What is highest safe RPM for stock 455 piston rods ?

Just rebuilt the 1974 455 engine I picked up for my 1972 Skylark. I never thought to ask but what is the general opinion on what is a highest safe RPM for stock piston rod ? They were checked and sized by the machine shop that did the engine. The engine builder there said his opinion was 4800 RPM. Looking for more feedback. Something is telling me I goofed by not going for h-beam rods, but this is my first Buick engine build.

All feedback is appreciated!!

 

Stock rods are strong pieces, many guys including myself have and are slinging stock rods with 600+ HP, just use good bolts that are installed correctly IE spotfaced caps and clean the beams up

 

I take my stock rods, aftermarket forged pistons (a tad lighter?) up to 6,100-6,200rpm. I did have the whole thing balanced though too. Been running that way since 2011.

 

You know the answer is going to depend on the weight of the piston, among other things.

 

Obviously the engine builder isn't familiar with BBB buildups. Stock rods with stock weight pistons are good to 5500 which is about all you need for most "regular" street buildups. Unless you have a big cam and some nicely worked heads there's not much reason to go higher. If you keep it 5500 and below they'll last a long time. I've had all kind of street going 455's in the last 40 years and really haven't had any stock rod failures even going into the 11's with them. Even the 11 second engines only needed 57-5800 rpm. The biggest thing I did was, as suggested, better rod bolts for the faster engines.

Hopefully some oiling system improvements were done. That is probably more important to keeping a BBB alive at higher rpm than anything else. What cam and how much headwork did you have done? That will help in making a decision on where to shift.

 

Did they Replace the bolts?

Easy way to tell.. do they have 6 or 12 point nuts on them.

JW

 

He must build Pontiacs. I used to take mine to 6200, now shift at 5800. Like everyone else says oil mods, bolts and clean up the rods.

 

Yeah, must have been thinking Pontiac rods which were cast. I take prepped (selected for core shift, polished and ARP bolts) to 6500 all the time.

For bone stock rods 5500 is fine unless you are running oval track and running that rpm all the time.....

 

Here are answers to a couple of questions. First the rods were checked and stock bolts reused. Second the pistons are TA_1621A
455 FORGED PISTON NO NOTCH speed pro L2353F 30 over with out valve notch.

Cam is TA_212-455 455H.470"-218'/.475"-230',112' running with stock lifters.

The Local shop that did my work is a big local Chevy stock car engine builder, but also does about 60 to 70 small Buick engine sleeve and short block rebuild for Land Rover. Maybe that is were he gets his lack of faith in Buick stock rods.

I'm looking at you folks for feedback from a practical and real use experience. So any feedback is appreciated. Have not run the motor over 5000, and have actually put larger 70 series tires on to cut the gear (another goof up I made putting in 3.73, will be changing to 3.42 over winter).

 

Forgot to include, assembly was balanced .

 

I don't really understand why ANY good engine builder would re use the stock bolts on the rods, when good ARP bolts are readily available and fairly inexpensive? I'm assuming that the rods were re-conditioned, so the additional cost of changing out the bolts would have been minimal. To me changing out the rod bolts is always a "no-brainer", even when doing a mild rebuild. I realize he's a "Chevy" stock car engine builder, but making small improvements like installing better than stock rod bolts is a detail that should never be overlooked, especially by a professional......at least in my opinion. What else did he "miss" while doing the rebuild?

 

Unfortunately His opinion , which he gave me a half hour ago was "Buick rods are the weak link, not the rod bolts".

 

Obviously he's one of those guys that "has all the answers" and not willing to listen to facts. These facts are based on many peoples experiences, including mine.

I ran stock rods for many years and always buzzed them up to 6500 and in some cases, (unintentional of course, lol) well beyond that. I've had my share of issues along the way........ blocks breaking, cam bearings melted, broken lifters, broken rocker shafts, etc., etc., but I never broke a rod. If I would have simply "looked over" the rods while doing the engine building and just stuffed them back in the motor, they may have very well been the "weak link".....don't know.......never took that chance. But when done correctly the factory Buick 400/430/455 rods are a decent piece.

And most of us wonder why there are statements made like "be sure to take your Buick engine to a Buick engine builder". In some cases I guess it's obvious.

Good luck with the engine. I'm sure if you keep the RPM down to a reasonable limit you'll be fine. My opinion is with stock rods that have not been "updated" I would limit it to 5000 or lower.
Again...... this is just my opinion.

Steve

 

My weak link rods have seen 8k rpm and 7k several times ha, he probably thinks Buicks can't be made to run either

 

I hope you meant 6K??? LOL

 

Nope 8k, happened at the nats last year the auto meter 8k tach buried when I left

 

I figured I hurt it but it's fine,...or seems to be ha

 

:spank:

I have had mine go to 7200 a couple of times before I got a rev limiter. Rods were fine (could not say the same for a valve on #2)

So the real world answer is your machinist does not know the week spots on a Buick 455. I run stock rods on a 650 hp supercharged 455.

 

Yeah, I hit the rev limiter at 7400 a few times....thought it was OK but unfortunately must have egged out some bearings and it later (bout 20 passes later) grenaded BIG TIME at Quaker. Track guy came up to me and said "this must be yours, still hot" .....a cam lobe. My son said he saw fireball....and it was daytime.

That was a solid lifter motor...my hydraulic cammed motor it BQUICK with float the valves (at 6800) before it gets up that high

 

I would, under no circumstances use stock 45 year old rod bolts. I don't care what they look like.

About 10 years ago I had a customer send me his 74 Stage 1 455, that was rebuilt to stock specs, and then promptly broke a rod bolt, which cost him his numbers matching block. His builder told him exactly what yours told you.

The motor did not burn a bearing up, or suffer any other issue. The stock rod bolt broke.

No problem with stock rods in this application, with good ARP bolts. I raced with them for many years, and eventually broke one (even with a super light 430 old school Jahn's pistons combo), but that was after many many 10 second runs.

For a couple hundred bucks, your risking your whole build. Like Steve, I don't at all understand any machinist that resizes rods with stock bolts, all one has to do is open the ARP catalog and there they are. Not like you have to find a nitch vendor or something. Replacing rod bolts is a fundimental rebuilding step, I would trust nothing this guy did, if he skipped that one.

JW