Jim85IROC

iTrader: (6)

Last night I finally got around to putting my pistons & rods into my block (402 stroker, compstar rods w/ARP 2000 bolts). The specs said 75 ftlbs or .0047-.0052" of stretch. At 75ftlbs I was only getting about .004" of stretch. Moving as high as 85 ftlbs didn't provide any additional stretch. I got nervous about going tighter to get the proper stretch. Should I stick with 85 ftlbs or keep reefing on them until I get .005" of stretch?

COPO9560

Stretch is a far better measure of clamping forces provided by the bolt. Unfortunately it is more difficult to measure than torque.

What lube are you using on the ARP bolts - this is very important. Have you run the nuts back off and retorqued and checked stretch? Might have to do this a few times to get torque and stretch in line.

Jim85IROC

iTrader: (6)

I'm using the goop that was provided with the rods/bolts. I went through 3 tightening/loosening sequences and saw no change in stretch for a given torque value. I'm just concerned that I'm going to wind up at 100 ftlbs or more to get to .005 of stretch.

allout06

iTrader: (11)

pfft 85ft lbs.... we stretch head studs at work with 9000psi . The machine will stretch the bolt a good inch, inch and a half lol no joke

93Z2871805

iTrader: (5)

Stretch is more accurate than torquing. However, people use torque specs all the time with great success. I wouldn't keep wrenching over torque just to hit stretch. If anything, call up ARP's tech line and see what they recommend.

BigRich954RR

iTrader: (1)

what were the rods TQ to for sizing ?

go up to 90-95 lb and see if it moves any but id hold there

JS01

iTrader: (10)

As long are your torque wrench is calibrated and you're using the CMD lube provided with the rods run them to 75 and don't sweat it.

Jim85IROC

iTrader: (6)

I torqued the rods to 75ft-lb during pre-assembly for my plastigage measurements, which is why I'm a bit gun-shy about going too far beyond that in order to get my stretch to .005"

raven154

iTrader: (14)

Well I have a question about this since you brought it up. This is a copy and paste from the latest instruction download from ARP for kit number 234-6301/234-6321 AKA ARP2000

I dont have a stretch gauge and was planning on installing my bolts per these instructions but it seem it takes much more than 45ft lbs to get to the proper stretch. I guess I'll just have to buy a stretch gauge now to verify the proper tq.

Well come to think of it, the both specs are different. 75 ftlbs or .0047-.0052" vs 45 ftlbs .0065-.0070" so I guess I'll be calling ARP to verify the correct stretch.

Part Number: 234-6301 & 234-6321
Application: CHEVY GENIII/LS SERIES SM BLK
Cap Screw without Washer - Rod Bolt Installation
[1] Please check the part-number(s) for your application
against the part-number(s) listed on the instruction sheet.
[2] Make sure there is an adequate chamfer around the bolt
hole on the connecting rod cap to clear the radius under
the head of the bolt.
[3] Use ARP Ultra-Torque Fastener Assembly Lubricant
to lubricate the threads of the bolt and the under head of
the bolt. Then install the bolts and tighten them hand
tight.
[4] ARP recommends using the STRETCH METHOD when
tightening rod bolts. Following the instructions for using a
stretch gauge, Stretch the bolts to . 0065 - . 0070 .
[5] If you do not have a stretch gauge, torque the bolts to
_ 45 ft-lbs using ARP Ultra-Torque Fastener
Assembly Lubricant.
[6] The connecting rods should always be re-sized after new
rod bolts are installed.
[7] A log should be kept on the original non-torqued length
of each bolt. Bolts that have any permanent deformation
or have increased in non-torqued length by more than
.001 in. should be replaced.
If you have any questions or need additional information please
contact us at (805) 339-2200 or by FAX (805) 650-0742

95ONE

iTrader: (1)

That's for the stock crack cap.. He said he was using forged Compstar rods.

He's probably using this ARP model code. 234-6402

even then it only says 55 lb ft.

raven154

iTrader: (14)

According to the ARP catalog, 234-6402 is an ARP 2000 pro wave and is for a 400ci chevy and its a stud with a nut. Looking at the catalog, we need the head style E while the 234-6302 is an A.

Jim85IROC

iTrader: (6)

I just called ARP. Their advice was essentially to call Compstar and see what they say.

They did verify, not surprisingly, that the stretch is the measurement that I should be going by... I'm just concerned that the .005" stretch is going to result in a very high torque number.

Jim85IROC

iTrader: (6)

Update... I called Callies. The tech at Callies agreed that I shouldn't just keep reefing on the bolts to get to the .005" of stretch, and agreed that I should leave them like they are (torqued to 85ft/lbs). He assured me that they will be "fine".

raven154

iTrader: (14)

Thanks for the info!! I just have to many irons in the fire right now lol

KCS

iTrader: (20)

I've always seen 75ft-lbs work perfectly with those Compstar rods. Did you lubricate under the head of the bolt as well as the threads?

Jim85IROC

iTrader: (6)

Absolutely! The threads and the area under the head were liberally lubricated with the supplied grease.