Test and Tune Dissappointment

[onequickchevy]

Well, I took my 63 to the track yesterday, and was not pleased. I knew I needed to do some tuning, but now I am rethinking my combo. I have a .030 over 350 with trw flat tops, a 292 / 501 comp cam, cast 1.94 heads, roller tip rockers, victor jr intake, mallory unilite mechanical advance, 850mech secondary carb, 350trans with 2800 convertor, and 12 bolt stock rear with a 3.7 is gear ( have not checked for sure). Best run was a 10.4 at 70 mph in the eigth. I know the carb is too big for my combo, but I had it and its brand new, I am thinking now going to a 280 grind cam, performer rpm and summit aluminum heads. Am I throwing in the towel too early. This thing sounds great, revs quickly, but doesn't start rolling real good until second gear. Any advice would be appreciated.

[cableguy0]

sounds like you might have a higher rear than you think. 3.07 was really common. the stock heads are definately a choke point for that motor everything is close. i would keep everything else and go with better heads if it was me. pull the cover off the rear and double check your gears. count the teeth and you will know for sure what ratio they are. what was your 60ft time?

[faribran]

Onequick, what track did u go to?

[onequickchevy]

really do need to check the gear ratio, I'm assuming and you know what that does.... anyway, the track we went to is Powerhouse toward PanamaCity. Between Powerhouse, and Cottonwood the distance is almost identical. I found a set of zz4 heads, are they worth getting or should I save my money for the AFR's or Summit, or Patriot.....AAAARGH! Anyway, my 60' was a dismal 2.40

[cableguy0]

if you didnt just completely blow the tires off i would bet that your gears are somewhere in the low 3.xx or high 2.xx range. pull that cover off your diff and count the teeth. that thing should come out of the hole better than that. with the state of the economy you can get good prices on used aftermarket heads right now. dart iron eagles are good. the zz4 heads would definately be an upgrade for you if they are the aluminum gm fast burn heads but i think they use the new style valve covers and intake.

[Rodms]

4.88 or 5.13 for 1/8 with 30 inch tire ,I know,You could try 4.56 but tire size must be ajusted,you probably have the old 3.08 gear,Thats what was in mine

[djracer]

A gear really helps to get these heavy heaps movin.

[ripdog28]

You do not need to pull the cover off and count teeth. Just mark the tire (on top) and mark the axle. Roll the truck fwd as you cound the rotations of the axle and tire. It is not exacting as conting teeth but it is close and faster. I would get new heads, not AFR unless you are doing a complete build with HP in mind. I love after market IRON. Dart, motown, whatever, just get some bigger valves.

[Wild83C10]

While gears would help. The combo is not great. The cam, intake and carb are too big for those heads.

Don't rip everything off and start over. Try swapping one thing at a time. Go with a performer rpm AIR GAP intake. That is the best all around intake. A smaller 650 vacuum secondary carb. Better heads. The cam should be last so you can match it to the combo.

[onequickchevy]

I will check the gear when we get back in town. Sounds like that needs to be first, then heads. Thanks for all the input and support. I was really hangin my head on this one...

[cableguy0]

i bet you would have a decent 1/4 mile time because that thing should pull like he!! on the top end. next time you go the track spin the tires taking off and i bet you pick up a couple tenths.

[onequickchevy]

Next time I go should be much better. I just scored a brand new set of summit aluminum heads for 500 bucks! 200cc runner 2.02 intake 1.60 exshast .64 chambers, half price deal and they are brand spankin new. Runnin out the door to pick them up right now!!!!!

[cableguy0]

good deal. those heads match great with that intake and carb. you might want to upgrade the cam some. you have a good bit of room to play with those heads as far as cam size. you also might want to move up to a 3000-3500 stall converter especially if you go bigger on the cam

[djracer]

I would be willing to bet the intake is hurting you more than anything on your combo with the exception of gears. I had a pretty good running mild sbc in an old camaro and I put a vic jr on it and killed it. I went back to it later with a big cam and more compression and it was fine.

[djracer]

Originally Posted by cableguy0

good deal. those heads match great with that intake and carb. you might want to upgrade the cam some. you have a good bit of room to play with those heads as far as cam size. you also might want to move up to a 3000-3500 stall converter especially if you go bigger on the cam

I agree totally.


What do you do with the truck?

[Rodms]

Might want to spend a little time matching the intake to them,That cams power band is 2500 to 6500,I take it you have a converter for that?You definetly got enough carb.All the rest is going to be in gear.

