Author Topic: GT350 1966 engine + gearbox restauration  (Read 3017 times)

gt350hr

  • Hero Member
  • *****
  • Posts: 2311
  • Randy Gillis in real life - 5353 original posts
    • View Profile
Re: GT350 1966 engine + gearbox restauration
« Reply #15 on: January 03, 2020, 12:30:53 PM »
   Thanks Jim for the pics! That tab ( or tooth as we in the industry call it) it the exact reason the pistons crack! that tooth comes way out of the block a BDC as the piston is "rocking" in the bore from the change in direction. That causes the skirt to flex ( the only way to cause a crack in aluminum) and work harden until it forms a crack. The "angularity" of the cracks indicate that the flex is very low on the piston which it would be at BDC. Removing stress risers from the skirts and keeping the piston in the bore stop the cracking.
Celebrating 46 years of drag racing 6S477 and no end in sight.

traxman

  • Newbie
  • *
  • Posts: 13
  • SFM 6S779
    • View Profile
Re: GT350 1966 engine + gearbox restauration
« Reply #16 on: January 03, 2020, 04:36:25 PM »
Thank you again all of you for your help  :)

These microcracks are impressive, I will try to check that in mine next time I have the opportinuty to see my mechanics.

I contacted Randy for the pistons and Jim and Brant for the remaining parts.

Since we need to resurface the cylinder heads + make the appropriate modification for unleaded petrol, we can bring the blocks and the crank shaft to the engine specialist to check the wear and dimension of the shaft and the current bore of the cylinders. As far as we have seen, standard bore will be okay for both crankshaft rod baering shells and pistons

gt350hr

  • Hero Member
  • *****
  • Posts: 2311
  • Randy Gillis in real life - 5353 original posts
    • View Profile
Re: GT350 1966 engine + gearbox restauration
« Reply #17 on: January 03, 2020, 06:22:53 PM »
    Anthony,
        You may not need to modify the exhaust seats for unleaded operation. Usually older heads with "miles" on them do not suffer seat recession like they did in the early 70's Gas formulations have changed a bit to reduce the problem ( in my opinion anyway). Plus the seats have "work hardened" ( read been pounded) for thousands of miles making the OK to use as is.
   Randy
« Last Edit: January 06, 2020, 10:22:31 AM by gt350hr »
Celebrating 46 years of drag racing 6S477 and no end in sight.

traxman

  • Newbie
  • *
  • Posts: 13
  • SFM 6S779
    • View Profile
Re: GT350 1966 engine + gearbox restauration
« Reply #18 on: January 04, 2020, 02:26:16 AM »
So you assume that I can safely use unleaded petrol without any modification of exhaust seat?

I was running this GT350 with unleaded petrol without any leaded additive, and we were wondering if it is safe/reasonnable for the engine over time

shelbydoug

  • SAAC Member
  • Hero Member
  • *
  • Posts: 4600
    • View Profile
Re: GT350 1966 engine + gearbox restauration
« Reply #19 on: January 04, 2020, 07:41:18 AM »
I remember a 289 67 Mustang that a friend asked for help with. When I went to remove the pistons, they stated to crumble.

That was the first time that I saw that. I had to take the pistons out in pieces.

As I recall, the car had about 100,000 miles on it and was burning a little oil. ;)
68 GT350 Lives Matter!

kingchief

  • SAAC Member
  • Sr. Member
  • *
  • Posts: 324
    • View Profile
Re: GT350 1966 engine + gearbox restauration
« Reply #20 on: January 04, 2020, 09:42:37 AM »
Others may disagree but in my opinion, if you are going to have the heads off why not install hardened valve seats?  My original engine was rebuilt in 2011.  Machine shop installed new hardened exhaust valve seats after cutting and honing new seats [see picture].  Magnafluxed rods and caps.  One piece rear seal and double roller timing chain.  Dyno yielded 310 hp in 2011.  Still runs super strong with NO leaks anywhere or issues.  I would recommend if you can, do everything while the engine is apart.  Yee shall be rewarded in the future!!!

Cheers,

Steve
SFM 6S406

gt350hr

  • Hero Member
  • *****
  • Posts: 2311
  • Randy Gillis in real life - 5353 original posts
    • View Profile
Re: GT350 1966 engine + gearbox restauration
« Reply #21 on: January 06, 2020, 10:37:26 AM »
   Steve,
      The reason not to do it is there is no reason to do it in the first place. IF the heads suffer from seat recession , then by all means have exhaust seats installed. If they do not , you don't have a problem to fix in the first place. Replacement seats have been known to "fall out" if installed with "too little" press fit , and crack the head under the seat if installed with "too much" press fit. Much paranoia was created in '72 when Ford cast a bunch of "junk" 351C 2V heads that had seat recession and horrible guide wear. As I mentioned gas formulations have been improved to reduce seat recession and it rarely happens now days.
   Randy
Celebrating 46 years of drag racing 6S477 and no end in sight.

traxman

  • Newbie
  • *
  • Posts: 13
  • SFM 6S779
    • View Profile
Re: GT350 1966 engine + gearbox restauration
« Reply #22 on: February 03, 2020, 11:48:53 AM »
We bring the block to our local shop to check the cynlinders.
Unfortunately, they have taken a conical shape through time... so we have to bore at 0.020"

acman63

  • Hero Member
  • *****
  • Posts: 1047
    • View Profile
    • Shelby Parts and Restoration  since 1977
Re: GT350 1966 engine + gearbox restauration
« Reply #23 on: February 03, 2020, 01:13:29 PM »
use a torque plate if available
SAAC Concours Chairman

Owner Shelby Parts and Restoration Since 1977

SAAC original first year member