Replacement Engine mounts. - Pontiac GTO Forum
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post #1 of 11 (permalink) Old 07-04-2018, 12:31 PM Thread Starter
 
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Replacement Engine mounts.

Happy 4th of July. Will be installing my rebuilt engine in a few weeks and am looking for recommendations on engine mounts. I have a 68 400 and a th400. Looking to keep the alignment the same as original. am open to all suggestions and pros a cons of each. Have a great and safe day.
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post #2 of 11 (permalink) Old 07-04-2018, 08:42 PM
 
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Originally Posted by deanhickey View Post
Happy 4th of July. Will be installing my rebuilt engine in a few weeks and am looking for recommendations on engine mounts. I have a 68 400 and a th400. Looking to keep the alignment the same as original. am open to all suggestions and pros a cons of each. Have a great and safe day.
I can't give a specific manufacturer recommendation, but I would match material type on the engine/trans mounts.

In my opinion, the rubber is most likely the best for street type driving and having a little fun. The rubber absorbs vibration better and does not transfer the vibration or sound as much as polyurethane types. I don't know who makes what, but I like this style I have included in the pic. The lower mount has that steel tang which if the rubber separates or splits, the steel tang will not allow your engine to "torque over" excessively and damage or twist things.

The polyurethane are harder and have less give and transfer vibration & noise through the car. Probably a better choice if your goal is to run your car hard or have a 4-speed and want to keep the clutch cross shaft from flexing too much.

If your mounts are known to be original, use these to make sure the replacements have the correct height, especially the trans mount as some of aftermarket ones can be thicker and will throw your driveline angles off.

BTW, the AMA specification for the 1969 GTO engine installation angle is 4 degrees 42 minutes. Assume this is with the chassis level and measuring off the intake surface (I don't think it rises at the secondaries). Would assume the '68 would be the same on this. So you can see that a thicker or thinner trans mount could throw off the engine installation angle which in turn would effect the driveline angle/pinion angle measurements. Food for thought.
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post #3 of 11 (permalink) Old 07-05-2018, 08:22 AM
 
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100% agreed with PJ....One more point I would make (and I usually don't go this direction) - buy American made motor / transmission mounts. I bought several mounts from CPP for my 56 Bel Air with a "nice" 350 and both sets of mounts from China failed. Third set from USA have lasted just fine.
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1965 GTO Convertible 3 speed tri-power drum brakes originally

Current setup:
400 cu in with tri-power
4 speed Muncie
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post #4 of 11 (permalink) Old 07-05-2018, 03:56 PM Thread Starter
 
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Thanks again Jim, I will go for the rubber mounts to keep things quite. Would the same apply to front suspension components? I want to tighten up the front end but still want a comfortable ride.
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post #5 of 11 (permalink) Old 07-05-2018, 08:02 PM
 
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Thanks again Jim, I will go for the rubber mounts to keep things quite. Would the same apply to front suspension components? I want to tighten up the front end but still want a comfortable ride.
Yep, same thing on the front suspension. The polyurethane bushings, or anything polyurethane, is more like a plastic - so not a lot of give and can transfer road noise. It will tighten the suspension and handling up a bit, and I have read that some can be prone to squeaking. The better pieces have a grease fitting and then a special grease must be used to keep things lubed up.

Anything polygraphite is tooted as having graphite in the mix and is self lubed and does not have a tendency to cause any squeaking sounds. I used these for my body mounts instead of rubber mounts as I wanted to stiffen up the body/chassis and am aware that they may carry a little more road noise through the car.

So that leaves rubber as your best option in absorbing road noise and flexing much better. If I wanted to tighten up the car, I would probably go with a higher grade & more expensive shock absorber and here is where I would install the polyurethane bushing - your front sway bar and sway bar links. Here is one example and they have the grease fittings. 1964-1968 Pontiac GTO LeMans Tempest Red Polyurethane Sway Bar Link and Bushing Set - www.a-resto-parts.com This would be an improvement using your factory 1" sway bar.

