421 small block dyno flog

[REW]

here is the scenario......421 sbc.....4.155x 3.875. 14.4-1 compression, Dart Conquest 215 heads, fully ported, Brodix HV1000 intake with dominator adapter, Carb shop 1050 dominator, H-beam rod, Bullet solid roller camshaft, 283/292 @ .050 (.698/.671 AFTER lash) on a 106 LS, installed at 106 IC. Heads flowed average #'s for a 215 runner deal, and went 310.5 @ .700I, 225 @ .700E (no pipe). The first night on the dyno, made a few quick pulls......4600-6600 rpm. Was lean at first, got fuel in the "safe" range, re-adjusted lash, got timing in the ballpark 40 degrees showed best believe it or not......(yes, timing pointer was correct to begin with.) Motor made a dismal 590 @ 6300. Power went flat thereafter. Now, when the motor was torn down before the freshen up, There was MAJOR reversion. We tried a new valve job, one that my machinist uses often and has much luck with, so I don't know how the reversion situation is as of the few pulls it has on it. My question is this......The headers we are using on the dyno are the same that are used on the car. They are cheap headers, but the actually fit the port "fairly" decent. They are Schoenfeld 1 3/4 primary with a 3 1/2 collector. Could this header be choking the engine? An acquaintance of mine had a 14.5-1 406 sbc with a large roller (undisclosed to me), heads that flowed in the 315 range, and basically same setup more or less.......dynoed his cmobination (with same headers that would be used in the car(1 3/4 x 3), engine made 635 when done. They were expecting much more. Anyhow, they put it in the car, and it ran 10.60's. Halfway through the year, they switched to a new set of headers (2 x 3 1/2). The car astoundingly went 10.19 on the first pass, and went eventually a little faster than that. At the end of the year they re-dynoed the same engine with the "new" headers and it made 691 hp. Does this sound reasonable? Is this a good possibility with our 421? Would headers cause the reversion problem? We expected the engine to make in the 650-675 range.........is that reasonable? (no vaccum pump or any fancy stuff like that). Any replies would be GREATLY appreciated.

[BigPurp]

Do you have any more info on the heads? Are you positive those are .050 #'s posted? If so thats HUGE. IMO You have a clusterfcuk of a combo here. Headers and heads are inline for a 6500 rpm setup but you have a 9500rpm cam in it. You need a whole lot more head flow and will definitely need at least a 2" primary 3.5" collector header.

Only a 215cc head on a high comp 421ci sb?

Really what do you want this thing to do? how much does the car weigh?

If setup right a 421 with 14.4:1 with that cam should spin 8500 easily and be making 800hp with no problem at all.

What are you running for fuel? Hoping nothing less than 110 leaded

I'm partially raising the b/s flag on this whole ordeal, nobody in their right mind would cobble a setup like that together.

[REW]

yes, the @ .050 numbers are correct. We have the same basic camshaft in a 406 sbc that has a standard (non raised runner) 23 degree head, that runs 9.60 on hp @ 3,460 lbs...........and it made peak hp @ 7100. (283/292 @ .050) with 14-1. Camshaft is only part of the game.......The thing wont pull 8500 if the cylinder head isnt there. If the 406 didnt run so strong, we wouldnt have tried it with the 421.

[REW]

and as far as the fuel goes....114 sunoco.
and as far as the cobbled up combo..........sorry you feel that way, our 406 seems to work VERY well. But it DOES have 2" supercomps, and a 6400 convertor.

[REW]

And just so you know......we used the heads, which probably measure somewhere around 220-222 cc's, because we had them, not because we thought they were the perfect head. I totally understand that a 421 could easily stand a head with a 230-240cc runner to go 7500+. Maybe even bigger..........but we've gotta use what we've got. We have a set of 10x high port brodix heads that flow MAJOR air and have a runner volume of 250 cc's that we thought about putting on this thing....But we decided to build an entirely different shortblock for them. By the way..........we had a very conservative cam in the engine before this, 272/280 @ .050, (comparable lift figures), and it was totally down on power too.......Im not new BigPurp........I just wondered if anyone has had a situation where a certain header was so drastically small that it lost that kind of power.

