Author Topic: QUESTION ABOUT CONVERTERS  (Read 593 times)

Offline dusterdave173

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QUESTION ABOUT CONVERTERS
« on: May 14, 2017, 08:34:30 AM »
I have had great luck with my first engine a little 355 CI with street heads and a circle track tight LSA small roller--It went 5.60 first pass ever and has done that for two years all with a "mystery" 8 inch converter I bought for $100 out of a pile at estate sale--I recently put a new 355 in with much bigger cam, a great set of max ported bigger runner heads--guessing it would run much faster--at the last moment I decided to leave the 'mystery" converter in and not use the new 8 in I had custom built just to see what would happen--well...darn thing ran exact same 60 ft it always does, same MPH, same ET
SO...I am guessing that converter has always been my limiting factor??? It seemed to MPH OK for the ET at around 122-123 so I guessed it was doing OK--it 60 fts around 1.20-1.22 all the time  so now I plan on dropping in the new converter and expect questions to be answered   My cheapo converter was always crazy loose acting but hey it worked and was fine for the "investment" LOL
Is that converter what was holding my other engine back? and now my new one? What do you guys think?
Thanks
I have always had a fascination with fast cars at the expense of more normal character development

Offline dusterdave173

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Re: QUESTION ABOUT CONVERTERS
« Reply #1 on: May 14, 2017, 08:36:15 AM »
I used that cam and other parts not because they were what I needed but what I got for stinking cheap when I was building my car
I have always had a fascination with fast cars at the expense of more normal character development

Offline BK

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Re: QUESTION ABOUT CONVERTERS
« Reply #2 on: May 14, 2017, 05:22:18 PM »
I went from 187cc intake runners to 215cc on a 355 once. Same converter same cam, almost the biggest flat tappet EP cam Engle sold. I needed to shift almost a 1000 RPM higher just to get back where I started.

Offline dusterdave173

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Re: QUESTION ABOUT CONVERTERS
« Reply #3 on: May 14, 2017, 06:21:13 PM »
That may be a direction--this engine has lots bigger cam with 108 LSA vs 106 on old cam--exact same pistons etc and I went from 195 runner to mack daddy ported 215 runner so guess I have to turn the $%^&* out of it  It is aluminum rod so first pass great second slammed a few plugs shut so have plug washers be here Monday--cutting it close!
Have Steel in Motion race this wk end--will run her hard and report back--chute out every pass for the fans  Google SIM it is an awesome show
I have always had a fascination with fast cars at the expense of more normal character development

Offline wideopen231

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Re: QUESTION ABOUT CONVERTERS
« Reply #4 on: May 14, 2017, 06:28:34 PM »
One thing I have learned about race car with auto trans is the converter  will make or break any combo.We changed  converter in lil brothers car and picked up .3 with no other changes. Loose will be consistent and tighter usually quicker. Most  converter guys can get you real close once you give them engine info.

My deal is set for 6600. Seems pretty close right now when checking in car.
Relecting obama is like shooting right foot because it did not hurt enough when you shot left foot

Offline ricardo1967

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Re: QUESTION ABOUT CONVERTERS
« Reply #5 on: May 14, 2017, 08:04:27 PM »
Hey Dave, do you have logged data of your runs? I think that would help to verify the converter match to your application.

Offline bikeguy307

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Re: QUESTION ABOUT CONVERTERS
« Reply #6 on: May 15, 2017, 10:16:00 AM »
A loose converter gives you a good 60ft but not so good mph for the et. When I switched my Roadster from 6600 down to 5800, I lost .02 in 60ft but my et was the same and my mph picked up almost 3. Im thinking the converter may be too tight, keeping the motor from getting into the power band of the camshaft. A tight conveter will have better mph than the et shows, your mph is more online with a 5.40ish et.

Have you stall checked this converter?

Offline masracingtd1167

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Re: QUESTION ABOUT CONVERTERS
« Reply #7 on: May 15, 2017, 01:34:07 PM »
Dave you really did the right thing by running the old converter first . Now by changing to the new converter you will be able to see a change bad or good !I agree that the better heads will want a little more RPM to take advantage of the power increase ! Knowing what the motor falls back to on the shift can give you a pretty good idea of the stall speed of the converter .

Offline dusterdave173

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Re: QUESTION ABOUT CONVERTERS
« Reply #8 on: May 15, 2017, 02:40:40 PM »
I plan on swapping it soon as I get a chance  Thanks everyone
I have always had a fascination with fast cars at the expense of more normal character development