[Formulajones]

Originally Posted by JUDGE3

many state a solid motor mount on the drivers side, stock mount passenger side works great also. think I may go that route.

That's exactly what I do here on builds these days. Can't even tell it's there. Put it on an forget about it.

[1968GTO421]

Originally Posted by 78w72

i use a chain from the front of the head down to a bolt/nut in a hole i drilled in the frame, very hard to see when everything is installed. has about 3/16" of slack & has worked great for ~5 years & lots of street abuse & at least 40+ low 11sec drag strip runs at 120+mph.

i also make my own improved version of a mity mount for the drive side mount & between the 2, i have yet to break a mount. but i agree the aftermarket mounts are crap & lots of people with higher power engines & good traction break them frequently. i have a 2nd gen firebird so the mounts are a little different & dont have that strap pictured above, but a limiter of some sort is a good idea at this power level & cheap insurance... when a mount breaks it can cause more damage than just the mount.

also with the chain there is no noise at all... & if there was a little noise its impossible to hear over the engine or while driving the car.

Very clean install and looks good besides being effective

[dataway]

If you do enough research on McMaster-Carr they have options for custom made cable (wire rope lanyards), pick your length, diameter, type of ends, coated or not.

I remember when I broke the OEM engine mount, luckily the engine didn't hit the hood. As a 19 year old kid it really surprised me when I saw the engine jumping around. As for the tangs on modern replacements, when I was installing mine on the engine while on the stand .... I couldn't for the life of me see how that tab engaged anything at all, I had to bend it about 1/2" to get it into a position where it would ever engage the other half of the mount.

[rohrt]

I would like to see some pictures to see how you guys are attaching to the frame. Did you weld in an embossment?

[78w72]

Originally Posted by 1968GTO421

Very clean install and looks good besides being effective

thanks!

there are other ways to do it & they all work good. but the chain was easiest for me on a 2nd gen firebird & like i said its very hard to see once everything is installed & does not look tacky or make noise... if the chain stretches i just install a new piece.

[Sirrotica]

So in 2-3 weeks brand new mounts rotted the rubber, and they completely separated with 450 HP on a dirt track with 8 inch Hoosier tires. This was with a T400, so it was shocked less with a AT than with a stick shift. Mind you this was in the late 70s before all the imported crap made it's way into parts stores in the USA. Best of my recollection I used Anchor mounts.

Of course I have no pictures of failed motor mount that happened 40 years ago, it never occurred to me to take my polaroid to the garage with me to take pictures. Motor mounts fail even in street cars with street tires with near stock engines, I replaced probably half a hundred Pontiac mounts ripped in half on pure street cars. That tiny interlock will straighten out quite easily, hence the reason Jim Hand had articles about strengthening it with a bolt shank welded to reinforce it. Simply put, the metal interlock does straighten out under repeated abuse, seen it many times.

I guess you don't abuse your stuff as much as you think you do, because the posters here have torn the mity mounts in half with street cars. I've broken a bunch myself and I've replaced a bunch of my customers cars with Pontiacs since the early seventies. It doesn't take a super stocker to break Pontiac motor mounts.

If you want to take a chance compromising the block with solid mounts be my guest, I've seen enough failed main bearings on Pontiacs in the #2 and #3 area to not want to tempt fate. The block is not that beefy, especially the earlier 2 bolt mounts. The 3 bolt style was re-engineered when the 455 long stroke engine debuted in 1970 for a reason. If you take all the give out of the motor mount by making it solid, the flex will go to the next weakest link. Some guy said that in his signature about "engineers doing stuff for reasons", yep it was Tom V.

I know well how the mounts snap in half, I also have seen evidence of block bulkhead distortion. Anyone can choose whatever combo they want to solve their problem, your car, engine and your money, feel free to post on the subject.

[Tom Vaught]

Originally Posted by rohrt

I would like to see some pictures to see how you guys are attaching to the frame. Did you weld in an embossment?

I suppose you could weld on a boss.

I personally drilled a hole in the frame when the engine was out of the car and installed a RIV-NUT. RIV-NUT gets tightened and is a part of the frame now but with no welding and it is crimped on both sides of the frame.

Install the strap/chain/cable with a bolt and washer and you should be good to go. I installed a stud in the RIVNUT, loc-tited it in place and can slip the strap over the stud and add a washer and locknut on the outside and it is not going anywhere and it still has a slight amount of movement. Easy to remove too.

Tom V.

The early 2-Bolt Blocks are not too strong in the pan rail area/mount area, but a dual engine plate fixes that weak issue of the block, just like splayed caps on a non drilled two bolt main blocks is a better deal vs a drilled 4 bolt main block with 2 bolt main caps.

Tom V.

