I am from a past position at Delco Advanced Development and Reliability Engineering , as the US ADRE facilities engineering coordinator. I am very impressed with your attention to calibration and following a predetermined process to create a controlled sequence that is to be followed in the testing of the product and use of in a different perspective than we usually see online

13 years of building race motors and some classes have stock rod rules, there was never a question about resizing the big end when changing the bolts. The more power you plan to make the more prefect things need to be.

Their is nothing like data to dispel or confirm a myth. Your efforts help all of us thank you for your time and efforts.👍🇭🇲

Great video Ed, I've gone through this same exercise a few times while building engines. Some rods don't move around nearly as much as others, my general rule of thumb is that you should always check/measure if your replacing rod bolts.

I love this! Definitely worth subscribing for....wayyyy back in high school I built a Pontiac 400 for my 2nd gen Firebird, I built it poorly of course but the advice I got from my shop teacher didn't help. I wanted to put better rod bolts in and he was all like "go for it". 3 months into running that engine the bearings were finished, this wasn't the only factor of course but it obviously helped. I was told after that about resizing rods, I was a dumb high school kid who got all his knowledge from magazines so how would I have known? Watching this brought that all back, and I love the full hardcore geeky confirmation aspect. Just awesome!

Dude thanks for all the time taken for the video! Much appreciated! Hopefully you've saved someone a major headache! I've never seen rods come back drone the shop without having machining marks on them. And I've seen serious damage done from this exact issue causing rod seizure on journal. If you aren't going to do it right then just don't do it at all

Not only bearing clearance but bearing crush! I applaud your diligence for precision but a few pointers. If you measure the rod in 3 places you can determine if the cap is misaligned now or merely distorted. Number 2 measurement alone won't give you that imfo. Couple other points; ALL measuring equipment should be close to 70 degrees and the subject your measuring also. Very difficult to use the mic to set the bore gauge in tenth of thousands. The finger pressure alone can throw the bore gauge off even tho your rocking it. A setting fixture is preferred. And yes any change in torque will 99% of the time change a bores dimensions. This goes for guys putting studs in main caps, one can get by without line honing if you use the exact same torque on stud as main cap bolt had! Good Video!!!

I had expected some change at the start of this, but that was way more than I had expected. Excellent factual demonstration!

Great video to show how to measure a rod first, Secondly thank you for putting this myth to sleep about if the big end needs to be resized with ARP rod bolts. Keep doing these types of videos so I can geek out with engine-building content!!!!

I suggest measuring in both diagonal directions to understand the variation in cap shift left to right. Obviously the ARP bolts/lube/torque do influence clearances shown in dimension #1. Appreciate the testing!

“Without data, you’re just another person with an opinion.”― W. Edwards Deming

I was pulling the pan off to replace rod bolts so i may as well rebuild the entire engine with a twin turbo setup and dry sump. Ahahah love it.

Damn, that was a really good example and demonstration. I really liked the saying about opinion and data too.

So - don't use ARP rod bolts if you don't want an egg shaped rod hole. You probably don't need ARP bolts unless you are racing anyway. This probably applies to any over torqued ARP or aftermarket bolts anywhere on the engine.

Good Stuff Sir! I knew the answer, but I really like how you laid out your video and explained every detail! Andy

Thanks for doing the work for me. Now we know just why the machine shops recommend resizing the rods.

Thanks for this, always had them resized but never known for sure if it was necessary. Now I know!

I'm 71 years old and rebuilding a 56 Chevy with a 1969 Corvette 427 that has sat for over 25 years from the last time I built it. Had a new cam part part failure, long story and nothing to do with the build process. Life got in the way, raised 2 fine sons, and am now starting over. Your attention to detail makes me question my sanity! ;) Thinking maybe I should just pay a machine shop to build the long block for me! I just really want to drive it again before I die! :)

BTW, awesome video. An engineer that actually knows how to turn a wrench - there are so few of us. I work with some engineers who don't know what a ratchet wrench is. Subscribing!

Great video! I didn't know there were people out there swapping rod bolts that were NOT resizing their rods. I can imagine those doing that talking trash about the bolts they put in after they spun a bearing.

Great video "Egghead" lol ! glad to see you back , sounds like your health has improved . Thanks Ed

Another great detailed video, thanks for sharing Ed!

Swapped out the rod bolts on my Chevy LSJ as the engine is in an Ariel Atom. 6 years of to the floor road race track abuse and a rod bolt finally let go. I should have gone with better rods and bolts. Nice video.

