1756cc Torque Specifications

[Chap]

Hello Everyone,

While in the process of rebuilding my engine, I've come across several discrepancies about torque specifications. Namely the connecting rod bolts, the International Auto Shop Manual claims it to be 54 ft-lbs, the Haynes Manual claims 38 ft-lbs and while ordering new bolts I asked Vick Autosports and they claimed 47 ft-lbs. So my question is this, what are the correct torque specifications for a 1976 Fiat 124 1800?

~Steve

[pope]

54 ft./lbs is in fact the factory spec.,

except in California where owners are not strong enough to get to 54, so they are allowed to tighten it as hard as they can....which is usually in the mid 30's.

[ventura ace]

You are wise to question the discrepancies you see between the various publications of shop manuals. I usually refer to 3 or 4 different manuals while doing any repairs on my spider, since I have found many discrepancies also. I think the problem stems from the fact these manuals attempted to cover several years production, but in many cases, there were changes made during those years.

I ran into the connecting rod torque question when I rebuilt my 1.8L engine, and ended up stretching a few bolts while trying to torque to 54 ft-lbs, as the manual said. Reading my Fiat 124 spider Shop Manual again (Import Parts America, Fiat Parts Division), I realized the the 54 ft-lbs was for 10mm bolts (2.0L engine maybe??), and not the 9mm bolts in the 1.8L engine. My official Fiat Workshop Manual for the earlier cars shows 36 ft-lbs for the 9mm bolts in the 125BC engine (1438 and 1608 cc) (Screw R 100 material), and 47 ft-lbs for the 9mm bolts in the 132AC engine (1592 and 1756cc) (R 80 material). My Autobooks manual says the same thing. My Haynes and Chilton manuals all say to use 38 ft-lbs for years 68 - 78.

I bought new bolts from Mark Alison. We discussed the torque confusion, and agreed that I should torque somewhere in the range of 36 - 40 ft-lbs, and I did.

If your bolts are 9mm, I definitely would not take them up to 54 ft-lbs, and I wouldn't advise the 47 ft-lbs torque either, since I know that some of my original bolts started to stretch somewhere around that torque level.

Alvon

[pope]

Alvon, you could be correct , I have a 75-82 official Fiat shop manual and It states that the connecting rod bolt is a M10 (R80 material). The defining clue is to find out what size bolt Steve has on his connecting rod.

[Chap]

The defining clue is to find out what size bolt Steve has on his connecting rod.

Just measured the bolts, they are indeed 9mm.

~Steve

[Chap]

Everything is in place now. Just wanted to thank you both for your help.

~Steve

[SLOSpider]

Wish I would have read this about an hour ago.....new bolts on order Monday I guess as one nut did not like to be at 54 foot pounds of torque and stretched the bolt....damn it Jim...I think that Ill use the 40 ft pounds as my guide to reinstall...always something ~!

[dreamer]

Just saw this thread and thought I'd ask where you folks source bolts? I am rebuilding my engine and noticed that the small bolt I believe it's an M10 x 1.25 x 65mm for the first main bearing cap is stretched so it's not going to torque to spec of 59 lbs. So again, where do you source these? Thanks in advance. Calvin

[3505jd]

Ventura Ace
Was torquing the conn rod nuts to 36-40 ft-lbs on your 'early' 1756cc successful i.e. no problems after start-up?
I have a page from the factory service manual for an 'early' 1756cc Fiat 131 which does call up 47 ft-lbs (R100 bolt, R80 nut).

[Nut124]

The older con rod bolt are smaller diameter than the later (post 78).

It is critical to know which bolt you have and apply the correct torque. If you torque the old, skinnier bolt to the late bolt spec, it will stretch and eventually fail.

When torqueing, if torque does not develop progressively and in the same way for all rod bolts, then start over. The rod bolts is the weak part of the pre-78 engine.

[3505jd]

Nut124

What is the correct torque for lubricated 1756cc 9mm connecting rod nuts?

[Nut124]

I checked my build notebook from 2 years ago.

In it I state that the spec is 38 ft lbs but no source is mentioned. It shows I did testing with the original set I had., which was already compromised by 54 ft-lbs. Additional permanent elongation seemed to start at about 45 ft-lbs. Torque below 42 did not result in permanent elongation. Book shows I torqued my new set to 39 ft-lbs. This set came from an unmolested engine.

No note on whether oiled or dry, but likely light coat of engine oil.

[3505jd]

Nut124

Thanks for that information. I was hoping somebody had done some testing on bolts that had been compromised at 54 lb-ft.
I would assume that you did not experience any engine problems using 39 lb-ft.

[Nut124]

Good so far. The engine sees 7500rpm regularly and has held together so far.

I did not use the compromised bolts. Used a new old set. I was building a high performance engine and did not want to cut corners there.

[3505jd]

Nut124

Big thanks for that information. I will be using a set of new conn rod bolts from Auto-Ricambi.
When you removed the over-torqued bolts, did you observe any bearing damage?