#21  
Old 04-09-2020, 05:54 PM
Doug Hopkins's Avatar
Doug Hopkins Doug Hopkins is offline
Chief Ponti-yacker
 
Join Date: Dec 1999
Location: Sebring, Florida USA
Posts: 833
Default

Quote:
Originally Posted by Hammertime Mike View Post
That's the route I'm taking this year. I'm also solid at the tranny mount. Will be in the same horse power range.
I'm gonna try the front plate and solid motor mounts, but keeping the polymer trannny mount. Some give at that point might be needed to avoid cracking. I knew a guy that tried solid mounts on a stocker and he cracked extension housings constantly until he went back to a soft tranny mount.

  #22  
Old 04-09-2020, 06:36 PM
Dragncar Dragncar is offline
Ultimate Warrior
 
Join Date: Mar 2004
Location: Humbolt County California
Posts: 8,283
Default

I would avoid solid mounts like the plague. Even with front plate.
I think a rear plate with rubber mounts and my elephant ears will do what I need. Or get the front plate too. A rear plate take the hit before a front plate anyway. It comes from back to front. Has to.
But any chance of destroying a block, all its parts and machine work because of solid mounts is something I will not do. Some blocks are weaker there than others but why take a chance.

  #23  
Old 04-09-2020, 08:55 PM
Doug Hopkins's Avatar
Doug Hopkins Doug Hopkins is offline
Chief Ponti-yacker
 
Join Date: Dec 1999
Location: Sebring, Florida USA
Posts: 833
Default

Quote:
Originally Posted by Dragncar View Post
I would avoid solid mounts like the plague. Even with front plate.
I think a rear plate with rubber mounts and my elephant ears will do what I need. Or get the front plate too. A rear plate take the hit before a front plate anyway. It comes from back to front. Has to.
But any chance of destroying a block, all its parts and machine work because of solid mounts is something I will not do. Some blocks are weaker there than others but why take a chance.
I've ran the solid steel fabricated mounts on the block and polymer trans. mount for three years (over 400 runs) with about 525 HP with zero issues. This season with about 700 HP I was thinking additional front plate would secure any movement made by the additional power. I might be wrong, but I don't see how it could hurt.

  #24  
Old 04-09-2020, 09:01 PM
Doug Hopkins's Avatar
Doug Hopkins Doug Hopkins is offline
Chief Ponti-yacker
 
Join Date: Dec 1999
Location: Sebring, Florida USA
Posts: 833
Default

Quote:
Originally Posted by Dragncar View Post
I had issues with Mighty Mounts and made a set of "elephant ears". Now the engine is rock solid.
Solid motor mounts only can have issues when using a 2 step. Its hard on blocks, they can crack.
What exactly is an elephant ear?

  #25  
Old 04-09-2020, 11:45 PM
Dragncar Dragncar is offline
Ultimate Warrior
 
Join Date: Mar 2004
Location: Humbolt County California
Posts: 8,283
Default

Quote:
Originally Posted by Doug Hopkins View Post
What exactly is an elephant ear?
They are 3" wide by 3/8 aluminum bars that run from the front 3 accessory bolts on each head down to the frame rails at a 45 or so angle. Have a 1/4" x3" piece of flat bar welded to the frame and use 2 3/8" grade 8 bolts.
It works but does put pressure on the heads, thus the head gasket maybe. I never have had a issue.

  #26  
Old 04-10-2020, 09:37 AM
Hammertime Mike's Avatar
Hammertime Mike Hammertime Mike is offline
Chief Ponti-yacker
 
Join Date: Dec 2008
Location: Tennessee
Posts: 986
Send a message via ICQ to Hammertime Mike
Default

Quote:
Originally Posted by Doug Hopkins View Post
I'm gonna try the front plate and solid motor mounts, but keeping the polymer trannny mount. Some give at that point might be needed to avoid cracking. I knew a guy that tried solid mounts on a stocker and he cracked extension housings constantly until he went back to a soft tranny mount.
I've been solid on the motor and tranny right along. I gotta add that I do not run a trans brake on my set up.

