so I found a complete 72 350. guy is telling me 56,000 miles on it. will let it go for $250.00. I think ill jump on that on. any pros or cons to a 72 engine versus the 70 in my car now? I imagine they are the same??????
If you're going to sh!7 can the pistons and rods when you rebuild, there shouldn't be any difference between the 2 engines. If you're planning on running it the way it is, then the '72 has less compression than a '70 so less power. Unless...., I have read here that '72 was a transition year(or is it '73?) when they were changing the rods to the cap screw style so you may get the cap screw rods and crank? The rods will still be crap, but the crank if you are wanting to do a performance build will internal balance with less or no heavy metal added to it if it is a cap screw crank. If you have Stage1 valves in your '70, the '72 probably will not have those?
I ran the ever loving piss out of a sbb with old style rods and a cheap ass set of low comp hyper pistons and stock crank with 8-10 lbs of boost. The old style rods get a bad rap. They have a weak(er) point as compared to the later style cap screw rods but are perfectly capable of most any 350 build other than something all out. There is nothing wrong with the stock rods or the pistons as long as you can achieve your desired compression ratio with the low comp dish. 9-9.5 or so on compression matched with the right cam and some head work, timing set up right, and a well tuned carb. good exhaust, will put a smile on your face. Spend the saved money on a well made torque converter with a 2200 or so stall, matched to whatever gear ratio you want and a limited slip diff. This has been said over and over. Learn more before you let someone talk you into spending lots of money for something that you don't need. Talk to Sean about what you want to achieve. He will help you. Jay
The 70 likely has higher compression pistons. Other than that they would be identical with the exception of the intake which is different at the choke stove IIRC. The used engine is just a block and rotating assy. unless you chose to leave it alone and run it as is. To make it new again you will need machine work on everything, and it will be at the machine shop forever. New pistons for the overbore. all new bearings, rings, timing chain and gears etc. AND, it's likely that you will find that the 45 year old front cover is not in very good shape also. As far as the heads go, how good are at removing broken bolts? Just depends on your goal I guess. Another thing to keep in mind for a street car is that bottom end torque is WAY more fun than a big bumpy cam that doesn't come on till 3500.
Nothing wrong with a 72, distributer is short on mechanical advance according to the book, and it may have extra coolant passages in heads, if so the heads need to stay with that block for best results.
Depending on the cam selection along with many other factors, it may like 18-20* initial timing. 14 * advance may be just what the doctor ordered. But yes. Pay attention to the coolant scallops. . Been there.
Not everyone is going to run or wants to run a turbo, which will cushion the rotating assembly when the piston is going down AND when it is coming back up. The old style rods earned that "bad rap" from all the failures they had. You don't see those engines today because they are long shredded and melted down made into Priuses of that day. When a rod lets go it makes scrap out of an engine in a very fast manner. The factory sbb cast iron rods are junk for any kind of performance engine, even a turbo engine because they were marginal even at factory HP levels.(period) It was pure luck that you didn't break one of those rods. The smaller the CID is the more it needs to spin to make decent power N/A.(period) The factory cast iron rods start failing above 6,000 RPM where a decently built N/A small block is still in its power band, either to 2,000 to 6,500 or 3,000 to 7,500 depending on cam of choice.(I'm talking hot street engine of coarse) In the factory configuration, the sbb 350 is a big fat stinky turd.(period) Why do you think they are discarded and BBB 455s are installed in their place? See above. The factory built the sbb series engine as mini big blocks trying to get low end low RPM torque out of them to propel the weight of the car. They didn't care what kind of HP they could make as long as they made decent low RPM torque, well guess what, that trend didn't catch on. Why does anyone think why there is minimal aftermarket support for the sbb engines? Because they were built so Grandma could drive her big land barge to the grocery store and back, never as any form of a performance engine. Fast forward 50 years after the factory built the first sbb 350 people are starting to build them as small blocks with good rods that will handle more than 6,000 RPM without risking failure. A single plane for it instead of that choke no flow intake so it can be built like a small block to make higher RPM HP the way smaller N/A cid engine make power! Nascar 358 cid engines make around 850 HP BUT they need to spin those things 9,000 + RPM to get it to that level with that few cubes! The only replacement for displacement IS, RPM. To make power without boosting a sbb it needs to spin to win, built like a small block. Building a sbb with its factory configuration low RPM blah blah blah is a formula for disappointment, might as well not waste your $$ and swap in a 455. Unless of coarse one only wants an engine to propel a car and isn't concerned about performance.
