skinny z

I've read various accounts of how poly engine mount inserts (using the OEM clamshell) will raise the relative height of the engine.
Anyone have any experience with the difference?
I'm ready to drop the fresh engine in and have yet to replace the chassis portion of the engine mount assembly. I've sourced aftermarket mounts (complete with clamshell ) from the likes of NAPA. I was surprised at the obvious difference in quality from the SAME manufacturer. Mounts made in India used what appeared to be OEM steel clamshells and had substantially more heft than the made in China version (thinner gauge metal for the stamping and considerably less material used).
Same part number.
It has me rethinking the use of rubber mounts altogether and going for poly instead. I don't want to do this at the expense and having to modify my headers because of the difference in installed height.
What difference, if any, does the poly insert make?

Primetime91

iTrader: (15)

It really seems to vary from person to person from what I've seen.

Another variable you have to consider, is how much the original rubber ones were sagging. The poly might just be raising the motor to its original height, but it's perceived as raising the motor more than it should. Just for what it's worth, I ran solid mounts, and I had slight header clearance problems (with Dyno Don's headers no less, supposedly the best fitting out there). But it appeared the motor sat too low with the mounts, not too high. But I never had rubber mounts to compare to, since they went in with the V8 swap

pound

iTrader: (7)

I have poly mounts with the Hooker 2055 shorties and am happy. They hold the motor better than rubber, so you'll get more vibration in the car though. Mine is not my dd so its not really an issue for me. I think people say they raise the motor higher than stock because they are probably swapping out the inserts for the first time and the motor is sagging on the 20 year old rubber which is obliterated with age.

skinny z

My existing rubber mounts were relatively fresh when I installed the headers and y-pipe. Maybe I won't see a difference then.
I can recall one thing I've learned though. After my swap from the 305 TPI to a carbed 350, the engine never sat level in the car. I even went so far as to swap left and right block mounts with no change in the nearly 1/4" droop on the passenger side.
It wasn't until I was into my latest build and filtering through my spare parts that I came across the infamous triangular spacer that fits between the mount and the block.
Building my pipes without the mount shim might be the biggest problem. I want to install it to level the engine.

Primetime91

iTrader: (15)

What's this triangular spacer? I haven't heard of it before, wierd. My motor sat level, and I never used anything like that

skinny z

I found it with (IIRC) the original V8 mounts that came from an 84 Z28.
It's odd too in that I was just reading about it somewhere. Seems somebody was looking for one.

khulsebus

iTrader: (2)

skip the rubber and poly mounts and go with the solid moroso mounts from summit. i ran poly mounts on my 85 t/a and then switched to the solid mounts. then on my 91 rs i went straight to the solid mounts. both cars were driven daily, so don't buy into the excessive vibration from the poly mounts.

1ADan

iTrader: (4)

i had run poly on my RS with shorties without issue and went that route again with my LQ9 swap. I would skip the rubber ones and go for the poly. Sounds like a few have had good luck with solids too, but they will transmit more vibration than most like. May also need to experiment with transmission mount combinations to limit vibrations to a tolerable level for you (I kept rubber there)

87350IROC

iTrader: (2)

The height difference for me was at least 3/4". That is brand new GM rubber vs new poly. The poly motor mounts raised the motor so much that my strut tower brace did not clear the engine and my SLP y-pipe rested against the floor of the car about 1ft in front of the cat. Needless to say I swapped them out for new GM rubbers and life is good again. The vibes from the poly mounts was crappy too, although that may be due to the y-pipe hitting

khulsebus

iTrader: (2)

I had a poly trans mount, along with a poly torque arm bushing and Lakewood LCA's with my solid engine mounts. There was no excessive vibration, and it didn't raise the engine. I was told not to run a rubber trans mount with the solid engine mounts, that I would break the tailshaft housing on the trans.

KITT1983

iTrader: (3)

What is the best motor mount for my 305 crossfire?

khulsebus

iTrader: (2)

It depends on what you want to do with your car. If you're going to keep it as original as possible, then there is nothing really wrong with rubber mounts. If you're trying to go for performance, then I would recommend going with poly engine and trans mounts. As I mentioned earlier, I had good success with solid mounts, although they are a little trickier to get lined up when installing the engine. Rubber is cheapest, if I remember correct Poly was more than the solid mounts, but it's been over 10 years since I bought them.

wishoradream

I'm gonna chime in with a little off topic, but I prefer the solid mounts from moroso. I pulled an 86 350 out of a 86 custom deluxe chevy, and didn't think about it until after I had already bolted and mounted the engine in my 82 z, but there is a difference in height on truck and car engine mounts, so needless to say I'm swapping those out, due to a clearance issue and the engine sitting at an angle. Just in case anyone happens to take the route I did, hope to save them the hassle.

KITT1983

iTrader: (3)

i plan on modifying it in the future. i just replace them two years ago with napa rubber motor mounts. they broke again.

khulsebus

iTrader: (2)

wishoradream, those are the mounts i was talking about earlier. i bought them back in 2002 for my '85, and reused them on my '91 in 2004. they worked great, except that they were a little tricky to get lined up when installing the engine back in the car.

GPSkinzhut

iTrader: (2)

I threw a set of Energy polys in to raise my Dyno-Dons off my K-member (came up about 1/2"). Did the trans mount as well. Vibration is noticeable but it's not intolerable. Hell, even helped me track down some rattles.

oil pan 4

iTrader: (1)

I was replacing the motor mounts on my 6.5L diesel engine (non turbo) about every year and a half. Last time I changed them in 2007 I put the poly inserts in.
They have held up well and I have had a turbo on that 6.5L for about a year now and the motor mounts are doing great.
I put motor poly motor mounts on my Z28 after I bought it in 2003 and have not had to mess with them at all. The ruber part of the mount on the drivers side was totally gone.

Note: the SBC and 6.5L diesel use the same motor mount.

KITT1983

iTrader: (3)

I replaced my motor and tranny mounts with energy suspension 3.1130G kit. The uses to handle better. The body vibrations are minor and ate due to the rough idle