__________________
  #27  
Old 04-10-2020, 09:43 AM
Sirrotica's Avatar
Sirrotica Sirrotica is offline
Ultimate Warrior
 
Join Date: Jan 2005
Location: Catawba Ohio
Posts: 7,190
Default

There's a lot more area to spread the energy to on a cylinder head limiting device, than there is on the thin pan rail. Using the front of the cylinder head to take the twisting stress, is probably the best scenario as the water crossover connects both banks of the block further spreading the force over the entire front of the engine and both cylinder heads.

I've studied the early 2 bolt motor mount design , as well as the late model motor 3 bolt motor mount re-design, and this is what I've found.

If you look at the double position motor mount blocks (70-76) stripped bare you'll notice that the old two hole mount area (59-69) only attaches, and straddles, the #3 main bulkhead. When Pontiac introduced the 455 in 1970 they also moved the motor mount position forward, and used 3 bolts, along with cast iron stiffening ribs. The longer motor mount with three attaching points straddles both the #2 and #3 bulkheads, halving the stress on the #3 bulkhead. The third upper mount bolt further spreads the load upwards towards the top of the block.

Even on the A bodies that used the 2 hole early design through 1972 on the 400, 350 engines. The 455 in A bodies in 1970-1972 used the newer late 3 bolt design. The 70-72 A bodies used the reinforced 3 bolt mount system only on the higher torque 455 engines.

When Pontiac redesigned their mount system in 1970, I always wondered what the advantage of the completely new system was. Years later I studied the double pattern blocks, and it finally sunk in why they redesigned the mount system to spread the load to 2 bulkheads and they also stiffened the new mount area with an additional ribs running top to bottom.

The anticipated extra torque of the longer stroke 455 was enough that Pontiac engineers thought it was better to spread the force over 2 bulkheads and have 3 attaching points on the higher torque engines. The positioning of the 3 hole motor mounts definitely is superior to the early design 2 bolt design.

There have been plenty of pictures posted over the years on PY that have shown the bulkheads cracking in high horsepower builds. I've seen images of both factory, and aftermarket blocks splitting. Many times it has been blamed on using the stock motor mount positioning in a high power build. Of course solid mounts exacerbates the problem of stressing the bulkheads

I'm far from a engineer, but common sense says that Pontiac re-designed the mount system in 1970 when they introduced the highest torque engine they had made to that point. Look at the engineering on a stripped block and I'm pretty sure most anyone can see the reasoning behind the changes.

I've been told that automotive engineers usually use a 25% safety factor above what the actual stress will be. Using that factor, the 1970 455 HO was rated 335 HP, and 480 ft. lbs. of torque, adding 25% to that, arrives at 600 ft. lbs. using the later design 3 bolt mount on a fresh piece of cast iron. Over that point is where Pontiac blocks seem to fail, especially when using the stock motor mount attachment points on 50 YO cast iron.

When using the early 2 bolt style mounts/blocks the limiting factors are going to be less than later 3 bolt style design.

Just trying to look at the engineering from the common sense vantage point. Maybe after looking at both the early 2 bolt design, and the later 3 bolt design everyone can see the advantages, and limitations of the later system. Hopefully looking at the engineering will save someone from over stressing a block using factory mounting points causing it to crack in the main web area.............

__________________
Brad Yost
1973 T/A (SOLD)
2005 GTO
1984 Grand Prix

100% Pontiacs in my driveway!!! What's in your driveway?

If you don't take some of the RACETRACK home with you, Ya got cheated

The Following User Says Thank You to Sirrotica For This Useful Post:
  #28  
Old 04-10-2020, 03:00 PM
Probird's Avatar
Probird Probird is offline
Ultimate Warrior
 
Join Date: Jul 2005
Location: Athens, Illinois
Posts: 3,187
Default

I use a front motor plate and stock rubber mounts as a front to back limiter. No mid plate. I wouldn’t use the steel mounts only. That puts a lot of stress on the block. You’ll probably be ok with the front plate. No way would I use solid transmission mount. I’d run no mount before I put it in there with a solid one.

