Questions on tuning a 598 bbc

[GJ]

Sup guys
I build a 598 bbc for myself .
The cam is 288/298 dur , 825/7xx lift , 114 lobe sep .Heads were borowed dart 345 pro 1 heads . Compression is 15.1:1 . I don't have vac pump . The only thing we did was putting the timing at 36 degrees (crank trigger) and put a out of the box demon 1190 cfm.
We went to the track yesterday and the car ran first pass 8.70@153 mph ,60 feet was 1.21 . Not bad for first try . The only problem is we didn't dyno it so we don't know where it makes peak power . We put the shift point at 7000 rpm . The converter is a nealchance and it stalls at 5000 rpm . We set the 2 step at 4000 just for now . I was thinking on on to a chassis dyno (dyno dynamics) and check were it makes peak power and torque . What I was wondering was the timing . I hear people running 38-40 degrees which sounds like alot .The dome is 39cc . We were in a hurry that we didn't even drop the fuel presure which was about 12psi . I think it was rich , we didn't check the plugs yet . We only had a few runs for testing . But I will doubl;e check these on the dyno . Any sugestions on timing and a good starting point for demon carb jetting . I know every engine is diferent but i just want to see if the jetting is even close to what I need . Thanx
GJ

[RayJE Carburetors]

12 psi is way too much fuel pressure


the king demon should have 130 thou needle and seats...... 7 psi will be fine for 800-900hp

[MDT]

i bet it'll like 35-36 degrees better than 38-40.

[bigjoe1]

I have an engine customer with a 598-- we run a 1250 Holley, 38 degrees and shift at 7500, go through the finnish line at 74-7500. It made 1070 HP at 7000 RPM. Your not too far off on your setup.

JOE SHERMAN RACING

[GJ]

Thanx guys
I am going tomorrow to the chassis dyno and see if i'm gonna pick up some more power with some more timing and carb tuning . Do many of you guys use wideband for tuning ? We dropped the fuel presure to 8 psi . We are gonna leave the timing at 36 now and raise it up on the dyno to see how much we gain on raising the timing only . So if it makes peak power at around 7200 rpm , what should the shift point be ?
Thanx
GJ

[bobbybigblock]

after the chassis dyno give us some #'s and what kinda vehicle is it in? Thanks!

[JS]

598 978 hp @6500 shift at 6800 - 7000 38 degree timing

[GJ]

Bobby , the car is a 2200 pound full chassis corvette (full fiberglass body) . A friend of mine had the same king demon as mine in a 565 engine in a dragster , it ran 8.20 with 1.5 turn airbleeds . The car was strugling at the top end . It was getting very rich . He said the only thing that helped alot was opening the airbleeds around 2.5 turn . With no change other then the airbleeds that dragster ran 7.82 . I hope thats not what is holding me back . Anybody else had troubles with king demons ? One other friend have a old cutlass that was running 8.70s with a 540 ci with a king demon 1195 cfm and they couldn't make the car et better not even with jet tunning etc , they put a regular holey 1050cfm carb out of the box and the car ran 8.40s . The carb I bought was from that same friend that couldn't make the car run with the king demon . I tought it would just need some more tuning . They said that on the chassis dyno the bowl in the back would empty or something like that .
I hope we could make the best power with this carb.
Thanx
GJ

[UDHarold]

Geomar,

I warned you about fuel system problems, your Barry Grant 400 is big enough. You need a 1/2" #8 line going to each bowl, and I would feed a 5/8" #10 line up to a Y-Block, that was opened up---whatever looks safe---and then put the 1/2" line to the float bowls.
If you are trying to run a regulator, you need one for each bowl.
On the 2 spare outlets, hook a #8 line to them, and then T off of it for your fuel pressure readings.
This has worked for me for 28 years.

UDHarold

[maxracesoftware]

Sup guys
I build a 598 bbc for myself .
The cam is 288/298 dur , 825/7xx lift , 114 lobe sep .Heads were borowed dart 345 pro 1 heads . Compression is 15.1:1 . I don't have vac pump . The only thing we did was putting the timing at 36 degrees (crank trigger) and put a out of the box demon 1190 cfm.
We went to the track yesterday and the car ran first pass 8.70@153 mph ,60 feet was 1.21 . Not bad for first try . The only problem is we didn't dyno it so we don't know where it makes peak power . We put the shift point at 7000 rpm . The converter is a nealchance and it stalls at 5000 rpm . We set the 2 step at 4000 just for now . I was thinking on on to a chassis dyno (dyno dynamics) and check were it makes peak power and torque . What I was wondering was the timing . I hear people running 38-40 degrees which sounds like alot .The dome is 39cc . We were in a hurry that we didn't even drop the fuel presure which was about 12psi . I think it was rich , we didn't check the plugs yet . We only had a few runs for testing . But I will doubl;e check these on the dyno . Any sugestions on timing and a good starting point for demon carb jetting . I know every engine is diferent but i just want to see if the jetting is even close to what I need . Thanx
GJ

GJ ... this is a Single(1)-4 Barrell Carb 598cid similar to yours .
but it has the 26deg Edelbrock Victor Race Heads on it,
and highly modified Sniper with Welded/Extended Runners
1026 Peak HP

this particular Combo only wanted 32 deg BTDC...but this greatly
depends upon Motor Octane, actual static and effective CompRatio
and Ve% as well as other factors involved to the point your Engine
is a unique Combination of Parts and may require much different
BTDC Timing .