Many will add the aftermarket 1 1/8" sway bar to improve handling, but it can actually make the front end to stiff and you can experience what is called understeer in tight cornering conditions. So if you do go with a larger sway bar, then this really needs to be balanced out by adding the rear sway bar just like the factory did. Of course you can go stiffer springs, but then ride comfort may be compromised a bit. (I found polygraphite front sway bar bushings at PST for the 1 1/8" bar, but nothing for the factory 1" bar).

So you have options, just need to do the research and then give it a shot.
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post #6 of 11 (permalink) Old 07-05-2018, 08:09 PM
 
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100% agreed with PJ....One more point I would make (and I usually don't go this direction) - buy American made motor / transmission mounts. I bought several mounts from CPP for my 56 Bel Air with a "nice" 350 and both sets of mounts from China failed. Third set from USA have lasted just fine.
That would be nice! Problem is, no mass produced Made in the USA rubber & steel motor mounts for our old Pontiac LeMans/GTO's or early Firebirds.

Following is a run down of motor mounts avail for the '64-72 Pontiac A-body with 326-400 engine:

-recent aftermarket rubber & steel, MADE in CHINA. Steel used in the mounts is thinner than previous mfg motor mounts. Use at your own risk, NOT used here! Neither is cheap Chinese junk suspension parts!

-previous aftermarket rubber & steel, most aftermarket were Made in S Korea, steel was same thickness as original. May be found as NORS, i have over 250 lbs of rubber and steel mounts out of a Green Light Auto that closed in the late 70's, it's been a process of elimination to identify many and have sold quite a few GM motor mounts that were tagged. The Korean mfg motor mounts were made back in the late 70's, 80's, 90's. Have also picked these up as Pontiac motor mounts at swappers over the years.

-Steel motor mounts. lazer cut and machine bent and welded, first avail little over 20 years ago for Pontiac GTO's and early Firebirds/69-72 GP. ...have one pair left. Made in & distributed out of OH. Nice quality mounts, but many racers have gone away from two steel motor mounts. Some use one steel mount & rubber mount, most others have gone to motor mount plates.

-Mity Mounts...these were nothing but cheap offshore Pontiac motor mounts with a limiter bolt which was installed, & then the price marked up 10 fold! Quite the money maker for the fellow that came up with them until most Pontiac Performance engine builders even on strong steet builds tore them up.

-Urethane Motor mounts...relative new to the market for older Pontiac A-body's. Expensive.. Butler may be only vendor to supply them, will do some checking.

-Revulcanizing/total remold of original motor mounts. Company out in the land of Fruits & Nuts has provided this service for decades. Typically been used for 20's, 30's, 40's, 50's cars, and low production 60's motor mounts.. An option, but expensive.

Thats basically it.
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post #7 of 11 (permalink) Old 07-06-2018, 06:39 PM Thread Starter
 
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I think I will be hitting the used but good section.
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post #8 of 11 (permalink) Old 07-07-2018, 07:51 AM
 
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I think I will be hitting the used but good section.
I personally would not go used - too many variables that could give you a mount that "looks good" and lets go a month from now. Even new factory mounts go bad - 1965 Chevy comes to mind. Compounding of the rubber can be at fault, poor adhesives can be at fault, or even incorrect curing times can cause problems. I worked in a rubber molding factory for 4 years in my youth and saw a number of reasons why parts fail. Rubber ages and I would not waste my money nor trust good used or NOS mounts.

An automatic car isn't going to put the stresses on the mounts like a manual trans where torque is applied on/off with each shift, and depending on how hard you are laying on the engine/drivetrain or how sticky your tires are when you side step the clutch - and it is the driver's side that will let go if at all.

OPGI has a set of rubber engine mounts said to be manufactured to OEM standards, $46.99 for the pair. I would not have a problem using these. I am not sure where I got the set for my last 400CI build (may have even been NAPA), but the car is a manual trans and I did a lot of burn-outs and hard redline RPM shifting. Got right at 20,000 miles out of the rear tires and the mounts are still good.

