Disappointing ET's with 408 - UPDATE

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jimmyray

jimmyray

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Update of your great reccomendations from this thread:
http://www.forabodiesonly.com/mopar/showthread.php?t=34341

A little history:
1st trip to track - Best time 13.95
afterwards, changed to new fuel pump, new spark plug wires
2nd trip to track - Best Time 13.42 (est)
afterwards, changed to Holley 750 DP with proform body
3rd trip to track - best time of 12.88

YOU WERE RIGHT!!! Car pulls much harder on top end with the Holley, and dropped over 1/2 second E/T!

Now we're talking! We had to cut the trip short at only 3 runs (13.12, 12.92, 12.88), as the timing chain cover was leaking a bit of coolant around the water pump inlet holes on the Drivers side. We let it cool, retightened, and it quit leaking. Hope I don't have to pull it off!

Launched were limited to 2500-3000 rpm, then feeding in the peddle off the line - traction limited. Afraid of slicks with an 8.25 rear!

I was introduced to a cool site for an online engine dyno http://www.speedwaybids.com/tech/ezonlinedyno.html
that indicated my E.T's are in the ballpark with my cam and compression. Should have pushed for 11:1, instead of my current 9.6:1. Been running 93 octane with no ping. Last fill up, I tried blending 1/4 tank 93, 3/4 tank 89 octane, still no ping!

I think there is another 0.300 to be had with tuning and better launches, but the online dyno indicates I may be hitting the limits of the motor. See attachment for details.

Also, I went the the Mopar Southern classic at the Atlanta Raceway (Nascar track), where that night they setup the pit road for 1/8 mile runs. Raced 10 times, won 8, and only lost to the same Chevelle because he jumped the start (arm drop). We stayed even the entire run, though. Below is pick of a Fox Body with slicks that I took easily.:-D We had to drive back on the track (wrong way) to get back to the starting line - How cool is that!

Atlant Show Drag Medley.jpg


Online Dyno Est.jpg
 
awesome! so what changes did you make, i saw you said it ran harder with the holley. were you running a edelbrock before? what cfm holley & eddie?

nice work!
 
More proof that Edelbrock carbs suck for performance. Glad you got some good results!
 
You beat the Mustang?!? But, how can that be? He has a hole cut in his hood with a big thing sticking out of it! His car has to be quicker than yours!:toothy10::toothy10::toothy10:
 
My 2 cents...

Don't waste your money on a header upgrade unless you go to a full length 1 3/4 or 1 7/8" tube header. They hang down and suck for driving on the street. Stay with the hang down hookers you got for the moment. Dougs and tti fit better, but you won't see any significant performance increase with either set up. Especially for the money they charge---BTDT You say you have 2" pipes exiting the mufflers... can that, as it's a restriction point. 2.5" all the way out the back is what you need or turn them down right after the muffler.

Work on the fuel system to insure adequate delivery. 3/8 minimum from sender forward. A 750 proform just isn't big enough to feed that beast.

Get the distributor timing/advance curve figured out. Simple as a spring change, but a pain on some mopar distributors.

Get it so it will hook. Work on leaving at different RPM's to see what the car currently likes. I had a car that ran 9.40's and it hated to leave loaded on the convertor. Load it against the verter and it would act all funny, left lazy. Leave at 1500, stab it, and it would stand on the bumper w/ 1.30 60'. Your car should run very low 12's pretty easy, IMHO. It should run 11's if you can get it to leave hard. If you could get it to 60' in the 1.4-1.5 range, that will pull roughly 1 second off the big end.

That engine should make close to, or exceed, 500hp when dialed in. I have a 360 with mild ede's ported, juice roller, slightly less duration, more lift, that we expect to make right at 500hp.

Best advice I ever got and live by to this day... Over-chassis and under-motor. Get the chassis sorted out and the car will ET regardless of engine. Lots of guys just throw more power at a car that doesn't work. Yeah they eventually go faster, but, with a working chassis, it's much easier. It's fun to watch a 450-500hp car that works take out a 700+ hp car with a bad chassis. Happens a bunch.

If possible, CHANGE ONE THING AT A TIME using a scientific approach. That way you know if THAT change was positive, negative or same. If you change more than one thing at a time, you have no idea which change was beneficial.

It's a work in progress... make it fun, a learning experience and keep a log book of changes. That way you know where you've been.

I did a quick deal using camquest and it came up with 484hp at 6000rpm and 494tq at 4500 using some rough guesses of what you have XR286HR and ede's with 250-260 flow. It improved to 499hp using a 950hp carb
 
Launched were limited to 2500-3000 rpm, then feeding in the peddle off the line - traction limited. Afraid of slicks with an 8.25 rear!
Click to expand...
PING clunk clunk clunk clunk clunk clunk clunk.
 
74Burntorange said:
dont use slicks then.... use mickey tompson radials
Click to expand...

I do have a set of M/T 14" G (equiv 255/60's) series Indy SS tires with the "hot and sticky" compound, wonder if they would hook better if I warmed them up first. Only problem is that they are 26" tires, which effectively increased the gearing (from 4.10 to 4.42), and may negate the advantage to stickier tires.

Thoughts?
 
the indy ss tires are alitle better than a standard radialtire and i would think alot better than a lowprofile tire, i would try them if i had them however they are not going to hook like a diagonalslick not even close but they hook alitle better atleast, just dont overdo the burnout with them just give them a quick heatup just so they start smoking and then let of if heated just alitle to much all traction just disapere:( my experience is only from the street but its my thoughts
 
There are also a few people running slicks on this page with 8 1/4 maybe ask what they use
 
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