Just try different BTDC Timing on the Dyno or DragStrip
and let the Engine tell you what it wants or likes.
i don't think anyone can tell you exact number, but just a starting point

i'd start off around 32 BTDC
and try 2 deg increments or even 1 deg increments
and watchout the 1st Torque/HP Numbers at the begining RPMs
on the Dyno and if you tryout 2 more deg BTDC and HP would happen
to be better...but TQ down low is worse..be careful..back down 2 deg
to keep it safe

choose the most BTDC timing that shows no TQ losses down at the
starting RPM point on the Dyno and that gives you the most
Average TQ and HP Numbers over your desired RPM Range

at 2460 Lbs it went
60FT= 1.108 at 12:38PM Run time
330= 3.208
660= 4.967 - 141.79
1000= 6.483
1320= 7.770 - 174.26



Friday Oct 20, 2006
4.600x4.500 = 598.4 CID BBC Chevy Engine
with 26degree Edelbrock Heads 2.350"Int/1.860"Exh
413 CFM to 418 CFM @ 28" w/.900" Lift
on 4.500" Bore Flow Fixture SF-600
Jesel 1.90/1.90 shaft rockers
Jesel fronr-drive distributor
MSD Crank Trigger
Royal Purple 5W/30 10 qts.
Moroso 3-Stage Oil Pump
Billet Fab alum pan 10.5" deep
CM solid roller standard core size 113 Centers
Moroso 4-vane vac pump
14.5:1 CR 227 cranking psi
2.375 Primaries x 35" inches 4.500 Collectors x 11
ProSystems Carb
32 deg BTDC .025" lash across

SF-901 Dyno 600 RPM/SEC
with Sniper's welded/extended Runner Divider Walls
Edelbrock Super Victor___ProFiler Sniper (Welded/Extended)
w/1" spacer______________w/1" spacer---(Profiler)
RPM--Torque--HP__________Torque--HP----(HPGain/Loss)
5500--821.1--859.9_______838.3--877.9--( + 18.0 HP )
5600--816.4--870.5_______852.6--909.1--( + 38.6 )
5700--830.3--901.1_______843.1--915.1--( + 14.0 )
5800--821.9--907.7_______836.7--924.0--( + 16.3 )
5900--824.9--926.7_______840.8--944.5--( + 17.8 )
6000--813.2--929.0_______827.8--945.7--( + 16.7 )
6100--808.3--938.8_______831.4--965.6--( + 26.8 )
6200--805.0--950.3_______825.8--974.8--( + 24.5 )
6300--804.5--965.0_______822.1--986.1--( + 21.1 )
6400--803.9--979.6_______816.2--994.7--( + 15.1 )
6500--797.6--987.1_______814.4--1000.8-( + 13.7 )
6600--792.2--995.5_______808.8--1016.4-( + 20.9 )
6700--788.1-1005.4_______804.4--1026.4-( + 21.0 )
6800--780.2-1010.1_______793.0--1026.7-( + 16.6 )
6900--764.6-1004.1_______776.2--1019.7-( + 15.6 )
7000--751.3-1001.3_______764.4--1018.8-( + 17.5 )
7100--742.7-1004.1_______745.9--1008.4-( + 4.3 )
7200--731.6-1002.9_______739.8--1014.2-( + 11.3 )
7300--723.9-1006.2_______720.5--1001.5-( - 4.7 )
7400--712.0-1003.2_______710.1--1000.5-( - 2.7 )
_________________


the 598 CID 1026 HP engine is in Leon Mark's 1979 Camaro @ 2460 Lbs.
that ran this weekend ...First time out with RaceCar
No Problem Raceway - Oct 28, 2006 Saturday noon at 12:38 PM
Incrementals were=>
60FT= 1.108 at 12:38PM Run time
330= 3.208
660= 4.967 - 141.79
1000= 6.483
1320= 7.770 - 174.26

their Weather Station reported=>
30.03 Baro, 67.0 F , 51.0 % Rh , 12 Ft Track Elev
with a Crosswind of 7 MPH

Weather undergrounds weather data for Bell Rose, La or Patterson
at 12:35pm was
30.14 Baro, 64.4F, 52.0% Rh, 6.9 cross wind NNW, clear, 20 Ft Elev

according to ET_Analyst ETAVBWIN simulation
its running the incrementals almost on the money for 1026 HP
..actually its running a little faster at the 1/8th mile than it should
for 1026 HP => 141.76 MPH

