Torque converter advice - Hot Rod Forum : Hotrodders Bulletin Board
Hotrodders.com -- Hot Rod Forum



Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans Advertise
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Transmission - Rearend
User Name
Password
lost password?   |   register now

Reply
 
LinkBack Thread Tools
  #1 (permalink)  
Old 10-20-2019, 05:21 AM
Registered User
 
Join Date: Jan 2016
Posts: 73
Wiki Edits: 0

Thanks: 8
Thanked 1 Time in 1 Post
Torque converter advice

Hi guys!

I'm a manual guy who has a c3 corvette with a th350. It's a bit of a 2 sided question, what converter would you advise? And is it possible that a cheap converter slips at higher rpm/higher speeds?

My engine spec is as follows:
350 4 bolt main
Lunati barebones cam, equivalent to the compcams 268.
416 heads with 1.94" valves.
Edelbrock intake and short headers into a true dual system.

The transmission is a th350, rebuilt with a hardened sprag race etc, transgo kit into a 3.55 rear end.

The combo works well, especially for a 0-60 pull, I get a consistent 4.9-5s as a 0-60 time. But what annoys me is the top speed. At about 90mph I'll be at 5k rpm. Almost as if the converter is too loose at higher speeds.
Is it possible for a cheap converter to do that? I bought a 10" jegs converter for a whopping 120$. Stall was advertised at 2.2k rpm. I guess you get what you pay for, but is this a typical thing for cheap converters? Or just bad luck?

Happy to hear your thoughts!

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 10-20-2019, 05:48 AM
55 Tony's Avatar
Registered User
 
Join Date: Nov 2018
Location: Cocke County, TN
Posts: 1,123
Wiki Edits: 0

Thanks: 135
Thanked 194 Times in 173 Posts
From everything I've heard, the TC sucks. So does mine and it's from TCI and wasn't nearly that cheap.
__________________
Young enough to learn ... too old to remember.
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 10-20-2019, 06:04 AM
'49 Ford Coupe's Avatar
1949 Ford Coupe RESURRECTION
 
Join Date: May 2012
Location: Austin, Texas
Age: 75
Posts: 548
Wiki Edits: 0

Thanks: 39
Thanked 88 Times in 76 Posts
I just woke up so forgive me... the first thing that comes to mind is that your RPM and speed once you are in high gear should be proportional to each other have you done the math yet? And if it is slipping a whole lot then I don't see how you wouldn't overheat something if you ran very long at 90. I guess I'll go get some coffee
Reply With Quote Quick reply to this message
 
  #4 (permalink)  
Old 10-20-2019, 06:08 AM
'49 Ford Coupe's Avatar
1949 Ford Coupe RESURRECTION
 
Join Date: May 2012
Location: Austin, Texas
Age: 75
Posts: 548
Wiki Edits: 0

Thanks: 39
Thanked 88 Times in 76 Posts
The 350 came in a "C" version with a lockup converter. That should help here's some info.
http://www.novak-adapt.com/knowledge...utomatic/th350
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 10-20-2019, 06:14 AM
'49 Ford Coupe's Avatar
1949 Ford Coupe RESURRECTION
 
Join Date: May 2012
Location: Austin, Texas
Age: 75
Posts: 548
Wiki Edits: 0

Thanks: 39
Thanked 88 Times in 76 Posts
Better yet, spend the rest of the day on this...you will be an expert by sundown..

https://www.google.com/search?q=th35...obile&ie=UTF-8
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 10-20-2019, 10:22 AM
chasracer's Avatar
True Hotrodder
 
Join Date: Oct 2018
Posts: 610
Wiki Edits: 0

Thanks: 41
Thanked 140 Times in 124 Posts
Use of the vehicle? Is this trans the original unit that came with the car? If so, Jegs tells you that the convertor you purchased is not intended for this transmission type - so let's not blame the torque convertor as connected with a typical TH350 it probably works just fine.


