When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I picked up a 1971 Oldsmobile Cutlass with the Rocket 350 and a 4 speed transmission that needs restoration. The motor has a bad rod knock. I'm looking for advice, suggestions and recommendation from you guys since this is a whole new game for me. From what I've learned the short time I've had it is that it's best to stick with an Oldsmobile engine for the sake of ease of installation in regards to motor mounts, wiring etc. So I've basically narrowed it down to 2 options...
1) Remove and rebuild the current motor. If so, should I stick with all factory spec parts, such as crank, pistons, heads etc? Or should I upgrade to higher compression pistons for example? Better heads? Etc?
2) Buy another 350 Rocket and then rebuild the other 350 in meantime. However, today I learned that manual trans Olds motors have a drilled crank. It will be tough to find another. If I go with a used 350, should I put in the crank from my old motor, or just order an aftermarket crank that is for manual trans? Possible that the rod knock would have damaged the crank?
Honestly, I want to get this thing on the road asap. I'm shooting for least time consuming, most effective way of doing that. I think if it wasn't for the crank I would've just swapped out the motors this week. I think in either case, I would like to put in a bigger cam. The motor did come with a Holley intake and 4 barrell Holley carb. What would you guys do? What would you upgrade?
Thanks - Konrad
Konrad, welcome to our site. Do you know how to use a dial bore gauge and micrometers? If so, you could disassemble the 350 you have and determine what it needs for a rebuild. If not, you have to get your machinist to do it for you.
I suggest rebuilding the 350 you have. While it's out you can put a performance cam and better pistons in it if you wish. Buying another motor to rebuild is an added expense.
I'd try to figure out why it's knocking before I did anything else
I will definitely try to figure out why once I get it out and start disassembling it.
Originally Posted by Olds64
Konrad, welcome to our site. Do you know how to use a dial bore gauge and micrometers? If so, you could disassemble the 350 you have and determine what it needs for a rebuild. If not, you have to get your machinist to do it for you.
I suggest rebuilding the 350 you have. While it's out you can put a performance cam and better pistons in it if you wish. Buying another motor to rebuild is an added expense.
Thank you. I've learned a ton from this community already since signing up this morning!
I've used a micrometer before, but never a dial bore gauge. I've replaced a motor before as a whole and did work such as headers, bolt ons etc, but never anything internal like this, so it will be a learning experience.
While I would like to just drop something in to quickly replace the bad 350, that crank is going to be a problem I think. So in this, case, I think I am also leaning more towards just rebuilding.
1) Remove and rebuild the current motor. If so, should I stick with all factory spec parts, such as crank, pistons, heads etc? Or should I upgrade to higher compression pistons for example? Better heads? Etc?
You should be OK using all of the original parts with the exception of the pistons. The replacement cast pistons not only have huge dishes, but are shorter than the factory pistons and will give very low (in the 7.x:1 range) compression. There are many higher quality forged pistons that will result in higher compression than the cast replacements.
Even a rebuild with higher compression pistons and a different cam will boost performance tremendously. Everything needs measured to see if an overbore, probably will be needed and if the crank and rods are salvageable, up to .030" undersize bearings are available. A good used motor just needs the end of the crank drilled for the pilot bushing or use one of the no machine bushings. I believe either the crank needs drilled or the input shaft shortned to work. If you car sits half the year like mine, now is the time to fix it. It all depends how long you can live without the car running.
You should be OK using all of the original parts with the exception of the pistons. The replacement cast pistons not only have huge dishes, but are shorter than the factory pistons and will give very low (in the 7.x:1 range) compression. There are many higher quality forged pistons that will result in higher compression than the cast replacements.
I've read about the dished pistons in later year motors, so this is definitely one of the upgrades I had in mind. Any particular pistons you recommend?
Originally Posted by olds 307 and 403
Even a rebuild with higher compression pistons and a different cam will boost performance tremendously. Everything needs measured to see if an overbore, probably will be needed and if the crank and rods are salvageable, up to .030" undersize bearings are available. A good used motor just needs the end of the crank drilled for the pilot bushing or use one of the no machine bushings. I believe either the crank needs drilled or the input shaft shortned to work. If you car sits half the year like mine, now is the time to fix it. It all depends how long you can live without the car running.
If I take the block and crank to a machine shop to clean up and bore the cylinders, will they be able to tell me what size pistons, rings, rod bearings etc I would need? I'd like to stay with this crank if it's still good.
