I have a 355 w/ a th350, 9 inch w/ 4.30 gears. i ran a 11.86 @115 and at the end of the track the motor was screaming at 7000-7200. to me that seems way to hi for what i am running. the converter i have now is a b&m 2800-3200. now i know this could be a few things, but to me this sounds like the converter slipping. on my last run when i was doing a burnout my friends said that the car was screaming and that the tires were not smoking at all, but that was my best run that night. i just want to make sure that its worth the 800 i am going to put out for a good converter. any suggestions.

 

7000 at that speed would be about right for a 92% converter and 26" tire.

 

Assuming a 26" tall tire

Tire = 26"
Finish line rpm = 7000
Finish line MPH = 115
Gear ratio = 4.30

Calculated converter slip 8.7%

I consider anything under 10% as good.

 

i have a 28 inch tall tire forgot to mention that. how did you calculate that

 

OK, A 28" tire puts it at 15.23%. That's a little high but it might not just be the converter. The tranny itself could be slipping in high gear.

A have a little formula in a spreadsheet to do the calculation.

The calculated MPH is
=sum((tire diameter x finish line rpm)/(gear ratio x 336))

Calculated slip is
=sum(100-((finish line mph x 100)/calculated mph)

You should be crossing the finish line in the 120-125 mph range.

 

i jsut had the trans built over the winter, it has all the race goodies in it now. it better not be slipping in hi gear but i guess anything is possible. are you saying i should be crossing the finish line between 120-125 at that times i am running or with a faster et?

 

he's saying for your RPM you should be running XXX mile per hour. not your ET or MPH for that ET. 15% is quite a large amount of slippage, and you're running a rather small converter for a built up motor. I'm running a 3500 and the majority of my friends are running 4000+ and some street drive them with big trans coolers as well.

 

i was thinking around a 4200 stall. i have been in contace with ati converter but i dont want to spend 700 bucks if that isnt the problem. of course the guy at ATI said it was but he wants a sale. ok thanks for clearing that up about the rpms

 

I had a 3800 stall 10" converter. That would be considered loose compared to a 4000 stall 8" or 9" converter which would be considered tight. My current 8" stalls at 5700 on the transbrake however I haven't tested it yet on the new engine. It may stall higher now.

A quality converter is worth the price. My converter was $1200 and I've already had it rebuilt once but that was because of engines causing the damage. I crushed a torrington bearing and bent some fins. Trouble is, if my converter fails again, it can't be rebuilt. There's not enough metal left in the case to weld it back up again.

 

so scince 15% is a lot a converter might be a good investment then. what shuold i expect to see from that any idea?

 

You need a tighter converter. Getting a converter that will slip below 10% should get you in the 120-125 mph range.

 

i finally got my converter from ati yesterday. i called them and gave them all my specs and they built me one. it is a 8 inch and i tried it in my driveway and on the road i live on and it stalled up to 3500 and i nailed it and it jsut blew the tires off. i brought it up some more and it pushed the car forward. i have mt 28x10's on it and they went up in smoke. the lines i left we really dark and it feels pretty good. i am going to the track fri so hopefully it will run better. any predictions? later guys

 

I did a calculation on my converter slip from the last race. Only 6% slip Watching my playback tach, I see my rpm doesn't drop below 6100 all the way down the track so the new engine has bumped up the stall speed. I need to do a full transbrake stall to really see what the converter stalls at now.

 

I would say 11.0@120. B&M are Complete Junk IMHO, Ive seen about a dozen now either slip like crazy or so tight they wont stall over 1800 (in a 540 no less) ATI is quality stuff and an 8 inch is just what that 355 needs. Hang on cause its gonna be wild.

 

ok guys so tonight i fially got to the track its been raining ever fri night here it seems. so my best time was a 11.59 @ 117.9 with a 1.563 60'. the firs trun it kinda stayed at the same rpm when it got into 3rd gear. i didnt change anything the next run it pulled the hole 1/4. a couple of runs it felt like it fell off a bit on the shifts. like when it went from 1st to snd it kinda booged i guess you could say or studdered. on a couple of run it chattered the tires on the launch. i guess i got some dialing in to do still. man this is fustrating. i was expecting to pick up more than 2 to 3 tenths. well any more info will deffently be helpful. i plan on go going to a better preped track next week.

