Chevy Nova Forum banner

My BBC 468 is slow....

37K views 122 replies 29 participants last post by  sbc1320 
#1 · (Edited)
I unintentionally high jacked this thread: SORRY.

http://www.stevesnovasite.com/forums/showthread.php?t=94468

So I started a new one.....
Why is my car so slow?

Based on the information in above thread and this....

Year: 73

Model: Nova

Body/Exterior: GM Bright Blue Metallic. All steel except fiberglass hood and bumpers. Mini Tubbed.

Front End: Moroso Trick springs, Lakewood 90/10’s, SSBC Dual Piston Disk Brakes Rotors, Low Friction Ball Joints and bushings.

Engine: Chevy Big Block on CAM2 110 Octane
468 Cubic Inches 13-1 Forged Domed Pistons Speed PRo
Solid Cam Shaft.....Comp cam 680/605..256/266 3500-6500
GM Iron Heads Gm12T F9/78 336 781
Large Oval ports 2.06 intake and 1.72 exhaust????
1.7 Aluminum Roller Rockers
Aluminum Valve Covers
Crankcase Evacuation System
Edelbrock RPM Air Gap Dual Plane Manifold
Holley Double Pumper Carb 770 (????)
K&N 5 7/8 x 14 Air Filter and Extreme Lid
Holley Blue Electric Fuel Pump w/ Regulator


Transmission: TH350 / 3600 Conv.

Rear End: Narrowed 9 inch, 35 Spline, Detroit Locker, 433’s, Rancho RS9000 shocks, Caltracs and Split leaf Monos on Sliders, CEE Frame Conn.

Exhaust: Headers with Flow master 44 Series, 3 inch

Wheels/Tires: M&H Race Masters street slicks, 28x12.5x15 on 10inch Weld Rim

Interior: Still have the back set and front buckets custom Blue Diamond tuck, stock dash and gauges. 8 Point Cage.

Electrical: ALL MSD: Dist. Coil, 6al, start retard and High RPM retard, 2 step

Accessories/Options: Single Stage Plate Kit 150-300 HP
 
See less See more
#3 · (Edited)
Aug 2007
first time out with the car...6 runs...brand new caltracs splt monos and ranchos....new to me 100% ...top hole, too much preload, shocks at 6
1.825 11.69 @ 117.07
1.684 11.56 @ 115.06
1.71 11.038 MPH unknown (150 shot) Slip shows 79.16MPH
1.73 11.572 @113.48
1.65 11.550 @ 115.27
1.70 11.58 @ 112.98

Last week 3 runs, over the winter i rebuilt the front end, moroso trick springs, lakewood 90/10, Low friction ball joints and bushings
caltracs set in lower hole, no pre load, launch from idle
1.62 11.71 @ 112
1.73 11.77 @ 114
1.64 11.70 @ 113

I expected alot more out of all the work and money i have put into this car.
I need alot more track time to tune it i guess.
 
#4 ·
Quote:
Originally Posted by NOVACA1N
John, I don't want you to take this the wrong way but...You have a 13:1 468 and you're only running 11s. Something is seriously wrong. Your 60 foots are dead slow, and I seen your car and suspension wise it is good. Just our of curiosity, what converter is in your car?

I dont know the brand or size, but the trans and convertor was redone this fall... the trans guy sent the conv. back to manufacture for rebuild....
3600 stall


My thought exactly WTF...or what i have i got wrong......thats why i posted about the timing queastion...


I just looked at some old time slips from the previos owner....

before any work that was done after i purchased........
it had the oldest front end known to man kind......still had the front sway bar.
slapper bars with multi leafs and worn out shackles, lowering blocks...you get the idea

best eighth
1.54
6.97 @ 98.71 MPH

What did i do wrong?
 
#6 ·
Your claimed HP, how was that recorded? Rear wheel?
I take it you DIDN'T build the engine/drivetrain?

Have you validated:
-the engine, as in comp. ratio/heads/cam.
-gear ratio.
-compression check, verify all mechanicals.
-are the valves set correctly?

What elevation are we talking about?

Your MPH relates to hp, so I'm taking a guess and thinking 400RWHP???? 117MPH just doesn't compute.

Does the car "pull hard all the way", or does it seem to "lay down" in some RPM range?

Are you running an alternator and running 14+ volts to ign. system?

Did you or someone you know build the trans?

