A few things to add: 1. I agree that stock rods are not a good idea over 450 HP or 6000 RPMs 2. The 74-80 rods are for sure stronger than the early rods 3. For under 450 HP either early or later rods are fine 4. Just because my engine stayed together with stock rods does not mean it would have lasted long at 8000 RPM 5. When Darryl R was doing testing back in the day they found that the limits of the later style rods were at about 6300 RPM and that was with ARP bolts, polished beams and stress risers removed. They blew up two engines on the dyno, that was in the 550 HP range with nitrous on top of about 450 HP. 6. If a rod fails on a Buick 350 then its a BIG mess normally the block, intake, etc is all taken out 7. Good rods are good insurance and a lot less $ then rebuilding it all again 8. If a rod breaks at 120 MPH you may not walk away from the potential crash. 9. It sounds really cool when you run it to 8000 RPM! Here it was at 8000 RPM and 20 PSI of boost:
addendum; the 73 century ran s/p and s/c. the dragster has run s/p and s/c. changed rod bearings every year until the 1.88's which I haven't changed in 3yrs. just dawned on me......why should I have to explain what I have done with a 350 when most of you are keyboard racers. my stuff is backed up at the track with plenty of people watching. maybe the somebody's better learn to back up their stuff with the buick 350 and not a chevy either.
The problem with this one is we never saw a dyno sheet. 8000 rpm? Next, I have hit the rev limiter at 6200 10 years ago on the nitrous and ran 11.81 and I Can prove that, did it with 2 different transmissions. I ran it on that shot about 50 times now, at least. I have well over 500 1/4 mile runs and all to 6 grand and that was Before the nitrous. Next I am not interested in spinning to 7500 Mr. Derek Next I did run on the dyno with the big shot and had 420 HP and 460 TQ I think that is over 500 motor HP and Well over 500 on the TQ That was a rear wheel dyno That was about 8 years ago. The dang engine is 22 years old now do you all think I am going to push those limits? Next I am not here to get into a pissing match just stating the facts. At least I stepped up to the plate and got it done. Next!
You don't have to but guys like me that are slowly putting a car together sure appreciate the discussion.
Forgot about your power adder runs, in that case the 1 3/4" primary tube headers would help. But at your N/A power level all that is needed is 1 5/8" primary tube headers. In the bold, me either. Mark should be good to spin to 7,500 with his new Molnar rods. He could even swap to solid roller lifters if he wanted to now that he has a roller cam for a little bit more RPM. Not sure why you want to switch to a S/P if your plans don't include eventually spinning more than 6,500 RPM? Spinning an engine that is setup to spin to 7,500 RPM is a blast to drive! Most S/P intakes sweet spot is 3,000 + to 7,500 + RPM power range. I know why you want a S/P, so you can spray a bigger shot of n0s? Running a TH350 trans with a manual valve body, revving to 7,500 RPM in 1st gear is a blast! Without doing the math I would guess that with a 3.73 rear gear the car would be around 60 miles per hour! Imagine dropping down to 1st gear @ a 30 roll and being able to hold it to 60 mph, hit 2nd and you're already gone! Those lets race at a 30 roll guys wouldn't have a chance from a dead start or from the 30 roll! With a S/P not only will it make power to a higher RPM, it will get to that higher RPM faster. Like gsjohnny has said before, "with a S/P intake on a sbb 350 it will breath like a dragon"! Thought you were thinking about doing a rebuild or another engine to build? Better rods now that they are available like Sean said is good insurance if a new build is still in the plans. With the new rods and a good set of 2618 forged pistons you could spray a 500 multi stage shot! You might need a parachute if you did that though? As for you Mr. gsjohnny, I for one love to read your posts about your experiences! And we basically agree about headers, only difference is that I was a bit more specific as to where the bigger headers would start to be helpful. Remember, 1 5/8" tube headers are WAY better than exhaust manifolds, even 1 1/2" primary tube headers are WAY better than exhaust manifolds. The OP didn't mention spinning over 6K or using any power adders, so the 1 5/8" tube header IMO would be more than enough for what he wanted to do and way cheaper than 1 3/4" tube headers to do it.
More spray. Thinking of future. Solid roller cam, Yep. Kidney stone drama bought me 2 sets of Aluminum heads Thanks Obame care.
Why be rude I was just adding some useful information. I have posted a photo of the low rpm low boost level dyno run witch was 450 hp at the wheels with way too much converter slip and tires rubbing. Then i swapped on some smaller tires upped the boost to 20 psi and put the rev limiter to exactly 8000 RPM. I drove it around town, strapped it on the dyno and wanted to see what would break. It blew the head gasket at 8000 rpm after about 8 pulls to 8000. The HP ranged from 580 hp to 590 on all the pulls but was way lower than what it would have been with a better converter. I can look for the dyno sheets. The torque converter was flashing right up to 6300 rpm due to not being able to hold the power. I have blown the head gasket on the number 3 cylinder 3 times in a row no matter how i set the timing or the carb. The other side of the engine has never had and issue, all the other cylinders on that bank are happy too so something is up. Perfect air fuel ratio and plugs were happy so I think it is torquing the engine over so hard the engine mount is distorting the block (derek pointed this out). So i am currently adding a mid plate and a front plate.