 

check your tranny, when my converter let go, it sent metal shavings all throught the tranny. mine was really bad, but its still worth a look

 

trans is fine just been built. it just feels like theres something left in it. i guess i will have to keep trying thing nd see what happens, and if not well it is what it is.

 

well got a few passes in scince new converter and ran a best of 11.455 @ 119.13. do you think with the listed combo above that a 750 would be better carb for this combo? if so what style, brand, etc........

 

Go with a Mighty Demon 750. They have an anti stumble feature built into them and are calibrated from the factory for motors with cams up to 260 degrees of duration @.050. I have ran mine with 4 different cams 244/252, 256/268 and 272/272 @.050 (solid flat tappets) and 266/278 @.050 (Solid roller) and it works flawless with all 4 cams. What kind of ignition are you running?

 

i am running a msd 6al box, msd pro billet dis. mech. advance, blaster 2 coil, moroso wires.

 

Do you have a 2 step module hooked up to your box?

 

no i dont

 

If you can afford one get one and an adjustable rpm module or chip. Set it to the the point just before your car starts pushing while power braking. Hook it up a momentary switch to activate it. It will allow you to put the throttle to the floor while engaging the 2 step (Holding the foot brake as well) and when the tree drops, release the switch and foot brake and BAM. This will help your 60 ft's and when the day comes when you put in a trans brake, you will have the neccesary electronics already to run it.

 

and this will help out the 60's what about the rest of the run. this is like a 2nd rev limiter right. i know what a trans brake does (i think) so this is kinda the same thing but a rev limiter. as you can tell i am kinda confused

 

Yes, it is a second rev limiter. Let’s say you have a 7k chip and a 3k chip in the 2 step. When you activate the momentary switch (that you hook up to the 2 step) only the 3k chip is activated. While this chip is activated you can open the throttle wide open and the motor will never rev past 3000 rpm's. When you deactivate the switch the 7k chip becomes active and the motor will not rev past 7000 rpm's. So you will be able to sit at the tree wide open throttle, only revving 3000 rpm's and when the last yellow light is lit, let go of the switch and release your foot off of the foot brake pedal. If you wanted to get pimpy you could install 2 line locks (one for the front and rear brakes) and tie these into the momentary switch that is used to control the 2 step and this would take away the releasing the foot brake pedal. This could help your total time because it will allow your car to come out harder out of the hole. Make sense?

 

yeah that makes sense. thats a lot going on off the light but hey i will deffently try this there not to expensive.

 

Or you could just install a transbrake. I don't think you'll get the car to stall up to 3k just holding down the brake. I know my car won't. If you want to leave the line hard, put in a transbrake and a 2 step.

 

i was thinking the tran brake to but from what you both are telling me is that i need both, or cant have one with ou tthe other. i can get my car to stall up to about 3500 with just the foot brake. 1bad406 congrats on the new best.

 

ah that new best is old, but the only video I have. I went 6.71 back in Feb.

 

i am looking into the 2 step but how about a cam swap the one i have is a 114 lobe speration so how about something closer any suggestions?
tommyboy any part number for that carb i saw them in summit/jegs but just want to make sure its the right one.

 

get something with 106 lsa if it's track only.

 

i called comp cams today and gave them all my specs about my car. the guy told me part number 12-908-9 heres the link to it in summit http://tinyurl.com/rdubw
the specs are 264/270 @ 50
.630/.630
106 lobe seperation

[ mod edited to prevent overflow ]

 

are you running a solid roller cam now? Just asking because I thought you were running a solid hydrualic lifter cam--the swap is going to be rather expensive. Are the performer RPM heads even set up for that much lift? I thought they were around .550-.575 max. from the factory. That cam is going to want more than 4000 stall but I agree it's better than what is in your car now. Should pick up much better with the 106 lobe separation, I'm running a solid lifter comp cam on a 106 lsa and besides it needing more idle RPM to keep the motor running, it's a real screamer above 3500 in my car, literally blows the slicks off on the street as well.

 

Jegs PN - 132-5402010GC

Are you running 5.7 or 6.0 rods? If you have 6.0 rods you may have to fly cut your pistons with the cam comp suggested. If you do get it, make sure you check the piston to valve clearance with a dial indicator and a soft spring installed. Check the Intake at 7-10 degrees after TDC and Exhaust 7-10 degrees before TDC. My cam is close to what they suggested, 266/278, 600 lift and I had to fly cut the intake .050 and exhaust .020 on the pistons.