The reason I'm asking is something that I ran across lately. At work we have a 90 GMC 1 ton with 350/th400. We bought it 6 years ago, the last owner said the truck got gutless with time. He bought a GM crate motor and there was little to no difference. We bought the truck and drove in on and off for six years. The thing was GUTLESS. Fast forward to three months ago, the trans blew up. I just rebuilt it and one of the forward clutch pack spring retainers broke, causing the clutch to drag all the time. It finally wore through, disinigrated, and all the springs went everywhere. It was like we went from a six cylinder to an eight cylinder.

My guess is somewhere in the mid 10's, with that much HP. I know you're missing something because my Malibu with a 400hp 355 ran low 12's 110mph.

Keep the info coming and someone will point you in the right direction.
 
#7 · (Edited)
What size cam? What size carb? Which heads and what work has been done to them? You 60ft's are in line with a 11.50 car, and your spped (which indicates HP) matches up with your ET pretty well as well. Too many varibales left unanswered, but I'd say it's a slightly mis matched combo. You probably have a big cam, but stock unported heads? A dual plane intake isn't what a drag engine wants, maybe switch to a Victor. You're running an 850 or 950 carb? Your convertor could stall a little higher for better launch.Also Flowmasters suck for performance, you need better flowing mufflers like Dynomax UltraFlo's.
 
#8 ·
If the car really ran 98 in the 1/8 before, your down about 80 hp. What does it run now in the 1/8 ?
I would do a compression test, a leak down, run the valves ( I hope you have the correct cam card and have the correct lash setting) , check for broken valve springs.
How do the plugs look? Are you running the same heat range the previous owner was? How old are the wires? Is the distributor locked out? maybe a stuck mechanical advance mechanism.
Pull the carb apart and look for junk in a fuel jet, a bad needle and seat, power valve loose, base plate loose. Change the fuel filter, check the vent tube to the fuel tank. How old is the fuel? Some fuel goes bad over time.
 
#9 ·
Wow your making no power for some reason. How does it seem to run? I wouldn't worry at all about the 60' times till you get it running right. You don't want to hurt the motor. Are you shure the timing is right? May have the wrong pointer/balancer combo on it? Fuel pressure?
 
#11 · (Edited)
I think you still need to confirm that the engine is a 13.5:1 468 BBC if you have any doubts.

You're close to where you were before your changes, maybe a little better 60' but your MPH will tell you any HP changes.

Like others have said. I'd verify the timing is right first and go from there. Make sure the #1 piston is at TDC and the balancer mark is correct, then put a light on it and see what you got.
 
#12 · (Edited)
WOW..........lots of questions to answer. .......

I did not build the motor........it came with the car...

Lets just pull the motor out and start from scratch and make it a 496 stroker or something. that way next time i can answer all those questions..........:eek:.............:confused:
 
#13 ·
Years ago my car ran those numbers with a 396 in it. Are you sure it is in fact a 468? Nobody will be able to offer you any real info without knowing alot more about the motor. Cam info and type heads would answer alot right after being sure it is a 468 incher. RM
 
#14 ·
Well when i blew a head gasket last fall, the mechanic pulled the heads and verified pistons were as advertised... he also measured the bore and said its a standard 454 bore by his standards......:confused: so unless a 454 can go to a 468 with a crank and not honed.....not sure.....:confused:

heads were verified by these numbers
GM Iron Heads Gm12T F9/78 336 781
Large Oval ports 2.06 intake and 1.72 exhaust????
Definatly not stock........


Here are the ad 's from which i bought the car...off of racing junk

this is a chevy nova that i've put alot of time and money in it.the car has a narrowed ford 9 inch rearend,with 433 gears,35 spline moser axles,nodular iron center section with a detroir locking differential.13 inch wide street slicks mounted on weld draglite xp wheels.also have a brand new set of drag slicks that go with car.the car is painted a blue/purple pearl.it has fiberglass bumpers front/back,a 6 inch bolt on cowl hood.a new 468 cubic inch big block chevy has been installed.it has 13 to 1 forged pistons,solid cam shaft& high performance gm heads.it has had porting and polishing work done.a nitrous plate system has been installed but never sprayed through engine yet.its adjustible from 50hp to 300hp.the transmission has been upgraded to a stage 3 trans.a hardned input shaft,doubled up the clutches,the bell housing has been cut and a blow proof bell housing has been installed.the stall converter has been matched to the car.it stalls about 3600 rpm on motor and should stall about 4500 rpm on nitrous.estimated horse power on motor is 600hp,and on nitrous is up to you.this car is street legal and a must see




new 468cu big block chevy with 600hp.nitrous plate system/never used yet.msd ignition,timing computer.mini tubbed with ford nine inch rear,35 spline axels,433 gears,detroit locker posi unit,fuel cell,8pt roll cage,frame has been tied in,disk brakes,blue diamond tuck interior,fiberglass bumpers,6 inch bolt on cowl hood.350 turbo trans with hardned input shaft & blow proof bell housing.car has been raced several times and ran a 690 on motor in 1/8 mile.car could run high 5's with right driver.
 
