I went out to assemble the short block for my '68 302 tonight and discovered all my pistons are on backwards. With the numbers on the connecting rods facing out and the beveled edge facing the counterweights on the crank all the arrows on my pistons point towards the back of the block.
Now I've heard a rumor that this increases horse power at the price of a little piston knock until it warms up, is this actually true? If so, are there any other adverse effects of running flipped pistons or will I be okay? Has anyone actually done this in their engine build? Will it kill my motor a lot faster? Should I stop thinking about this and just go back to the shop to have them put the pistons on the right way?
I guess I should mention that I'm running cast pistons if that makes a difference. Also can someone confirm that I'm actually putting the connecting rods on correctly?
Keep the extra horsepower and don't worry about it. Yeah, you may experience a little piston skirt "slap" when the engine is cold but other than that I doubt any ill effects. FWIW, you may even have LESS cylinder wall wear on what would normally be the "loaded" side.
With the numbers on the connecting rods facing out and the beveled edge facing the counterweights on the crank all the arrows on my pistons point towards the back of the block.
Do you have a picture showing that the arrows "point" towards the back of the block? I ask because my pistons have a > on them. The > is towards the front of the block, but if you call it an arrow point, it points towards the back of the block. I discovered that the > is indeed suppose to be on the side of the piston towards the front.
Allen, I can take a picture tonight but my pistons have an arrow cast into the top very clearly, no notch. I know the notch you're referencing too, my stock pistons had it.
Seriously?!? I inadvertently did the same when building a stroker a couple years ago and EVERYBODY I talked to said it was no bueno! I ended up tearing it all back apart, splitting the rods/pistons, flipping them around, etc. Wish I'd have known that little secret then!:shrug:
Greenstang, did you disassemble the engine and number the rods or did the shop? Reason I ask is it's pretty common for a shop to simply install the pistons on the rods correctly with no regards to rod numbers on a complete rebuild. With pin offsets, you'll have 4 piston notches facing the rod bevel, and 4 facing away. If you swap sides (spin the piston/rod and install on opposite bank) all of your notches will face forward. The only reason(s) rods need to be numbered and go back where they were originally is if the engine is being re-ringed using original pistons, or crank radius was repaired/reground and rod(s) machined for exact clearances. Otherwise, any rod can go in any cyl number position as long as the bevel is facing the radius. Yes, reversing the pistons is an old trick for a couple of hp but does promote noticeable piston slap. The hp you'll never notice except at a track or on the dyno. The slap you might.
I disassembled the engine and brought it to the shop for inspection and machine work. The block was bored .020 over and I got the new pistons and rings accordingly. The crank was not ground, only polished and the rods and mains have not been resized. Bearing clearances were still good (something like .0012) and everything was still round. I am just going off the numbers that Ford stamped on the rods and caps in the factory. Is it possible that I can just swap the banks of pistons?
I wish I had your problem. I found 351 Cleveland pistons in my 289.
If it was my engine, I would have the pistons swapped to the correct orientation. My last 2 Chevy trucks had piston slap and needed to be warmed up before the noise would stop. I just hate hearing metal to metal contact every time I turn the key.
I had a Toyota Sienna with piston slap. I gave it to my daughter some time ago and it's still going strong with over 160,000 miles on the odometer. I wouldn't worry about it at all.
Rick,
They ARE bank specific! #! is #1 and #2 is #2 NOT #5. Ford IS specific about which side of the rod is stamped AND that the number be facing out on the bank it is installed in. Engine assembly plant workers had a specification book to work off of. I have a few of those books for various 289 engine builds. Same information is in the shop manual. Please correct your post.
No correction needed. ALL of the connecting rods are identical no matter the number stamp, cylinder numbering, or bank. Are you saying if you needed a replacement connecting rod because #2 cyl spun a bearing and trashed the rod that's you'd buy.....specifically.....a replacement rod for #2 cyl? My comment on numbering refers to common machine shop practice which is stamping the rods front to rear in order. As in 1-2-3-4-5-6-7-8. So, what is the 2nd rod cylinder number on a Ford? 5 correct? Follow me here. If you wanted to keep the rods where the factory put them they'd number 1-5-2-6-3-7-4-8 front to rear. When rebuilding an engine ANY rod can go in ANY position cylinder number wise AS LONG AS orientation is correct as in chamfer. Doesn't really even matter if the bearing tangs face up or down unless the rods have a wrist pin oiler hole. Back to the OP's question. He has the rods/pistons swapped bank to bank. That simple. With pin offsets the machine shop will install 4 pistons with arrow facing rod chamfer and 4 opposite. (4 chamfers face front and 4 rear) IRREGARDLESS of numbering. Go out in the garage and grab a connecting rod. Hold the big end in your left hand and small in right with chamfer facing forward. Now, 180 the rod big end to small end in your hands. It now fits the other bank (crank) correctly and the number on it is still outboard............... BTW, the old racers trick of swapping pin offsets (in a good running engine) involved nothing more than swapping the piston and rod "assemblies" side to side. No turning pistons around, no reorienting rods, just swap em. Yes, I know first hand. I'm an old racer. Also, if you have a sec, compare GM/Mopar firing order as well as cylinder bank numbering to Ford. You'll see exactly what I don't need to correct.
Z
Have I done it? Sure 50 years ago when I had no money I did anything I could for some extra power. Some of the "Pro" drag racers I hung around with ( as you mentioned) laughed at me when I told them what I was doing. Some felt sorry for this enthusiastic "kid" and helped me with outdated parts they had and contacts at Ford for help. Little did I know that would lead me to a 40+ year career in the automotive aftermarket industry with 20 of those being in the racing piston business.
Now I'm looking forward to retirement LOL.
Here is a picture of my pistons are requested. Pretty tough to screw this arrow up. I also took a picture of how the number one piston would sit if it were installed in the correct bore with the correct rod orientation.
Before just rotating them the other direction and also considering that the pistons are backwards, I would verify that the big ends of the rods have the chamfers facing the counterweight sides of the crank. this is absolutely vital. Both sides of the rod big ends are chamfered but one side has a larger chamfer. This side must face the crank counterweight or there will be,,,,,,,,,trouble.
Rick I'm clear and have been from the onset. Maybe I read your post oddly. Ford numbers their rods at the engine plant and stages them in racks for installation. Some OEMs didn't number their rods but not Ford. Do they have to stay in that order ? of course not. Do you have to use a #2 rod in #2 cylinder? no . BUT when the engine is upside down ( as you were saying in your post), yes the first one is #1 and the second is #5 etc. That is probably where I was confused in your post. Since you mention looking at other engines like GM's that number 1 IS #5 on a Ford and #2 is #1 on a Ford yet their firing order is the same as a 289 except the distributor turns in the opposite direction. ( Not 351 or late 5.0 , that is "cam swap" firing order on a Chevy)
When I re read your post I understand. I also saw your sentence and commented because it didn't make sense at that moment. No "waring" needed we are on the same page. I'm probably just as old of racer as you are.
Victory! I put the piston marked #5 in the number one bore, double checked bearing clearances then checked again. Looks like swapping over the banks will work just fine. Thanks so much y'all, not the first time you've helped me out, and I'm sure it's not the last.
As a guy who has wasted thousands of dollars on sub par machine shop work in the last 16 months, make them fix it. Accepting stupid "day one" mistakes from machine shops only encourages them to continue with them.incompetence rules! If they can't orientate pistons on rods what else did they screw up. I know first hand what else they can screw up. Everything!
Nailbender. Please please explain to me what you'd want them to fix. As installed. all pistons faced arrow rear. That tells me they're installed correctly on the rods but were installed on the wrong side. Not wrong but not as intended from a piston slap vs hp install. Now if one or 2 pistons faced the wrong way with the rod correctly installed, the OP would have a gripe. Please enlighten me.
I'm calling that wrong on a motor that is for street use and wrong for the non professional racer as well. Piston slap isn't just a little love pat. It's metal scraping metal unnecessarily. It will wear out the pistons and the cylinder sooner. Not the outcome I'd want from an engine overhaul
Where are those folks here that said "Your motor has been rebuilt" because my con rods had numbers stamped on them? If it doesnt matter where they go, why number them?
So as long as the chamfer is correct (rod to crank), it doesn't matter which rod goes where?
Allen
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