My 462 is finally at the dyno shop and its time to guess what it'll make. I'm going up to break in the cam this friday, and then we make pulls next week. The build: 70 SF 455 .030 over TA Speed pro 1/16. 1/16, 3/16 pistons .007 in the hole, 23cc dish. 10:1 .038 orange crush head gaskets 3.90 stock stroke 71 661 heads, Stge 1 11/32nd valve, perf valve job, 71/70 cc, bowl clean up but unported TA 1125 valve springs, 67-69 1.59 Rockers Stock 70 intake, B4B plenum style Camcraft 218/230 110 hydraulic flat tappet cam, installed 110 ICL straight up 2.3" (?) diesel flanges exhaust manifolds - maybe done by Jim Rogers? 6 qt TA pan accurate balance with TA SFI balancer and OEM MT flywheel 110 dist with 12 initial/32 total by 3000 RPM (subject to change) 71 540 Q-Jet with 1/2' spacer (three different carbs/individual variations to test: stockish/full cammed/mid range) This is a mild build, intended shift point 5500. It's going in my 71 GS Auto, 3950 with me, 3.73 gear. It'll also be interesting to compare this to the next engine going on the dyno, a similarly built 71 Pontiac 455 HO built by the machinist for a customer. Hmmmm...
No, "540" is the last 3 numbers of the carb serial number, denotes a 800 cfm 71 carb. Good luck, you should see a nice torque number with that one, in the 470-485 range. If you have a set of headers at your disposal, bolt them on for a pull, would love to see the difference between them and the exhaust manifolds. JW
Thanks Jim - interesting guess, the desktop dyno (2000 version) puts it at 396hp @ 5000 and 475tq at 3500 - I've never put any kind of stock in those numbers, and always just used the program to bench test cam combos.. I have headers, stock manifolds and the diesel flange manifolds (which may have been done by Jim Rogers?) to try out with 2.5 inch head pipes. the break in and initial pulls will be with the stock manifolds and stock primary 540 (it has some mods to the secondary circuit, but I wanted to see how stock primary jetting/rods/bleeds would work with this size cam) I'll run through various combo's (I've got the dyno as long as I want it) but my intended optimal tune (and most time spent) will be Stock primary Q-Jet, spacer/dual snorkel GS air cleaner/diesel manifolds.
X2 I do not have a set of Jim Rogers, but have Herche's variation of ported exhaust manifolds on my motor. I've seen it discussed here before, but, for a "mild" setup, I'd love to know the improvement with headers on your build. Troy
If someone cares to explain, and I’m not bashing anything but just wanted to know what’s the advantage to building a 462 that makes less torque than a stock 455?
He didn't. The stock 455 made closer to 460-470 torque on the dyno.. in production form.. in a 300rpm/second sweep test...I have seen it many times. When I questioned Dennis Manner on this, his reply was that when they rated them, they were allowed to block off the heat riser, and also the numbers were corrected back to a old SAE spec, which dictated 60* dry air.. The new spec is 72* dry air. So the correction factor is different. I believe they also used a "steady state" test.. which means they ran it to 2800rpm, and then held it there. That will also produce higher numbers on a dyno, vs the "sweep test" that is commonly used today, where the engine is accelerated at 300 rpm per second. We see this pheonomon on every dyno sheet, the first number on the torque will always be higher, because the test starts from a predetermined rpm level, where the engine is held for a second or two, before the test starts. So the first set of numbers is always discarded. Even fooling with that will change the numbers.. a 400rpm/sec sweep test will produce higher numbers. So the short answer to your question is "The testing methodology was different". JW
Thanks Jim - I had no answer to this other than I generally dont see 500 ft lbs until you get into the 450 hp range in modern dyno tests..
Cam break in tonight.. good temps, good pressures, clean Oberg filter.. gonna cool, retorque and start making pulls Saturday, weather permitting.
So made the first pulls tonight - already ran into the air hat issue previously mentioned on this forum (to the tune of 23 hp!!!). Beat Jims torque guess with stock manifolds and no spacer but still having issues where power drops off after 4300 rpm.. gotta chase it down, something tells me its electrical..But its an ass kicker up until then! More to come!
Thanks for sharing this and I am really interested in the results as well, since this is very similar to my build. Hope you get it all sorted out and can make same good pulls with it. I am liking that it has already done better than 485 foot-pounds of torque!
Rhett, Assuming that you used a Buick air cleaner base, and then duct taped the air hat (less the carb neck adapter) to the air cleaner base, to get the air numbers.. look carefully at them. Anything going on in the valvetrain will result in the air numbers going backward.. Engines are positive displacement pumps, the faster you spin them, the more air they consume, until positive control is lost in the valvetrain. JW