Now if you want to go inexpensive, keeping in mind many use the same supplier, RockAuto has motor mounts. I have purchased many parts from RockAuto and never a problem. They carry ACDelco brand stuff and they stock many obsolete and older parts. https://www.rockauto.com/en/catalog/...tor+mount,5552
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post #9 of 11 (permalink) Old 07-07-2018, 06:12 PM Thread Starter
 
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Had a look at all the sites and it seems for the higher end mounts all they list are left side mounts. it seem a little strange they don't carry sets or both sides. Can the same mount be used on either side.? that may be a stupid question. Thanks for the info.
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post #10 of 11 (permalink) Old 07-08-2018, 12:19 PM
 
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Dean, not sure where you are seeing just the driver's side mounts advertised. For quick convenience, I cked Butlers website, and am seeing pairs, even though the Mity Mount is refered to as a mount. From longtime hands on experience with Pontiac, Olds, BBC's, and even 429-460 Fords, the torquing over of the V8 engine typically stress the drivers side mount the most. Pontiac, at least, was wise enough to use throttle cables on its '64 and later V8 A-body's & '68+ V8 Firebirds this eliminated binding of throttle rods/linkage, Chevrolet learned that one the hard way. In the early to mid 70's, Chevrolet had a service campaign to install small cable and bracket sets as limiters off drivers side motor mount to the upoer control arm shaft, this was on all mid 60's to '68 model small block cars and light trucks. This was a fairly expensive recall campaign due to the massive amt of vehicles built, and each different chassis took a different small kit. https://www.autosafety.org/chevrolet-motor-mounts/ Through the '80's and into the mid 90's I continually ran across these small bracket and cable packages in dealership buyouts. Many longtime Pontiac'ers have fabricated similar torque limiting devices using a fabricated pair of brackets & a cable. Others have fitted torque limiting straps or crude chains.

When it comes to replacement motor mounts, I stand by my earlier assessment, been ordering in, as well as picking up locally, and installing replacement older usage motor mounts for a long long time. upon ordering many, it seems to be only one mfg of our old Pontiac's rubber and steel standard motor mounts. Doesn't matter where one orders them from, the cheaply mfg mounts are the same. Jim's quoting OPGI's mounts as "built to stock specifications", well, i would have to put that as comical. All OPGI is doing is offering for sale the same thinner steel junk motor mounts, & since the holes line up, they can claim what they want to claim.

In respect to NORS (new old replacement stock) motor mounts, quite a few of us have sought them out & used them for years. Of the two dozen plus pairs I've installed/or sold to locals which have installed them theirselves, these what amount to 15 year old, to mid 70's manufactured rubber & steel mounts have proven to have held up very well. Much of that I attribute to how the mounts were stored. In the case of the large boxes of the Green Light stock I hauled in near 20 years ago, they had been indoors on the bottom shelves of family owned business. The large main room where the gondola shelving took up a good portion, had been air conditioned for decades. In such a favorable storage conditions, the rubber mounts showed no deterioration. Nothing like if they had been stored in hot shed with barn tin for a roof.

The replacement rubber & steel motor mount situation has slowly gotten worse as NORS supply's have been depleted. Down to two pair of "long style" Pontiac motor mounts that i personally need. Am also in a situation where need several more pair for upcoming projects. The whole mess is just something several of us have noted for several years. A long time specialty repair shop owner in the MetroPlex who happens to own numerous performance Pontiacs noted a few years ago on PY that in a period of over 18 months he'd had to put 3 pairs of replacement motor mounts in a customer's 74 SD T/A. All due to lack of a quality rubber & steel replacement motor mount. The '70-74 V8 Birds use the same long style motor mount, as do '70-73 factory 455 A-body's & '71-74 Pontiac B series. Its been very disconcerting situation, but I can report a solution is being prepared and it won't be a manfactured in India thin steel and rubber mount, or a version of that same junk import mount with a limiter bolt installed.
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