When do you need HD head studs?

[400exstud]

What kind of stuff do you have to do to your engine before you need bigger head studs?

[nosliw]

compression over 11:1. not sure if that's all though.

maybe even with just a 440? i've heard guys on here say the 440 is a good bore as long as you get the headstuds......

[RiderTRX400ex]

generally with higher compressions and big bores... compressions over 11:1 like nosliw said

thats what id say anyways, IMO

[MarkyNark]

I dont know why some folks have problems with head studs pulling out and others do not. I ran a 13:1 compression piston in a 440 kit for years and never had a problem. I finnally conceded this week and got a HD stay bolt kit since Im running NOS. I pulled the old studs out and they were perfect - no thread damage or anything. It makes me wonder if some folks torqued them correctly to begin with.

[Pappy]

Originally posted by MarkyNark
I dont know why some folks have problems with head studs pulling out and others do not. I ran a 13:1 compression piston in a 440 kit for years and never had a problem. I finnally conceded this week and got a HD stay bolt kit since Im running NOS. I pulled the old studs out and they were perfect - no thread damage or anything. It makes me wonder if some folks torqued them correctly to begin with.

well stated. ive often thought the oversize headstuds were not required unless you had issues with the stock ones that noone seems to want to replace when they do an engine kit.

[MarkyNark]

BK,

Actually, I think that it’s exactly opposite of what you said. I think that EVERYONE is replacing head studs and spending the 2-3 hours of labor to do it. I know there are guys on here that have had problems with the studs pulling out. The part that I have a hard time with is understanding why mine never did pull out with a 13:1 compression piston and a 440 bore. I mean, that’s pretty dramatic. I just wonder if there are rather unscrupulous service techs out there actually causing the problem by not torquing the bolts correctly to begin with and then blaming the problem on the stay bolts. Then they get another 3 hours of labor to fix a problem that should have been taken care of with a properly maintained torque wrench. Like I said, I'm not pointing fingers - just trying to make since of the problem and the evidence.

[Pappy]

i agree about the torque wrench, i just have seen so many folks get say a 440 11-1 kit, install it or have it installed, then blow a head gasket or re ring it and dont even buy new stock headstuds. i thought most headstuds had a stretch value that actually was designed into the stud, after one use they are usually recommended to be replaced.

if i have another engine built, the head will be oring'd, especially if the compression is high or a turbo/nos is employed.

in any event, ill leave the engine building to well known builders or someone who has demonstarted thier ability to me..lol too much money is wasted by trying to get someone who doesnt do these engines and having them make costly mistakes.

[MIKE400EX]

Another likely reason is that many people try to run too high of a compression ratio on too low of an octane fuel. Cylinder pressure soars with even the slightest bit of pre-ignition or detonation, and can compromise a gasket or studs in a split second. It's hard to hear it with the loud pipes and helmets etc.. Not all 11:1 (example) engines produce the same cylinder pressure when running.
Good point about the torque wrench, and make sure that it's an accurate one, not something that gets kicked around the garage floor or is used for a breaker-bar.

[MarkyNark]

That makes sense too. I know Im going to run 110 with my 12:1 because I'll be trying to keep the pressure down with NOS. Race gas can be worth every penny - But, I think some guys try and push it because of the cost of the fuel. Its pretty minor in the grand scheme of things.

[bwamos]

Originally posted by Pappy
in any event, ill leave the engine building to well known builders or someone who has demonstarted thier ability to me..lol too much money is wasted by trying to get someone who doesnt do these engines and having them make costly mistakes.

I agree completely. It's amazing how many mechanics are out there that have no business working on an engine, lol. They may even know how to do it.. but like any day to day job, they get lazy.

I now do all of my own wrencing unless I just dont have the skill, or the tools to do it. Porting/Polishing/Valve job is an example. Then I get a time proven mechanic to do it for me, like Mickey Dunlaps crew.

Should have seen the jetting job the ATV dealerships did on my 330ex a few years ago.. lol (before I forced myself to learn jetting). They had a 118 main, with the air screw all the way out, and the needle all the way up.. lol. (I run a 142, 2.75turns, middle notch).

Some of the dealerships "mechanics" seriously didn't even know what I was talking about when I said I needed my carb jetted.

