LilJayV10

iTrader: (5)

ok, i am sitting here considering my options for my 406. Cost as always as an issue, and I want to drive my car by this summer. So i guess what I am asking what I can get away with. I do want to go with 5.7 rods(i have read this is better than the 5.56 rods, i am not for sure why, can someone please explain?)I have a set of stock 5.7 rods, how much power can these take? I was looking at SCAT 4340 rods for $249-279. I am planning on running Keith Black Silvo Lite Pistons. The cam will be a 274xtreme cam, or a 282xtreme roller if i decide to spend the money to roller the block. The heads are 461 w/ 2.02/1.60, pocket ported, polished, screw in studs, roller rockers. I expect, or hope rather for 400-450hp at the crank. Any opinons on how this poor boy should go about this? I know i dont need any crazy parts. I have seen people run insane fast on stock parts. the car will be used as a weekend driver and when its nice outside, so i dont want to make it a race car. Any opinons would be appreciated. Anyone else sit and contemplate what they are gonna do to their cars? I can't be the only one. Thanks guys.

91L98Z28

I'm currently building up a 400 for my 71 camaro, and also went the 5.7" rod route...

comments:

if you plan to live below 5500rpm, and it will be a street driven vehicle (quick runs through the RPM's but no sustained high RPM use) the stock rods with good ARP bolts should be fine. If you plan to do lots of upper RPM sustained use, then consider the upgrades (better rods, better crank, good harmonic balancer, etc.) You really don't want to wind 400's too high anyways though. It's not a 302 I don't recall off hand what heads the 461 casting is, but you will probably be induction limited to low 5k anyways. 400's need 15% more air than a 350 at same RPM... so a 350 setup that will flow to 5800 will only hit about 5000 on a 400...although that's a gross oversimplification. but the powerband will be lower, and the point where the motor quits making power will be lower.

If you can swing it, defiantely go for the XR282HR hydraulic roller. no problems wiping out a lobe on breakin, and it's pretty good HP for the bucks. Only comment would be that if you aren't the type to spend time in the upper rpm's (above 4500, say), then i might step down a size on the cam to get even more torque in the lower end.

Question, i assume you are putting a carb on this? these cams are quite a bit much for a stock GM computer... although the extra 50 cubes will help tame them...

Anyhow, the combo i'm building up for my 71 is as follows, in case you are curious about my buildup
400 0.020 over (405ci), GM fast burn alum heads (the zz430 heads) set up for 400 use (steam holes), KB pistons, summit 5.7" stage 2 rods, crane 232/240 @0.050 solid roller (0.525/0.543 lift) on narrow base circle for connecting rod clearance (which is problematic on a 5.7" rod 400), crane roller rockers, scat crank, edelbrock performer rpm air gap intake, holley 750, 1 3/4 headers, flowmaster exh, . I am kinda hoping to tickle 500hp, but anything over 450 is good. (if GM can get 430hp out of a 350 with these heads and a mild cam, i can do at least 450hp out of a 400, same heads, and bit more cam!) This will be about 5800rpm motor, the bottom end should be good enough to handle that, even though 6000 makes me nervous on a 400. oh, and CR is about 9.6:1. I wanted 10:1 but got the 22cc dish pistons instead of the 18cc dish...KB doesn't rate them right

91L98Z28

A few extra comments, not to knock you down or anything though

450hp on that head is probably a bit out of reach, mainly because the motor just isn't going to breathe at the higher rpm's to make that kind of HP. all is not lost though - you will be making big torque numbers, probably around 400 ft-lb, to mid 4000 rpm. An extreme example of this is the 78 firebird my family owns. it has an olds 403 motor. only rated 185hp i think, and it only has 2.53 gears, but when you punch it, it can STILL spin the tires or put you back in your seat. it's only a 15 second machine but fun on the street because of the massive torque.

I compared the difference between the flat tappet cam, and the roller cam, in desktop dyno. it predicted the roller would be worth about 30hp, mostly because you get better lift, for a longer period of time, and the engine will breathe better on the top end. i think you should definately aim for the roller. I noticed that those cams are 110 lobe sep angle....if you like a lopey rough idle that's great, but if you want to try and go for a smoother idle/better low rpm characteristics, you might want to get something with 112 or higher. Comp seems to love the lower lobe sep angles though. I went with crane mainly because they grind their mecahnical roller cams with less agressive profiles that will last on the street. the comp guys were telling me about changing valvesprings every 10-15k miles, i didn't want that. crane said they go less agressive on the lobes, but they can get 60-80k out of the springs as long as you dont float them. none of that applies to a hyd roller though...just the lobe seperation angle does

LilJayV10

iTrader: (5)

thanks for your reply. i dont plan on going higher than 5800rpms,not all the time and not for a sustained time. just enough to get down the track, or the next stop light, however there my be a few runs down the expressway at 2am racing my buddy in his police cruiserbut that will be about it. in the new hot rod, they put the 282xtreme cam in a 383 with stock vortec heads and got 500hp at 5800. the 461 heads are the old double hump heads, they have been pocket ported and gasket matched. i have them laying around so thats why they are going on there now, i would like some trick flows or AFR 220's, but that wont be till later this summer. I have no idea what flow numbers my 461 heads have. thanks again for your reply.

