Calling all you engine guys...I need information on a possible set of used connecting rods.

http://forums.corvetteforum.com/show....php?t=2127170

I found the 5.5" rods to be too short after installing new pistons on the 400 rods. The new pistons didn't say they were anything but a standard pin configuration yet they were too far under the deck.

I measured, and sure enough, these new pistons are for 5.7" rods.

Now, what I need to know...because I am looking for a used set of forged rods...is will any set of 350 forged rods have the same center to center length and journal size, to fit a 400 crank?

I have heard there are small journal 5.7" rods but I don't know what they came out of, and I will need what I assume to be large journal rods to match the 400 crank?

Anyone have information that might help me locate a set of used 5.7" forged connecting rods for my 405 project? Maybe someone have a set under their work bench that they could measure for me?

Thanks to everyone...EXCEPT Len aka Jughead aka Paranoid. !!!

 

Matt,
(EDIT - Removed Erroneous Info - Sorry!)

Eagle can sell you what ever you need for about $200 and they are very nice! That is hard to beat as they come ready to install, weight matched, better fasteners, etc. Think about it before you spend money on old stock rods to resize them and add good bolts. You can easily spend more even if the stock rods were "Free" in the first place.

-Mark.

 

Thanks for the info mark...so what you're saying is...there are NO large journal 350 5.7" rods from factory engines?

 

(EDIT - I am still full of it here again)

-Mark.

 

The 400 crank was ground down and I have +size main and rod bearings.

At which point does it become the 5.7" rod journal size? Any of the standard cut sizes?

This isn't looking good for my wallet.

 

You guys are giving me a headache.....I'm glad I dont do much heavy engine work.

 

OK, I'm a little lost here so let's "connect the dots"

First, as noted all SBC connecting rods are forged except for the late-model LT1 (not LT-1) rods which are powdered metal (and are sold as the new "pink" rod from GMPP). There are certainly billet rods, but there are no cast rods. Power capability is based on the bulk of the lower end (some are better than others) and the size/type of bolt/capscrew used. Big generalization - but good rule of thumb.

A 400 factory crank has the same rod journal size as a 350 crank - 2.10. The mains are bigger at 2.65 vs. 2.45 - but the rod journals are the same. So if you're looking for a 5.7" rod for a factory 400 crank - any SBC rod will do. Early SBCs - 265-327 had "small journal" (2.00) rod journals.

If I'm missing something here, tell me

The cheapest aftermarket rods I know of are the Scat I-beams that sell for around $180 - and they're balanced with ARP rods. Available in floating and pressed pin.

 

Bill, thanks for chiming in.

I have two sets of 5.7" 350 rods from some Vortec engines. Can I just use one of the sets, change the pistons over, and expect them to work just fine? I will likely have ARP studs installed but will the rods themselves work okay?

Thanks again.

 

Any large journal ( you won't see too many small journal rods for sale ) 5.7 in. rod will fit both a 350 or a 400, that's all there is to it.

 

Either set of those rods are fine. Some key notes:

- If the pistons are pressed-pin, I generally consider them junk if they've been pressed off Talk to your shop about this - opinions vary.

- If you replace the bolts, the rods will need to be resized - no debate

- You may find that by the time you get your used rods in shape (fluxed, cleaned, resized, bolts, etc.) a set of new ones as noted will be cheaper. "It is not logical - but it is often true" - the cost of machine work is just significantly higher than overseas manufacture. NOTE that your stock rods are also not stroker-clearanced.

Finally, double-double check your pistons - for a 3.75 stroke, 5.7 rod and a 9.025 block deck the piston compression height should be 1.425...there are a lot of variable here, so be sure you've got all the right numbers

You're welcome to MSN Messenger me at billla@warbird.org real-time if I can answer any questions - I have a call at 9-9:30, but I'm available after that

 

Thanks Bill. Would you mind giving me a brief idea of what needs to be done to the stock 5.7" rods, the stroker clearancing, so I can inquire as to the price of that or if it's something I can do myself. Never dealt with a stroker or the requirements before. Something I can do in my garage with an air power die grinder and some bits?

The pistons I ordered, the ones that I just installed, made no mention of being for anything other than a 5.5" rod. Once I saw there was a problem I measured and was certain it needed a 5.7" rod. I then took the part number of the piston and called them direct and asked about rod length and they confirmed 5.7" rods with that piston.

Considering it's a 400, with no deck work, and a turned 400 crank...can you see any problems using the Vortec rods? I just got off the phone with the machine shop. They said I would not need the new ARP studs unless I planned on winding the engine up past 5500 constantly. This I won't be doing. I prefer cruising and low RPM torque kind of fun. He said the stock rod bolts would work fine.

 

Yes there are many variables when dealing with rods and they shouldn't just be bolted on without a competent machine shop going through them

Unfortunately this cost money, as a matter of fact my brand new $700 4340 H Beam stroker rods had to be resized

 

Since the piston head issue was partially a responsibility of the machine shop they have agreed to magnafluxing the rods, and change the heads over for free. I might not do the ARP studs, but I will want to do the clearancing myself or if I cannot I will farm the work to the machine shop.

