Wondering if anyone has found the ultimate motor mounts for a 4BT conversion. The only bad thing about my conversion (Scout II) is the legendary rattle and hum @ idle. Are the P30 repowers a place to start? I have looked at a bunch of options and was wondering if anyone has the cure... other than a counter balancer! This was adressed ealier but surely some new angle is up for discussion! Thanks... .
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Ultimate 4BT Motor Mounts...
- Thread starter Slaughter
- Start Date
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I'm using the front mounts from an '89 GMC Topkick (w/ 8. 2 Detriot) on my conversion.
I have not actually got the truck running yet, so I have no idea what these mounts will be like. I'll post back later when I have a better idea of how these actually work. Just wanted to toss out a possible idea.
I have not actually got the truck running yet, so I have no idea what these mounts will be like. I'll post back later when I have a better idea of how these actually work. Just wanted to toss out a possible idea.
4BT engine mounts
I contacted LORD engine mounts. They performed a 4BT engine and NV4500 analysis for me and came up with their 3. 12" diameter "Flex-bolt" sandwitch mount p/n J-5425-1 for the two in front. and p/n J-5425-15 for the two that go under my transmission support plate.
My calculated front axial load rating (axial)was 1,020 lbs. the front mount spring rating (compression) calculated at 2,165 lbs. /in. The rear mount load (axial) rating was 600 lbs. and the rear mount (compression) spring rate was 1,250 lbs. /in. You can see these at www.lordmpd.com. I did not buy them because they are rubber vulcanized to the two metal plates without any tension stops. however, I thought the data on these two mounts might be transferable to another brand with tension stops. The numbers are for the front mounts: Shear max static load- 157 lbs. , shear spring rate- 455 lbs. /in. ; compression max static load- 1020 lbs. , compression spring rate- 2165 lbs. /in.
Rear mounts: Shear max static load- 92 lbs. , shear spring rate- 220 lbs/in. ; compression max staic load- 600lbs. , compression spring rate 1250 lbs. /in.
An important note on my front engine mounts were that I moved the mount to a point between the front and mid engine mount holes to reduce the bending moment at the bellhousing and adapter plate. It's the same as another project (photos) posted on TDR where they made their mount base plate tiied into both the front and mid-engine mounting holes.
I also have two charts that were provided in the calculations that show at what engine RPM's the peak 2nd order vertical and role transmitances occured along the RPM range of the engine. The vertical transmitance peaks were at 200 and 300 rpm and the 2nd order role peak transmitance was at about 400 rpm. I also noticed that this peak tails off slowly as you move toward an 850 rpm idle point. This shows why you can improve engine disturbances by increasing your idle speed. In essence you move toward a lower role rate region of the 4BT engine. I can e-mail this chart to anyone interested. I cannot post it hear because of the 32K attachment size limit of this site. It becomes too distorted to view.
I contacted LORD engine mounts. They performed a 4BT engine and NV4500 analysis for me and came up with their 3. 12" diameter "Flex-bolt" sandwitch mount p/n J-5425-1 for the two in front. and p/n J-5425-15 for the two that go under my transmission support plate.
My calculated front axial load rating (axial)was 1,020 lbs. the front mount spring rating (compression) calculated at 2,165 lbs. /in. The rear mount load (axial) rating was 600 lbs. and the rear mount (compression) spring rate was 1,250 lbs. /in. You can see these at www.lordmpd.com. I did not buy them because they are rubber vulcanized to the two metal plates without any tension stops. however, I thought the data on these two mounts might be transferable to another brand with tension stops. The numbers are for the front mounts: Shear max static load- 157 lbs. , shear spring rate- 455 lbs. /in. ; compression max static load- 1020 lbs. , compression spring rate- 2165 lbs. /in.
Rear mounts: Shear max static load- 92 lbs. , shear spring rate- 220 lbs/in. ; compression max staic load- 600lbs. , compression spring rate 1250 lbs. /in.
An important note on my front engine mounts were that I moved the mount to a point between the front and mid engine mount holes to reduce the bending moment at the bellhousing and adapter plate. It's the same as another project (photos) posted on TDR where they made their mount base plate tiied into both the front and mid-engine mounting holes.
I also have two charts that were provided in the calculations that show at what engine RPM's the peak 2nd order vertical and role transmitances occured along the RPM range of the engine. The vertical transmitance peaks were at 200 and 300 rpm and the 2nd order role peak transmitance was at about 400 rpm. I also noticed that this peak tails off slowly as you move toward an 850 rpm idle point. This shows why you can improve engine disturbances by increasing your idle speed. In essence you move toward a lower role rate region of the 4BT engine. I can e-mail this chart to anyone interested. I cannot post it hear because of the 32K attachment size limit of this site. It becomes too distorted to view.
"I cannot post it hear because of the 32K attachment size limit of this site. It becomes too distorted to view. "
You could upload it to your readers rigs gallery and then either post it in this thread or let us know when it is in your gallery.
Matt
You could upload it to your readers rigs gallery and then either post it in this thread or let us know when it is in your gallery.
Matt
I got the truck running. I don't think the GMC Topkick mounts are the hot ticket if you want to reduce vibration!
This is my first experience with a 4bt, so I don't really have a good basis for comparsion. At idle, it is about the same as a skid-steer loader (Bobcat w/ Kubota diesel). Well, maybe not quite that bad... .
Once you get it off idle, it smooths out, but is still a bit rougher than my 6. 5 liter GMC diesel.
This is my first experience with a 4bt, so I don't really have a good basis for comparsion. At idle, it is about the same as a skid-steer loader (Bobcat w/ Kubota diesel). Well, maybe not quite that bad... .
