Did I %#^* Up?
 

So I just finished installing my new engine and the first one I've ever built myself. I have Manley forged rods and supertech pistons. I had my crank polished and balanced but didn't have my rods balanced as they were very close out of the box. I have the car running now and running well except there is much more vibrations when I rev the motor than when stock. I haven't put it back up on jack stands to look for anything loose or overlooked but after researching a bit I'm a little concerned I caused this by not balancing my rods. Thoughts?... I'm not opposed to pulling the motor again and tearing the motor apart but would rather not if not needed. Thanks in advance.

There are dozens of people here with built engines who never balanced any part of it. My guess would be something else is wrong or got messed up.

or you also installed mazdaspeed engine mounts?

I have never had any shops completely balance my motors. Never had an issue due to that.

Cranks are balanced to a calculated "bob weight" which is derived by weighing the reciprocating mass. The rod (with bolts), piston, pin, pin retainers, and rings are part of this calculation.
If the machine shop did not have your parts the crankshaft could only be balanced to what ever the "standard" for the original parts was. It is not balanced to the new parts. If this was the case I'd change machine shops.
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The above is complete BS regarding inline engines; I have built FAR too many V8s recently.
Sorry, I will try to not spread incorrect information in the future...
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If they had everything (and they should have demanded everything that touched the crank including balancer and clutch stuff) you're fine.
All the brand name stuff are damn close to each other (+/- 2 grams is common) and you will have more than 5 grams of oil riding on these parts during operation. Super fine balancing is a waste of time and money IMO.
Balancing makes for a smoother motor but it is not a requirement. Unbalanced stuff works fine.

If you can feel the vibration by just reving the motor up I'd look for loose stuff. Harmonic balancer, flywheel, clutch would be my first suspects...

Pertains to 90 degree crank V8's. Has nothing to do with in-line 4's.

Yep, Ive heard that if a shop tries to bob weight an inline 4, grab you stuff and run away.

Thanks for the replies everyone. Makes me feel better hearing from you that most likely I should be ok. Im going to assume my problem is elsewhere since its only when I rev it up. I should know more after i get under it tonight and check everything out. I did have a hard time installing my ATI Super Damper so hoping that isnt the problem area. While running it appears to rotate smooth. Fingers crossed its something that doesnt require pulling the motor again.

ATI pro tip, heat it in the oven for about 10-15 minutes @ 250°F, apply Moly Lube -aka cv grease. it will go on 1/2 way by hand then slide the rest with proper tools. easy.

[QUOTE=ryansmoneypit;1439409]ATI pro tip, heat it in the oven for about 10-15 minutes @ 250°F, apply Moly Lube -aka cv grease. it will go on 1/2 way by hand then slide the rest with proper tools. easy.[/QUOTE

Pretty much what I did the second time except I didnt heat it up. I wanted to but the wife saw me turning the oven on with car parts in my hand and I got the look and took the hint real fast that wasnt gonna happen. Greased it up and ran it in with my old crank bolt. Bottomed out nicely so I would be surprised if that was causing any of my vibration. I just spent about 30 minutes under the car and everything is tight and installed correctly. I was really hoping to find something obvious but unfortunately that wasnt the case.

This may have been a joke, but did you check your motor mounts?
They tear with a sideways glance.

I installed new OEM mounts when I had the motor out. I just double checked them and they are tight.

I just came in from the garage and while the car was up on jack stands I started it and got underneath it. I hear strange sounds coming from the damper area or the water pump pulley. Could also be my new covers rubbing on the idler pulley.

Honestly it seems to be quieting down and not vibrating as much when I rev it. I very well might be paranoid and over reacting since I've put about 3 miles on it since dropping it in. I took it out and did the flyin Miata break in recommendations and haven't been out since. Maybe this is normal engine break in things? It's all new to me.

I'd try your old damper. Did you install a different flywheel? I assume it's vibrating in neutral? Remember installing the thrust washers? Did you plastigage the bearings?

I'm ready to rule out the damper only because it seems to spin perfectly without any noticeable deflection.
Same flywheel
yes to nueatral
thrust washers in
plastigauged everything and everything was well within specs.
Tomorrow I'm going to try about a few more miles on it after loosening my PPF bolts and making sure everything is lined up correctly to rule out some type of misalignment in the drive line and see what happens.

If it's a neutral thing, PPF shouldn't matter, but there is an adjustment spec to the transmission height that affects the driveshaft angle.

Dumb question, but you're letting it get good and warm first? Your slugs should have more clearance than the cast stockers. You might be noticing? I thought the Supertechs were supposed at cold slop.

