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Rebuild C4 Or Replace With C6

  • Thread starter Thread starter Nathaniel Donnelly
  • Start date Start date Feb 18, 2016
  • Tags Tags
    289 302 c-4 c-6 engine kit rebuild tranny transmission

Nathaniel Donnelly

Member
Feb 9, 2016
39
3
18
San Diego
Feb 18, 2016
#1
  • Feb 18, 2016
  • #1
Hello Stangnet!

I've noticed the C4 in my '67 vert is starting to take a while to engage when cold. I realize that this may mean a rebuild to replace all the worn junk inside. Not sure of the history of the tranny, but suspect it has never been rebuilt.

Right now, I have the numbers-matching 289 bored to a 302, but I believe the only upgrade is the cam. Not too familiar with driveline. Sounds beefy, but not much power. Low to mid 200's HP maybe? Very soon, I plan to replace the exhaust manifolds with headers, and put a new kit on the existing engine until i get up to around 350 HP.

My question is, should I spend the money rebuilding the C4 if that's what it needs, or should I just replace it with a C6? I know a threshold exists where I should move up to the heavier duty tranny.

Please advise. Thank you!
 

horse sence

15 Year Member
Nov 29, 1999
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Wile Coyote's stunt double
Feb 18, 2016
#2
  • Feb 18, 2016
  • #2
A well built C4 will hold 400 HP easily .A C6 is quite a bit heavier .
 
Reactions: 1963_Falcon_4dr_wagon and Nathaniel Donnelly

Nathaniel Donnelly

Member
Feb 9, 2016
39
3
18
San Diego
Feb 19, 2016
#3
  • Feb 19, 2016
  • #3
horse sence said:
A well built C4 will hold 400 HP easily .A C6 is quite a bit heavier .
Click to expand...
Thanks, Horse! That helps out a lot!
 

66 Signalflare

Active User
May 24, 2016
23
2
13
May 25, 2016
#4
  • May 25, 2016
  • #4
I replaced a six cylinder engine with a 289. 289 now has EFI and is rated at 270HP. C4 is holding up very nicely.
 
V

Vaejovis Carolinanus

Member
Apr 29, 2016
42
3
18
Charleston SC
May 29, 2016
#5
  • May 29, 2016
  • #5
What would be a avg/ fair price to have a C4 rebuilt?
 

66 Signalflare

Active User
May 24, 2016
23
2
13
May 29, 2016
#6
  • May 29, 2016
  • #6
Not sure but you can get the rebuild kits on-line from $99 to $300 neighborhood. I bought my Mustang in 1989 and it had the small six with the C4. 24,000 miles on the car. Now I've got 35,000 on the car with a 270HP V8 in front of the C4 vice the small six cylinder.
 
V

Vaejovis Carolinanus

Member
Apr 29, 2016
42
3
18
Charleston SC
May 29, 2016
#7
  • May 29, 2016
  • #7
Mine is not horrible but since it sat up for a year or more I feel I should do a fluid change like I did with the engine and I am thinking about changing the vacuum modulator valve at the very least.
 

Nathaniel Donnelly

Member
Feb 9, 2016
39
3
18
San Diego
Jul 30, 2016
#8
  • Jul 30, 2016
  • #8
You guys are a bit over my head, haha. I don't have the knowledge or time to rebuild my c4, so it looks like I'll be taking it to the shop to have them do that, with the understanding that I want it to be able to handle about 400hp in the future.

Any advice on what I should let them charge me? Are there differences between a typical rebuild and a performance rebuild?

Thanks in advance!
 
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