Convertor adjustment for new combo

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B3422w5

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Hey guys, want to bounce this off you for thoughts.

old combo. 10 to 1 360, airgap, eddie heads with very minor work, Dougs headers, 950 hp, howards solid cam.. 260/264.. 565/ 565, on a 106, in at 102.. convertor flashed just over 5k behind this combo

new combo, 12.5 418, single plane port matched excellerator, 850 carb, same Dougs Headers, moderately ported same eddie heads 272 max at 550 lift, 2.05 intakes installed, very solid low lift numbers, same cam as above, but installed at 104 vice 102.
Wondering where i would want this to now flash.... my thoughts, extra torque and compression would probably make the convertor now flash 5200 ish.
With the small heads i am guessing i would want it to flash 4700 is, so tightened up 400-500 rpm... does this sound about right.
Shop that screwed this together for me thought more like 4500 flash, to me that seems a bit low... thoughts?
I am aware the heads are small, and the torque peak will come in pretty low. I was always taught optimal was 300 or so rpm over peak torque?
 
I think I’d leave it and try it where it is. More cam, more compression. But I would also put that 950 hp back on.
 
Sorry not sure where I got more cam from. My thoughts are still similar though. Your torque peak won’t change more than a couple hundred rpm. But I also know you bracket race this car and dialing it in precisely is important. I’d see how the new combo affects the converter before I re-stalled it.
 
I agree with above, id try it as it is, to see how it reacts, and whether i liked it.
However... unless you plan on revving it to the same rpm as the 360, i would expect to tighten it up some. I think the torque will launch it, and the mph improve with it tighter. .
 
33IMP said:
I agree with above, id try it as it is, to see how it reacts, and whether i liked it.
However... unless you plan on revving it to the same rpm as the 360, i would expect to tighten it up some. I think the torque will launch it, and the mph improve with it tighter. .
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I only shifted the 360 at 6100-6200. Had all stock bottom end, still went best of 11.26 at 3300+
This one probably shift at 6300-6400
 
I think your pretty much correct in your thinking. My combo is pretty close to yours it sounds, your heads are a bit better i'm still on a 2.02 valve intake small tti step headers and apprx 11.25:1 same duration cam 750 holley, looking to try a 950hp and i'm flashing right about 4800 off the line by the looks of the gopro in car and shift 6500. has run 10.56 with apprx 3350lbs and 4.10 gear. Not sure where your goals are but it will get your attention off the line.
 
I had a convertor built by ATI for my car when my last one broke. I told them I wanted an 8" 5000 stall convertor as that's what I broke, but was a different make. At the time I had a 440 10.5:1 but was planning on putting my 360 back in so that's the specs I gave them to build the new convertor to. The 440 ran 11.2s. Car weighs 3030lb with the small block, never weight it with the big block. The new convertor pretty much did everything the old convertor did before it broke, but picked up very slightly in mph. When I put the 360 back in the car it had Edelbrock heads, 10:1, ran 11.70s. My dad built a 408 short block and stuck the Edelbrock heads on and ran 7.00s in the 1/8 (never went to a 1/4 mile track that year). This year he swapped the Edelbrocks out for Trick Flows 190. We shifted all the motors at 6000 and they trapped 62-6400. I'd atleast try your current convertor and see how it does before changing it. I have a uncle who races a chevy that has had 2 convertors built and tried 2 other ones from friends. I know some were 8" some were 9". Some would 60' harder, some would mph more but they all ran within a tenth of each other. Car runs 9.70s and has a PG. He did all the testing on back to back weekends as he was trying help his spot on the tree. I think unless the convertor is completely off it will more than likely be good enough unless your trying to get every last .001 out of the car.
 
scampy said:
I think your pretty much correct in your thinking. My combo is pretty close to yours it sounds, your heads are a bit better i'm still on a 2.02 valve intake small tti step headers and apprx 11.25:1 same duration cam 750 holley, looking to try a 950hp and i'm flashing right about 4800 off the line by the looks of the gopro in car and shift 6500. has run 10.56 with apprx 3350lbs and 4.10 gear. Not sure where your goals are but it will get your attention off the line.
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Thanks. My heads dont flow big numbers at all(272 max) but low numbers are very solid. I have 1 5/8 Dougs headers.
I am hoping for 10.70’s in good air.
Just talked to the convertor guy. Gonna send it out a week from Monday. Want it closer than it is now.
My guess is it would have flashed 5400ish behind the new motor. That's way to much when i am gonna likely shift it at 6300-6400
 
I think you are pretty close, I would think 4800-5000 would probably be optimal...but that's just my guestimate.

Edit: Mine flashes a little over 5k...not sure on the exact number because I always forget to look.
 
Well I know you said you’re already sending it in but if it’s a tight 5000 and flashed to 5200 with the old engine, 5300-5400 wouldn’t be terrible with the new engine. Especially in a race only deal. It sure would be nice to have a comparison with a before and after but I bet you will pick up a little ET if it does indeed flash to 54-5500 with more torque from the bigger engine.
 