I just thought of something Mr. Derek for months now Everyone here has been saying that this SP3 can be put on a stock engine and now since I have it on MY engine you want to know why I would put it on my engine if I am not going to spin it to 7500 rpm. Now what is this intake, A RACE intake or one that can be put on a stock engine. You all bounce back and forth on this.
It was never me that recommended that intake for a "stock" engine, a "stock car" engine is a different story. I was the one that always commented or hinted to, that anyone using this intake should highly consider upgrading the rods so it would be able to be used to its potential.
I am not being rude I just asked a simple question, You are the one that claims you hit 8 grand and 8 PULLS before it blew the head gasket. Anyone that knows anything about a dyno is that you get a dyno save and a sheet IF you choose to print it out. Flashing the engine to 6300 rpm and hitting 590 hp on a rear wheel dyno means over 650 hp on a stock bottom end and at the same time hitting 8 grand with 20 lbs of boost. Funny Mine only flashed to 5 grand with a 125 shot of nitrous and that was with a loose 3500 convertor. I guess I have nothing to worry about. Well Derek what you say you agree. Did I strike a cord here.
Guy, think what you want and do what you want but why get into pissing matches all the time? I never said 8000 RPM was a good idea if a person cared about the health of their engine, even with good rods. Internally balancing the engine, light rods and pistons, belt driven oil pump, these are all things that can work together to safely raise that RPM. Do you really think that 20 psi from the turbos is equal to your 125 shot? Try to lighten up, we can agree to disagree.
Interesting about that #3 spot. When I was running a 215 with 16 psi+ under a Roots type I was slowly nibbling away the top ring land on the #3 piston. All the others were fine, and eventually blowby became a problem. The nibble was to the outside and slightly towards the front, so under the exhaust valve I think. I was using block side mounts. Jim
Hi Jim, that is very interesting! Also my old car that I sold the new owner had the EXACT same issue. Blown head gaskets 3 times in a row ONLY on number 3 cylinder. And that was also a mild Buick 350 with twin turbos. He gave up on it and sold me back the engine and trans and I will do a detailed assessment of that engine when I have a chance. My plan is to use a steel mid plate, retain the stock engine mounts, and use a setup like this on the drivers side head:
I went to front head mounted engine mounts and so far no problems on the 340 but it doesn't have many miles. I guess the theory would have to be slight deformation of the side wall of the block, but I'd have thought the bosses were too far down to affect the ring package or head gasket. Very strange. When you do the teardown I'm sure you will look at the point of failure. Seems unlikely it would be in the same spot but it'd be good to know if it is. Jim
I know this is a 'header' thread, but since the single plane got brought up, I might as well weigh in and step into the ring myself. I don't think anyone (not even me) has ever 'recommended' that the single plane be the preferred manifold for stock engines, though there are a few things to consider when looking at how dual plane vs single planes work. Keeping it simple and straight forward, power bands from 2000-5500 are dual plane friendly, while power bands from 3000-8000 RPM are single plane friendly (usually between 3500-7000 or so, depending). Which intake is right for you? Ask yourself a few questions: 1) do I intend on spending more time above 3000 RPM? 2) is my engine's peak torque above 3500 RPM? 3) is my engine's peak horsepower above 5500 RPM? If you answered 'yes' to all three of these questions, then get yourself the SP3; otherwise, you're probably better off with a dual plane--although... If you have a tight powerband that exists between 3000-5500 RPM (and you answered 'yes' to question number 1 above) you could still benefit from the SP3, though it wouldn't make use of its full potential. The SP3 would show better gains with headers and freer flowing heads, while the dual plane would be more forgiving without these. No keyboard/bench racing here, just science and another POV.
The other aspect overlooked is how the single plane can benefit from better overlap/header strategy than what 'might' have been optimized when it was a dual plane. Both single planes and headers are often referred to on message forums separately and/or reactively towards how they contribute to the entire engine combination. Questions are always structured as "how much will this ONE part ADD to my (generic) combo?", rather than looking at the complete paradigm. Instead of battling over header diameter and it's effectiveness or validity, some forethought could be planned into the overall package, along with re-thinking the cam overlap to do what it's supposed to do... assist the initiation of the breathing cycle. Builds like these are where the discussion transcends statements like "Buicks need xxx LSA angles" and stuff like that. People be spending major $$ on shiny parts but won't consider something like Pipemax to get past the 'ol Desktop dyno's vague parameter setting of "small diameter header, performance muffler"and other metrics.