[REW]

Two cam companies reccomended similiar grinds........Lunati....part # 50177, and Cam Dynamics.....(part # ??) Joe Sherman did a 421 in the Sept '02 issue of Hot rod. It had similiar compression and a REGULAR 23 degree head. The cam he used was 282/290 @ .050. It made 690 horsepower............seems the cam is'nt too far off now, huh?

[let r eat]

Might make a big peak but I bet the torque curve is hampered. There's airflow differences between the 421 and the 406 that are not being taken into account. Larry could tell you more about the header deal. I see no problem with 690hp out of that head combo if correct.

[Ron Miller]

REW,
I had a reversion problem with a 364 c.i. 3 9/16 stroker that I raced in the mid 80's. This motor by no means was a serious effort by todays standards. I did'nt even know the flow numbers on the heads and it was never dyno'ed. It had about 9.5 comp. and a small solid lifter cam. Ported 292 Turbo's w/a older style Victor Jr out of the box topped off w/a Holley 750 vac sec. The cam was a old General Kinetics grind that was @ .050 260/270,535/555 w/a 107 lc. I started out with a Hooker Super Comp header that was a 1 3/4 tube size. I raced this motor for 2 years with the small street headers and I did noticed it had a bad reversion problem in the intake. It always looked wet with a dark brown stain in the bottom of the plenum. At the end of the run the motor would come down poping & banging. I chased the jetting,timing,different lash settings and collector extension. It cleared up a little,but the problem was still their and I was not happy with that. While all this was happening the car ran around 11.70's @ 117 m.p.h. I talked to alot of other racers about this problem and know one had a real good solution. So just for the hell of it, I changed to a Hooker race header. I was saving the headers for a roller cam that I was going too run. The tube size was 1 7/8 i.d. that used the adapter port plate. Guess what ??? The reversion problem was gone and it pissed off the motor. The car never pulled the wheels off the ground with the street headers. The motor sounded very strong and pulled better through the gears. At the end of the run the motor would come down clean with no poping/banging. I had guys ask me if I put a big block in the car. The e.t. and the m.p.h. picked up a bunch too. The car ran 11.30's @ 124 m.p.h. with a best e.t. of 11 teens. So I would think that their could be big gains for you with the right header size.

[ou812]

With 106 lobe center and that big of a cam, reversion is easy to get. 2" headers should be the minimum with that engine and the rpm intended.
Probably the reason its going so lean is reversion. A valve job alone will not kill reversion, and if all he did was the VJ to try and stop it, then your low lift numbers are probably quite low. The 106 lca is good for poor low lift flow, but if the exhaust cannot escape in time at high rpm, then it will dilute the incoming charge. I have seen big gains on 383's going from 1 3/4 to 1 7/8 on 12.5 compression flattappet cammed 230cc heads.
The only other thing is with the big engine, high compression, and big cam the intake port air speed will be high at 7000+ rpm, so maybe your intake port speed is too high? Do you know the velocity numbers (fps) at or around .700 lift of those heads? That might help to know...
Brian

[flyin ryan]

here is the scenario......421 sbc.....4.155x 3.875. 14.4-1 compression, Dart Conquest 215 heads, fully ported, Brodix HV1000 intake with dominator adapter, Carb shop 1050 dominator, H-beam rod, Bullet solid roller camshaft, 283/292 @ .050 (.698/.671 AFTER lash) on a 106 LS, installed at 106 IC. Heads flowed average #'s for a 215 runner deal, and went 310.5 @ .700I, 225 @ .700E (no pipe). The first night on the dyno, made a few quick pulls......4600-6600 rpm. Was lean at first, got fuel in the "safe" range, re-adjusted lash, got timing in the ballpark 40 degrees showed best believe it or not......(yes, timing pointer was correct to begin with.) Motor made a dismal 590 @ 6300. Power went flat thereafter. Now, when the motor was torn down before the freshen up, There was MAJOR reversion. We tried a new valve job, one that my machinist uses often and has much luck with, so I don't know how the reversion situation is as of the few pulls it has on it. My question is this......The headers we are using on the dyno are the same that are used on the car. They are cheap headers, but the actually fit the port "fairly" decent. They are Schoenfeld 1 3/4 primary with a 3 1/2 collector. Could this header be choking the engine? An acquaintance of mine had a 14.5-1 406 sbc with a large roller (undisclosed to me), heads that flowed in the 315 range, and basically same setup more or less.......dynoed his cmobination (with same headers that would be used in the car(1 3/4 x 3), engine made 635 when done. They were expecting much more. Anyhow, they put it in the car, and it ran 10.60's. Halfway through the year, they switched to a new set of headers (2 x 3 1/2). The car astoundingly went 10.19 on the first pass, and went eventually a little faster than that. At the end of the year they re-dynoed the same engine with the "new" headers and it made 691 hp. Does this sound reasonable? Is this a good possibility with our 421? Would headers cause the reversion problem? We expected the engine to make in the 650-675 range.........is that reasonable? (no vaccum pump or any fancy stuff like that). Any replies would be GREATLY appreciated.