 

As said above by a few, the 400 crank has the same size rod journals as most all 350's. Though the 67 Camro 350 did have small journals same as a 327 and earler engines.But to confuse it some the late 327 had large journals. All the 350 and late 327 rods have 3/8 rod bolts and most all smaller engines had the 11/32 bolts. So any 5.7 rod you fine with 3/8 bolts will work for you. The item on rods bolts is correct you do not need better bolts, but not knowing the history of the old rods I would put new bolts in them and the cost is not much more for good ARP bolts so I would do that. And yes sometimes you can get away with not resizing the rod when new bolts are installed but, you need to measure them after they are installed for sure and you will probaly just need to hone the rod slightly. Always shoot for the high side of the spec. And DO NOT belive anything Plasta Gauge will tell you!! Measure everything correctly. Good luck

 

I wish I had better answers here. I need to note that the final authority here is your machine shop. Every engine builder has different standards and what they find acceptable based on their experience...and you can go nuts trying to reconcile between two (or more) of them.

At the very least, the rods should be cleaned and magnafluxed to ensure they're not cracked. Rare, especially for late-model rods - but it happens. This is a shop operation unless you have the home game from someone like Goodson.

Second, they almost certainly need to be resized to ensure the correct bearing clearance - what makes a small-block live is correct bearing clearances! Certainly the rods can be chucked up in a rod vise, torqued down and measured...and if they're within spec then just run 'em. This is also a shop operation unless you have a rod vise and snap gauges/micrometer or bore gage (preferred).

If the bolts are replaced - regardless of the type - the rod needs to be resized. On overhaul, I consider all torqued fasteners junk...I'll reuse ARP stuff 2-3 times, but the stock bolts go in the trash. But, this is just IMHO - so if your shop is saying to stick with the stock bolts that are already in the rods...this is a decision you and they need to make. I understand the budget constraint...but if there's a place not to go cheap, this would be very high on my list.

As for stroker clearancing, there are two aspects. First the rods need to clear the block - and they should in a 400 block...but this MUST be checked! You can do this grind at home if needed.

Second, the rods need to clear the cam - and this MUST be checked during mock-up. You can do the grinding at home on the top of the rod bolt to get clearance...but I want to be direct without being alarmist - take off too much and you'll throw a rod cap for sure. This is one of those things that I honestly don't recommend a home builder do unless you've done it before or someone can loan you a SUCCESSFUL clearanced rod for comparisons.

Not sure if all this is helpful or confusing. As you're finding - a stroker is a very different animal and crosses the line between an engine assembler - selecting the right parts and bolting them together - to an engine builder that makes parts do what they want

 

Partially? Who did the design? If they picked the wrong piston and pressed them on, then IMHO they owe you a new set, also pressed on.

This is one of the hard things about working with a shop - being really clear on who's responsible for what I hit a rock when I moved to Seatttle with a shop where we...disagreed; I now have a great Level 4 shop that has done outstanding work.

 

It's all becoming very clear and I like my options.

I will use one of the sets of Vortec rods. The machine shop will clean and magnaflux the rods. I will ask their opinion on replacing the studs again after they have the rods, and I will have them check the tolerances using new bearings...this I already do when using used rods.

I will be happy with the price, and confident with the outcome.

Thanks so much for the help.

 

At the risk of being contrary, I'll respectfully disagree here on these. It's all based on experience, of course - and I'm just sharing my differing experience.

- The bolts act as an index for the cap - it's a press fit, not a precision fit. In replacing the bolts, you're destroying the stock index..and the caps will not be straight. Aftermarket higher-end rods establish an index with a pressed sleeve so that the fastners (usually cap screws vs. bolts and nuts) can be changed without having to resize the rods. I can pretty much guarantee that if you press in new bolts and don't resize the rods you'll be sorry.

- Generally, the tighter side of the spec is the best place to be for the SBC on the street. There are some exceptions, but as a general rule of thumb tighter is better.

- For all the malignment, Plastigauge is workable as a measuring tool for stock-level rebuilds.

 

NP in your opinon. I have been working and running an auto machine shop for 35 years and I'm talking with that back round. After the stock bolts are pressed in you check the rod for round on a pin gauge with is a fancy dial bore gauge just for rods. Alot of the time you can just hone the rod to size this way. And this is better than a resize if the rod comes out round and on size. The reason is that to resize a rod you cut the cap and rod matting surface and bolt them back together. This now makes the bore small so you can hone the bore back to size but at the cost of shortening the rod some.( not always good.) As far as the rod to the high side of spec this is always the way to do it because of heat buildup which makes the rod smaller. This is not how you set rod bearing clearance but bearing crush is. And too much crush reduses the oil wedge which is locaded at the parting line of the rod. The thickness of the bearing and the crank size set the clearance.

 

Agreed that crush is what's determined by the big-end size (I was generalizing, but we've moved to the specific) but when you say broadly "shoot for the high side of the spec" it implies that larger bearing clearances are better - and that was the aspect I disagreed with.

Also a generalization regarding "resizing" - I would consider a hone to restore the big-end "resizing" to some extent even if the cap/rod aren't cut...but IMHO the risk is that the cut wouldn't be even across the bearing contact surface if the cap was cocked...i.e. the cut would take care of a high spot but not a low spot.

We can agree to disagree - which was part of my comment that when working with a shop the final authority always needs to be the shop and not "some guy" like me on the Internet!