building a 496 need some pointers/thoughts
07-23-2006, 11:01 AM
#1
building a 496 need some pointers/thoughts ok just picked up a 98 vortec 454. not sure of the casting #'s but i think its the L29. i read some where that they are the best flowing oval port BBC heads ever produced form GM. just wondering what you guys think. also it has a factory roller cam which i really like. the motor is going in a 55 chevy bel air. just a street car but might go to the track for a little fun. i buying a steel crank, 4340 h beam rods and forged pistons. compression will be close to 10.5:1. have a edelbrock dual 4 barrel intake and was wondering what size carbs to run? 2 650's or 600's?? also need a little help on cam choice. thing 240ish dur @.050 also what valve springs are you guys running on these big blocks? oh yea this has a turbo 400 too
thanks
nick
thanks
nick
07-24-2006, 02:34 AM
#2
I would suggest running just the 600 CFM carb's. I'm not a big fan of running 2 quads on a small intake like that. All the carbs will do is dump fuel and cause it to puddel on the bottom of the intake. If u want to run dual quads, Run a tummel ram or an isolated runner intake. Stay away from edelbrock carbs, biggest waste of money I've ever spent. On the issue of the cam, run a higher duration number for higher RPM usage out of the motor. I would'nt run any bigger than a .600" lift cam on the street. U can find springs to match. Just make sure the springs are rated for your cam lift, not your valve lift, 2 totally different measurements. Also, if your going to run nitrous or other forms of force induction, make sure your cam has a LSA(Lobe Separation Angle) of 114 degrees of more and get a smaller lift cam, .454"-.550" inches of cam lift. Your rocker ratio has an effect on your your valve lift ( not cam lift) multiply your ratio by your cam lif, ex. 1.6 ratio rockers x .550" of cam lift = .880" of valve lift. this measurment is the amount the valve actually comes off the valve seat. these are all things you need to consider when you build this motor.
07-28-2006, 10:58 AM
#3
Why the top dollar super stout bottom end for a mostly cruising street car? If the crank and rods in that engine are not hurt, they could definitely hold up to 600hp reliably for a long time. The stock cast crank and small 3/8" truck rods are a lot stouter than most people give them credit for. Just spend money on a good set of forged pistons and a balance job. Then if you need a new crank/rod combo, the price of a 496 stroker kit is about the same price as would be an all forged 454 setup. (This is what I just built.)
The L29 heads are good heads, but not from a high performance standpoint. They are bigger than the peanut port (truck) BBC heads but not as large as the traditional large oval ports (781,049,215,063). They have a high swirl small combustion chamber to help keep compression up. They also have a non-adjustable valvetrain that would need to be converted over to adjustable if you use much more than a stock cam. Porting and chamber work may do more harm than good with these heads (screw with the swirl design).
You may be better off finding an early set of closed chamber 396 heads (702,206,215,063s) that will flow better, keep your compression up (without use of a large flow impeding dome), and not require conversion to an adjustable valvetrain.
A hydraulic or hydraulic roller cam in the 240@.050 range is a good choice and I would aim for around 550-600 lift and 110 l/s. This would give a broad powerband and not lope very bad but still have a good sound.
The oval port heads are definitely the way to go for a heavy street car under 500ci that wants to make all its power before 6500rpm. A mildly built 454 with oval ports can get a 3500lb car into the high 10s in the 1/4 once you get it hooking all that torque.
Caleb
The L29 heads are good heads, but not from a high performance standpoint. They are bigger than the peanut port (truck) BBC heads but not as large as the traditional large oval ports (781,049,215,063). They have a high swirl small combustion chamber to help keep compression up. They also have a non-adjustable valvetrain that would need to be converted over to adjustable if you use much more than a stock cam. Porting and chamber work may do more harm than good with these heads (screw with the swirl design).
You may be better off finding an early set of closed chamber 396 heads (702,206,215,063s) that will flow better, keep your compression up (without use of a large flow impeding dome), and not require conversion to an adjustable valvetrain.
A hydraulic or hydraulic roller cam in the 240@.050 range is a good choice and I would aim for around 550-600 lift and 110 l/s. This would give a broad powerband and not lope very bad but still have a good sound.
