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.

[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!

[Super73]

[QUOTE=prostreetC-10;4339841]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. QUOTE]


Are you sure he is not seeing more than 100% VE?? With the info provided and head data I got from summit, the motor actually sees 104.2% VE according to Engine Analyzer (With a few guesses on combo 11-1cr and 1 5/8 30" headers).


Also take in to consideration every intake has flow restrictions often requiring more CFM from the carb to help over come that issue. This goes for head restrictions too..

In a perfect world, I would agree that you don't need a bigger carb than the motor can pump, but the world is not perfect.




I happen to be on Summits web page for other things and I got a pop up askling if I needed assistance (First time I have seen that) So I asked about flow numbers for the 200cc 64 chamber head you are using. Only info I got was 261cfm/176cfm @ .600

If you give me ALL the details of your build, I will put it in Engine Analyzer and see what it says for your motor.. Most of it I figured out looking at the thread but I don't know:
Header tube diameter and length
Compression ratio
What center line the cam is installed at

I plugged what I could find in and guessed on a couple things. I guessed on headers (1 5/8 and 30" long) and compression ratio (11-1).. The TQ of the motor does not start going up drastically until 3,200-3,300. TQ peaks about 5,000rpm (437ftlbs) and HP around 6,200 (467hp). Actual CFM according to the program in the upper RPM's is 705@6,200 and 733@6,600..

[prostreetC-10]

[quote=Super73;4340895]

Originally Posted by prostreetC-10

Are you sure he is not seeing more than 100% VE?? With the info provided and head data I got from summit, the motor actually sees 104.2% VE according to Engine Analyzer (With a few guesses on combo 11-1cr and 1 5/8 30" headers).

I made the mistake of jumping through the posts before replying. I made the VE call thinking he was still running the old iron 194 heads.

How does that E.A. compare to Desktop Dyno? I've heard the DD comes back with some "in your dreams" results at times. Man....If I had that, I'd run freaking combos for hrs and hrs and hrs!!!!!

[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.

[cableguy0]

What suspension is under the back of that thing? If its got the coil springs in the rear. Upgrade to a coil overs in the rear and put drag shocks up front. You need weight transfer. Move the battery to the back and put in a fuel cell too.Get as much weight off the nose as you can.
On a side note I would skip testing anything with that POS demon. Find a friend with a holley and borrow it to try. Vac secondaries tend to play nicer in heavy vehicles.
The best thing about the ford 9 inch is that it takes all of 30 minutes to change gears. Get yourself set up with 2 third members. Run one with a 4.56 or 5.13 gear for the track and another one with a 3.73 to run around on the street.

[Cole Trickle]

Originally Posted by 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.

What size ET street are you running?

How much PSI?

That stall is hittin the tires really hard. If the tracks not prepped there is no way stock suspension will come close to holding a big launch.

Maybe airlift helper bags in the springs?(It worked wonders preventing my converted 06 GTO from unloading the suspension and hooking mid 1.6x on the 17" ET street radials)

[Super73]

He has a 4,200 rpm verter, who cares about TQ under the curve from a vac secondary. It isn't going to help him go faster as he spends no time bellow 4,200 rpm..

A coil over in the rear suspension is not needed if the right spring is selected for the weight and intended useage (IE squat or antisquat). To tell you the truth, I prefer a long light spring here too regardless if I have my truck set up to squat or rise.

[onequickchevy]

Super 73,

Your guesses are right on the money. My cam is a Comp 292/501 and is installed straight up. If memory serves (and sometimes it doesn't) that cam is ground 4 degrees advanced. I built the bottom end of this motor almost 15 years ago. It is a forged TRW flat top pison, cast crank basic rebuild. It had very little run time at all when I snatched it out of my 57 BelAir to put in my truck. It was a fun truck, but rather slug like until making the head swap. I had a 750 Holley in it first, but it seems to like the larger flow with the heads. I don't know what the jets are front and rear so I am no help there, but I can go look if need be. Is there a junkyard source for a rear spring, or do I need to order some from a specific vehicle or source? I do need to move the fuel celland battery to the back of the truck. The tank is on the front right of the bed to offset my weight ( 12 gallon tank) and the battery is still in the stock location. My rearend is the stock 12 bolt, and there is no spool available for it so the 9" rearend is a sooner than later project. As I said, I do have a Powershot kit but it's a waste until I actually can put the power to the ground. Any particular shock setup you guys prefer to run front and rear? Sorry to be so long winded, but jsut looking to make it as fast as possible on a budget. I still have less than 3 grand total in this thing, and man it's a blast!

[Super73]

Prostreet..

I have modled probably 10 motors that have been on engine dyno's. If I have all the acurate info on the motor, EA normally comes back with 2% of actual power and typically is on the money about peaks (+/- 200rpm). I have used DD on the same combos and it has never had the same consistancy nor acuracy. DD is utter garbage IMO, even thoughs others will argue that it is dead on.


Onequickchevy, I think a 750 carb would probably work very well in your application. An 850 might be a little overkill, but I don't think it is killing your ET/MPH by much if dialed in. Carb to Carb the 850 shows an extra 6hp up top over a 750 but really only after 5,200..