[cableguy0]

the big issue with the heads is the gear is going to seem even worse now. you will need at least a 3.73. im at about 10-1 comp with 200cc heads and a hydraulic roller cam 238/246@.050 .548 lift 108lsa vic jr and proform 750 2500 stall isnt enough and it definately dislikes the 3.42 gear on launch. once i hit about 3300rpm its like a switch gets flipped when the power comes in. get yourself a 1 inch 4 hole spacer it will help a bit with bringing back some of the bottom end torque. mine helped a good bit when i first went to a vic jr

[onequickchevy]

Just got back with the heads. The seller was not completely honest, they had been put on one engine and then a bolt was dropped into the carb by his son. Son was afraid to tell dad, sooooo dad turned the engine over to crank it the first time and ouch. The heads still look pretty good though, there is some imprint of threads in number 4 combustion chamber, but that should not matter. I spoke to the machine shop that checked them out. He said they replaced a few valves and polished out the chamber just enough. He said they will be fine. When we get back in town from short vacation its time to tear into it. DJ racer, I drive it when I can. It is just one three projects that I am working on. I also have a 57 Belair that is getting a big block four speed, and a 72 Skylark with a bunch of Poston upgrades. The engine in the truck I built almost fourteen years ago and never cranked it until recently. Life really got in the way. Built it when bigger had to be better right?!! Anyway, long story well.... long, I cruise it, drag it and just all around enjoy the crap out of it. Patchpanels are on the way now.

[cableguy0]

yea that wont hurt anything so long as the valve seat is torn up. at least they were at the machine shop and you know they are in good shape

[onequickchevy]

Dragging this back from the dead, I actually forgot I posted this. I put the heads on forever ago, and it runs like a different truck. Also put in a new HEI w/ high voltage coil, and a 4200 stall. Best time last weekend was a severely traction limited 8.70 at 86 mph and a dismal 1.98 60 foot time. It is spinning my et streets so hard the tires look like they are bouncing. (As noticed by a friend of mine watching the run.) The majority of my runs were spinning for about the first hundred feet and then really making up for it on the big end. Now my big issue is traction. I do indeed have a 3.73 gear so that is decent for now until I put the 9" in it. I have access to some 5.13 gears (for the 9"), but I still cruise this alot so I think they are too much. I am thinking 4.10 for the 9 inch w/ 29 inch tires. Opinions? I have until the track opens back up to get it back together. Fun street bruiser for sure!!!!

[bigsnookmaster]

I wouldn't put too much gear in it if you want to drive it on the street most of the time. I run a 3:70 gear in my 68, but I also have a 406 with a mech roller. If you really want to have fun, put a 150 shot of nitrous to it!

[prostreetC-10]

Your carb is not just too big.......it's WAY too big and hurting you more than I think you know. A 355 spinning 6,500 with 100% VE, and you are no where near that, is coming in at about 658 cfm. You also don't need the mech secondary either. If you do drive this on the street, you'd be amazed at what a 670 avenger would do for you. You would have great throttle response and more than enough cfm. I'd also swap out the mech distributor and get an air gap or rpm manifold. You make a head upgrade and things might change but never enough to need that 850. Those carbs are flat pigs with their 1 9/16th venturis. Not too street friendly either.

[onequickchevy]

Pro street, the heads are upgraded to Summit street strip aluminum heads, and the distributor is a high output hei now as well. The carb is BIG, but it does not exhibit any of the typical over carb symptoms. It does not load up at idle, bog, black smoke at any time, or hesitate one bit. When I stomp the pedal it takes it all. It has excellent street manners (aside from the converter but I can live with that) and really seems to work pretty dang good. I have a friend with a 650 race demon I could borrow and try, but really my issue seems to be more traction related now. I am thinking of going full slick, and trying that. I also have a 9" Furd housing that will go in but I have to get new axled to match my lug pattern. I have picked up a Powershot Nitrous kit, but have not put it on yet because I need to hook up first not just spin. I am not opposed to cutting the bed, and may do that to run a large offset rim and bigger ET Streets. I am overall pleased but need tuning and input. Thanks for your reply and direction!

[prostreetC-10]

I didn't realize that the thread started 2 months ago so that's a good thing.

The problem with over-carburetion is that you don't often "feel" it but performance will be down......and I'm sure that's why you started the thread. You often won't feel a bog because an 850 and a 600 actually have the same basic accel system except the shooter size. It's once you have the right carb and that sucker pulls hard all the way through to readline that you realize this. The 850 will also hurt your 60' times. You loose a lot of velocity and booster signal with those huge holes. A 750 DP would still be pushing it but a guarantee you'll take 10th off your E.T. (a little more in 1/4 than 1/8th).

That 650 race Demon would be a GREAT place to start if it's tuned right to start with.

[onequickchevy]

Well, I will try it and see. Any tips on the traction side of things? I feel like it has very low 8, high 7 capability. Either way it's respactably quick for what I have in it.