Thread: slow 496

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hi new here from oh i have a 3400lbs 68 chevelle 496 tci-th350, 2800 stall 4.10 gears. here's the problem, my best time was 11.5 at 119 avg 11.7 looking for advise to wake up motor, runs solid just semms slow. 10.25 comp merlin 269 oval head rpm-airgap intak hyd comp cam 574-578 jetted ededelbrock 750. the short block has forged componets internal balanced and machine shop grinded valve releifs on the deck to unsroud the valves.what top end and solid roller cam should i use. goal is mid 10's motor

there are guys here running 10's with sbc's you need a bigger carb i would try an 850 dbl pumper or a 950 hp holley . what are you shifting at? i would also run a single plane intake like a strip dominator. but you should be able to get your times with that one unless your cranking some rpm's. what are your 60 foot times? how big is your cam????

it all ways the engine ? never any thing else??? fuel line size pump or pumps the 750 afb carb is a good street carb but will need more work for the strip and is to small any ways . move to a holley type carb for racing .what is the header size and ex .what the 60 foot times . is the car spining the tires ? stall is it out to lunch were you timing at how much were is it all in at ?you carb is to small your cr is abit low you need more stall so for what your doing ? car is heavy other then that it not bad times for a street engine if your running a ex and street tires i have customer s running fast with a 411 gears but there engine are pump up alot more then 10.25 your engine is about what i build as a street engine the intake should not be that bad you may want to try a open carb spacer on it

Pat put you on the right path IMO. Edelbrock carbs Im not fond of. Id take a QJ for the street any day and for performance a holley style carb is the way to go.

take note: Do not change aa bunch of things at once. First do the carb, tune it well and I will bet you are going to see a big difference. After the carb is all worked out then Id go to the Cam. If the car is primarily track then by all means Pat can set you in the correct direction and even probably get what you need for the best price. Now I know Pat among other solid roller fans will disagree with me on this but I still just dont like a solid roller for the street. Yes they can live if you are carful with your parts selection and maintenance. But if your like me, I wouldnt be tormented while driving on the street with a solid roller worrying if my lifters were gonna fail. If the car is a street with occasional strip Id just go with the old school solid flat tappet. regardless the solid or the solid roller IMO is gonna add more performance as well over you hydraulic flat tappet stick.

Then of course do look into all the other suggstions Pat has made with header size, fuel line and pump etc etc. The man has been around the perfomance block quite a bit and should be considered and authority..you cant go wrong with his advice IMO.

I concur.... 750cfm ain't nearly enough for racing. I would put you at least 950 or 1050cfm for that motor. We need to know more of your cam specs (duration, LSA, etc)... heads might be a little too restrictive but this will be a balance between how quick you want to go and how streetable you want to keep it. Judging between your et and mph I would say you will see a world of difference with a shorter (numerically higher) rear gear (4.30 or 4.56).... You can stand more lift (.600+) and duration (~270@.050) especially with 496 cubes but then you're probably looking at a higher stall (~3500). Do you want to go as fast as possible or do you want street friendly or somewhere in between? I agree more cfm in carb is first place to start... if you're serious then big cam, single plane intake and shorter rear gear will get you low 10's but not so good street manners. Really should have bigger rect port heads.

For reference I have 10.8:1 439ci 255/264@.50 .630/.630 110lsa single plane 850dp (too small) large oval heads but the wildcard is high altitude... 3300lbs 11.5 @ 117 best with 4.56 gear and 29" tire pump premium (should be ~10.8-10.9's at sea level)

