I gotta agree....that MPH looks pretty weak. It's only picking up 19 mph on the back half.

Have you been through fuel system? Pump, lines, filters, float levels, floats not hanging on jet extensions, air horn not too close to hood, vents not restricted etc etc?

Sure sounds like it's running out of fuel. Does it sound alright otherwise?


JIM

 

Thanks for the reply its running a holley blue ..1/2 lines plugs looked good ....i think i might have been on the chip the last 200 ft or so ...was hard to tell but it kinda felt like it had a stutter to it my tach was staying right at 6800 to 6900 and I have a 6700 chip in the msd .. do you think it has too much gear ?? was going to put in a 4.56 a little later in the yr .

 

Yes you have too much gear. I'd suggest 4.11s with a 468". That will most likely pick up the top end some. It also sounds like your rev limiter is working as it should. I'd expect about 117-118 mph with that E.T. but it might even pick up more if it was on the chip before the end.

 

Like Jim said. You mph is pulling you down. 1/8th mile should calc. to about a mid 11.30@118.
Try a 7000 chip.
4.88+28.5"tire+118mph= 6800rpm. This doesn't account for any converter slip.
4.56's may be your best choice. May even pick up more ET and MPH.

 

With a small block i gain 25mph from the 1/8 to the 1/4 in one of my older set ups but that engine had no torque and all HP, your 1/8 mph/et is fine

How much gear you have in the back?

 

I am also thinking fuel issues. That thing is built for the top end with 320cc runners and 2 1/8 primary headers.

 

Yep, it's going to like to spin. Pull that chip out of it and see what happens. I've found that shift lights and rev limiters just annoy me!!


JIM

 

well I guess I will throw in a 7000 chip and put the fuel pressure gauge on it ...will the holley blue pump supply enough fuel ?? I have a mallory 250GPH just havent put it on yet...thanks again for the replys ...by the way i made 6 passes today 12.17 @ 111.35 ...11.68@112.13...11.68@112.46...11.54@112.79 and a 11.59@113.91...seems like that 112 is about all I can get out of her...the only changes were tire pressure 16 down to 14 and shock setting full soft to med a to hard ....

 

By the way your vette is way cool ...love the video ...sounds great going through the gears.

 

What kind of converter are you running? You say 4000rpms, is it an 8"? Correct if I am wrong but wouldnt this combo want some more stall? like 5500 or so?

I would think this combo should be in the 10s.

 

What kind of converter are you running? You say 4000rpms, is it an 8"? Correct if I am wrong but wouldnt this combo want some more stall? like 5500 or so?

I would think this combo should be in the 10s.

It could with that 1/8 mile if the HP was there on the big end, Too much gear or no fuel

I dont think it needs that much gear, i would say 5,000-5,400rpm stall and 4.10's with a BB like this

 

its a tci ....10" I believe ...yeah it probably would like more stall ...but I street drive this car alot cruise's and stuff like that ....and I am hoping to get into the 10's ...the track was so so today opening day...so it was pretty greasy ...

 

You can drive a big converter on the street, drive normal in low gear and tach it up a little in second gear and throw it to high gear and lift on the shift then get back on the throtle {sort of like a stick} and the converter will semi lock up, then when you go to accelerate from that steady speed you will feel it slip again, try it someday

 

the tire is a 295 drag radial it is 29.5 dia. would a 4.30 be better ...with the tire it would be close 4.11 right ...thats why i was thinking 4.56 which should put me a round a 4.30 or so ???

 

it was kinda hit and miss my worst was 1.95 2nd pass and my best 60 ft was 1.58 and that was the last run of the day ...air pressure was 14 psi and shocks set @ full stiff...it pulls the left front about 10 inches seems to have hooked pretty well ...the last time this car was on a track was about 1987 Detroit Dragway (R.I.P.) so its all about learning starting line rpm and shift points ...car has a trans brakeand a 3 step but i have havent used them yet .

 

The proper/well built converter can have a hi stall and be efficient. My 540bbc with a th400 and 4.86 gears has 6% slip at the top end. This is with a 6000rpm stall 9" spragless converter. I had the sam effientcy with My ATI 8" that stalled to 6400rpm with the same combo.

 

I've had several people tell me that a spragless converter never locks up and are real power wasters. If you have a 10" converter it should only be slipping somewhere along the lines of 300 rpm at the finish line. A car with a 4.88 gear and a 29.5" tire should be running 6200 rpm at 113 mph, plus slippage. That means your converter is slipping about 600 rpm or about 9 1/2%. This is excessive slip and will become worse if you reduce the gearing to 4.56s,4.33s or 4.10s. My son's car will stall at 5500 on the brake and still is only running 6900-7000 at 146 mph with 3.89 gears & 28" x 10.5W tires . The other 10" (tighter) converter only slips about 150 rpm at this power level.

 

thanks for all the replies ....I will look at dropping gear ratio and install my fuel gauge.

 

2-1/8" headers? I think Ed Henniman would call that a 3-tube size error...

 

Don't worry about gear ratio right now. Pull the chip out of the rev limiter. The fuel system is fine but should have a gauge. When I first ran mine it had a 427, powerglide, and 4.88 gears. This went 11.20 at 118 with 1 holley blue pump. I would run it as is for now, if anything the gear is helping it leave. See where you are under full power. If that cam is the XR292 it should go to 7000 without a problem. If that car gets into the low 11's high 10's a gear change then may be in order.

In fact I just found some old time slips all passes in the 11.20's were with 7.13-7.15 1/8 mile times at about 95 mph so this will give you an idea of where you stand.

 

thanks ...i'm gonna change the chip ..hook up the trans brake and try it again in a few weeks ..I'll keep you guys posted .

 

Chevelledave.....thanks...see what ignoring a rev limiter can do?

I'd leave it out until you figure out what it wants to do. The 4.88's are a lot of gear...but many a 454 has run them and trapped a lot better than 112 mph. Something is off here. We're not making the power at the end that we're making in the middle.

JIM

 

It on the rev limiter, plain and simple. He needs to put a 7500 chip in it and let it run. It would still probably bite better with a 4.56 or 4.33 gear and maybe even be faster and quicker.

 

OK so if the car was on the chip at say 1200 feet or so ...costing me ET and MPH ...what does that tell me about my converter ...do I need to tighten it up ..or is being on the chip messing up the percentage of slip ...what would the trap RPM and sslip be at say 118 MPH...what is the calculation used for this ...also what is this 9 1/2 % percent costing me in performance ??..Thanks in advance Dave.

 

I think theres a couple of ways of looking at a converter. My belief is to have the stall right at peak torque for a 3 speed and 4-500 rpm higher than peak with a 2 speed.
While the converter is "on the stall" it is multipling the torque. This will in almost all situations result in quicker ET's. I will gladly give up a small precentage of effientcy on the top end to gain the reduced ET by having the torque multiplied.
Some guy's say...use the torque range of your BBC to muscle the car down the trac and run a tight converter. They think by using more of a wide torque band they will go faster. What they are missing is the torque muliplication while on stall of a looser converter.

Which ever way you do it is cool. This is just my opinion.

 

just out of curiosity what kinda power you guys think this thing is making ,,,its a 71 chevelle full interior street car it weighs abut 3800 car and driver ??

 

To give you an idea, my combo made 540 dyno hp and weighed 3675 the first day out and went 11.20's. So it's hard to say with yours because the numbers aren't representative of a full run. And I agree with the 7500 rev limiter. The rev limiter should not be there in case you miss the shift light, it should be there in case something breaks. I have an 8000 rev limiter in mine and shift it at 7500.