The oval port heads are definitely the way to go for a heavy street car under 500ci that wants to make all its power before 6500rpm. A mildly built 454 with oval ports can get a 3500lb car into the high 10s in the 1/4 once you get it hooking all that torque.
Caleb
07-28-2006, 11:17 AM
#4
OOPs, after typing all that I didn't notice that you planned to build a 496 to start with. Disregard all that stock bottom end stuff then. I thought you were buying all new parts and still keeping it a 454.
If you do keep the L29 heads and a cam as suggested, you will have a total torque monster that will be through by 4800 rpm. You definitely need an older set of large oval ports, there is about a 30cc difference in the intake runner size between the two styles of heads. Also, unless you have some major suspension upgrades, this engine will make gobs of unusable torque at a very low rpm, so you may want to step the cam up in duration just a little bit. Keeping it around 245-250@.050 for a hydraulic cam would be a good start for 10:1 compression. If you decide to go solid flat tappet or mechanical roller add about 8* to the .050 duration to be ~ equivalent. You should still have in excess of 500lb/ft by 3000rpm stepping the cam up to this size and make all your power by 6500rpm.
I am using a solid flat tappet set-up in my 496 with Schubeck ceramic lifters and my cam is 255/263 @.050 110 l/s and 612/630 lift. I chose this cam working with a cam designer to match my 10.5:1 compression and make 600hp/650lb/ft with large oval ports with a little work. Since I bought these, I got a screaming deal on a set of AFR 335s with 114cc chambers and jesel shaft mount rocker arms. The heads are a little big but the have good velocity, so I don't think they will hurt me at all. New goal is 700hp with the same set-up.
Caleb
If you do keep the L29 heads and a cam as suggested, you will have a total torque monster that will be through by 4800 rpm. You definitely need an older set of large oval ports, there is about a 30cc difference in the intake runner size between the two styles of heads. Also, unless you have some major suspension upgrades, this engine will make gobs of unusable torque at a very low rpm, so you may want to step the cam up in duration just a little bit. Keeping it around 245-250@.050 for a hydraulic cam would be a good start for 10:1 compression. If you decide to go solid flat tappet or mechanical roller add about 8* to the .050 duration to be ~ equivalent. You should still have in excess of 500lb/ft by 3000rpm stepping the cam up to this size and make all your power by 6500rpm.
I am using a solid flat tappet set-up in my 496 with Schubeck ceramic lifters and my cam is 255/263 @.050 110 l/s and 612/630 lift. I chose this cam working with a cam designer to match my 10.5:1 compression and make 600hp/650lb/ft with large oval ports with a little work. Since I bought these, I got a screaming deal on a set of AFR 335s with 114cc chambers and jesel shaft mount rocker arms. The heads are a little big but the have good velocity, so I don't think they will hurt me at all. New goal is 700hp with the same set-up.
Caleb
07-28-2006, 11:53 AM
#5
what is the difference in the Gen IV blocks and the Gen V and VI. the L29 heads say that then cant be interchanged?? i have a 71 402BBC and 2 396's also. one is a 66 and 67 i think... both were originally only 325hp versions though. not sure on the heads but if i can bolt them up should i run them with the roller can set up? i bought this vortec motor cause it was a roller set up and that keeps the cost down from having to convert one. thanks for the input also. oh yea my goal is just a realiable street torque monster that will roast the tires. am i headed the right way? so the L29 heads arent as good as they are made out to be. well thanks a lot. please let me know if i can run the older 396 heads on it. will i be close to 500 hp at the flywheel you think? thanks
nick
nick
07-28-2006, 05:18 PM
#7
Staging Lane
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the rods are a thing, the only ones we found that might fit in the block with a min of oil pan rail grinding, are the eagle ESP, the ends are small and as the motor turns check the rod bolt to cam lobe through the front and center block openings, if your block core has a shift in it from the factory ( HAPPENS ALL THE TIME ) the bolt will hit the cam you need at least .025 or at 5500 RPMs or so it will make contact the small specs of steel will play havic in the motor and we have seen one that loosened the rod bolt and it fell out not a good thing hahahaha jz