Pre watching this I thought you'd say it didn't matter, I was ready to jump on you because you don't know what that rod (motor) went through. But you got it right! Also I reconditioned rods late high school through college & saw differences in manufacture tendencies after capping them whether they were close or way off.

It's because of the increased torque on the bolts that it changed. If you changed the bolt but still torqued to factory spec you see very little change. It still is a yes and no for a resize. If you plan on changing the amount of torque on the bolts then you need a resize. Main bearings do the exact same thing when you change the torque of the bolt. It can also change when a bolt is slightly longer or shorter or a stud is used on mains.

I did the same test with stock gen4 LS rods and found that ARP bolts put them out of round just like you found with Ford. Nice job testing!

Just found your channel. What a great, easy to understand video. Thanks!🤓

Excellent video. This is why I wont spin a wrench anymore, especially with modifications. Theres no end to the time and money that can be spent making something "better "

Interesting video. I come from the world of BMW E46 m3s, high strung motors with tight tolerances. Rod bearings are a 60k serviceable item. Everyone seems to get away with using aftermarket ARP bolts and just torqueing them (no stretch measuring). My engineer brain cries bloody murder every time I hear this, and your findings are exactly why.

Hi Ed - Thanks for this excellent video. I'm a mechanical engineer too, and appreciate the attention to detail. I'm about to start the reassembly of a 2110 cc air-cooled VW engine (82mm stroker crank w/90.5 pistons) for my 1970 Crew Cab pick-up. I had this engine together about 10 yrs ago, but paid someone to line-bore and build the shortblock for me because I was doing 60-70hr weeks at work. I built up the rest like a Swiss watch. The engine seized up (on the main thrust bearing) after about 3-4 hrs runtime. A real heartbreaker. By good luck the beautiful new crank was okay after a competent machinist dressed the journal, re-did the line-bore, and set me up with a new properly sized bearing set. Everything's been sitting in enclosed tubs on the shelf ever since, and now I finally have some time to put it back together. The problem is that somewhere along the line I read that ARP bolts are designed to yield ever so slightly when torqued to ARP's recommended level. That being the case, they are not to be re-used. Or so that source said. It seems like a conundrum, because if that's true then when you torque them to measure & re-size the rods, you'd instantly lose everything when you disassemble to install the rods on the crank. You'd be chasing your tail, so to speak. I'd like to get your take (and maybe that of some of the erudite gearhead commentors below) on this matter. Thanks - and you have a new subscriber.

Love your look on things and technology.. thank you

This is why attention to every detail is critical to preparing fitted parts for assembly.Thanks for proving this obscure concept,who wooda thunk it.

When I first seen the video title I was worried you' were going the other way. I once reconditioned a set of BBC rods with stock bolts to with in a couple tenths. Owner later decided to upgrade the rod bolts. He didn't believe me it was going to change the dimensions. I changed the rod bolts using a support block for the purpose then remeasured the big ends. 4 stayed in spec (but with greater use of tolerance) and the other 4 was out of spec. Another time a customer that had work done from a different shop was told to torque his 302 rods to 45 ft/lb. I informed him that the torque should've only been around 30 ft/lb and that all bolts should be replaced due to over stressed. He ended up paying for the new bolts and the original shop installed them but said they didn't need reconditioning. I've no clue as to how they changed the bolts but the big ends were .006 to .007 out of round. He's never been back to that shop.

When in doubt ...... test! Love it👍😊

Nice video. I was suspecting a change, because of the higher torque speck on the ARP bolts. Wonder if the clearence would change on new rods... I may try that same test. Thank you Sir.

Good Video. Fortunately for me unlucky for a buddy of mine I was taught this lesson a long time ago. You always check the big end of the rod. I have seen rods that did not change, I have seen seven that did not change but one did. Most of the time all eight need resized. The little Ford rod will take tons of abuse without failing, the block splits first.

This video brings home to me the importance of having the knowledge and technique necessary to use precision measuring instruments. It ain't no automatic! Three different people could measure a rod and come up with three different measurements.

Outstanding video, certainly thought me a thing or two.

Going from 23 lb-ft with oil lube, to 35 lb-ft with UltraTorque is a significant change in bolt tension. It is no surprise the big end changed shape, getting wider and shorter. But now the width of the big end is above Ford's max spec so this rod cannot be resized to spec. If the new bolts were installed to Ford specs, much of the benefit of the stronger bolt is lost, but it is still an improvement. My solution here would be to use =0.001 bearings and go with it.

A few years back I rebuilt a BSA A65 engine. I found that the original rods and caps were round enough. I used ARP rod bolts and measured the stretch, just using a standard micrometer. Once together, I checked the torque. It was within a pound-foot of what BSA specified for the rod bolts. The next time I'll do this will be once my Triumph Trident needs a complete rebuild. I have new steel rods and caps for this, and the ARP bolts which came with the rods. No need to resize for this.

Our mentors are so important. It's important to remember them.

Great information bub!

So glad you took the time to do all that. Now I dont have to. Thanks....👍

"While I'm in there" = motor rebuild.

Nice video. Thanks for sharing.

Great show and tell.

Great video, I've always heard but never truly knew.

I expected a change, but, I was surprised at the amount of change in the up/down measurement. I wasn't surprised at the change across the big end. After thinking about it though, the parting surfaces are fairly rough from the factory, so you may get more "crush" of the surface metal than a rod that has a smooth ground surface, like after a resize.

amazing work !!

Interesting. Thanks for explaining your method of verifying the C clamp is a precision device now....I feel this has helped me understand some measuring tools.... I want to check the wear on a subaru engine piston bore, so a tool like this and properly measure 3 & 9 and 6 &12 positions as you move up the wall...maybe focus on the highest wear area ? just below the TDC of the piston.... thanks.

I appreciate the information , me I want to have the rods resized after installing the bolts . I been told the same apply if you install main studs.

Based on some of the comments (thanks) I realized I should have included the fact that when I reinstalled the stock rod bolts (while forgetting which one was from which side), and re-torqued to factory specs, the rod measurements came back as P1: 2.2392" and P2: 2.2394", so within .0001" of the initial measurements, and a complete A-B-A test. The dimensional changes were definitely due to the higher clamping force from the ARP bolts, and not cap alignment, press fit, etc. And for those suggesting just using the same stock torque with the ARP bolts, that negates the advantage of the improved bolts. You need the greater clamping force to hold the rod together at the higher RPM loads.

Great video Ed you put some good edit and time in this and will prove alot for people who dont know that swapping bolts is no big deal!!#$

Can you measure the diameter of the bolts where the caps meet? Seems to me the cap is spreading outward with the stronger bolts, wonder if this is helped by a dimensional difference in the bolt? Or excess clearance in the dowels?

It replaced rod bolts on a 351 that I did a budget rebuild on and had to use a brake cylinder hone to get the proper fit on the crankshaft journals . If l would have had the funds to have a machine shop , I would have done that then spend about 10 hours getting my required bearing clearances . Even though it was a lot of work , I got it running and I have driven it about 35K miles and it still has excellent oil pressure

Priceless!

That was a really interesting video. As a precision machinist (3~5 micron tolerances, manual machining) and a motorcycle tech it isn't something I've come across before, (even though Triumph motorcycles used bolt stretch since 1950's) Maybe because motorcycles are much higher rpm engines and have to use better quality materials? (imports, 12~20,000rpm) One thing I have found, setting bore gauge is much easier on a piece of 'foam rubber' sheet, 1/2" thick or so. Laying micrometer down is way easier than trying to 'balance' things using a micrometer stand You don't need to touch working ends of micrometer or bore gauge so heat from your hands doesn't make things change dimensions (more critical with aluminium as it has such a high expansion rate compared to iron/steel) Ambient temperature is another factor that needs to be taken into account if your working somewhere 'cold' as body heat can change dimensions more than at a slightly higher temp. (std temp used to be 68f, don't know if that has changed now 'everything' is metric?)

Good video very informative

Check if the nuts are rubbing in the corner of the mounting surface they sometimes are too wide for the flat surface and hit the side.

Sounded like you had some taper too, also you have a sample size of one. Yes if one comes up out of tolerance then your done anyway. However, if it came up in tolerance, I wouldn't say it was good based on one sample.

Many years ago apps 35 . before I had access to people who could resize rods (I now have a rod hone) I put many sets of bolts in without resizing. I would reduce the press fit of the unfurl to close. To the size of the ones I removed and install them if they where less than 001 out of round I used them. Don't recall having a problem.

Great video I learned a lot from this

I know I learned the hard way if you install main studs you need to align hone. My 350 Buick got the full ARP stud treatment. Ran great and would wind up to 5500 no problem. However, by 25,000 miles I was running 20psi oil pressure when hot. No knocking. I imagine it’s sloppy crank bearings.

Wow I remember getting hit with the resized rods thing ! Very interesting!

great video!

That was bad news but good to know.. thanks for posting. I wonder if the same applies to the main bearing caps..

New subscriber. Just found you. Interesting conclusion

Just found your channel. Subscribed.