Once you get it off idle, it smooths out, but is still a bit rougher than my 6. 5 liter GMC diesel.
Considering one of the 4bt's I took out of a frito lay truck last year had over 600,000 miles on it and was still running the original motor, I will deal with the vibration issue. Hopefully I will find a counter balance kit for my current engine at some point down the road, but forr now I just bump the idle up at stoplights to smooth it out currently. This has proved to be much cheaper to do and satifies me enough to not be unhappy with the repower. Most of thre liquid filled high tech motor mounts I have seen and/or used for various vehicles in the past were not very impressive for the money. They also did not live long under high torque conditions. I will stick with the P-30 mounts, cheap and easily available with little mods needed to get the engines into most GM powered vehicles.
Comparing the 4bt to a 6. 5 just don't sit right with me. Something about longevity and economic scale of use being on an entirely different page between these two motors.
I have a case skid loader with a 4bt in it and to be honest, my jeep shakes more. Then too, my skid loader weighs 3 times that of my jeep. If only the 4bt's in the skid loaders had automotive injector pumps on them, I would be swapping out the skid loader's engine and selling the case. Oh well, probably better to just look for a balancer kit for mine in the end.
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I didn't mean to imply that the GM 6. 5 liter was the gold standard for comparison. Still, it is actually a good motor when used in its intended application (light duty truck, no extreme towing). I've got close to 170K on mine with no problems other than a poorly designed injection pump which GM replaced under warrently with an improved version.
The 6. 5, being a v-8, is a fairly low-vibration diesel. I don't think my 4bt will be this smooth. I'm not sure how much the situation can be improved through different mounts. I will probably do the same as you have done--keep the idle speed up and keep my eyes open for a balancer kit. Also, I used several bottles of lock-tite while putting this beast together, so hopefully this will keep the major parts from rattling off!
The 6. 5, being a v-8, is a fairly low-vibration diesel. I don't think my 4bt will be this smooth. I'm not sure how much the situation can be improved through different mounts. I will probably do the same as you have done--keep the idle speed up and keep my eyes open for a balancer kit. Also, I used several bottles of lock-tite while putting this beast together, so hopefully this will keep the major parts from rattling off!
Didn't mean to be taken serious, Sorry. I see the 6. 5's as a reasonable substitute to a gas 350 smallblock. They do work in that type of use quite well, Towing in my eyes is limited to an ATV trailer or load under 10,000 lbs. That is about the only time I have seen them hold up long term. This is not a bad thing for them, they were as you said yourself, a light duty truck engine.
The lock tite is a must, good to hear you thought of it. I went nuts torquing down bolts for weeks on end before tearing the thing completely apart and red coating anything that turned.
The best thing about a 4bt is the character they have and the love em or hate em followers who run them. I personally love em. Hard to justify a 6bt in a cj-5, even with long fenders, it is a cramming exercise of 5lbs into a 2lb sack. I have a few leads on used engines as well as well as bad motors which have balancers in them. If I can find useable parts in these, I will post them here in the future.
The lock tite is a must, good to hear you thought of it. I went nuts torquing down bolts for weeks on end before tearing the thing completely apart and red coating anything that turned.
The best thing about a 4bt is the character they have and the love em or hate em followers who run them. I personally love em. Hard to justify a 6bt in a cj-5, even with long fenders, it is a cramming exercise of 5lbs into a 2lb sack. I have a few leads on used engines as well as well as bad motors which have balancers in them. If I can find useable parts in these, I will post them here in the future.
I have had no problems with the P-30 mounts in any of the trucks I have used them in. They are more than adequate for light duty trucks and SUV's. I have not tried to tow long distances or long term with the 4bt's so I couldn't tell you if the mounts have enough mass to hold up under the torque of towing, but for everything else, they have been good. I have yet to have one break or have the rubber come apart in one if them.
I've posted my two engine mount analysis (by Lord mounts) pages in Reader's Rigs as "4bt mount disturbances" for anyone who wants to see calculated engine disturbance data for a 4bt/nv4500 with front mount moved back from the front hole locations roughly 8"
The Bosch 190's work well but I cannot compare since I did not try running with stock injectors. When I turn up the fuel it feels like a V8 when i pull up hills.
Exhaust is a 4" stainless system designed for a newer dodge. I cut wedges out here and there to create tighter turns and also for opening up turns. Just depends on how much you rotate the wedge you cut out before rewelding it back into the system. The turndown from the turbo was a cut up casting. Like the exhaust, I cut a wedge out of the turn-down in order to get a faster turn-down so that I would clear the firewall.
Exhaust is a 4" stainless system designed for a newer dodge. I cut wedges out here and there to create tighter turns and also for opening up turns. Just depends on how much you rotate the wedge you cut out before rewelding it back into the system. The turndown from the turbo was a cut up casting. Like the exhaust, I cut a wedge out of the turn-down in order to get a faster turn-down so that I would clear the firewall.
If your using the Chevy clutch/flywheel that comes with most of the 4B's you can try this trick using 89-93 Dodge CTD isolators to eliminate most of the felt vibrations. The test was done under a no load condition but proved to work good on the road. If you use any other clutch/flywheel all bets are off.
Steve
Steve
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MOF I used the same isolators and drilled about 15 holes through each one parallel with the metal plates for the what I consider a no vibration ride. I can see out my side mirrors with no significant vibration. Certainly not more than what my 1st Gen 6BT had. I thought it was Steve that tried this first.
That's incredible that a couple of 3/8" holes will make that much of a difference. 
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Matt
#adMatt
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tabell said:
See post #15 for a link to the full set of pictures.
Steve
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Issue 128 – Digital Version
Digital Magazines
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Back Issues
Subscription Status
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Ram Diagnostic Trouble Codes
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