Originally Posted by My442
A knock suggests that there is too much rod bearing clearance.
There is a distinct possibility that the offending rod(s) and crank are junk.
The only way to determine this is disassembly and measurement.
I understand and agree with what you are saying, and forgive my ignorance, but what exactly would I need to measure? In a situation where there may be a rod knock, would that be the excess clearance between the rod and rod bearing, saving the crank?
If I take the block and crank to a machine shop to clean up and bore the cylinders, will they be able to tell me what size pistons, rings, rod bearings etc I would need?
Yes.
Originally Posted by konrad
what exactly would I need to measure?
You would have to use a dial bore gauge to measure the cylinders and see how concentric they are. You would also have to use a micrometer to measure the crank journals and bore gauges to measure the connecting rods.
Unless you have all of these specialty tools and experience doing these measurements it's generally best to have your machinist do it. If you want to take part in the rebuild process ask your machinist to return the short block to you after machining. Then you can bolt on the heads, oil pan and intake/exhaust manifolds.
I agree. That's probably best way to go for me. Thank you all for advice. Going to pick up engine stand today or tomorrow and start taking it out.
Out of curiosity - what does a machine shop usually charge for checking and machining a block? Do they also machine the crankshaft journals, or is the crank pretty much scrap if the journals are damaged?
The crank can be ground undersized so you can use oversized main and connecting rod bearings. I doubt the crank in your 350 is toast, especially if it still runs.
i'm with jamesbo.i would exhaust every option before pulling the engine.thru the last 35 yrs or so i have bought probably half dozen cars with "rod" knocks. one was a 350 chevy with a broken flywheel,one was a 400 pontiac with a converter bolt that came loose and hitting the block,and one had a chunk of carbon break off in the cylinder.weird things happen.i personnaly would hate to pull an engine just to find something really stupid happened and it could have been remidied for next to nothing.
First, you can drill a crank for a pilot bushing, so don’t spend big bucks on a 4 speed crank.
Second, find a machinist your comfortable with, preferably one that’s familiar with Olds engine practices. Olds engines don’t like the same clearances as your chebby and ford engines. If the clearances aren’t set right during assembly, it will “clearance itself” resulting in more clearance in your wallet and bank account. If he argues with wanting the clearance on the loose side of specifications, find another. Do you have any Olds friends who can steer you towards a good machine shop?
lastly, don’t cut corners on the bottom end. If the replacement pistons are lighter than stock, most likely the rotating assembly will need to re balanced. I think all the Olds 350 rods are the same casting until the later lightweight engine blocks, so if a rod is in fact bad a replacement is pretty easy to find. Degree the cam, pay attention to valvetrain geometry, camshaft technology has come along way since 1971. Take advantage of almost 50 years of innovation.
A friend recently bought a 72 442 that had been sitting for a long time due to a rod knock. He got it running and it did make a terrible noise. Pulled the valve covers off and found a broken rocker arm. Even a blown header gasket can make an awful racket. Welcome, get the engine fixed and enjoy your Olds
I know a guy who made a boat load of money in the used car business before salvage laws in MA. He bought a cadillac at auction that was stolen and recovered off the road. It ran but had a bad knock. After looking closer he found the oil pan was dented from the ground impact and the crank was hitting it making the noise. He then cleaned it up and sold it for a good profit Im sure.
If you check the condition of the oil in your filter and perform a compression test and still have doubts as to the condition of your engine you can have the oil professionally analyzed. These folks can tell you if your bottom end is on the way out. They have a great reputation on the truck websites I frequent.
i'm with jamesbo.i would exhaust every option before pulling the engine.thru the last 35 yrs or so i have bought probably half dozen cars with "rod" knocks. one was a 350 chevy with a broken flywheel,one was a 400 pontiac with a converter bolt that came loose and hitting the block,and one had a chunk of carbon break off in the cylinder.weird things happen.i personnaly would hate to pull an engine just to find something really stupid happened and it could have been remidied for next to nothing.
Other possibilities did cross my mind initially when I first heard it, but the noise does get louder as engine warms up; I found metal and dirt like chunks on the dipstick; and after driving around the block, it seemed to have lost some power - I was not able to spin the tires as it would bog down, whereas initially, when I first picked it up I was able to without a problem.
Thank you all for your suggestions - I'm taking everything that is being said into account. Because I did find metal on the dipstick, I'm thinking it definitely needs to be pulled out and looked at. I'm hoping maybe it is just a broken rocker arm, but my gut says it'll be bigger issue than that.
