The long-ish rod ratios hurt the powerband (cylinder fill) until after the heads and cam are choked and on the downslope past the hp peak, where the strategy is to use gears and rpm to hang on a bit longer when the competitor is out of rpm. The gears add the lost torque back. The long rods' mechanical leverage shines when the engine runs a narrow rpm sweep, too. I'd use a race duty part over putting any time into the factory stuff if there's any choice, even though the factory stuff is suitable. If considering 305 pistons and cost is a priority, the dished versions of forged are usually cheaper than flat top and many have had the dish edge completely cut off for stroker or long rod with perfect success. They're either .070" or .130"? deep.
These are all good thoughts and insights. Perhaps it would be best for me to hold off on things until I can get the 340 pulled. If the crank is no good it will be easier to know what direction to head. I'll focus my efforts in the mean time in getting the parts I already have ready. Going back to the block, any input on what oil mods should be done? Also, what about a torque plate for when the boring is done? I found a place to heat treat my heads to T6, and I'm wondering if the rocker shaft bolt holes still need inserts if I treat them? Thanks again for all the input, its a great luxury to have extra eyes and minds to catch things and share experience.
Derek, Summit has 6.2 small journal Chevy rods for around $500. https://www.summitracing.com/parts/sca-6620020/overview/
If you are going to spend the dough on heat treating your heads it seems foolish to me to not go in welding and move some ports around and really make some power with this. I have to point out that if there's an attempt to save money on questionable pistons, a $500 mediocre rod seems out of place. There are 6.250 rods and many other candidates out there. Keep looking, you'll see plenty. Take your time, things pop up randomly. I'd rather see a $500 305 circle track piston and a <$250-300 rod. Really, with these good quality parts contemplated I'd rather see the max stroke to the point of a reduced base circle cam, being that anything existing can be reground smaller for $60-80 plus the ride . No worries of rod ratio... A combo gaining popularity is the Windsor/Cleveland blocks having a 4.170-4.250 stroke @ 9.5, 9.3 deck heights. The 1.46 ratio lives just fine with good parts and really pulls the intake port hard. You can use a much bigger than anticipated top end without losing so much low rpm snort. More than a few Olds small blocks have taken near that length arm...I'm cutting down a 455 crank for one right now. I have zero worries with it 'only' being a 6500 rpm deal. No negativity to anyone intended. The OP has a lot of research to do yet.
I think it is more of an advantage to concentrate on light weight parts rather than rod ratio. Any rod/piston combo that minimizes the compression height in a slipper style piston is going to result in a longer rod ratio, whether that is desired or not. Neither the rods or pistons have to be Buick, and I still don't understand the logic behind the massive wrist pin that Buick engines use when you can easily use one that weighs half as much or less. Piston prices seem to be pretty uniform. Hypers are all pretty much going to be in the $300-500 range and forged are all going to be around $700-800. The nascar rods are the zinger in this mix, you can't get that kind of a deal on pistons because of the bore size. So to save money with quality parts the nascar rods are the option. You have to deal with the big end size and watch the offset. But the savings there can be enough to justify the custom forged pistons. Going that route every detail of the pistons can be specified, from wrist pin size to offset to skirt style to crown configuration, allowing you to build exactly the engine you are after. In other words you get a lot for the extra money. If you use a smaller wrist pin, watch the rod weight, and go to a slipper style piston you can keep the weight down and the engine will be more responsive, as well as capable of higher rpm. And btw, teflon buttons are a lot heavier than any of the three common type of wrist pin clips. I have them in my 340 but should have used standard snap rings. And don't automatically assume that because the piston guy has been in the business forever that he will suggest the best options for you. That often will not be the case as the teflon buttons above point out. Consider his suggestions but do your own research before OK'ing them. Jim
To legitimize that article they would of needed to build 2 engines, one with the standard 5.7" sbc rods with longer pistons with the same stroke to rule out that the extra power was from the un-shrouded valves because of the big bore! Running pump gas with 11:1 compression with a sbc 400 block is nothing new, I even done it with the factory shorter sbc 400 rods that are 5.565"(talk about short rod ratio, 1.484:1) with the sbc 400 stroke of 3.75" and cast iron heads not aluminum like they used. Although the cam I had was 15* more duration @ .050" than theirs but again I was running cast iron heads! That is why it would helped them prove their point if they did back to back sbc 400 block dyno pulls with the long rod and one with the standard sbc 5.7" rods, short piston vs tall piston. If you want to see an impressive power from a 87 octane pump gas engine that more than likely cost less than the sbc in the article AND used factory cast iron heads, take a look at this; http://www.v8buick.com/index.php?threads/the-dyno-numbers-are-in.200499/ "N/A it made peak torque at 4800 @ 449 ftlbs HP was at 5300 and was 422. this thing was an animal with torque at 3500 it made 423 and never dropped below 400 until 5500 and was still 396" This is a small bore long stroke engine with a choked off TA dual plane intake! Imagine if it was an Edelbrock RPM Air Gap like they used in that article. Notice how it made same torque at 3,500 RPM than the sbc and kept making more to 4,800 where it peaked. The low rise factory copy TA intake is why the HP peaked at such a low RPM, with a RPM Air Gap that HP number would of probably kept rising a few hundred RPM limited by the cam where it would of stopped. Speaking of cams, the sbb used an flat tappet cam NOT a hyd. roller cam that they used in the article to get their numbers. The build in the link is what is possible with nascar take out rods and a 3.990" stroke with a .040" overbore. Now lets talk about that price tag they put on that engine in the article, $150 for the block! WTF, that is only the core charge for one of those that still needs to be machined! So add another at least $600 for machining, they didn't put the cost of the roller rockers, valve covers, fluid damper, balancing and so on that wasn't on the price list. Granted the sbb has 20 more cubes than the sbc, but the sbb only has 8:1 static compression because it was built for boost. One built to be N/A with around 9.8:1 topped with the new single plane and a little bit bigger cam(like the Crower lvl. 4) would be a real fun street engine! Even built the same way with low compression and the same cam would be a real fun street engine! The one in the link didn't get any press because there really isn't anything they are selling with that build, the one in the article is trying to sell the AFR heads.