[tom s]

IM with FJ on real HiPo engines,with stock type I just use stock ones and had no issue.Tom

[64speed]

With my huge V belt front accessory drive you can’t really see anything behind the alternator and power steering pump so I think I am gonna use a piece of plastic covered cable and just loop it around my frame rail and bolt it to the head. Tractor Supply here sales the cable and will cut it and crimp it together so that’s no problem. How much slack should I leave for some engine movement before it just tears the mount all to hell

[STEELCITYFIREBIRD]

I had/have major movement in my drivers side clamshell mount with only ~400-600 miles of really aggressive street driving on plain radials, it was/is a Sealed Power mount circa 2004.(Yes my car has been down WAY too long ) So I will be modifying that. NO oil on it, just poor materials or too much abuse for mounts intended use.
Clamshell mounts do contain travel positively and well, I don't know how well old style do. Slop in that mount makes the car shock the tires on launch and shifting, I don't like the feel (un loads tires on shifts/4 speed) and can mess with mechanical clutch linkage function.
With the torque you'll have on tap, if you get traction, you'll find ANY/ALL the weak links real fast!
You used a 455 block IIRC, lesser issue with block strength over early blocks... IIRC.

I've been told the same by some smart "older" (than me ) guys, solid left, stock type right works well, that's what I'm doing.

Listen to the smart old guys, lots to learn...the easy way!

[HoneyHush]

I figured I would share an experience I had with this type of deal. It really depends on how stiff the rest of the car is that kind of dictates how “tightly” you snug the engine down. On my 79 z28 with a healthy sft cam and 3500 stall with 4.10 gears on ETStreets it would 60 foot high 1.4s to low 1.5s. The stock driver side mount always got sloppy so I welded a bracket on the frame and mounted a turnbuckle up to the driver side head. Worked good for a while until on the last run at the track I felt a huge jerk in the drivetrain. Drove it 30 miles home and still couldn’t see anything wrong. The next morning pulling it into the garage to examine it felt a huge crash and turned it off. Looked under it and the stock th350 bell housing had broken clean off all the way around the pump mounts. Guess the strap worked too good for the amount of flex the chasssis had.

[JUDGE3]

Originally Posted by HoneyHush

I figured I would share an experience I had with this type of deal. It really depends on how stiff the rest of the car is that kind of dictates how “tightly” you snug the engine down. On my 79 z28 with a healthy sft cam and 3500 stall with 4.10 gears on ETStreets it would 60 foot high 1.4s to low 1.5s. The stock driver side mount always got sloppy so I welded a bracket on the frame and mounted a turnbuckle up to the driver side head. Worked good for a while until on the last run at the track I felt a huge jerk in the drivetrain. Drove it 30 miles home and still couldn’t see anything wrong. The next morning pulling it into the garage to examine it felt a huge crash and turned it off. Looked under it and the stock th350 bell housing had broken clean off all the way around the pump mounts. Guess the strap worked too good for the amount of flex the chasssis had.

that's interesting.

did you have sub frame connectors?

[HoneyHush]

Yes it had south side machine bolt in subframe connectors with their lift bars. It had new poly body mounts as well but no cage and it was a t top car.

[HoneyHush]

Forgot to mention it was a 9.8 compression 461 bbc and the carb ran lower to mid 11’s .

[sdbob]

A local racer had a 69 Firebird ,'Barneys Arco' ,with 69 RA IV car was in mid 11s in mid 70s.10.5" tires. T400. Roll bar with supports dont remember if it had full cage.He put in solid mounts then started braking Trans cases at block. I gave him an early reinforced case. Dont remember if he cured problem.

[Bill Eveland]

I have welded a steel pin onto a factory type mount on driver side to make it more of a solid. Very little movement

[Tom Vaught]

I will stick with my strap on the engine (with slight clearance), My Lakewood shield, and my factory rear trans mount on the cross-member.

I have only run 11.53-11.55 at 117 with this car on a 9" slick. Many have gone faster, I do not want to twist up the body,
64 GTO Vert. Those times were run in 1977 at the Detroit Dragway track. I have the time slips somewhere.

Tom V.

[Dragncar]

I had problems. Made some "elephant ears" and it cured it. Engine is rock solid now and I do not worry about my block with a 2 step.

[SRR]

When we built our 70 Tempest drag car I welded a chain to both sides up front and bolted with a little slack to the head because in my thinking in case of a violent roll over I wanted the engine to stay in the car.

Back when I was a teenager I had a 66 Caprice with a 396 auto. I was making a left turn and as I hit the gas the pedal went to the floor and the inside tire started smoking up even with my foot on the brake. A motorcycle Cop witnessed it and pulled in behind me after I got it stopped and said I know you didn't do that on purpose because of the terrified look on your face! Apparently this car missed the recall.

[Tom Vaught]

Obviously glad you are ok!

Tom V.