engine cross member question
 

hello new guy here.what a great site this is. i am hoping for a little help. is it possible to have the engine cross member in backwards? i bought an abandoned project with the frame already finished. after looking at pics on here im thinking it is possible that it is in backwards. does anyone have a pic of the bare frame so i can see the cross member? it is a 68 gmc 2 wd short bed
thanks bryan

Re: engine cross member question
 

Post a pic, sure someone will chime in as to if it's correct or not

Re: engine cross member question
 

pictures...of mine I think it would be real hard to get this backwards....but anything is possible show us a picture

Re: engine cross member question
 

what was the question again......? my mind drew a blank when I saw Zicc's framework.That is NNNNIIICCCEEE!

Re: engine cross member question
 

... ah shucks... thanks for saying :)

Re: engine cross member question
 

Did you knock out all the rivets for the frame cross supports? How are you putting them back in? Bolts and nuts or replacement rivets?

Re: engine cross member question
 

check out post #100 in my Doc & Kim build 7/16 Pan Head alan keyed stainless little pricey but i like them ...

Re: engine cross member question
 

I'm curious about people's experience with the lifetime of bolts used in place of rivets. Rivets place thousands of pounds of clamping force, and are smooth (and fit quite closely in the holes, as well). Bolts are put in with hundreds of pounds of clamping force, and usually are installed in holes that are oversize. One might end up with the frame racking to some degree because of the hole slop, at a minimum.

Re: engine cross member question
 

X-member correct orientation for oil pan clearance

Re: engine cross member question
 

I thought about that ...7/16 is pretty tight and in some cases i had to hone a bit... I also replaced all grade 5 with grade 8 ....I will be driving this truck and report back in a few years if I see any slop:)God Willing

Re: engine cross member question
 

What length? Or are they all different?

Re: engine cross member question
 

wow thanks for the help. i will try to post a couple of pics. it looks like my cross member is in right but the engine mounts are not. my engine perches are hanging off the cab side of the cross member.from the pics it looks like they should be hanging off the front side. i have a 5.3 from an 02 silverado and a 200r4 in it. with the engine slid all the way forward it is tight to the cab
(dirty dingo mounts).

Re: engine cross member question
 

here is an attempt at pics you can see the mount is hanging over the cab side of the cross member. is this backwards?
thanks bryan

Re: engine cross member question
 

Correct for a small block mount. The factory ran the brake line across the rear of the x-member though..........if it that matters to you

Re: engine cross member question
 

so the mounts are in the proper location? is it possible to move them to the front of the cross member? would i have to drill the lower holes? i think i bought brake lines for a 70 with disc brakes. i thought it should go along the back but this is the on way it would fit.

Re: engine cross member question
 

If my memory is right mostly 1’’ few 3/4 some 1 1/4 on the pan hard c member and nylock nuts and flats

Re: engine cross member question
 

Also make sure that there are no threads on the bolt where it goes through the frame. Any movement will end up hogging the holes.

Re: engine cross member question
 

wow that is very nice. is yous a v8? my crossmember is in the same as your but my motor mount perches hang over the back edge instead of the front edge like yours
thanks bryan

Re: engine cross member question
 

zicc1835 Nice work on the frame!!!

Re: engine cross member question
 

Would be true, but grade 8 bolts are strong enough so long the proper shank length is used. Meaning the section of the bolt with no threads is inserted the full length of the frame and nylock nuts are used with washers and torqued to spec. One should always periodically inspect their hardware security though and rivets do fatigue over time.

This is a good rule of thumb.

T = K x D x P

• T
Target tighten torque (the result of this formula is in inch pounds dividing by 12 yields foot pounds
• K
Coefficient of friction (nut factor), always an estimation in this formula
• D
Bolts nominal diameter in inches
• P
Bolt's desired tensile load in pounds (generally 75% of yield strength)

http://www.zerofast.com/sites/defaul...-Fasteners.jpg

Re: engine cross member question
 

If you want a little more strength, use grade 8 fine thread hardware and stay away from the grade 5 ny-locks and lockwashers. Use a crimp nut and torque them down to the rated spec. I think (off the top of my head) that a Gr8 7/16-20 torques to 70lbs. I did a conversion from 2wd to 4wd about 25 years ago on a 71 with a front x-member for the spring hangars. I bolted the member to front of the frame rails and did that very thing. Never had to touch the bolts again. They never came loose or moved. Sold the truck to somebody in Washington state.

Re: engine cross member question
 

Good info hear for all thank you

Re: engine cross member question
 

It's good to discuss bolt strength for the replacement of factory rivets, but remember that Grade 8 bolts while stronger in tension, are definitely more brittle in shear. The Grade 5 smooth shank portion of a longer, slightly oversized 7/16"UNC or UNF bolt might be a better choice. torqued to spec, they will be stronger than 3/8" bolts, and may better handle the side loads a shifting, driving frame may impose on them.
Since my truck will become a Sunday driver, i don't think bolt choice is an issue, and certainly crawling under from time to time to put a wrench on anything you can reach would be an add.