Interesting vid !!!!!!! 👍👍👍

Don't know how I came across your channel but I've watched a couple videos. Even though some things already aware of, its nice to watch how people do things either the same way or to learn a new way of doing. Plus have to support our local Manitoban's

I was hoping to see your decision to for go the new bolts or pull the engine? You didn't seem put off I guess you already know the out come. Thanks.

I’ve only replaced rod bolts twice, both times Chrysler V8s. Both had to be resized. Oh and on a Cummins. The Cummins did change the rod size no doubt but it was still within spec.

This is great! Thanks. But now try it with the bearing shells in. You will see what I mean.

One important thing about metrology is the temperature the measuring is done at. Iif you're serious, you can buy circular standards, in a range of sizes, which would avoid any possible cosine error if the internal dial gaude was slightly off when in the micrometer.

So in conclusion put new rod bolts in a loose engine lol

Ok question for you: rebuilding a 5.0 and the bottom end looked decent (explorer motor / was cared for). Planning to reuse the rods / boring .030 because new pistons are within 5grams of old so I don’t plan to rebalance. Targeting ~300hp street motor but might wind it to 6k here/there. Would you add the ARPs to the rods? Mic’ed the rods and they are in spec. Also - did you check twist on yours? Might mount mine in the lathe and check with an indicator too. Alternative plan is to order full rotating asm from summit but only if necessary (ie- reuse is too risky) Opinions welcome / what would you do?

Very Informative! Cheerz!!

Replaced the rod bolts many times in used engines and worked ok. No issues. Guess I was lucky, and many other guys were too. Great information. “If you look for problems, you will find problems; if you look for solutions, you will find solutions.” - Andy Gilbert Check your main bearing clearances with new bolts, or studs. Its always god to know.

Yer changing out a bolt with a stronger bolt....what's changed...??...only the resistance to deformation...right....??

Thanks I was wondering about that one what if you set the torque with the arp bolts to stock bolt torque would it still change that much

Nice! This too is becoming a lost art.

I was not expecting the bore to change that much. Thanks for sharing.

That is odd. It is as though there is more metal to the outside of the bolt than the inside and that is probably true. Which suggests the fix is fine sand paper on a surface plate with one side of the cap slightly raised to bias the mating surface. *I wonder how round it is with no toque?

i used a close fitting mandrel in the bearing bore when replacing rod bolts.

Now do the test over with a fractured cap rod and a doweled cap rod, i bet it won't change much if at all. 😉

That surprised the hell out of me!

Might not be clamp load affected , likely just the cap has taken a new position on the rod with the bolt changes

The last few years I've been taking 3 measurement; 1) 45 degrees to rod centerline 2) parallel to rod centerline, and 3) 45 degrees to rod centerline, but on the other side of centerline. More than a few times I've seen measurements at 1) and 3) move in opposite directions with both the existing bolts, and after a bolt change. If you are not routinely looking at this data, maybe you should.

Well now I would like to see the same test on main cap bolts/studs!

what happens when you re use a stretched rod bolt? I have heard that torqueing factory bolts 5lbs more wont hurt, but I got that tip 30 years ago from a top notch circle track magazine.

Good video.

I’m not an engineer, but my mind, works like yours!😀

When clamping a rod in a vise it should be done on the big end of the rod just before the parting line generally. After resizing a rod you can change the bolts using the same style & brand bolt if done properly. Bill Jenkins addresses this in a couple of his books. I have done this myself with no problems. The rod must be torqued and securely clamped over the parting line doing one bolt and retorque at a time. Always re-check sizing. Don't clamp a rod on the small end of the rod, avoid twisting the beam. I've resized so many connecting rods in my life I've lost count. Also its a good idea to change the nuts after a few retorquings.

I have a question, does this require sacrificing a set of new ARP rod bolts or can they be reused after stretching them ?

WHAT WERE THE READINGS WITH THE SHELLS INSTALLED ?

I think I’m missing something here. The arp bolts have taken up nearly a thou of clearance and caused the cap to be out of round outside of the specifications. How is this a good thing?

I have a dial bore gage mounted on my rod resizing machine, and have found rods to be out of rouund diagonaly!

I would like to add a point they have come across one setting dial board gauges with a micrometer. When you calibrate a micrometer with a standard spindle and a micrometers under about 2 pounds of longitudinal force which takes up the backlash in the screw. When you insert the board gauge into the micrometer there is a very very minimal force from the dial indicator. The micrometer may have one to three tenths of backlash. If you want to get around this problem you need to use gauge blocks or a rain gauge. Just saying.

Excellent video, learned a lot. What gage standard set do you use?

Great shirt!