Noob asking why. Are most inline 4's a symmetrical crank shaft? Is it because there are equal amounts of mass moving in the same direction at equal distances from the center of mass of the crank. Are 90 degree cranks asymmetrical therefore requiring bob weights?

If it vibrates with the car not moving then ignore the PPF and pay attention to the engine, flywheel, and other rotating components there. Imbalanced components that generate enough vibration to easily feel them will destroy the main bearings in short order.

Figuring it out shouldn't involve hoping it goes away. :2cents:

Regarding the ATI Damper- without heating the damper, you are making things really tough on yourself. It is also kind of a No-No to use the crank bolt to drive the pulley on. Moly infused grease is a MUST. You will 100% damage both the crank and the damper if you use most anything else. As an alternative heat source, I often use a heat gun propped up and blowing through the center of the damper. On a low setting it takes about 10 minutes.

Could your vibration be tune related? Or a camshaft off by a tooth? If you installed aftermarket adj cam shives then be suspect as they do not come out of the box anywhere close to oem settings. Don't run it hard until you get it figured out. I cracked an forged crower crank once by taking "just one more lap" when trying to figure out a funny engine vibration... It was the damper coming apart. Good luck.

I think im dealing with a flywheel or clutch issue like many of you mentioned. While sitting in the car in neutral if I rev the engine I feel most of the vibrations around the tunnel area. When I stand outside the car and rev up the engine its nice and smooth with no noticable ugly sounds. I can lay my hand on the motor while reving it up and it feels very smooth. Cant imagine what i could have done wrong installing the flywheel as ive done that several times before without any problems but im going to drop the tranny to double check and at least rule that out.

I also have stiffer valve springs so maybe thats causing some valve train noise?

Once the car is warm and idle comes down it sounds normal except for the vibration under accerleration.

Thanks for all the suggestions. I will report back after dropping the transmission and checking to see if I screwed something up in there.

I had a clutch spring fall out on a different car a very long time ago. Drove fine, but had vibration under accel.

So my two problems are vibration when reving in neutral and a strange noise coming from the front of the engine while running. Not a knock knock noise but something I haven't heard before. Decided to remove alt belt since I only have one belt and to my surprise noise is gone!!.... either my old alternator or brand new gates water pump is responsible. At least I know it's not internal. Still have the vibration but will investigate further once the tranny is out.

I guess I like to waste time, I balance most all the performance builds I do, to .1g of mean

so pistons are that close, small end of rod and the over all of the rod

Most 4 cylinder cranks are close from the factory as far as balance goes, but they still can be better

I normally take the H-bal n bolt, time belt gear, crank, flywheel with bolts and pressure plate and bolts to be first individually balanced then balanced as a unit

I have seen rotating the pressure plate throw the balance off as much as 52g, and commonly see 20g

So once I get done with the balance job, the pressure plate is indexed to the flywheel

Now IIRC, there is some clearance work done on cyl 1 just behind the water pump on the 1.8l, so with spec stack, your new water pump shaft may be lightly touching Cyl 1

**EDIT**
Thought I did a write up on the Manley rods..
https://www.miataturbo.net/engine-pe...ng-rods-65527/

Thanks for the write up on the rods. I did read your entire post as I was reaserching my build. I guess my lesson learned here is listen to everyone here and not the machinist. The shop that i took my block, crank and head to is a very good shop and the guy who owns the shop is very reputable and does great work. He knew I had aftermarket forged rods but only asked for my pistons once he determimed if my block requried boring. I guess i assumed balancing the rods wasnt needed since he didnt ask for them.

The ATI Damper is quite a bit heavier than stock one would that cause anything??

On a side note I did just take it out for a 15 mile shake down and it seemed to run fine. Maybe im just being over freaked out since ive never built my own motor before and havent really given everything a chance to settle into place.

Going to change the oil for the first time tomorrow so fingers crossed everthing looks ok

Just a little update. I changed the oil and other than a little discoloration from all the assembly lube the oil was as clean as when I put it in with no signs of metal or shimmery bits. I'm pretty confident there's no metal on metal interference taking place. I still have a vibration around 2.5- 3k that I need to figure out but will know more after I drop the tranny and reinstall flywheel and clutch to rule that out.

Are you sure you haven't put the engine mounts in upside down?.....there is a metal tab that is supposed to fit in a locating hole (or something like that).....if you fit them wrong you may have metal to metal contact on each side.

I've checked that already but thanks for the input. When I was out driving it sounds like a heat shield ratteling under the car somewhere so I'm going to get under it again tonight. Hopefully I'll find something obvious. I noticed the down pipe contacting the shelf in the engine bay so I'm sure that is contributing to it but doubt it's solely responsible.