Test and Tune Dissappointment

[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..

[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.

[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.

[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!!!!!

[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..

[Marv D]

Originally Posted by Super73

....
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.
..

I could not agree more. EA is like anything, garbage in and it will spit garbage out. But no matter how careful and exacting your are with Desktop Dyno,, it was always VERY generous.

I've used Drag Analyzer to model a complete package and (it imports the engine simulations) It's like the rest of Performance Trends stuff,, pretty darn accurate.

And did you know.. Performance Trends just got into the data logging industry. Racepack it aint, but it's not a $4000 data logging package either.
looks pretty interesting at a reasonable budget price.

http://performancetrends.com/dtm-hdwe.htm

OK,,, hijack off, Sorry

[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)

[kpeztruck]

I had springs in the stock location on the rear of my truck for a few races. I admit they were 5" lower springs, so the spring rate was way too high. What I ran into, was that when the rear suspension tried to seperate (anti-squat) the factory mounts prohibited this motion. I swapped to rear double adjustable coil-overs, and an anti-roll bar, and 1.34 60' times on radials. This was with Moroso trick springs and QA1 stocker star R series in the front set fairly loose. I have an 540 BBC leaving on 200hp nitrous, and turning on another 250 .8 out. Paul