LilJayV10

iTrader: (5)

oh, and yes its going to be carbed, right now i have an edeljunk 750, a stealth intake and a port matched to the 461 heads edeljunk RPM intake, the exhaust is hooker LT/SC 1 3/4, I am either going with true duals or a homemade 4 inch single exhaust, which i dont know yet. a 700R4(i wanted the 6 speed thing, but its not gonna happen right now, i finally accepted the fact last night, lol)with 3.42 rear posi. i dont figure i need 3.73's or 4.10's with that much tourqe. you said something about changing springs every 10K miles? is that with the hydraulic 282xtreme roller? if so, i dont think i need all that drama, like i said its a street car i want to drive not a race car.

jcb999

461s don't have boltholes in the end of the heads.

LilJayV10

iTrader: (5)

mine have the the bolts hole brazed in, so the new style acceries will work.

91L98Z28

the changing springs thing was only pertaining to my explanation of why I chose a crane cam. compcams told me that their mechanical roller cams have agressive lobe profiles, and that i'd be changing springs every 10-15k miles. crane told me that their stuff will last a normal lifestyle (80k or so) because of the less agressive lobes. the crane mechanical roller is still way better than a flat tappet, that's for sure; but i wanted something i could put together and enjoy for a while, not do major work to every 10k. anyways none of that applies since you are talking about hydraulic cams.

4" exhaust is awful big even for a 400, a 3" should be fine provided that it's mandrel bent. Again with the 461 heads and a dual plane, you just aren't going to be revving the snot out of the motor so you don't need the 4" in my opinion. The ideal setup in my opinion would be 1 3/4" long tube headers, one of the new X-style crossovers, then 2.5" dual all the way out to a transverse style muffler and 2.5" tailpipes. but thirdgens are hard to do true dual, so the single 3" is acceptable compromise, 3" to transverse muffler then 2.5" or 2.75" tailpipes.

What gears do you have now? 3.42 is absolutely plenty for a 400, you are probably going to annihilate the rear tires in 1st gear with a 700r4 anyways. The 78 firebird in my family has the Oldsmobile 403 with "only" 180ish factory HP, 2.56 rear end gears, and an automatic th350 with a low stall converter. it will STILL spin the tires...well, not all the way through first gear but on a hard launch it will break them loose. my guess is that your 400 build, with the 700r4 first, and 3.42 gears, would smoke the tires all the way through first gear unless you backpedaled.

as for the 383 that made power at 5800rpm... the vortec heads are quite a bit better than the 461 casting, and they had less cubes too. I haven't seen the latest hot rod but i don't think a stock pair of vortecs could actually make 500hp without at least SOME work.... but hey i could be wrong.

again, not knocking your combo, but i'm thinking you will be in the 375hp range, but you will be making a TON of torque from pretty much idle up to 4500 or so. Your shift point will probably be 5200-5300. the motor would wind higher, but it will be strangled up there, so you'll be quicker by shifting sooner to keep the motor in it's powerband. the cam should be good for 5800 in a 400 with good intake and exhaust, but it's those heads that just aren't going to flow up there. It is kind of like how L98 motors are strangled at 5000rpm by the 305's TPI.... your 400 is going to get strangled by those 461 327ci heads.

i think the motor will be very enjoyable to drive and should easily put you in the 13's. HP numbers are nice to see on paper but motors with big fat torque curves is what makes driving fun! One good thing about your combo (cam/displacement) is that a bolt on set of good heads should give you a BIG jump in HP/top end power...something to look forward to in a year...

LilJayV10

iTrader: (5)

4 inch would me to much? if dual 2.5 would be good, i dont see how one 4inch pipe would flow as much. i know this has been discussed alot on here. i have defended the true dual setup on 3rd gens, and I might try it, I have seen it before on a formula and it looked really good. the only thing is i want to lower my car some, and I refuse to have a dragging exhaust system, i had a 82 regal I put true duals on and ran into that problem.

91L98Z28

as for 4" vs 2.5", yeah 2.5" + 2.5" is 5" but that's not how you calculate flow of a pipe.

flow of a pipe is directly related to it's cross sectional area, which is calculated as pi * r * r

the cross sectional area of a 2.5" pipe
pi * 1.25 * 1.25 = 3.14*1.25*1.25 = 4.90 sq in

cross secional area of 4" pipe
pi * 2 * 2 = 3.14 * 2 * 2 = 12.56

cross sectional area of dual 2.5" pipe
4.90 sqin + 4.90sqin = 9.80 sq in

thus...4" pipe has 28% more flow area than dual 2.5". a 4" single is about the same as a 2.82" dual (if they made such a thing).

if you wanted same flow as dual 2.5" in a single pipe, then 3.5" pipe is a lot closer (a single 3.5" is 9.61 sq in) and probably easier to fit under the car too.

I think dual 2.5" to a nice Y pipe into a big 3.5" cat with 3.5" to a transverse muffler, with 2.5" tailpipes, would be easier to implement. just my opinion

LilJayV10

iTrader: (5)

whoa, i had no idea thats how you figured that up. thats interesting. I appreciate all the time you put into your replies. Thank you. :hail: