DIY press fit con rod install

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Racin'Jacin
Posts: 328
Joined: Tue Oct 28, 2008 11:01 pm

DIY press fit con rod install

Postby Racin'Jacin » Fri Jun 26, 2020 11:33 am

Hey Guys, I thought this might be helpful if you've never done this before. Background: I am putting together a "fresh" motor for my old convertible. An old Rambler straight six. A 195.6 OHV to be exact. Always wanting to learn a wee bit more (or maybe SAVE a little $ ) I decided that I'd install the press fit connecting rods myself. I've only done this a couple times and I HIGHLY reccomend anyone that wants to try this - to give it a whirl on some junk parts first. Having said that here's what I consider crucial:

1. Double check ALL measurements first. keeping in mind heating the rod end up to a STRAW color is gonna be in the 450F range so you're getting around .0025" of growth and you're somewhere around .0005" to .0020" of interference so you can see you're NOT getting a LOT to play with. (and yes these numbers are all approximations - but you get the drift). If you've got something AT or ABOVE the optimal high side interference fit you may want to run a hone thru it first.

2. Clean clean clean everything. Moreso if you have old or nos parts - oil gets dried and or sticky and you dont want ANYTHING messing you up!

3. Borrow or make a fixture. This is NOT as elaborate as it migth sound. All you are wanting to do is to have a STOP for the pin. This fixture could literally be made from wood. Now CLAMP that fixture to your bench!!!! Better yet bolt it down.

4. Understand the piston and rod ORIENTATION. Put reminder notes on your fixture so you dont install anything backwards!!!!!

5. Get a heat temp gun a propane torch and practice with it - find a junk rod - heat it and see where its at - BTW I reccomend NOT doing this in direct sunlight - you wanna see the color not be overwhelmed with sunshine. When I heat the rod I use a regular benzomatic and heat evenly on either side constantly changing from side to side - There's no magic here - you just want to heat it consistently and evenly as possible.

6. I also reccomend a "pusher" - I used a scrap of metal turned down to fit inside the wrist pin - again - no magic - nothing special.

7. DON'T dilly dally!!!!! Be CALM!!!! But go like hell!!! You have 2 seconds to get it in place!!!!!! Once you do your first one you WILL feel like a BOSS. Just wait until you screw one up!!!!!! In anotherwords - don't get cocky.... instead be methodic!!!!!!! Practice practice practice - then throw those away!!!!!!

8. Put a drop of oil on either side of the wrist pin and call it a WIN!!!!

BEFORE YOU GIVE IT A GO....do a search on youtube and watch a few videos. It's good to see it in action. If I had more experience - I would have videoed it, but as a newb I didn't want the distraction. Personally I put this off for years - thinking the magic was too difficult. Now, I think differently. Yes there's a bit of a pucker factor - that's why practicing on some junk parts is a good idea. I hope I've inspired someone to at least give it a whirl on soem junk parts!!!!

BTW I've seen guys do this with No Fixture and for whatever reason (probably more time) they all seem to heat the rods to a BLUE or beyond color. there's quite a bit of controversy about heating rods that hot. Again I'm no expert but it seems most agree that heating to a STRAW color is the safer bet. YMMV.

Jacin
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Fred32v
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Location: Munson, OH. retired

Re: DIY press fit con rod install

Postby Fred32v » Fri Jul 03, 2020 9:55 pm

I never built anything where the pins were pressed fit into the rod.
I appreciate that you took the time to show us what you did and how you did it.
It was a fun read. I can't want to hear that Rambler run.

If this were on Face Book, I'd have given you a thumbs-up "Like".

Strange kind of fun!
Fred32v
GMC Canyon Crew Cab Short Box 4x4 V6!

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Racin'Jacin
Posts: 328
Joined: Tue Oct 28, 2008 11:01 pm

Re: DIY press fit con rod install

Postby Racin'Jacin » Sat Jul 04, 2020 12:11 am

Fred, My first motor rebuild was a small journal 327 Chevy. It had press fit rods, but I took it to the machine shop as I was still under the impression then that there was "magic" involved.

Last two motors I did both also had press fit, the turd motor in that nightmare MG were press fit and of course my little rambler six. This old Rambler motor is pretty unique. It was a "converted" flathead motor that was basically originally designed in the 40's. Largely oversquare whcich makes sense when you think that ALL cars were stick back then so some "extra" low end torque was welcomed. By any standards they are NOT big performers, but for a classic around town cruiser is about perfect. My biggest problemm is that I've been tripping over this motor for the better part of 15 years so just FINDING all the parts has been challenging. SLOW but sure - I'll get it one way or another.


Jacin


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