 

tommyboy thanks for the part # on that carb that wasthe one i was checking out, so thanks. my cam now is a roller .577/.608 so i changed the springs on the heads from edelbrock, as well as put in screw in studs guide plates etc. my converter flashes at around 4200 and thats what it says on the cam. this by all means is not set in stone so any info would be great. you guys are the racers so this is why i want your guys input. my rods are 6 inch so i will ahve to check on that piston clearance.

 

Good link for this post.

PERFECTRUN RACER'S CHAT :: Torque Converter Slippage Calculator

a TON more here also....

Wallace Racing - Automotive Calculators
and here
Hotrodders Auctions.: Horsepower Calculator

 

Blue beast - your car's set up is very close to where I am heading - 4.30 gear 9 inch rear and Th-350 swap is what I adding now to my setup in sig - and 28x10.5x15 tyres - I also went with an 8 inch converter but I got mine set up by a smaller outfit out of NY - Protorque - good people to talk too

I also rebuilt my 355 - went with forged 11cc TRW dome pistons and looking for 12:1 compression out of my milled to 60cc WPII iron heads - but my car may be a little lighter than yours as I am all stripped out interior for drag use and lexan glass, glass hood,

I take it your times are N/A times - so you are actually running mid 11 sec times out of your combo - that would be great if I can get there N/A -My best so far on nitrous was 11.169

My best in former trim in sig N/A is 12.0 @ 112. - my cam is a solid lift but its only a 244/250 @ .050 duration cam - on a 105* lobe

I know you seem to be getting recommendations for large duration cams - my view is that you need higher compression to make power with these large duration cams

For me - I am sold on mid range torque oriented cams - mine is a short track oval grind and with the tight lobe - most pundits say these cams don't perform well with nitrous

I have had very good results with nitrous - my best 1/8 mile was a 6.9 but am hopeful that with the increased compression I can run mid to low 11's - which is my bracket class - without nitrous

How much does your car weigh? your n/a times are very good to my mind if you are close to stock weight

 

my car weighs in at 3205. caribbean how did you run 11.1 @ 104? that mph is slow. mistype i am assuming. anyway how much did you spray for that pass? i am abuot ready to say f it and go buy a motor already done all i got to do is drop it in and be done with it just tune it.

 

yeah I have been flamed all around for that time slip since posting it - no misprint at all

I lifted off throttle slightly to turn off nitrous WOT switch and up shifted to O/D at the 1000ft. marker during that pass - car was veering towards the middle marker cone - tried to coax it away - second time it did it near the marker I just lifted off quickly and up shifted to stabilize the car

I use 225 hp pills - I upgraded my Cheater system with a Big Shot injector plate kit - 82/91 jets

on that same pass I did my best 1/8 mile time of 6.944@98.25 on a 1.540 60 ft

Here I am amazed at your times with near to stock weight and you don't seem too satisfied

I think your car is doing well - my suggestion is to free up some of that hp with a weight reduction program - I went with manual steering box form a S-10 1986 model (that might not be practical if you are daily driver ) and perhaps an electric fan/ water pump combo swap. I went with the proform electric pump price and performance is excellent ( you will need an alternator bracket from Alan Grove Components to work with water pump) and an electric fan.

plenty search material here on weight loss ideas

and of course, I would still consider a more mid range torque friendly duration cam - thats what gets you down the drag strip

Finally you can always spray it - 150hp setting should have you in the tens easily - but that is always an option - I personall think you are a cam and couple pounds away from a low 11 N/A car

There is a book for our cars - how to run 11 secs. n/a in a F-body - I wish I had bought that book ten years ago - right before I decided to rebuild my LG4 305ci with flat top pistons and a big cam to boot looking for big power - I have learned alot since

keep at it - my dream for rebuilding the engine is to run solid 11 N/A - a real competitive class at our local track - and only use the nitrous for ***** out competition

Keep at it - it will come

 

i actually have a tube k member, a arms, manual sterring rack, all ac and heater gone. if you check out my car domain site u will see theres nothing in the engine compartment expect the motor. my car came stock with the electric fan motr so that still on there. no electric water pump yet. that book your talking about i actually have one somewehre i think its at the bottom of all my super chevys and chevy hi performance magazines. if i remeber correctly they start wit ha 400 small block. that always helps to. this by all means is not a daily driver to much money and time invested in it. check out my site and you'll see everything i have done.