evans280z Posted September 19, 2006 Share Posted September 19, 2006 whats the best stall to use with this combination for the 1/4 mile?400 sbc 40 over,double hump head(164/202 valves),solid roller cam 567 lift,flat top pistons,3:54 rearend,tires 26/8.50/15" Quote Link to comment Share on other sites More sharing options...
jap tin Posted September 19, 2006 Share Posted September 19, 2006 how much duration at .050 on the cam? Quote Link to comment Share on other sites More sharing options...
evans280z Posted September 20, 2006 Author Share Posted September 20, 2006 duration 242 Quote Link to comment Share on other sites More sharing options...
jap tin Posted September 20, 2006 Share Posted September 20, 2006 4800 rpm. Quote Link to comment Share on other sites More sharing options...
evans280z Posted September 20, 2006 Author Share Posted September 20, 2006 so i need a 4800 stall? i got 35-3600 stall in now and seem like its slowing me down why is that. seeing that you have more experience than i do Quote Link to comment Share on other sites More sharing options...
jakeshoe Posted September 20, 2006 Share Posted September 20, 2006 Converter selection is based on peak torque. A quick check on EA shows that combo as having a peak tq at about 4000, with almost the same at 3500 rpm. If it has a 3 speed auto you wouldn't go over a 4000 and would usually use a 3500 rpm converter in this combo. Otherwise you are leaving 500 usable rpm since torque is virtually identical at 3500 as it is a 4000 rpm. On a race application or with a two speed you would go about 3800-4000 rpm. You would want to speak with a converter manufacturer and be sure they know the weight of the car, the lighter car will cause a converter to not flash as high. 242@.050 is a fairly short duration cam in a 400+ cube engine, and it shows because peak HP is at 5000 rpm, if you have a converter that flashes to 3500, and you shift at 5500, that only leaves you 2000 rpm of usable power. Quote Link to comment Share on other sites More sharing options...
jap tin Posted September 20, 2006 Share Posted September 20, 2006 He already has a 3600 rpm converter and he says it seams slow. I say go with a looser converter. My first Z I took draging was a low compression 350, 8.5 comp, 1 5/8 headers 750 dp holley with a 5500 stall converter, it ran 10.90's with a 26X8.5X14 slick. That was with a TH350 trans. with a 3500 converter it was a slug, like pulling a skier out of the water with a old 25 horse evenrude out board. Call Coan and get a 8" converter for it and wake it up. Quote Link to comment Share on other sites More sharing options...
dr_hunt Posted September 20, 2006 Share Posted September 20, 2006 X2! Quote Link to comment Share on other sites More sharing options...
jakeshoe Posted September 20, 2006 Share Posted September 20, 2006 Too much converter slows a car down. I ordered a custom converter and asked for a 3400-3600 flash for a Chevelle I have, mild BBC combo. The conveter I received flashed 4400 rpm, well above my request, it slowed the car down 4 mph and .5 in ET in the 1/8th mile compared to a much cheaper 2200 converter. So basically I did not receive what I requested and because of my relatively low shift rpm of 5800 rpm and very limited rpm range, 1400 rpm, it didn't work. The car needed the converter I requested based on the torque curve. Simply installing a looser converter doesn't make a car faster. A tight converter always "feels" faster to me from a roll, and sometimes from a standing start than a loose converter. However the looser converter will work better on more rpm happy combos in a drag racing situation IF it isn't too loose. An advertised "5500 rpm" converter may not flash stall nearly that in a lightweight deep geared Z car. You have to base converter selection on engine torque, rpm range, (both based on CID and cam selection and compression) and the vehicle gearing and weight. GOOD converter manufacturers have built enough converters that they have a database to reference using all the vehicle parameters and hit the stall right where it needs to be. Coan is a good manufacturer I usually recommend PTC to my transmission customers but there are many good ones. PTC, ATI, Coan, Continental, etc. My best suggestion would be to call a couple of the manufacturers and ask their suggestions, be sure you have all the vehicle statistics and a TRUE expectation of what you want. Converter selection is like alot of other things, it is combo specific but there are trade-offs depending on the REAL intent of the car, is it a drag only car, a mostly drag with some street, or a street with some drag racing. If I were selecting a converter for it, there wouldn't be a huge difference in any of the different intended uses because the engine, vehicle weight and gearing have more to do with it, but there would be some variation. I would happily give up .1-.2 in the 1/4 for a much more streetable converter on a more street oriented combo, but on a drag only car, I would give up the streetability for every .01. Quote Link to comment Share on other sites More sharing options...
evans280z Posted September 20, 2006 Author Share Posted September 20, 2006 with the 3600 stall will switching to 3:90 rearend make any difference Quote Link to comment Share on other sites More sharing options...
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