Either purchase a convertor tht is correct for this trans or change out the trans to a non-lockup type unit.
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 10-20-2019, 02:41 PM
ericnova72's Avatar
More for Less Racer
 
Join Date: Jan 2007
Location: S.W. Lower Michigan
Age: 52
Posts: 17,627
Wiki Edits: 0

Thanks: 271
Thanked 3,191 Times in 2,679 Posts
What is your rear tire diameter, so that we can figure what the RPM at 90 mph should actually be, to see if you really have a problem??

27" tire and 10% converter slip is 4300 rpm, 26" tire and same slip is 4600 rpm roughly..... a 25" tire diameter would put you very close to 5000 rpm.

A 10" converter that only stalls 2200 rpm is not a high quality piece....you get what you pay for and $120 is nothing. Anything decent is going to cost you in the vicinity of 4 bills.
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 10-20-2019, 03:38 PM
Registered User
 
Join Date: Oct 2016
Location: United States
Posts: 304
Wiki Edits: 0

Thanks: 116
Thanked 76 Times in 63 Posts
The first thing I see is 350 4 bolt main with 1.94 intake in ****416 heads. CC: Engine RPM falling or poor performance above 5,000 RPM. This is exactly what you would expect with 416 heads.

The 416 head is a 305 head and will never flow enough even with 2.06 intakes. Begs the question... what is your exhaust size? The engine, (any engine) is just an air pump, and that is all it is. Chevy small block always has trouble with exhaust scavenging. 416's with 1.94's had 1.5 exhaust and is too small for the flow you need at the RPM you want to run. This is the primary reason most cams are dual pattern units that are typically .010 inches deeper and 10 degrees @.050 longer on the exhaust side to help increase the removal of the exhaust gasses (scavenging). Also you have a volume flow that is a 15% increase over the heads' original design criteria. There are just too many aftermarket aluminum heads out now that will be a much better match for the 350, and still keep the 58 cc chamber if that is a chief consideration.

On the TC question: yes, get a good quality TC in the 2200 to 2500 stall range. If the TC is failing at the RPM you mention, you are looking for catastrophic failure right around the corner. What is Trans Temp doing when you are noticing the problem? If you don't have a trans temp gauge, I would get one and check the temp when you see the trouble. Its's a data point that might help diagnose a potential problem.

On the tranny, if its not, I would go with a 350C as previously mentioned, or a 2004R, or a 700R4, both have lock up TC's.

On the scavenging issue do the math, and you might try 1.6 ratio rocker on the exhaust valves. See if that improves things.
Reply With Quote Quick reply to this message
  #9 (permalink)  
Old 10-20-2019, 05:41 PM
Registered User
 
Join Date: Jan 2016
Posts: 73
Wiki Edits: 0

Thanks: 8
Thanked 1 Time in 1 Post
I can go over 5k rpm in 3th, maybe I misworded it ( not a native english speaker).
The 5k at 90mph was just an example. I can go to 6k (and over) if I wanted too.
Little video of my "problem", just playing with the throttle gives me about 1k rpm difference. It just doesnt feel tight enough for me.

https://youtu.be/ACZLXKgYaJI
Reply With Quote Quick reply to this message
  #10 (permalink)  
Old 10-20-2019, 05:42 PM
Registered User
 
Join Date: Jan 2016
Posts: 73
Wiki Edits: 0

Thanks: 8
Thanked 1 Time in 1 Post
Tyre is a 255/60/15 btw, wich is 27.2 iirc?
Reply With Quote Quick reply to this message
  #11 (permalink)  
Old 10-20-2019, 06:05 PM
Registered User
 
Join Date: Oct 2016
Location: United States
Posts: 304
Wiki Edits: 0

Thanks: 116
Thanked 76 Times in 63 Posts
Quote:
Originally Posted by ImDusky View Post
I can go over 5k rpm in 3th, maybe I misworded it ( not a native english speaker).
The 5k at 90mph was just an example. I can go to 6k (and over) if I wanted too.
Little video of my "problem", just playing with the throttle gives me about 1k rpm difference. It just doesnt feel tight enough for me.

https://youtu.be/ACZLXKgYaJI
Saw the video, not sure what it's showing. Were you pulsing the peddle and rpm gains but car doesn't change acceleration?