TT5.9mag said:
Well I know you said you’re already sending it in but if it’s a tight 5000 and flashed to 5200 with the old engine, 5300-5400 wouldn’t be terrible with the new engine. Especially in a race only deal. It sure would be nice to have a comparison with a before and after but I bet you will pick up a little ET if it does indeed flash to 54-5500 with more torque from the bigger engine.
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it was actually loose with the 360
I had a 4500 flash 727 convertor and trans and went 1.62 and a best of 11.26 with the car.
Took the 727 out, replaced it with a good 904, and bought a convertor. After the swap, car went best ever 11.33, and 60 footed 1.52. Also ran less mph than the 727 did.

so the 904 setup was a tenth faster in 60 foot, but 7 slower in the 1/4 at less mph.
I have actually had 416 eddie head deals before. With these small heads, torque peak is pretty darn low, and peak power probably wont be much( if any) over 6000.
I really think a 5400 convertor would hurt the mph a bunch.
My old eddie combo had a 727 and ran 10.70’s with a 1.44 60 foot with a 4800 flash vert. Those heads were not fully ported either, similar flat tappet this motor has, bit less compression. Was done past 1100 feet.

i do street drive the car too, but how its manners are aren't much of a considerstion...lol
 
I dropped my gear from the 4.30 back to 4.10 to help bring the rpm down a few in the traps. I may try shifting back to 6400, so far going from 6600to 6500 seemed to have no effect. My drop back is to apprx 57-5800 on the shifts so its a small window. My heads are just the "stage one" deal from hughes so like 250ish by their charts. I think you will make your goals with ease unless your weight is way up
 
B3422w5 said:
it was actually loose with the 360
I had a 4500 flash 727 convertor and trans and went 1.62 and a best of 11.26 with the car.
Took the 727 out, replaced it with a good 904, and bought a convertor. After the swap, car went best ever 11.33, and 60 footed 1.52. Also ran less mph than the 727 did.

so the 904 setup was a tenth faster in 60 foot, but 7 slower in the 1/4 at less mph.
I have actually had 416 eddie head deals before. With these small heads, torque peak is pretty darn low, and peak power probably wont be much( if any) over 6000.
I really think a 5400 convertor would hurt the mph a bunch.
My old eddie combo had a 727 and ran 10.70’s with a 1.44 60 foot with a 4800 flash vert. Those heads were not fully ported either, similar flat tappet this motor has, bit less compression. Was done past 1100 feet.

i do street drive the car too, but how its manners are aren't much of a considerstion...lol
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Yea that’s kinda what I meant although re-reading my post it wasn’t clear. I meant I bet you will pick up a little by having it reflashed a little lower with the new engine if it does flash to 5400 or so. I knew you had your car pretty well sorted and foot braked it, but I’m really surprised by the mph drop with the 904. You attribute that to the converter alone?
 
TT5.9mag said:
Yea that’s kinda what I meant although re-reading my post it wasn’t clear. I meant I bet you will pick up a little by having it reflashed a little lower with the new engine if it does flash to 5400 or so. I knew you had your car pretty well sorted and foot braked it, but I’m really surprised by the mph drop with the 904. You attribute that to the converter alone?
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Yes i do. Its amazing the 60 foot picked up a whole tenth... typically 8... usually 1.54, but went 1.52 a bunch in good air.
Yea, i lost 7 hundreds and about 1-1.5 mph... sloppy in high gear is what blame it on( convertor) Slowly gave back ET further down track i got.
Only other possibility is the tranny has a brake( which i have yet to use) and have wondered of that effects ET at all
A&A brake.... but i doubt it.
I honestly figured, having gone 11.26 with the 727, that the car could come close to threatening the 10’s after the swap
Boy was i wrong...lol
 
Don, when I went form my 408 to the 434 I followed Lenny's suggestion and didn't have anything done to the converter. After the first pass one of my buddies asked if there was problem with the transmission as he couldn't hear the shifts. It slowed down everywhere, the 434 was driving through the converter. It went back to Ultimate once, then to PTC. In the end I wound up with a new Coan.
 
Another anecdote : there was a guy who raced at our 1/8 mi.drag track with a 51 chevy coupe, with a small inch sprint motor that he shifted at 8000+. Lots of people told him his trans or converter was garbage, eight grand from one end to the other, sounded like he left in high gear. He thought the converter was perfect, it stalled at six grand......
He finally changed converter, picked up almost a full second.
 
33IMP said:
What were your eighths with the 904 vs the 727?
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i honestly don't remember the 1/8’s back with the 727, could try to dig up some old time slips. Ran more 1/4 then, track changed to just 1/8 two years ago, except test and tune nights.
With the 904 they were mostly low to mid 7.20’s, ran some high teens in real good air. 94+ mph, never hit 95 that i can remember
 
justinp61 said:
Don, when I went form my 408 to the 434 I followed Lenny's suggestion and didn't have anything done to the converter. After the first pass one of my buddies asked if there was problem with the transmission as he couldn't hear the shifts. It slowed down everywhere, the 434 was driving through the converter. It went back to Ultimate once, then to PTC. In the end I wound up with a new Coan.
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i can understand that. But i am going from a 10 to 1 stock stroke 360 to a 12.5 to 1 418 stroker.
I am 99.99 percent sure the convertor will flash probably 5400ish behind the new motor, based on what it flashed behind the old motor. If i didn't change it.
I am also 99.99% sure that this new motor wont run anywhere near its best hitting at 5400when peak torque will be probably 4500 with such a small head. These heads dont go 290, they peak just over 270, and that is at 550 lift.This thing will be a tractor..lol
 
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