replacing head bolts a must ?

JWMX3 · Post by **JWMX3** » December 13th, 2005, 10:35 pm

It says in the manual "recomended" to replace, and i know they are torque to yield bolts, but for ~130.00 cdn i really only want to replace them if it would be stupid not to, can they be measured or checked in any way to determine if they are reusable ?

lakersfan did you put new bolts on your kl ?

custommx3 on your rebuilt ze ?

PATDIESEL · Post by **PATDIESEL** » December 14th, 2005, 1:35 am

I wouldn't use them again if Mazda sais not to. Also, for that price you can get some ARP head bolts that will hold a ton more than stock.

jschrauwen · Post by **jschrauwen** » December 14th, 2005, 5:38 am

Just a guess here - but I would imagine it would be because the tensil strength may be drawn into question if they are the original head bolts and their integrity to withstand re-torquing may be in question due to the repeated heating and cooling that the older engine has been subjected to and the previous previous original torquing it recieved. Don't want to run the risk of snapping even just one.

PATDIESEL · Post by **PATDIESEL** » December 14th, 2005, 10:14 am

My thoughts as well. If you break one of hem you will be hating life. Taking the heads off to get one bolt out is a ton of work. It will also cause you to have to replace a head gasket, which are not cheap.

Do the right thing and get new head bolts.

Spinkx79 · Post by **Spinkx79** » December 14th, 2005, 11:26 am

PATDIESEL wrote: Also, for that price you can get some ARP head bolts that will hold a ton more than stock.

Not for that price you wont, i bought the ARP block and head stud kit for $500+ USD. So figure half for heads only and your still double the price of stock.

lakersfan1 · Post by **lakersfan1** » December 14th, 2005, 1:17 pm

In the Haynes manual, or the Mazda manual? The Mazda manual as far as I know says to check the length for stretch, and if they're within spec, you can reuse them. As far as I know only Haynes/Chiltons says to just replace them. I reused mine.

JWMX3 · Post by **JWMX3** » December 14th, 2005, 2:53 pm

lakersfan1 wrote:In the Haynes manual, or the Mazda manual? The Mazda manual as far as I know says to check the length for stretch, and if they're within spec, you can reuse them. As far as I know only Haynes/Chiltons says to just replace them. I reused mine.

yah the haynes said replace, i imagine most of the time they are in spec but i'll check anyways

edit- quote from mazda manual "Replace cylinder head bolt it distance is not 5.26-5.29" (133.7-134.3mm)

PATDIESEL · Post by **PATDIESEL** » December 15th, 2005, 9:43 am

Spinkx, I know I priced some head bolts once when looking into a head build on he K8 (mannny years ago before the ZE was around) and didn't remember them costing that much. Maybe it was a buddy price since I know some guys with race cars. Whew, they do geta pretty pennie for those huh!!

Anyway, how are you supp[osed to check specs? Is it just the total legnth. I thought you would have to check for stretched threads, butthat would be difficult. (maybe by running a die around the bolt and see if it catches???)

JWMX3 · Post by **JWMX3** » December 15th, 2005, 10:38 am

PATDIESEL wrote:Spinkx, I know I priced some head bolts once when looking into a head build on he K8 (mannny years ago before the ZE was around) and didn't remember them costing that much. Maybe it was a buddy price since I know some guys with race cars. Whew, they do geta pretty pennie for those huh!!

Anyway, how are you supp[osed to check specs? Is it just the total legnth. I thought you would have to check for stretched threads, butthat would be difficult. (maybe by running a die around the bolt and see if it catches???)

it is total length 133.7 - 134.3mm, there is a diagram in mazda manual showing it, you just measure the "neck" of the bolt not the bolt head itself

lakersfan1 · Post by **lakersfan1** » December 15th, 2005, 11:14 am

Head bolts are $80 a set from Flatlander Racing.

PATDIESEL · Post by **PATDIESEL** » December 15th, 2005, 3:40 pm

Performance or OEM replacement Lakersfan1?

lakersfan1 · Post by **lakersfan1** » December 15th, 2005, 7:23 pm

PATDIESEL wrote:Performance or OEM replacement Lakersfan1?

Just OEM. Only place I ever saw 'performance' was a head stud bulk buy some time ago. I thought those were custom head studs, though.

babyblueMX3 · Post by **babyblueMX3** » December 17th, 2005, 9:59 am

I reused my stock headbolts because they were within specs on my boosted ze..They hold damn fine on 20pounds
most cars have 8-10 head bolt per head. Meaning like 8 bolts for 4 cyl engines.
We got 8 bolt per head so that is 8 bolts per 3 cyl.
so we have 16 bolts to hold the power of the engine when most engine use 8-10

and yes ARP studs cost an arm an a leg. Spinx even got his in the group buy on probetalk. I'm currently taking dimensions and will be sending them to ARP so they can make some again. I called them after the group buy and they said nothing was listed for the kl

JWMX3 · Post by **JWMX3** » December 17th, 2005, 12:36 pm

Mine are all streched past the limit

i guess thats what 300,000 kms will do

markmclean · Post by **markmclean** » December 26th, 2005, 11:58 pm

torque to yield bolts must be replaced because they are high in silicone content much like hypereutectic pistons. Upon proper torquing they stretch. Subsequent uses will not be able to withstand additional torquing. If they dont fail completely, resulting in breakage, they simply wont achieve proper yield. another option is (if the engine is being rebuilt) having your machinist install hardened studs in the block that can be re-used.this practice is common in race type applications.Good Luck