I found two machine shops around me. Called one yesterday and explained the situation. I honestly have never done this before so I didn't know how to talk to them. I asked for a ballpark price on checking out the motor and a few what ifs, but he was not able to give me a quote - I guess it's understandable. He said to remove the motor, separate the heads (to save some money) and bring it in, along with the heads.
There is another one that I will call today, but again, not sure how to compare the two. I will stress, as someone above has pointed out, that Olds like to have small clearances, as opposed to Chevys.
Konrad, I would be wary about using the first shop if he's unwilling to give you a ballpark figure. When you speak to a machinist ask for quotes for the following:
1) Engine block honing with new bearings and rings using the original pistons, connecting rods and crank.
2) Engine rebuild with new bearings and rings with .030" over pistons and the original connecting rods and crank.
3) Engine rebuild with new bearings and rings with .030" over pistons and new connecting rods while using the original crank AS WELL AS truing the deck and heads with a full valve job.
This is just a basic idea of what to ask the machinist. I didn't mention line honing of the main and cam bearings or install of new valve guides. As you might guess, rebuilding an engine can get expensive quickly.
Talk to "Olds people" in your area or even on here for recommended shops. It pays to get it done right the FIRST TIME. If you have questions or don't understand, ASK. Determining whats wrong will tell you what needs the most attention. Take the time to get it done right.
Sounds like a miss shift over rev on bad oil. Hard lesson to learn...
Keep in mind an Olds shouldn't be revved until valve float like a small block Chevy. It simply isn't designed for high revs. 4500-5000 max on a stock 350 engine. Olds is a low end torque based engine. Not a high revving short stroked RPM based engine. Anything over 5K RPM on an Olds needs fortification in the upper and lower end. These aint no DZ302 Z28 engines! All the work is done under ~5000. You're over the torque and HP peak over ~5K (on a stock 350 or 455). Well, some will argue a bit more for both engines, but for your purposes lets stick to 5K as an occasional max.
You have metal on the dipstick!?! Its toast....Do not turn this engine over again. Further damage will be inevitable. Time to yank it. Drain the pan and watch out for sharp objects. Do open up the oil filter as suggested just to see how bad it is. My bet is you will find chunks in the pan. Either way time to dissemble and inspect to see if anythings salvageable.
Try to save the OEM block if it matches the cars vin. The rotating assembly as well if its not total junk. If its not a matching block go find a good used early 350 or 455. My bet is you'll be looking for another rotating assembly.
Have the crank drilled for a pilot bearing if its not there. I have never been a fan of cutting off the trans input shaft and using the retro fit bearing, its a short cut and not a good one . Too much input shaft deflection will be the end result...IMO and thats never favorable in this application. The engineers put that pilot there for a purpose.
Expect 3-5K for a strong stock rebuild. Depends on parts used/reused and how much machine time is involved. This is where a running engine with good compression and oil PSI would put you farther ahead. In comparison a stroked 650HP 455 turn-key engine with most of the "goodies" is easily a min $13-15K+ with a good core 455 block.
Finding a builder who is well versed in BOP engines is not an option its mandatory!
Buy Bill Trovato's book on building Oldsmobile engines. There are several things that must be implemented into the build to provide proper durability/longevity. Rochester NY isnt that far of a poke from central CT to have a engine rebuilt correctly with a warranty.
Having a 350 Olds is much easier than a 455, many more failures with them, heavy parts and larger diameter journal's. Clearances put to the high end of factory clearance specs should work fine. I have revved my stock 76 bottom end to 5000 RPM a few times, still has great oil pressure. One place to make sure is done right is center exhaust guides clearance. I believe .0028" minimum clearance is needed or valves can seize, it has happened to few guys. The 4 spd does make over revving much easier, a rev limiter might not be a bad idea. Contact Cutlassefi (Mark Remmel). He knows cams and our Olds V8 in general. He brought a really nice 10cc dish forged piston from Mahle with a 1mm ring pack, would give you low to mid 9 to 1 compression on your 350, stock is 8 to 1. Contact him at fastone01@hotmail.com
Last edited by olds 307 and 403; November 28th, 2018 at 10:45 AM.
I think you miss read my post, Olds clearances need to be LARGER than the typical chebby stuff. As much as we like to brag about how indestructible Olds engines are, the blocks and rods aren’t the greatest from a performance standard. The way the engine mounts bolt to the side of the block tends to distort the main bearing bores, resulting in metal to metal contact. That’s why all the really fast cars use engine plates. The connecting rods are pretty soft metal, the are pulled out of round pretty easy. All this means you need to provide added clearance during assembly. If this was a stock cruiser that will never be revved past 3500, the stock clearances would be fine.