Th OP never said he wanted to make huge power or rev it to the moon. He simply indicated that he wanted to build a replacement engine. Are forged rods and pistons going to make a moderate build any faster? A good street cam is going to give up at 5500 anyway. All of your posts assume the person wants to build a race engine. Derek. You sound like a broken record sometimes. You make it sound like every pre 73 350 is a time bomb and that is simply not the case. I think you are frequently giving bad advice. It's obvious you don't like the SBB and simply want to turn it into a SBC. BTW. If you have to rev high for power, that won't be a fun cruiser.
Nascar 358 cid engines make around 850 HP BUT they need to spin those things 9,000 + RPM to get it to that level with that few cubes! The only replacement for displacement IS, RPM we don't even come close to nascar engines. we're lucky with what we have. now if you have 100 million floating around, then we could possibly come close.
ATTENTION ALL BUICK SKYLARK OWNERS WITH 1972 OR OLDER 350 ENGINES. Stop driving them now and upgrade your rods. Failure is eminent. I wonder how many bumble bees are out there that don't know they can't fly.
You make good points Jay, no need for fancy parts in most of the engines people talk about on here... as it sits most mild builds will not makes power over 5500 and that’s ok... focus on the low and mid rpm torque range and use a cam big enough to bring the peak HP up to 5500 from about 4800 where the stock engines fall off. 73 engines may or may not have the later rods, 74-80 have them for sure. 73 was the cross over year.
I never said or implied that any sbb even comes close to a nascar engine, that was just used as an example of how an N/A small cid engine has to spin to make that kind of power. I will say that a sbb 370 stroker with heads that could flow around 300 CFM could make 600 N/A HP but it would need to spin to around 7,500 to do that. Having a small block that can only make power to 5,500 is a steaming stinking turd. JW even said with the dual plane intake a sbb 350 runs out of air @ 5,300 RPM on the dyno. "Are forged rods and pistons going to make a moderate build any faster?" I'm glad you asked that Jay, the answer is a definite YES it will(if), here why; If the forged rods are lighter than the factory rods(the nascar take out rods that I recommend definitely are) and an AutoTec piston and ring kit will definitely be lighter than a "stock" replacement piston, plus if available at the chosen bore size will have less drag with a thinner modern ring pack.(the new OEM rings are way thin now so don't try to say they wouldn't be durable because the new factory stuff runs for hundreds of thousands of miles) So even with the crappy air choking dual plane intake the engine will RPM faster from idle to WOT and would more than likely not die out as fast, perhaps a couple hundred more RPM before its done because of the lighter components. NOW add the SP3 single plane intake with you coveted factory '68 to '73ish rods without a rev limiter and even just a solid flat tappet cam that could make it rev more than 6,500 in short order, would be a ticking time bomb!(that is without staring at a tach ever time your foot is an the throttle) "A good street cam is going to give up at 5500 anyway. All of your posts assume the person wants to build a race engine." The cam only gives up because of the air choking dual plane intake that is only designed to be good to 5,000 RPM. And my posts are for building a rock solid foundation that will be durable for many many miles, not necessarily to just "build a race engine". That depends on what kind of cam, valve train and head porting level one chooses to run. "Derek. You sound like a broken record sometimes. You make it sound like every pre 73 350 is a time bomb and that is simply not the case. I think you are frequently giving bad advice." I think it would be VERY bad advise to recommend the your coveted '68 to '73ish rods for an engine build that someone is going to go with the SP3 intake, that would be a ticking time bomb. If you don't like my free advise, don't take it. Its not like I'm trying to get people to spend gobs of $$ on an engine build. I bought a set of nascar take out rods for $79 plus $14 for shipping, it costs $80 to have a set of your coveted '68 to '73ish rods reconditioned AND that doesn't include the cost of new bolts!(another $120 IIRC) Those are the same rods I gave to Mart that he is going to use for his build.(they all checked out within .0001" of each other and were even closer on the roundness!) It is going to be $200 for increasing the stroke, mains only need polishing so those won't be reground. So only @ a mere roughly $100 more than using factory rods. What gives? Why am I the bad guy giving "bad advise" on how to build a relatively budget friendly performance build? Heck, if one didn't want to increase the stroke and went with a set of the 1.889" rod journal nascar take out rods it would probably only be an extra $100 to grind the crank down the little extra. SO around the same as using crappy reconditioned rods! Sorry for the bad advise Jay, you go ahead and put me on ignore so you don't have to read my bad advise anymore. So what's wrong with "fancy parts"(quote from Sean Gaskin) if they cost less than reconditioning crappy heavy brittle cast iron factory parts? That's a VERY funny quote coming from Sean, most of the failure information I have read is from him! "It's obvious you don't like the SBB and simply want to turn it into a SBC." I actually like the sbb platform a lot, it has a lot of potential if the factory designed shortcomings are corrected. It doesn't seem that you are aware(trying to phrase this mildly) how an engine works, its an air pump, the smaller the pump the faster it has to spin to move the same amount of air as a bigger pump.(basically) ALL brand small displacement engines need to spin faster(and or quicker) to make more than the factory designed power and that includes the sbb engines.(NOT just a sbc) The rods that failed with the factory configuration have already failed 40 to 50 years ago. If those rods weren't a problem, then WHY were they redesigned? The new design certainly couldn't of been less expensive, heavier means more material which means more cost just from that 1 aspect. In a factory configuration that the engine was built from there that has survived in that configuration will more than likely stay ok in that configuration. To use those rods and add more power/RPM is just asking for problems when I have so often posted my "bad advise" on how to inexpensively avoid re-using those rods in a re-build. Take it for what it is, free advise, if you don't like it don't use it. No charge. I will also add that no, the OP hasn't revealed what his intentions are for how he wants to build this engine, was just giving him some free info and alternatives.
