your reporting back, JE's comments. Good luck, and...

RACE ON!!!

 

I see your point with the 6 inch rod combo. but wouldn't having a raised pin location give you "the ability" to have a shorter overall skirt. and as a result give you more clearance.

Well it's besides the point I guess. I grinded all the pistons now. cleaned them all up, and tomorrow night I am going to go back over each and every one and make sure the clearances are perfect now. I am kinda hesitant on grinding any more off the pistons, not that I grinded all that much. but I just don't want to alter much. I am going to try to find a friend who has a scale so I can see how much I really altered on the pistons. I doubt much, but heck if there is any difference I might as well make them equal again.

This leads me to another question. is the crankshaft really effected by the weight of the pistons and rods? for instance since it was all balanced, and now I have grinded off the bottoms of the pistsons a tad, would making the pistons/rods assem be of equal weight again be sufficent, or does it really need to be matched up with the crank too?

I am paranoid, and probabily just over worrying about nothing here, but I just want a extreemly healthy engine that will run for a very very long time.

 

I see the point you are making, but it takes a certain amount of piston skirt to stabilize the piston in the bore. An interesting note, however, pistons for longer strokes and rods are typically lighter than others.
Probably. It doesn't sound like you've removed much weight. Matching the weight IS the first and most important item. The "rule of thumb" in balancing, is that the "bob" weights are made up to equal the rotating weight (things like the big end of the rod, rod bearings, etc) plus 1/2 the recprocating weight (things like the piston, rings, pin, etc). Different machinists have their own formulas. Some like to "overbalance" the assembly. That means to make the bob weights a percent or two, heavy. The point of mentioning this is to demonstrate, that the equalization is paramount. The actual weight, is a little open to interpetation. It sounds to me as though you'll be fine. Good luck, and...

RACE ON!!!

 

I try to the best that I can within reason.

I know the more I assemble and disassemble the more likely I'm going to hurt something-dirt, dropping, etc. I had to grind 3 of my piston skirts, but I'm not about to tear it down and take it back to the shop for balancing.

You also have to wonder how exact do things need to be with all the flinging oil in the bottom end at 6000 rpm or whatever.

Also, with the beefier rods and pistons I expected some situations with the block, etc., I still like my route better than the oil support ring deal.

:)

 

You did nothing wrong by picking the 5.7 rods because you could have the same problem with the 6.0 rods. it is right the skirt on the 6.0 rods are shorter but that does not mean that you would have more clearance because the counterweights on a crank for a 6.0 rods have bigger counterweights, that is why engine builder like to go with the 6.0 rods because if they want to internaly balance the engine it will cost less because you will not have to use as much mallory because the counterweights are bigger so they dont need as much mallory.
My brother has build a few 400+ engines and he likes the 5.7 rod over 6.0.

Jay

 

Alright, thanks for all great respones, I have about 50 thousanths now, went and bought a nice digitial "cooking scale" that weighed down to gram. re weighed all my pistons with rods bearings, and rings installed, and it came to 1392 grams on all of them. I figured there would be a larger variance since I just grinded and grinded till they cleared, But I guess I didn't hamper the weight at all. I am however going to double check the crank, and have it re spun this week. I am pretty sure it's just fine, However I have come too far to start assuming things. So on a good freaking note, I will have the engine all together this weekend again. The only thing I need before it goes in the vettis a scatter shield. .

 

The way you present it, it sounds like you're good to go. I don't know the accuracy of your "cooking scale", but the normal scales used for balancing are expensive. A differences in piston weight might show up better if they were weighed by themselves, but I realize that dissassembly is a lot of work. If the pistons are truely within 1-2 grams of one another, you're, set. I know it has been an ordeal, and a lot of anguish, but it looks like you are about done. Good luck, and...

RACE ON!!!

 

Well I finally got my crank back from the balancing shop. and they had to add a little weight to the front counterweight. But then it occured to me. I am overly paranoid. I started wondering why, I already had the crank balanced. then I grind a little off every counterweight, and it comes back only needing a little weight in the front???? why only the front. I don't see a reason to ask him really since I know pretty much nothing about this aspect of the work. But I do ask, whats would happen if an engine is not balanced correctly or not balanced? would it gernade it's self? he says no, it would just vibrate alot. That makes me feel better, being I could tell right away if the engine is right or not.. But now I ask you fellow memebers, what are some of the effects of a balance issue?

 

We had problem with our 'good' race engine and threw a spare together to get by. After running the rest of the season that engine was torn down for rebuild. Upon tear down the rod and main bearings look acceptable for a season of racing. One rod weighed 27 grams heavier than the rest. The total engine balance wasn't even close. I wouldn't knowingly run an engine that far out but it did perform well.

In a general 1 gram = 11 sheets of typing paper.