#18 ·
My car has a 468 w/ 12.5 to 1 pistons, Square port Iron heads (mild port and polish) with 2.19 in and 1.88 ex and 118 cc combustion chambers and H/S 1.7 roller rockers, Team G intake, 850 Holley w/ a Blue FP, Comp Cams flat tappet w/ a 580 in and 605 ex lift, Headman 1 3/4 primary and 3" collectors , T400 3500 stall conv 12 bolt (not narrowed) 4.10's w/ a spool, ladder bars and coil overs.
Car weighs in at around 3100 with me in it and has ran a best of 10.554 @ 128.78 this past week. I only have 5 run in the car or in any car that fast, so my experiance is little.

So with your combo something must be missing or not set right. Go over the car and pick peoples mind at the track and here. You might find something you never looked at or thought to.
 
#21 ·
That 6.90 ET he posted on the ad you bought it from tells me it is not running to it's potential for a 454 which it must be if it is a stock 4.250 bore. My car with a 396 in it ran 6.90 1/8 mile ETs and 11.20s in 1/4 mile. My 468 similair to what he says your motor is ran 6.70s and 10.50s as I recall. I can go look in the old books but that is pretty close if not right on. I think you got a camshaft and head mismatch. Get a casting # off your heads if you can. RM
 
#25 ·
The stock 781 castings with 2.06" valves flow in the 240 to 250 cfm range. Sounds to me like the car is running good for those heads. Maybe the car ran 6.90's with the High perf heads that didnt come with it when you bought it? Being that its for sure a standard bore engine, and not a 468, I suspect some parts were swapped before the sale.

What does it run in the 1/8 right now?
 
#27 ·
The heads are not high performance heads, stock oval ports basically. I always run the rectangle port iron heads. Closed chamber on the 396 combos and open chambers on the 468 combos. Those oval port heads can be reworked to run but that's about all I'd expect from them like they seem to be. JMO, RM

And being late at the tree doesn't slow down the ET. The ET starts when the car breaks the beam so the ET is right but the reaction time is bad.
 
#28 ·
So you lost 3 mph from the previous owners best, and then another 2 in the last year.
When you lost the head gasket, did you have water in the oil? Has the valve lash stayed consistent? I'm thinking the camshaft might be going away.

Another thing to think about is fuel. I switched from Sunoco Gt 100 to ERC 110 and lost 2 tenths and 1.5 mph. Have you switched fuels between this year and last?
 
#31 ·
What do you have for a converter? What brand? Stall? Looks and sounds like its blowing through your converter. As your RPMs go up in first gear your car accelerated less.

Sounds like the engine itself runs good though. Id guestimate you should be mid 10s on motor and break into the 9s on a 150 shot.

Your suspension dont look right either, it unloads way too fast off the line. Could be your converter doing that as the RPMs go up also.
 
#36 · (Edited)
Staging

I know that you're getting advice from all angles, but all I can tell you are my experiences.

I had the same problem with launching my Malibu that you describe. Because where I was racing was allways a pro tree (even for brackets), I knew that I would have to finely tune my launching.

What I ended up doing was making a homemade two-step, and using two line locks, front and back. At this point I'd like to mention that I had 3500 converter as well.

What worked for me was sitting the throttle position in the TRANSITION between primary and secondary's(mech. sec.). At this spot the motor would sit on the rev limiter. Too less or too much throttle and the car would creep. I launched about 2200, and I put the bigggest pump(secondary) and #30 dischargers in the carb. One button on my shifter when held down activated my two line locks and set bottom rev limit. Let go of the switch, at the same time pin it, and it was like being shot out of a cannon.(1.4 60ft on 8" wide slick STREET CAR)

IMO if the car isn't leaving crisp (on two step) then the carb setup isn't right. That thing sounds wicked, so if it isn't a mechanical problem(compression, cam) I think that I'd be looking at the converter.

Something else....When I watch your video, I think your front end is coming up too fast. This will sound a little strange.....but....what I did was instead of buying drag shocks was I found the absolute cheapest oil shock that I could and then removed the rubber stopper on the a-arms for more travel. It worked and was drivable on the street as well.
 
#37 ·
When U set the the line lock, how do u set it? Do U just pull up and stand on the brakes and then push the line lock button? Or do U push the line lock button and then pump the brakes till the pedal get's hard(what I do)? Do u just roll into the throttle or do U just stabb the throttle?
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top