If that's the case, you need to take to trans shop.
Reply With Quote Quick reply to this message
  #12 (permalink)  
Old 10-21-2019, 01:23 AM
Registered User
 
Join Date: Jan 2016
Posts: 73
Wiki Edits: 0

Thanks: 8
Thanked 1 Time in 1 Post
It does accelerate. But to me it just feels like the 1k rpm spike is too much slip coming from the converter. I might be wrong, not being used to how automatics drive..
Trans should be good, it's a rebuilt unit anyway and does the same in all gears
Reply With Quote Quick reply to this message
  #13 (permalink)  
Old 10-21-2019, 05:44 AM
ericnova72's Avatar
More for Less Racer
 
Join Date: Jan 2007
Location: S.W. Lower Michigan
Age: 52
Posts: 17,627
Wiki Edits: 0

Thanks: 271
Thanked 3,191 Times in 2,679 Posts
If the video was showing what happens when you stand on the gas while cruising and it flares in RPM like that, then it is definitely a poor piece, either it is poorly designed and made, or something has gone wrong inside of it....a 2200 rpm stall converter should flare maybe 200-400 rpm doing the same thing you did in your video, at cruise rpm above 3000 rpm.

On thing I did notice from the video...unless the sound quality was really bad, it does not sound like the tach is accurate at all....motor didn't sound at all like it was jumping to the 4000 rpm indicated by the tach.
Reply With Quote Quick reply to this message
  #14 (permalink)  
Old 10-21-2019, 06:22 AM
Registered User
 
Join Date: Jan 2016
Posts: 73
Wiki Edits: 0

Thanks: 8
Thanked 1 Time in 1 Post
Quote:
Originally Posted by ericnova72 View Post
If the video was showing what happens when you stand on the gas while cruising and it flares in RPM like that, then it is definitely a poor piece, either it is poorly designed and made, or something has gone wrong inside of it....a 2200 rpm stall converter should flare maybe 200-400 rpm doing the same thing you did in your video, at cruise rpm above 3000 rpm.

On thing I did notice from the video...unless the sound quality was really bad, it does not sound like the tach is accurate at all....motor didn't sound at all like it was jumping to the 4000 rpm indicated by the tach.
Ill email jegs and see what they say. It's only a few months old.
Yeah, sound quality isnt perfect, the car is very noisy inside so a lot gets lost because of the drone 😅
Reply With Quote Quick reply to this message
  #15 (permalink)  
Old 10-21-2019, 06:48 AM
Excellenceautosoluti's Avatar
Registered User
 
Join Date: Nov 2016
Location: Pinehurst North Carolina
Posts: 188
Wiki Edits: 0

Thanks: 83
Thanked 28 Times in 25 Posts
Call these guys.
Performance Torque Converters - Specializing in Race Converters & Transmissions Design & ManufacturingPerformance Torque Converters | Specializing in Race Converters & Transmissions Design & Manufacturing
I just spent around $800 for a nice converter from another place and picked up .2 and almost 5mph in the 1/4 mile. Everything people say about a quality converter compared to what you have is true.
These fellows at PTC took a little bit to get back to me, and I had already bought from someone else. But they were about $300 less. PTC has a stellar reputation, and my next purchase will be from them.
Not affiliated with them.
Reply With Quote Quick reply to this message

Recent Transmission - Rearend posts with photos

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:
Insurance
Please select your insurance company (Optional)

Log-in



Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are GMT -6. The time now is 02:59 PM.


Powered by vBulletin® Version 3.8.8
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.