I've often wondered why Buick completely re-designed these rods. If there was a known failure point, seems they would have simply fixed that, rather than re-design the wheel. The failed rods that Sean has shown have been from situations where someone has tested their limits. I wonder if they had problems back in the day? They started making the 350 in 67 and did not re-design the rods until the smog era began in 73 or so. Seems if they (old style) were prone to failure something would have been done WAY before 73. The 70 SP1 was a pretty hot engine. Was it prone to rod failure? Were there many rod failure issues back in the day? My mom's 69 sure would take a licking. My brother and I beat the snot out of it. From 73 on the rods were COMPLETELY different and installed in smog cars making anemic amounts of power. Wonder why?
Good point. Why stronger design if they castrated the horsepower? I think those special headed rod bolts got too pricey.
Derek. I don't think you will find anyone in my area that would be willing to machine the crank for the Nascar (chevy) take out rods. One assumption you always seem to make is that everyone reading here is a machinist. That being said, you can't just take a bunch of parts to a machine shop, and say, "make this work". With all other things being equal, forged rods and pistons will likely get you nothing unless you take advantage of that by other means. The dual plane intake makes nice low end torque. SP3 does not. Nor will it fit under the hood. Probably not happy in freezing temps either. I was under the assumption that the new rods and bolts in the NOS short block that the OP asked about would be just that, and not need to be re-conditioned. Just an assumption. I believe I have the air pump concept. Turbos are king. The OP asked about an NOS short block that in theory already has all of the necessary parts machined properly to make a nice mild to moderate build. Not quite sure how you got so far away from that. Jay
I think a stronger rod (if that is in fact proven in a laboratory test) may simply be a byproduct. There had to be another reason for completely changing everything about the rod design.
Must of been a coincidence when they went from the sbb 340(that used the same rods) that had heads that could only flow an anemic 135 to 150 CFM on the intake side to the sbb 350 with heads that could now flow 190 to 210 as cast out of the intake and all of the sudden they needed to redesign the rods? Go figure? Good thing the intake chokes the air flow for the sbb 350, it helped it live. The GS350 was the same engine as the '68 and '69 4bbl 350s, the factory over rated it by 35 HP thinking the GS hood would give it that much more HP when it has been proven it does not. So anyone with a GS350 thinking there engine will make 315 HP on the dyno is going to be disappointed if they actually have the engine dynoed! Its going to be even less than 35 under because of the over rated compression ratio they also had. I'm sure the redesign was on the drawing board before they were neutered after 1970. Probably why they thought they had to under compress and over rate those engines back then? They weren't afraid of the engine making to much HP when they redesigned the rods, their fear was with the extra air flow the engine would be able to RPM faster than the older design could handle. Sean always claims the old style will handle 450 HP, well a small block anything with 350 or less cid is going to have a very hard time hitting that number without revving it past 5,500 RPM, not a problem with an engine with 105 more cubes like the BBB 455 to do but not a 350. And Sean is the one that always has claimed the old style rods start to fail over 6,000 RPM, I thought he knew what he was talking about because he is supposedly writing a book about the sbb engines? Either way, the nascar take out rods are a great deal that have proven to work VERY well in several builds posted here. I guess haters gonna have to hate. A board member here used a set of AutoTec pistons in his track tested build and with NO other changes went almost 1/2 second faster in the QM! With just lighter pistons, Hmm didn't someone say that there would be no difference using forged internals? I wonder how much faster he would of went with a set of take outs? The nascar take out are around 100 grams lighter per rod than the older style sbb 340/350 rods depending on what weight you get them in.
Get the guy to lower the price, give me his number and I'll tell him a low price and tell him it's ridiculous that he wants 250, core go for 100$ I'll tell him. Me and my friend run this all the time, sometimes we have to when dealing with unreasonable prices. Then you tell him 200$. It works. Kick a tire till the tire goes flat, then keep kicking it till the rim falls off. Make sure the engine turns or no deal.