-Chris

the cam is comp extreme energy 284-296 dur 574-578 lift hyd. timming 16 in 36 total and it runs best shifting at 6000. on the 28-10.5 slicks 60 are 1.7 not (spining bolts and tubes) fuel line is 3/8 sending unit up 8an out of the edelbrock 110 pump . the plugs look good and i jetted up the carb. the headers are 2inch primarys i picked up a 10 from the previous 1-3/4. i only drive the car 10 miles from home anyways and am leaning twoards drag racing, i tow car to track.what if i start with a carb what would be the best, all i want are 10s

wouldt a tci 3000 street fighter converter stall at 3600rpm because of the torque? would that make me slow down because of the low end torque. right now i have a bm 2300-2500 converter and i figured it would stall at 3000? i can only foot brake about 2000 before the brakes wont hold the car? dose that mean the converter is to tight. besides that would a bigger carb help that much? im up for any ]advice

also the cam is a comp extreme energy 284-296 dur 574-578 lift. timming is 16 initial 36 total and runs best shifting at 6000. 60's are 1.7 with slicks (screws and tubes) headers are 2 inch pri picked up a 10 from the previous 1 3/4. fuel line is 3/8 sending unit to the carb. i tow to the track and only drive the car to beat on it 200 mile a year. you tube the run at chevelle video 3 and 6

Pat and Richard (techinspector1) I would say are the resident experts (what ever happened to erik?). But I'll take a stab... How fast do you want to go? (read how much $$$$ you willing to spend?)

I plugged in your specs to desktop dyno and dragsim and it looks like you are running out of gear at the top end (around 1000')... would you agree?

Carb -> Either 950cfm Holley 4150HP (or similar) or 1050cfm dominator (or similar)... the 1050 will give you about +10hp over the 950

Heads -> Move up to rect port... pat will have best suggestion but I think Brodix BB2 Xtra 365cc will be good

Cam -> Comp XR286R .653/.660 248/254 @ 0.050 110 LSA solid roller (or similar)... we need to keep duration kind of low to make up for your low CR...

Intake -> Super Victor will work nicely but there are other more spendy single plane rect ports that may perform better....

Torque convertor -> 4000 stall (flash) is perfect for this combo... you'll want foot brake stall up to 3500

Tire -> go up to a 28" tire or you'll still be running out of gear at the top

If you stick with your oval heads you're leaving about 50hp on the table...

So here is what dragsim says:

Your current setup: 11.25 @ 117.5 1.658 60'
My suggested combo: 10.21 @ 134.3 1.509 60'

As for HP numbers:

before: 478hp @ 5500, 539tq @ 4000
after: 655hp @ 6000, 631tq @ 4500

Of course this is desktop dyno and won't be exact real world but I think reasonably close... you should expect mid 10's with this combo.

What are you running for a rear-end? I'm thinking your th-350 will be borderline and a 10-bolt would be too....

If you do all the work yourself, I think you're looking at ~$5k

My two cents and as said there are much smarter folks than me on here so there will be other suggestions...

-Chris

thanks for your advice i was thinking about that exact cam. i know the heads are small but do you think i would bennifit from 456gear,carb,cam and converter upgrade and only buy heads if i dont hit 10s. i really like the numbers on that cam. the rear end is 12 bolt 31 spline axels c clip elim. im not a tranny guy but im confortable with th350 put a few together. im shooting for mid 10s

bigger carb 1050 set of 2 1/8or 2 1/4 headers more cr about two points or more bigger cam something like 268 279 @ 050 on 108 714/710 or around there bigger heads 325/330 cc runners super vic intake . to use what you have now bigger carb and a wee bit more stall any thing more then that you will be running over the heads and cam so not much more gear . first thing inside the engine is $hit cam that hyd cam and move up to a soild roller they work fine on the street if you use hippo lifters you can not go nuts on the dur with low ch will be a dog down low could try a 112 lsa and more lift in the 650 255/260 @ 050

would the compxr286r be to much to stuff in this engine

i agrre very much about the hyd cam

Originally Posted by 6801

would the compxr286r be to much to stuff in this engine

i will not use comp cams would have to look it up or give me the numbers so i can look at them?

comp xr286r 653-660 lift 248-254 @50 110lsa solid roller