This is a great thread because I always try to salvage what I can and replace the least parts.
Olds64 - had a good suggestion when he said to check your compression before disassembly, if you have a gage or borrow the one from Auto-zone.
Also, too, take your time on disassembly because you are looking for the obvious like scored-bearings and journals (the noisy one will be obvious) and burnt valves (if your compression is low) and stuck piston oil-rings. Inspect cam lobes for wear, and if lobes look to be good, and the lifters are not noisy, then you may wish to run-them. There is a good chance that your piston to cylinder-wall clearance is acceptable within specs too. If the book says 0.0025 for clearance, and you have 0.0038 to 0.0042, I think you could run those pistons and would never know the Difference. Loose is better than Tight here.
If you choose to change pistons, then you have 3-choices: Forged, Hypertectic or Cast. Hypertectic are hard to beat. I like Forged for strength, because I have replaced cast pistons with fractures in the skirt-to-body. yep.
I bought a pickup with a bad auto tranny to use as a daily work pickup while I was restoring another. After taking the transmission to my trans-guy and re-installing, I was able to drive the pickup. Well, the logging company that I had bought the pickup from did not tell me that the engine had a knock. I purchased another engine from a wagon that had an engine fire and the guy said it had a "recent rebuild." I drove the pickup with 400M engine knock for one-year, while I rebuilt the so-called "recent rebuild" engine. Interesting thing I found was, yep, the oil rings in the (recent-rebuild) engine were Stuck-solid. So, the rest of the engine was in good useable condition and upon checking the main bearings on the crank, and the rod bearings on the crank with Plasti-gauge, I lapped the valves and put the engine back together after a good "Glaze-Breaking" (cylinder honing with proper cross-hatching). I did not change rings because the end-gaps checked to be within "Allowable Tolerances" as shown in the service manual.
After I put the freshened engine into the early ford crewcab, it ran like brand-new, and a Fed-Ex driver stopped me one day asking if I would sell him the pickup. I told him yes, when I complete the build of my "other" crewcab. The one I was driving was purchased as a temporary pickup to use while I was restoring the other for a Driver.
I ran into the guy 3-years after I sold him the pickup with the 'freshened-up' engine, and he said it was running Spectacular.
Hopefully you will be able to get away with a reground crankshaft, valve lapping and cylinder honing. Then you can decide what to do about the 2.bbl carb. and camshaft. Note: I have had very good luck with Clevite Camshafts. I have one currently running well in a 20-year ford 300 six refurb.
The Comp Cam I installed originally had a lobe go flat within 4-years, so I installed a Clevite '60's grind.
Mentioning the 2-bbl carbs, I had a $250 Chevy 283 with 2-bbl., bored .060 with TRW super-stock forged pistons with loose tolerances and that engine grumbled until those forged pistons warmed up. It would pull my buddies $3500 327 with 4-bbl with ease. Sometimes loose works.
Just 3-days ago I was polishing the crankshaft journals on an old 1946 ****** engine. You wouldn't believe the wear on the journals. OMG, and you know that engine ran for Decades to get that much wear, and was probably still running when it was disassembled. ( I will send this crank in for Polishing ).
I wanted to polish the journals to mic them so I know just how loose this engine was while still running faithfully for decades.
When I was a kid back in the early '60's, the machine shops would Knurl Pistons to stretch and expand the piston skirts raising metal for a tighter fit.
Today I just don't see Piston Kurling anymore. Your machinist probably doesn't even own a piston knurler. hahaha
Enjoy "freshening-up" your engine !
Len
Last edited by Greaser007; December 4th, 2018 at 09:45 AM.
When I was a kid back in the early '60's, the machine shops would Knurl Pistons to stretch and expand the piston skirts raising metal for a tighter fit.
Today I just don't see Piston Kurling anymore. Your machinist probably doesn't even own a piston knurler.
Valve guides can also be knurled instead of replacing them. For an Olds, head work is extra important since our motors use hydraulic valve lash.
Len, everything you mentioned is spot on. You can generally find "junkyard" build articles in magazines like Hot Rod or Car Craft. As you said, sometimes all an engine needs is new bearings/rings and a good honing.
BTW, are you a member at FTE? If not, signup and shows us pics of your truck!
