Factory Piston Pin height

[Decible]

Anyone know what the factory pin height is? And how much you can lower it without getting into the ring pack?

Sponsored

 

[GregO]

Anyone know what the factory pin height is? And how much you can lower it without getting into the ring pack?

So you're looking for Compression Height.
I'll reference you to Wiseco, They advertise (1.176") compression height.
Click on the pistons in the link to pull up listed dimension.
https://www.wiseco.com/product-cate...-sets/domestic-piston-sets/?wpce_search=91444

What's your goal with this question ?

 

[Decible]

So you're looking for Compression Height.
I'll reference you to Wiseco, They advertise (1.176") compression height.
Click on the pistons in the link to pull up listed dimension.
https://www.wiseco.com/product-cate...-sets/domestic-piston-sets/?wpce_search=91444

What's your goal with this question ?

Hey Greg,

I was wanting to see what the factory CH was to see how much the piston sat inside the bore at TDC. Then I wanted to see how much stroke you could run with a 5.85 rod keeping the piston in the bore at the factory specs seeing JP does a CH of 1.165.

 

[GregO]

I wanted to see how much stroke you could run with a 5.85 rod keeping the piston in the bore at the factory specs

Off the cuff about 4mm added stroke.

 

[engineermike]

I went through all this some time back and had convinced myself that 5.4 was possible but then mmr said they don’t recommend it on forced induction so I built a 5.2 using predator parts.

 

[Decible]

I went through all this some time back and had convinced myself that 5.4 was possible but then mmr said they don’t recommend it on forced induction so I built a 5.2 using predator parts.

You know I was doing the math Mike and I’m thinking with a 3.8 to 3.84 stroke this could work with forces induction.

I wouldn’t run 30lbs at 9k but I think 22 to 25 at 7800 to 8k would be okay

I also wouldn’t run 12 compression but 10 to 10.25

 

[GregO]

You know I was doing the math Mike and I’m thinking with a 3.8 to 3.84 stroke this could work with forces induction.

I wouldn’t run 30lbs at 9k but I think 22 to 25 at 7800 to 8k would be okay

I also wouldn’t run 12 compression but 10 to 10.25

Did you calculate your combinations piston speed ?
I’d be concerned about using shorter rods and increased thrust forces.
Undersquare high rpm motors are counter productive.

 

[engineermike]

You know I was doing the math Mike and I’m thinking with a 3.8 to 3.84 stroke this could work with forces induction.

I wouldn’t run 30lbs at 9k but I think 22 to 25 at 7800 to 8k would be okay

I also wouldn’t run 12 compression but 10 to 10.25

A man after my heart. This is very close to what I was planning a while back:

https://www.mustang6g.com/forums/threads/pistons-please.129967/page-4#post-2777692

Lowering coyote compression is taboo I’ve learned!

 

[Decible]

A man after my heart. This is very close to what I was planning a while back:

https://www.mustang6g.com/forums/threads/pistons-please.129967/page-4#post-2777692

Lowering coyote compression is taboo I’ve learned!

It maybe taboo but my experience from other turbo builds I did in the past when stroking lower the compression and running more timing generated better results than more compression.

 

[Decible]

Did you calculate your combinations piston speed ?
I’d be concerned about using shorter rods and increased thrust forces.
Undersquare high rpm motors are counter productive.

Greg I haven’t done this yet….Mike did you get around to calculating this?

 

[engineermike]

….Mike did you get around to calculating this?

Yes and much more. Piston speed and rod ratio are concerns. I was using the LS7 as an established acceptable limit but I found some bmw that was even worse. I even went as far as calculating cylinder wall loading. I had ultimately concluded it was ok at 3.84 as long as you weren’t trying to greatly extend the rpm range. I was going to use that, 5.85 rods, and stock predator pistons and block. (I like oem components where possible). Compression would have been a tad low but ok I think. But after mmr said they wouldn’t recommend it (and they make the crank) it scared me off since no one else is doing that.

 

[engineermike]

It maybe taboo but my experience from other turbo builds I did in the past when stroking lower the compression and running more timing generated better results than more compression.

What fuel are you planning?

 

[Decible]

What fuel are you planning?

93/e85/and q16

 

[Decible]

Yes and much more. Piston speed and rod ratio are concerns. I was using the LS7 as an established acceptable limit but I found some bmw that was even worse. I even went as far as calculating cylinder wall loading. I had ultimately concluded it was ok at 3.84 as long as you weren’t trying to greatly extend the rpm range. I was going to use that, 5.85 rods, and stock predator pistons and block. (I like oem components where possible). Compression would have been a tad low but ok I think. But after mmr said they wouldn’t recommend it (and they make the crank) it scared me off since no one else is doing that.

I was a little concerned with the rod ratio but I’ve seen so many boosted ls7’s live and a ton of hard use boosted BBC with 1.4x rod ratios that I think it would be fine. With a compression height of 1.165 with. JE fsr piston…the more I think you could keep the piston and valves from making contact and it would been a good little street/strip motor. If I was going to do a hard used motor I’d probably do a 5.2.

 

[engineermike]

I’ve tuned 3 sc combos at 9.5/1 and one turbo setup at 9.5/1. The weakest one made 950 rwhp where it ran out of 2650. The blower cars all liked 22+ deg of timing or more, but the turbo car didn’t gain any power past about 18-19 deg timing. So the beauty of turbocharging and low compression is that the lower compression generates more exhaust heat which ultimately lowers turbine drive pressure and makes more power. Timing is similar, which is why mbt is lower. Low compression and turbos go hand in hand, and for pump gas the benefits compound.

Sponsored