I wouldn't trust them to put on a pipe, let alone do engine work.. lol.

[FoxRacing81]

I have Ross 11:1 426cc Piston, Cometic Flex Steel Gaskets, HotRod H-D Crank and Rod, Port/Polish, and Hotcam Stage 1....When I first got it all installed, I rode through 1 gallon of gas and then 2 of my headstuds pulled out...

The reason they pull out from what I have heard and it makes sense is from excessive heat at low rpms, and once you put a load on it going to high rpms, it pulls them out.....

If your on a stock bore, don't worry about head studs.

[MarkyNark]

Originally posted by FoxRacing81
I have Ross 11:1 426cc Piston, Cometic Flex Steel Gaskets, HotRod H-D Crank and Rod, Port/Polish, and Hotcam Stage 1....When I first got it all installed, I rode through 1 gallon of gas and then 2 of my headstuds pulled out...

The reason they pull out from what I have heard and it makes sense is from excessive heat at low rpms, and once you put a load on it going to high rpms, it pulls them out.....

If your on a stock bore, don't worry about head studs.

What octane level did you run with that 11:1 piston?

[MIKE400EX]

Fox...,
If it was pump gas then there's the clue. The HC Stage 1 does not have the duration and creates significantly more cylinder pressure than the Stage 2 does.
I don't think the heat is causing a problem by softening up the aluminum (it would have to get upwards of 400F), or the studs either. The heat would promote preignition though.

[MarkyNark]

Originally posted by MIKE400EX
Fox...,
If it was pump gas then there's the clue. The HC Stage 1 does not have the duration and creates significantly more cylinder pressure than the Stage 2 does.
I don't think the heat is causing a problem by softening up the aluminum (it would have to get upwards of 400F), or the studs either. The heat would promote preignition though.

Exactly.

[FoxRacing81]

94 pump gas.

Ahh alright...I gotcha. Thanks.

[MarkyNark]

Fox,

This is a good thread for those that put higher compression pistons in. This is my general rule of thumb when it comes to piston compression and octane levels ...

11.5:1 compression to run on pump premium (98 octane)

12.5:1 compression for race gas (105 octane).

14:1 compression for race gas (110 octane).

If I had a 11:1, I would probably simply go with Pump Premium. Pre-ignition can kill a lot in a hurry.

[MIKE400EX]

Foxracing,
Is that Sunoco 94? In New England Sunoco dropped the 94 and now call their 93 ULTRA...and of course didn't lower the price any!
Just curious.:grr:

[FoxRacing81]

Originally posted by MIKE400EX
Foxracing,
Is that Sunoco 94? In New England Sunoco dropped the 94 and now call their 93 ULTRA...and of course didn't lower the price any!
Just curious.:grr:

Yup...Sunoco 94.

That sucks man. I've heard that Sunoco 94 is the cleanest burning pump gas you can get though.

[underpowered]

i have a 2000 400ex 426 bore, 11:1, cam, stock head studs, running on pump gas 93. My motor was built by the quadshop so i believe he torqued it to specs, but the headstuds pulled out of teh cylinder once on me already. i used heli coils to put them back in and have not had any problems since. It is just luck in some case. i know people with 12.5:1 440 without even as much as a blown head gasket on fabric gaskets when i have blown 1 fabric and one flexsteel already. the third one is holding up great but the first two only lasted about 1 month each.

[400exstud]

Call me dumb but what exactly is pre-ignition?

[MarkyNark]

Originally posted by 400exstud
Call me dumb but what exactly is pre-ignition?

No problem ... Pre-ignition is when the normal combustion chamber exposion happens early - on the upstroke instead of at the top of the stroke. This is also called pinging.

If you run a high compression piston, the lower octane fuel wants to burn early when its compressed too high. By burning early, the combustion chamber exposion is trying to force the piston down, when its on the way up. KABOOM!

[underpowered]

pre-ignition is also known as Spark Knock. IT is a common problem with hich comp motors an people who do not know much about them. tey try to run low octane and them complain of noise.

[400exstud]

Now I see why it is call PRE-ignition and is so lethal to your engine!!!:eek:

Talk about advancing your timing.