There is much better info being shared in some of these threads than the brief marketing exercise, ahem...article occasionally posted. No agendas.
Hey, Everybody has their own opinions/likes/dislikes. I was thinking the 6.2 Eagle modified Chevy rods with the 1.63 compression height AMC/Jeep 4.2 pistons would be good for a street Buick 300 build. Inexpensive forged rods and better "reverse dome" dish/slipper skirt design.
Not bad, but I don't think I would use $510 rods that would need to be altered at an additional cost and install cast pistons that cost $87.99 for a set of 6. Those rods have bronze bushings too, not sure how well a wristpin would press into a bronze bushing? Maybe if you can find a set of 6.200" nascar take out rods with a .927" wristpin that has the 1.889" rod journal size to help keep cost down for grinding the crank? They try to get more $$ for the rods with a .927" wristpin though but if you could get them for $250 or less it would be worth it.
I could mill the non chamfered big end myself. I know the 215 using the SBC rods need to be milled .050 on the non chamfered side. I would need to see the difference in the 300 Buick and SBC rods. The pin size of .931 would be a perfect interference press fit. Same principle as using the steel tube spacer in Chris's build. I would get the more expensive Hyper pistons. Chris tried getting a Ebay supplier to add 2 pistons to a V6 order and said he couldn't do it. We ended up getting 2 four cylinder sets anyway. Silvolite will add 2 single pistons to the order. Or you could get 4 six cylinder sets off Ebay and have enough for 3 motors, LOL.
Yeah sometimes I wonder if the research will end! Here is where I am on one block-- lifter valley deburred and pickup passage opened to 1/2 inch. 9/16 kinda worries me. Anything else I should be doing?
No negativity intended on the article. Trying to get people to think beyond the sheeple mindset about what's being said. Please regard some of those as opinion articles with some loose documentation to support what's being suggested, and sometimes with the same weight as any opinion here. There's no secrets given there.
These really open up the affordable connecting rod availability. Lunati spacer bearings allow use of cheaper and more common 2.1" big end rods on 2" crank pin. http://www.lunatipower.com/Product.aspx?id=309&gid=184
Very interesting! Be aware though if in the plan is to use a sbb 350 crank in either the sbb 300 or sbb 350 block, cam clearance can become an issue VERY fast with a rod that has a wider bolt to bolt dimension than what came from the factory. Plus a lot of those sbc rods are sporting 7/16" bolts which lessons clearance even further. Those would probably work with the 300 crank though because of its shorter stroke cam clearance isn't as much of an issue as it is with the sbb 350's stroke. I was considering making spacers from 1.889" bearings to go to the Mitsubishi rod journal size of 1.771" for even more stroke! That would be a 4.070" stroke, with a .030" over bore in a sbb 350 would make a sbb 375 so I decided it wasn't worth it for that little of a gain. Although if the undersize available for that size was used that 4.070" could go to 4.100" to a 377.88 cid sbb. (Hmmmm) With a good block that can be bored plus .105"(because this is where the good rings are) might be worth the effort though?(392.83 cubes!) But there is the cam clearance issues the more stroke there is to consider though, and the larger housing bore rods would need to be used so the bolt to bolt dimension is a bit wider too. So a small base circle cam and probably clearancing the rods would also be needed to do something like this?
I would concentrate on the 3/8" size capscrew rods. The 7/16" may clear in the 300, or need slight clearancing. The same rod in 2.1" size is about $150 cheaper than the 2.0" size. Supply and demand I guess. The Lunati spacer bearings also allow the 6.25" rod if the 7/16" bolts will clear with the 305 SBC or 2.3 Ford pistons. Lots of possibilities. If you have your stock cam reground to a performance cam at Delta Cams you will reduce the base circle some. Then you need longer pushrods.
I'm looking over an engine built with bearing spacers here right now that was previously built by a reputable race type builder on a proven platform. This particular example was very unhappy with the spacers, showing signs of being very close to disastrous failure after little more than run-in time. The owner did not hear detonation and even with Avgas, it still shows clear signs in the usual places anyways. If there was no other rod choice I would strongly prefer welding the crank or even welding a non-work hardening alloy material rod and re machining it, including more heat treat....long before using a rod bearing spacer. And then for that amount of work, it might be just as well to carve rods out of stock. Hope I'm not neggy on the spacers thing, I might not bat an eye to it if I weren't looking at one right now. This one's the mains and the idea of rods scares me much more. Picture what happens when the big end pinches in and how easy it is to find det. before fully tuned in.
Eh, send Derek some surplus Fortal 7075 along with some Ebay rod bolts and a roll tap or two with a tighter class fit. They'll probably outlast the rest of the engine.
If you're playing with a sbc 400 with "bearing spacers" that are made out of actual bearings, yeah those things are scary because of a bearing's built in side clearance at the parting line that wouldn't support a bearing on top of it the way it should. The better way to go is to get the thicker bearings they make for that conversion. The ones I would make would be bored and honed to size from an "undersize" bearing that would have more material in it to remove to make it actually round to properly support a bearing's backside. Plus it would remove the soft outer layers for better support as well. If I owned at least my very own Prototrak mill I would probably consider making custom rods, not sure if I would want to make 8 rods on a my manual mill I have now though.
I believe the Lunati bearings just have thicker backing and are one piece. Basically conversion bearings. I've run Lunati cams and their quality seems first rate.
