Ford Muscle Cars Tech Forum banner

1 - 20 of 86 Posts

·
Registered
Joined
·
1,506 Posts
Discussion Starter · #1 ·
Well guys...I am TOTALLY baffled and confused

How the HELL can I go from a 1.94 60' time from last year, to a 1.73 60' Today and STILL run my old 13.4 E.T with 6mph less trap speed?
The car launched like a rocket from the start all the way to the 330 mark and then seemed like it quit. What the F**k happened!

Here are last years numbers on the left and today's on the right:

60'.....1.944 60'.....1.736
330....5.644 330....5.352
1/8....8.632 1/8....8.420
mph...82.16 mph....79.42
1000..11.224 1000...11.112
1/4....13.423 1/4.....13.404
mph...104.35 mph....98

Ok, the temp. outside was hot. It was 85* with 34% humidity. It was much cooler last year when I ran those numbers but still.....

Here are the changes I made to my car since last year:

Sumped fuel tank with Holley Blue pump an -8AN line
Went from a 3310 Holley to a 4150
Replaced 2400 converter with an Edge 3700 stall

I'm hoping it's only because my new carb. needs tweaked or because of the hot weather today.....or both.
I don't like how my mph speeds are down either. It means I lost HP somewhere... a lot of HP!

If I had today's low end numbers with last years top end numbers, I would be in the 12's. I don't under stand how I can gain over 2 tenths in the 60' and NOT run any better on the top end. I though .2 in the 60' usually means about .4 in the 1/4 E.T?

I need some help guys.
 

·
Registered
Joined
·
501 Posts
I see you went 1300 more RPM on your stall. Did you raise the shift RPM to take advantage of the added stall? May be the valve springs cannot handle the added RPM's. WIth that much stall the cam is also a little on the small size(IMO). Just some things to look at.
 

·
Registered
Joined
·
1,506 Posts
Discussion Starter · #5 ·
No, I didn't raise the shift points. I kept it at 6K, like I did last year.
Should I have raised the shift points to around 6500?
Is it possible to have too much stall for the track? I don't have any drivability problems with it on the street. There is a slight rpm raise when going from cruising to full throttle though.
 

·
Registered
Joined
·
1,305 Posts
Sounds like you ran out of fuel... Did it flatten right out or bog/studder?
 

·
Registered
Joined
·
501 Posts
On 2006-05-28 14:30, 82GT wrote:
No, I didn't raise the shift points. I kept it at 6K, like I did last year.
Should I have raised the shift points to around 6500?
Is it possible to have too much stall for the track? I don't have any drivability problems with it on the street. There is a slight rpm raise when going from cruising to full throttle though.
As long as the engine will pull to 6500 I would try and shift at 6500. But if it is going flat before 6500 the raise will not help you. Lokks as you picked up .21 to 1/8 mile so you mast have started to flatten out around 450ft. Did it flatten out between 2nd and 3rd or was it after you shifted into 3rd? If it happened between 2 and 3 you could be having and issue with the transmission. I have had that issue before when the car would quit pulling between 2 and 3 then I would grab another gear and it would start pulling again. Something to think about.

_________________
68 Cougar XR7 306 C-4 AKA: "Heartbreaker"
1/8 mile 6.91 @ 99mph 60Ft 1.46 Wheels up 11.06 @ 121mph 1/4 mile


<font size=-1>[ This Message was edited by: econodrag on 5/29/06 6:28am ]</font>
 

·
Registered
Joined
·
1,506 Posts
Discussion Starter · #8 ·
It will rev to 6500 without problem. It seems to quit pulling between 2-3
Even my 15yr. old son, who was watching, said my car seemed to lose power after the 1/8 mile. He said the engine didn't sputter or anything...just seemed to slow down.
With a Holley blue pump and -8AN hose from sump to regulator and -6AN from regulator to carb. I should be able to feed it plenty of fuel.
What if I bumped fuel pressure from 5 to 6psi or so?
I'm going to check my fuel filters and see if they are clogged maybe.....
 

·
Registered
Joined
·
501 Posts
"It seems to quit pulling between 2-3"
Could be a problem with the transmission.

"What if I bumped fuel pressure from 5 to 6psi or so?"
I run a minimum of 6 1/2 psi on all of my cars. So it could be fuel related.
 

·
Registered
Joined
·
1,506 Posts
Discussion Starter · #11 ·
On 2006-05-28 15:28, econodrag wrote:
"It seems to quit pulling between 2-3"
Could be a problem with the transmission.
Ooops...I meant to say it seemed to quit after I shifted to 3rd gear......it flattened out.
 

·
Registered
Joined
·
55 Posts
Hmmm.....your mph is down at both the 1/8 mark and the 1/4 mark.That means HP is down. The ET is being supported by your other improvements (converter).If it were me,I'd put the old carb back on for a session and see what happens.If it's better then tune the new carb to make it work.If not,you will be on a detective mission to find the missing power.It's in there somewhere.


Terry
 

·
Registered
Joined
·
2,617 Posts
I think it's gotta be in the carb jetting... the combination of both warmer weather (less hp) and air/fuel being off could easily cut 20hp without you noticing it 'running bad'. I'd get some clean spark plugs, make a full throttle run, check the plugs and bump the jets a couple sizes one way or the other depending on how the plugs look.
 

·
Registered
Joined
·
1,506 Posts
Discussion Starter · #14 ·
I can't slap on the old carb because it was sold on Ebay to help offset the price of the new DP.
I think my jetting is currently 69 primary and 76 secondary.
 

·
Registered
Joined
·
1,233 Posts
what rpm are you turning at the 1/4? is it the same rpm before you changed the converter?
 

·
Registered
Joined
·
1,950 Posts
On 2006-05-28 16:22, Motorhead wrote:
I think it's gotta be in the carb jetting... the combination of both warmer weather (less hp) and air/fuel being off could easily cut 20hp without you noticing it 'running bad'. I'd get some clean spark plugs, make a full throttle run, check the plugs and bump the jets a couple sizes one way or the other depending on how the plugs look.
He's on the right track. The carb is just leaning out at the big end. You've improved torque a bunch but only while the bowls are full. You need to watch the fuel pressure. It sounds like you're draining the bowls.

1) Install fuel gauge and see
2) You might need to bump the pri and sec jets a bit

If you have access to a chassis dyno you could tune this out but you need to run it from 1st - 3rd (which can be done if the dyno guy knows what he's doing...) and mimic the fuel conditions...
 

·
Registered
Joined
·
1,506 Posts
Discussion Starter · #19 ·
I am turning about the same rpms through the traps as last time(~5600).
I also have a fuel pressure gauge mounted on the carb but I can't see it during a run.
My friend has also mentioned that I should check my float levels because, even though I bought the carb. rebuilt, it's hard to set the floats correctly without it being on the car.
This would all make sense then what you guys are suggesting. I probably have enough in the bowls until the 1/8 mile and after that, it can't keep up anymore.
How do you check which set of jets need to be changed?
 

·
Banned
Joined
·
2,833 Posts
I'd say you're to rich. With the DP you get alot more fuel the whole start of the run. With the 3310 it came on when the carb needed it. Jet down. Had the same issue with a 850DP. Especially when it's hotter.
 
1 - 20 of 86 Posts
Top