Converter Lockup approx. = 93.0 to 93.5
Tire Growth Rate = approx 80%
2.465 GForce Launch
90.0% Drivetrain eff in both gears

Powerglide with 1.80 1st gear
4.10 rear gears
2460 Lbs weight with Driver
7300 Shift point
7600 approx Cross RPM
A1-Converter approx 2:1 Multiplication 6000 Stall (a little too high)
17.3" wide Tire x 33" on 16" wide 15" dia Rims

Chris and Mark report .... extremely responsive and very crisp
throttle response with ProFiler Sniper Intake
they said they could probably Leave on the Footbrake
the Car's got so much bottom-end Torque and responsiveness

[maxracesoftware]

Geomar,

I warned you about fuel system problems, your Barry Grant 400 is big enough. You need a 1/2" #8 line going to each bowl, and I would feed a 5/8" #10 line up to a Y-Block, that was opened up---whatever looks safe---and then put the 1/2" line to the float bowls.
If you are trying to run a regulator, you need one for each bowl.
On the 2 spare outlets, hook a #8 line to them, and then T off of it for your fuel pressure readings.
This has worked for me for 28 years.

UDHarold

i can't stress enough how important is what UD Harold pointed out.

the very 1st thing i do after we take off the Customer's Engine off
the Dyno is to go over with the Customer what type of Fuel System
and its Flow Rate and the Lines/Sizes Venting, Fuel Cell specifics , ETC.
and explain to Him everything required as far as Fuel System
specifics to keep up with the new level of Engine Performance.

what was OK with the old Engine Combo
will not keep up with the much better new Combo.

i even had a Reher-Morrison 540cid 850 HP BBC on the Dyno
that the Customer was complaining was not runing anywhere
near the ET and MPH they expected.

at the very same time they purchased the new R-M 540cid
they also put in a new Harwood Fuel Cell ,
but forgot to unplug the Fuel Cell Vent.

the RaceCar would 60 FT and 330 Ft ET like it had 850 HP,
but by the 660 Ft mark it was already starting to loose ET/MPH,
and by the 1/4 mile it was way off in MPH and ET

on my Dyno i told him there was nothing wrong with the R-M 540,
and asked what else did you do or might have done ?
that's when his mechanic mentioned they installed a new Fuel Cell
at the same time as they put in the RM 540
and i asked check and see if theres a Venting problem
or Fuel delivery problem. Check how long in seconds it takes
to pump 1 gallon...then go back and check how long it takes
to pump 5 gallons ..it should be 5 times as long, if it progressively
slows down to a trickel or anything less than 5 times,
theres a Venting problem.

i had another Racer Customer that had the weirdest Problem
i ever ran across ...He noted after much testing that his RaceCar
always ran a bunch faster when his Fuel Cell only had a couple
of gallons of Gas...if he filled the Fuel Cell up...he ran a whole bunch
slower.

After putting the Car on a Lift, i saw he had a Rubber triangular shaped
frame bumper that was squashing or clamping down on the AN Braided
#10 Line as it was just running underneath the rubber bumper.

so as long as there was less rear Car weight the rubber bumper
would not choke off Fuel Flow,
but when he filled the large Fuel Cell completely,
the rubber bumper choked off Fuel flow.

[GJ]

The fuel fuel system has 10 an coming out from the pump to a small regulator which has 2 outputs and from there 8 an from the outputs to each bowl . The problem that the regulator had 12 psi was that the pump didn't had much return , and the gauge at the pump wasn't working so we couldn't could set the presure of the return . We tried opening the return some until we could get the presure down to 9 psi on the regulator but it drops 1 psi when reving in park . I hope it doesn't keep dropping when it have some load on it going down the track .
Maxrace , thanx for all that info .
GJ

[GJ]

I could buy a new holley 1250 for cheap . Would that be better for my setup or the demon 1195 should work fine too ?
GJ

[briancb1]

Some people would say keep the demon, others will say get the holley.

I personally had a race demon that wasn't much fun, switched to an Holley HP and had a more stable fuel curve.

Im sure everyone can agree though that you need to get it tuned by a professional.

[UDHarold]

GJ/Geomar,

You said the regulator was a 'small regulator'.
Use TWO regulators, one on each exit of the Y-Block, and then 1/2" line to the float bowls.
Put a 1/2" line connecting the 2 spare outlets on the regulators, then T-off of it for your fuel pressure gauge. This gives you the average fuel pressure from the 2 regulators.
About 7 to 8 lbs should be plenty.
I have used systems like this for 28 years, with various fuel pumps.
All fittings should be #10 before the Y-Block, #8 after the Y-Block and the regulators. Small fittings act as restrictor jets in your fuel system.
Good Luck---I'm hoping for some 7s.......

UDHarold