i don't think your headers are your problem.i did a 461 cube small block (340 based ) for a customer of mine & we used his old 1 3/4 x3" STAHL'S knowing they would be too small. engine has a 260ish @ .050" BULLET solid roller,INDY 230's & INDY oval port intake that i ported,HOLLEY 4150 w/ a proform body (flows 815) 12.4:1 c/r 94 octane pump gas,using a 340 resto block from MA MOPAR.o.k. headers are too small but the guy couldn't really afford a new set a that point so we'll run the old one's for a year or two. 636ft/lbs 744h.p. 1008 cfm through the carb 125% v.e. ran 9.75 @ 138mph on OCT.9/05 through the mufflers,nat.aspr.,non-tubbed 68 barracuda, drove to & from track. i still believe the engine needs a bigger header but i have a hard time saying 1 3/4's are hurting this deal.time & time again i see smaller suprising me & bigger not.for me if i see reversion ( usually from a new customer bringing his engine to me for the first time ) i 'll go to the intake or cam(timing). good luck.

[BigPurp]

Two cam companies reccomended similiar grinds........Lunati....part # 50177, and Cam Dynamics.....(part # ??) Joe Sherman did a 421 in the Sept '02 issue of Hot rod. It had similiar compression and a REGULAR 23 degree head. The cam he used was 282/290 @ .050. It made 690 horsepower............seems the cam is'nt too far off now, huh?

Ok but what was the lsa, and IC?

I honestly think you would have a much more useable powerband if you pulled that cam back A LOT. I don't know what the obsession is with people wanting the biggest cam they can find, but w/e. You have marginal heads that will not support the flow needed to bring that cam into the powerband. Put a cam in it that will work with the heads and the power will come around.

The headers aren't helping but I don't think thats the major source of your problem.

[SupStk]

REW,
I tend to agree with the others that the cam too much.

I'd consider trying something 273-275 degree range at .050.

I've done several of these engines and on my dyno they make 700+HP. The heads I've been using are flowing in the 325 CFM range, but use the smaller cam. I can't speak for your friends combo, but I can tell you what works for me.

There isn't a day when I don't learn something when testing, but almost 70 horses from a header change seems unbelievable.

Just something to ponder, the long stroke SBC's haven't been making much more than the 406's, just doing it at less RPM.

[REW]

yea, I dont know any more than anyone else on here, just trying to learn myself. It baselined a dismal 615 @ 6400..........so all I can think is that the head is even smaller than I anticipated. I know it is 220 cc's or so. Im sure it will make more tomorrow, as we just basically got the timing set and whatnot. It made 557 ft lbs at 5000. I hope we can find more, the dyno operator says no problem, but I have my doubts, lol. I guess if it makes 650 or so, screw it. Th weird thing is, We had a cam that was 272/280 @ .050 on a 106, installed at 102.5 IC, and it ran like sh*t in this longblock too. I think maybe it's cursed.

[REW]

One more thing.........Is the only reason that this is making peak power so low with that huge cam because the heads are so small? (220cc)
Because I know of several 406 sbc's that have VERY similiar heads and smaller cams and peak much higher............I realize the air demands of both are different, but it still confuses me.

[REW]

BIG PURP.........
I see what you're saying about matching the heads with the cam.......I do. But people crutch small runners with larger camshafts all the time........Lunati has a camshaft that is 280/290 @ .050 .660ish lift, that is specifically designed for use with the sbc turbo head........170ccs or so? So isnt this technically crutching a small head? Not trying to be a smartass.....just trying to figure this out.