__________________
Come take a ride http://www.youtube.com/watch?v=P7Y8Awfk2I0
2008, 2013, 2015, 2016, 2019 Central Il Dragway Mod track champion
and 2015 IHRA Div 5 Mod champion
  #29  
Old 04-10-2020, 03:48 PM
Bill Eveland's Avatar
Bill Eveland Bill Eveland is offline
Ultimate Warrior
 
Join Date: Apr 2004
Location: Glasford Il
Posts: 3,650
Default

I used these chevy rear mounts that I cut and welded to work for a Pontiac bellhousing , could use instead of a midplate. also can mount solid of course.

https://www.amazon.com/Steel-Chevy-E.../dp/B074WHNR7B
Attached Thumbnails
Click image for larger version

Name:	mount.jpg
Views:	258
Size:	40.8 KB
ID:	536935  

__________________
Illinois Outlaw Gassers

6.27@107
9.97@131
  #30  
Old 04-10-2020, 09:10 PM
Scott Stoneburg's Avatar
Scott Stoneburg Scott Stoneburg is offline
Ultimate Warrior
 
Join Date: Sep 2007
Posts: 2,179
Default

I am and have always used stock rubber mounts, the 2 bolt mounts due to year of the car. I have always had some sort of limited tied to the front of the head. Currently i have a 1" CM tube with hiem ( hope i spelled that right ) joints from the head to a tab I welded to the frame. ( see pic ) What would the advantage be to switching to a motor plate. Front only or front and mid plate. And would the front plate be more sturdy than having the ears from each head to the frame.
Attached Thumbnails
Click image for larger version

Name:	20190321_065624-1.jpg
Views:	238
Size:	56.8 KB
ID:	536970  

  #31  
Old 04-10-2020, 10:47 PM
Dragncar Dragncar is offline
Ultimate Warrior
 
Join Date: Mar 2004
Location: Humbolt County California
Posts: 8,283
Default

I had a set of motor mounts that hit every mount bolt on a 70s block. Think it was 5.
Did they come stock on anything ? Or are they aftermarket ? I used them before the Mighty Mounts and they worked better. Engine moved less with them.

  #32  
Old 04-11-2020, 11:02 AM
Sirrotica's Avatar
Sirrotica Sirrotica is offline
Ultimate Warrior
 
Join Date: Jan 2005
Location: Catawba Ohio
Posts: 7,190
Default

Quote:
Originally Posted by Scott Stoneburg View Post
I am and have always used stock rubber mounts, the 2 bolt mounts due to year of the car. I have always had some sort of limited tied to the front of the head. Currently i have a 1" CM tube with hiem ( hope i spelled that right ) joints from the head to a tab I welded to the frame. ( see pic ) What would the advantage be to switching to a motor plate. Front only or front and mid plate. And would the front plate be more sturdy than having the ears from each head to the frame.
On my 69 GP dirt track car I had a 69 428 HO block and of course used the 2 hole mounts, as there wasn't any other mounts available to use on that particular block, and chassis. Engine was roughly 450 HP, which at the time was good for cast iron D port heads.

A set of brand new mounts (late 70s time frame) at that time were a lot more robust than the Korean mounts of today, made with silly putty. They still would break in 2-3 weeks. The steel interlock would twist and break, then the rubber would delaminate. I then incorporated 2 turnbuckles tying the left and right cylinder heads directly to the frame (right side was to counteract abruptly braking when entering turns), and decelerating at the same time. I never broke another mount for 2 years after adding the turnbuckles to the cylinder heads, until the car was retired.

The twist load was transferred to the cylinder heads with no adverse effects in 2 years of circle track racing. That's a bunch more than running a quarter mile at a time in a straight line. Roughly 13 miles around a 1/3 mile dirt oval every week. I still have the engine assembled, just as I pulled it out of the car back in 1980. The motor mounts are pristine.

I even did a few smokey burnouts on the driveway in front of the gas station I ran at the time:



During that time frame no one was using motor plates except in tube chassis super late model cars. Using a stock frame car, the turnbuckles worked just fine for keeping the engine from twisting in the chassis and breaking mounts. It also transferred the stress from the bottom edge of the block to the cylinder head area. Primitive by today's standards, but it worked just fine at the time.

