Not to run too far off tangent, but regarding a 305; 1.940 heads are capable of more than 275cfm, or 600hp worth of airflow. A 420" engine sees that at 65-6800 without serious compression. A 305 would need to see 9000rpm to pump that cfm. The engine would be a senseless one to build with so many better alternatives out there (for less cash).
Then after all the theories are laid out and guidelines are set, A 564 ci NA Pontiac comes along and makes over 1200HP with 400cfm Edelbrock Performer cylinder heads. Not to mention peak power not coming till 8500rpm ....
Theories are ment to be disproven, but I wouldn't expect a 564, or any big cube motor set up for dragracing to make peak power at low rpm. We don't have 10 or 12 speeds in the trans so with mph will have to come rpm
I set up a 565 top end to run around 7000 rpm for reliability and less frequent tear downs for brackets. It definitely would like more cam (if it were meant for max output). The gears used allowed it the mph it could do.
Sorry, should of wrote un-ported. Yeah, those Vortec heads(even the 305 Vortec heads) were pretty awesome for a sbc head!(last gen) Even adding more stroke to the sbc 305 to increase cubes it would still need to spin to the moon because with a standard bore and a 4.00" stroke crank it still would only be 350.79 cid.
I wonder how much ring friction difference there is when you consider there is less ring to wall contact with a smaller bore. So even though the piston travels further would there be that much more friction over a larger diameter piston that has more ring to cylinder wall contact even though it has less travel? I'm not questioning the experts here, just curious! Bob H.
I think by the time you are weighing factors like ring friction differences at 11,000 rpm, we are waaaayy past the OP's budget and goals! (no offense ) I was just adding another facet to the vortec talk with an oversimplified example, I know that Derek has quite a bit of experience with that platform. The best way to choose a bore/stroke is to get out your wallet and make a phone call unless you are trying to break records, then you have to finance more efforts and get yourself in the game.
So with John's 477 in the dragster and JW's 555 we are looking at a stroke of 3.750 and 4.365, respectively, with both engines utilizing a 4.50" bore. Are both of these examples using the "Standard" Tomahawk block? Or are they using the raised cam version? Both strokes look like they are within the range for the stock block. Using the raised cam version gets you 3" mains and the 54mm Ford camshaft. I didn't know if these upgrades are desirable enough to merit choosing the raised cam version over the standard Tomahawk, even if the stroke being used doesn't require it. Do you need to have a timing cover made specifically for the raised cam version or is that only on the raised cam AND tall deck version? Also, does the raised cam version automatically move you into a scenario where you need to use a belt-fed distributor? Looking at the pics of the engine in a '64 that JW is working on, you can see the coil on plug setup and I didn't know if that was a required type of upgrade or just a no-brainer with the E.F.I. Again, just thinking out loud...
I went with a 4.25 stroke and 4.38 bore, stroke choice was made mostly in part to its an easier fit in the block and with forced induction you can keep the cid on the more conservative side. Bore choice was made simply because I wanted room to bore if I or it messed up. If you start with 4.5 bore you are then sleeving if something happens. My setup will be 2k HP capable, but I'm only going for 1k to 1200 at the ground and only once and in awhile, will spend most of its time at 800 to 1k with hopefully single digit boost #s Lot of guys are going away from coil on plug past couple years, it's just "more stuff" to fail, they seem to do well up to 1500hp then,...I'm sure the problems alot of guys were having will be rectified or figured out but that's the trend rite now. But for a clean engine bay and efficiency up to that level it's very effective Raised cam block does require a custom drive setup, it's my understanding Jesel has it avaliable, but that's a couple grand alone
How much work does it take to fit 4.5 stroke into a stk block......is there a lot of clearance issues
I'd be surprised if any 4.5 stroke stock blocks are holding up.....unless total fill...even then....too much stroke kills....I'd rather be bored.
Bruce most of what I've been talking about is in relation to a Tomahawk block. As far as I can tell there is no fill or girdle required with the TA blocks. So my questions now are revolving around which TA block is the best bet. So Hugger, with your bore and stroke you're looking at a 512 cu. in. Did you go with the standard TA block? The raised cam block costs more to begin with and costs you more to get setup with a Jesel or custom setup, is anyone using the raised cam or tall deck version? John E., is your 477 a standard TA block or raised cam version? JW, is that 555 a standard TA block as well? With the additional costs associated with the raised cam version, what is the determining factor for choosing this route? Is it parts availability, power level, durability, or what??
The standard block by far is the most popular due to its ability to utilize stock front cover arrangements, ability to make plenty of cid for what most guys want and yes I have the standard 54mm 3in main block. So yea imo, it's parts availability that makes it the popular choice, but for big cid the tall deck and or raised cam is your friend. The standard cam block will support 572cid, the raised cam will go to 604cid and the big boy 11.2 tall deck race block will go to 732iirc. I asked Mike if he had sold a "Race Block" yet, think he said just a couple, and I wanna say he has a race block there waiting for a new home And for the guys that already have a solid rotating assembly in their stock block , the 3.25 main block is the popular choice
What’s wrong with power down low? I make 772/710,and it’s done at 7100. I like to put as much stroke that will fit. Yes,I want a big bore,but I don’t want paper-thin cylinders either. I like to leave plenty of meat in there for future machining,cooling,and better ring seal. I would be fairly conservative with a stock block,but that Is also why a TA block is planned for the near future.
On the BBF side (sorry, I have to keep referencing a different family of engines as I have WAY more experience with them than with BBB, but still an engine), I've seen many times where given the same engine set-up, for peak HP numbers the cubes really don't matter (this obviously has limits). Given the same heads, cam, intake, carb, etc., a stock stroke 460 will make almost identical peak HP as a 4.3" stroke 521" or a 4.5" stroke 552". The peak rpm the HP is achieved raises with the shorter stroke, but the number is almost always close the same. The longer stroke makes it's torque (and more of it) quicker and at lower RPM, but since it's making more of it, it's HP figures out the same when doing the math. As far as what bore/stroke ratio is best, it really depends on the kind of racing or driving you want to do. Almost no one in the BBF world uses the 4.5 stroke in a drag race application (except for high end stuff that they put parts in to let that long stroke rev), they generally use a 4.3" or a stock crank turned for 4.1" or so. But the mud bog guys use the 4.5" all the time, and it's the most "fun" on the street with the immediate hit of the torque. I'm certain my Mach 1 would be quicker in the 1/4 with a shorter stroke and it being a 460-521 cube engine, but the fun factor is through the roof with the 4.5" stroke 552 it has now. You also have to start thinking about piston speed when you get into high rpm engines. 7000 rpm with a 4" stroke is not the same as 7000 rpm with a 4.5", as the piston has to travel another 1/2" with each stroke, therefore the piston speed is greater, causing much more stress on the rotating assembly components. The FPS on the 4" is 77.8 and on the 4.5" is 87.5. But, if you lower the peak rpm on the 4.5" down to 6000 rpm, we end up at roughly the same FPS as the 4" at 7000 rpm with it being at 75 FPS through a 4.5" stroke at that 6000 rpm.
To deal with the piston speed,I also run as long of a rod that I can. I run the shortest piston that I am comfortable with,then fill in the blank with the rod length. The billet cranks also allow me to have a small journal SBC rod size,2.00”
Me too. I'm running 6.8" rods on BBC journal size. This allows the 4.5" stroke in a stock Ford block with no clearancing. The pin is into the oil control rings, obviously, but with the support ring I've had no oil burning issues through thousands and thousands of miles.