Lots of great information - thank you all again for chiming in with your suggestions and recommendations.
I got some pretty high quotes from shops for engine rebuild, so I had to really think what I'm going to do with this. My current budget doesn't allow for an expensive rebuild right now, so I ended up selling the car a few days ago. I regret it a little because it was a 4 speed. I'll have to keep my eye out for something more in my price range, not too pretty, but a driver at the least.
Last edited by konrad; December 6th, 2018 at 12:11 PM.
I understand the car has been sold but here's some info for reference. It seems there weren't many numbers being thrown around. There's a local machine shop that just did a "rebuild" on a '72 Rocket 350. Cost: North of 8 grand. The horsepower ended up at 335HP I think - a relatively mild build with a good idling cam. I'm sure they changed the camshaft and worked on the heads... I think pistons and rods. This was done at a place that I would consider a "high end" machine shop. Personally, I'm not sure I'd use them even though I stood up at the GMgr's wedding. They're just too "high end" for my tastes. There are crate motors available for dirt by comparison: First google search for olds rocket 350 crate engine $2,300 out the door.
I've got a Rocket 350 / Turbo 350 that I almost yanked in favor of a GM LS engine (swap). Boy, you want to go down a rabbit hole, look at Chevelle / LS swaps which would be nearly identical to a Cutlass / LS swap.
I finally relented (in this round) and started to work on a fuel injected Rocket 350 for my '72 Cutlass - gosh do I have mixed feelings. But at the first hint of a rod knock...... I'll be posting in another section.
Currently gathering parts and should have a fun the first week of the new year with exhaust, fuel system, radiator... maybe trans and rear end.
Last edited by GammaFlat; December 29th, 2018 at 03:05 PM.
Reason: Compliance with forum guidelines. oops - my bad :|
Valve guides can also be knurled instead of replacing them. For an Olds, head work is extra important since our motors use hydraulic valve lash.
Len, everything you mentioned is spot on. You can generally find "junkyard" build articles in magazines like Hot Rod or Car Craft. As you said, sometimes all an engine needs is new bearings/rings and a good honing.
BTW, are you a member at FTE? If not, signup and shows us pics of your truck!
Olds64,
I haven't joined the "ford-trucks" site. I probably should, but oh well, I am already on 5-interest groups for my different vehicles, and lacking time to visit them.
I was a member of "oldfordcrewcabs" yahoo interest group 20-years ago, but the group moved to oldfordcrewcabs.com and I lost interest.
The 4-door '77 4x4 longbed F-350 Ford pickups have either been converted from 2wd to 4wd by someone, or had a chassis extension, or body on newer-frame.
Do you have one ? or know someone with an early ford crewcab pickup ? I will see if I can send you a photo of it.
Len, that's a beautiful Dentside. I love the crew cabs. I own an 86 f250 supercab with the 6.9l IH diesel. I was torn when buying the truck, I wanted a crew cab, a diesel AND 4x4 but they are few and far between. I love Ol' Red though.
Sorry about the thread hijack everyone.
Interestingly, the injection pump in my diesel truck is the same one used in Oldsmobile diesels. The Stanadyne Roosamaster rotary injection pump. I am going to rebuild it soon and post a thread on our site for FYI.
Missed out on two accounts I guess?
I have a 1969 oldsmobile 350 original 4 speed engine with number 5 heads that I pulled from my cutlass never been apart, with about 102,000 miles on it. I have kept it all these years thinking if I ever sell the car I would include the original engine, ( I have had a 1969 455 built for her) but was considering selling the engine to make room in my garage.
Missed out on buying a 71 cutlass in need of a motor... LOL.. I look half heartedly for something to put the 350 in after I finish this project ( if ever LOL)
Anyway I agree with what was said above I used Larry Hansen Racing ( No Relation) in Middlesex NJ he knows Oldsmobiles, ( and Pontiacs) and I am sure a straight rebuild would come in somewhere around 2500-3K I went with the Keith Black Pistons, I also added a bunch of might as wells that brought my build up quite a bit but what the heck.
Sorry you sold the Car Konrad but I do understand....
Konrad,
I am sorry to hear that you have sold the project, but when times are good again, you can find another Olds.
Thank you for the interesting thread, and it is fun to converse here and exchange thoughts and experiences.
Similar to Eddie Hansen, we all probably have numerous "engine-treasures" tucked-away under the bench waiting for a ''donor-vehicle'' to put them into.
November 27th, 2018, 09:32 AM