__________________
Brad Yost
1973 T/A (SOLD)
2005 GTO
1984 Grand Prix

100% Pontiacs in my driveway!!! What's in your driveway?

If you don't take some of the RACETRACK home with you, Ya got cheated

  #33  
Old 04-17-2020, 11:38 AM
sberbs's Avatar
sberbs sberbs is offline
Member
 
Join Date: Jul 2018
Posts: 48
Default

Quote:
Originally Posted by younggto View Post
I made a pair of these for this year to use in conjunction with my existing solid motor mounts and poly trans mount. Figured they’re not a bad idea; less flex equals more power to the ground and reduced stress on the block.
Did you just cut the plates out you used or are they made someplace?

Sent from my Pixel 3 XL using Tapatalk

  #34  
Old 04-18-2020, 06:44 AM
chuckies76ta's Avatar
chuckies76ta chuckies76ta is offline
Ultimate Warrior
 
Join Date: Jun 2004
Location: Canada
Posts: 3,078
Default

Quote:
Originally Posted by Bill Eveland View Post
I used these chevy rear mounts that I cut and welded to work for a Pontiac bellhousing , could use instead of a midplate. also can mount solid of course.

https://www.amazon.com/Steel-Chevy-E.../dp/B074WHNR7B

Bill: Any idea what mount you used? I like that setup.


Thanks
Charles

  #35  
Old 04-19-2020, 10:20 AM
Bill Eveland's Avatar
Bill Eveland Bill Eveland is offline
Ultimate Warrior
 
Join Date: Apr 2004
Location: Glasford Il
Posts: 3,650
Default

If you wanted a cushion there could use these but would have to fabricate a mounting system for it . There is a spot on the mount for a stud to go thru. Or could make some sort of adapter plate like a midplate would require. But that was with a stock case th400. They wont fit my ultrabell.

https://www.speedwaymotors.com/Unive...-Kit,1199.html

__________________
Illinois Outlaw Gassers

6.27@107
9.97@131
  #36  
Old 04-19-2020, 04:01 PM
chuckies76ta's Avatar
chuckies76ta chuckies76ta is offline
Ultimate Warrior
 
Join Date: Jun 2004
Location: Canada
Posts: 3,078
Default

Thanks for the info Bill.. That would work.

Charles

  #37  
Old 04-19-2020, 06:48 PM
Bill Eveland's Avatar
Bill Eveland Bill Eveland is offline
Ultimate Warrior
 
Join Date: Apr 2004
Location: Glasford Il
Posts: 3,650
Default

They dont fit the best with chassis headers, depends on how the tubes are. I ended up going to a midplate and frontplate. In the middle of welding all the brackets in place.

__________________
Illinois Outlaw Gassers

6.27@107
9.97@131
  #38  
Old 05-17-2020, 03:33 PM
younggto younggto is offline
Senior Chief
 
Join Date: Sep 2005
Location: Erie, PA
Posts: 382
Default

sberbs, they were my own design. Sorry, was having some log-in issues.

  #39  
Old 05-18-2020, 01:17 AM
Old Man Taylor's Avatar
Old Man Taylor Old Man Taylor is offline
Ultimate Warrior
 
Join Date: Dec 1999
Location: Escondido, CA, USA
Posts: 6,945
Default

I do not like any motor mount on higher HP cars, especially solid ones. I believe they help contribute to the blocks we see cracking. I run elephant ears on my racecar, and a poly mount on the trans.

  #40  
Old 05-18-2020, 08:05 PM
ZHAWK154's Avatar
ZHAWK154 ZHAWK154 is offline
Member
 
Join Date: Apr 2008
Location: south florida
Posts: 43
Default

Anybody out there making these “elephant ears” for purchase?

__________________
1979 trans am - 462' #12 heads
2001 sunset orange trans am firehawk #154
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not 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

Forum Jump


All times are GMT -4. The time now is 05:39 AM.

 

About Us

The PY Online Forums is the largest online gathering of Pontiac enthusiasts anywhere in the world. Founded in 1991, it was also the first online forum for people to gather and talk about their Pontiacs. Since then, it has become the mecca of Pontiac technical data and knowledge that no other place can surpass.

 




Copyright © 2017