Jeep Strokers

20xj00 wrote:

Cheromaniac wrote:

GASnBRASS wrote:And I've dropped the 87 octane requirement; this is just a summer toy so I'll run 91+ octane and a higher compression.

In that case, here's an alternative mini-stroker build spec:

4.2L Wilder mini-stroker

AMC 232 3.500" stroke crank
Jeep 4.0L 6.125" rods
Silvolite UEM-2229 +0.060" bore pistons
9.6:1 CR
CompCams 68-235-4 210/218 degree camshaft
Russ Pottenger ported HO 2.00"/1.55" 62cc cylinder head
Mopar/Victor 0.043" head gasket
0.040" quench height
Ford 24lb/hr injectors for '96-'04 engines
268hp @ 5300rpm, 303lbft @ 3900rpm

Would you have to run 91+ in this set up? What would running 87 do?

I'm new here and to all of this. I'm just trying to learn as much as I can before i potentially stroke my 4.0.

This combination will work fine on 87 if you do the LS valve upgrade.
The stainless Manley Chevy LS 1 exhaust valve that I
use is a tulip design which means there's a dish in the top of the valve. The purpose of this recess dish on the top of the valve and 25° under head angle/radius helps to improve the exhaust air flow, but at the same time it picks up 2 cc's in combustion chamber volume. That typically moves us up to a 60cc combustion chamber and helps lower the static compression ratio

Russ Pottenger wrote:

20xj00 wrote:

Cheromaniac wrote:

GASnBRASS wrote:And I've dropped the 87 octane requirement; this is just a summer toy so I'll run 91+ octane and a higher compression.

In that case, here's an alternative mini-stroker build spec:

4.2L Wilder mini-stroker

AMC 232 3.500" stroke crank
Jeep 4.0L 6.125" rods
Silvolite UEM-2229 +0.060" bore pistons
9.6:1 CR
CompCams 68-235-4 210/218 degree camshaft
Russ Pottenger ported HO 2.00"/1.55" 62cc cylinder head
Mopar/Victor 0.043" head gasket
0.040" quench height
Ford 24lb/hr injectors for '96-'04 engines
268hp @ 5300rpm, 303lbft @ 3900rpm

Would you have to run 91+ in this set up? What would running 87 do?

I'm new here and to all of this. I'm just trying to learn as much as I can before i potentially stroke my 4.0.

This combination will work fine on 87 if you do the LS valve upgrade.
The stainless Manley Chevy LS 1 exhaust valve that I
use is a tulip design which means there's a dish in the top of the valve. The purpose of this recess dish on the top of the valve and 25° under head angle/radius helps to improve the exhaust air flow, but at the same time it picks up 2 cc's in combustion chamber volume. That typically moves us up to a 60cc combustion chamber and helps lower the static compression ratio

So what would be the negatives of running this setup with 87 octane vs the previous setup with 91?

20xj00 wrote:So what would be the negatives of running this setup with 87 octane vs the previous setup with 91?

None that I can think of.

Cheromaniac wrote:

20xj00 wrote:So what would be the negatives of running this setup with 87 octane vs the previous setup with 91?

None that I can think of.

So the 4.2 wilder recipe with the LS valve upgrades would run fine on 87, with no loss of hp/tq?

Increasing the combustion chamber volume to 60cc utilizing the LS valve swap will help keep the static under 9.5:1 making it easier to get by with 87

20xj00 wrote:So the 4.2 wilder recipe with the LS valve upgrades would run fine on 87, with no loss of hp/tq?

My 4.2 Wilder recipe already has the LS valve upgrade factored in. You can increase the 11.5cc dish of the 2229 pistons to lower the static CR if needed to run the engine on 87 octane, but then why would you want to run a higher performance engine on catpiss?
Here in Europe, the lowest grade of fuel available is 95 RON (91 octane US).

Cheromaniac wrote:

20xj00 wrote:So the 4.2 wilder recipe with the LS valve upgrades would run fine on 87, with no loss of hp/tq?

My 4.2 Wilder recipe already has the LS valve upgrade factored in. You can increase the 11.5cc dish of the 2229 pistons to lower the static CR if needed to run the engine on 87 octane, but then why would you want to run a higher performance engine on catpiss?
Here in Europe, the lowest grade of fuel available is 95 RON (91 octane US).

Well if there is no down side or loss when running lower octane fuel, why pay more for higher octane fuel? Seems like a waste, no?

You misunderstand. You can run higher compression and/or more timing on higher octane fuel which will make more power. They are saying pick the fuel you plan to run then build your engine with as much compression and quench as you can that will still let you use your desired grade of fuel or you are leaving power on the table which is something a lot of stroker kits do.

SkylinesSuck wrote:They are saying pick the fuel you plan to run then build your engine with as much compression and quench as you can that will still let you use your desired grade of fuel or you are leaving power on the table which is something a lot of stroker kits do.

Exactly.