My Build and Performance

Performance mods and Advanced Stroker discussion.
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elbaldo3
Posts: 2
Joined: March 31st, 2021, 7:01 am
Stroker Displacement: 4.6
Vehicle Year: 1999
Vehicle Make: Jeep
Vehicle Model: TJ
Location: Austin, TX

My Build and Performance

Post by elbaldo3 »

Jeep Stroker 4.6 Build

Scat Crank
Keith Black 8.8:1 Pistons
Howards F1 Cam Duration 257/263, Lift .443/.448,
Melting HVSP oil pump
Block decked .015
Edelbrock Performer Head Ported but not Milled.
Johnson Hylift slow leak down Lifters.
Trend 9.600 Push Rods.
Scorpion 1.6:1 Roller Rocker Ams
Felpro .040 Head Gasket
62mm Throttle Body with spacer
24 lb/hr fuel injectors @52psi from Caddilac XLR 4.6
Cold Air intake
Header with 3 in exhaust pipe to Cat and 2.5 back
Flow cooler water pump (using waterless coolant)
Center force Flywheel (17 lb heavier than stock)
Center Force Stage 2 Clutch & Pressure plate

Jeep Setup
2 in budget lift
1.25 in body lift
1 in wheel spacers
31 in tires
Stock 307 gearing.
Have Dana 44 from Rubicon, next project.

I have a few questions that I hope someone can answer for me. I did a lot of research on this and many different sites before beginning my build but I guess there is always the unknown & unforeseen. I just entered my numbers on the compression calculator provided on this site. I was astonished to see a static compression ratio of 10.54:1 is that possible with the build listed above? Is my cam big enough to support that? The engine runs good but feel it has more potential, it pulls fairly well but from between 60-65 trying to pass someone or climb up hills I dont have to drop a gear just give it more gas and it will eventually make it but is slow to accelerate. I visited RC Injectors website and used their calculator, I am guessing that I am making around 260 HP and they recommend 27lb/hr injectors. Any thoughts ?

Thanks,
Randy Bobandi
I made it to triple digits!
I made it to triple digits!
Posts: 152
Joined: December 22nd, 2020, 8:50 am

Re: My Build and Performance

Post by Randy Bobandi »

How did you get 10.5:1 compression? What is the bore size? Don't those pistons have a 27.5cc dish? I got 9.4:1 from the parts you provided.

That camshaft is very mild. How much lift can your valve springs support?

24#/HR injectors are only good for about 240 Crank HP. You're probably around 180 HP to the tires. I would get some 30#/HR injectors in that unit, at least. Also, what fuel pump do you have?

You should invest in some tuning time. HPTuners is compatible with most 4.0L Jeep models. What model Jeep is this? Early TJ?

3.07 differential gear ratio is another issue holding you back. Sure, you'll burn a little more fuel with 4.10 gears, but the Jeep will be way more fun to drive. Passing folks on the highway wont be as much of an issue either.

Also, what do you mean by Johnson Hylift Lifters? Johnson only makes roller lifters.

Why a high volume oil pump? Do you have a custom oil pan with a giant sump?

Keep an eye on that Flowkooler water pump as well. They just press a different impeller onto a super cheap Chinese Standard water pump. They typically don't last more than one or two years.
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Cheromaniac
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Posts: 3180
Joined: March 8th, 2008, 12:58 pm
Stroker Displacement: 4563cc
Vehicle Year: 1992
Vehicle Make: Jeep
Vehicle Model: Cherokee
Location: Cyprus
Contact:

Re: My Build and Performance

Post by Cheromaniac »

I have your stroker at a 9.21:1 static CR based upon the following specs:

Block deck height 9.438"
Rod length 6.125"
Piston compression height 1.353"
Stroke/2 = 1.948"
Deck clearance 0.012"
Head gasket thickness 0.040"
Quench height 0.052"
Combustion chamber volume 55cc
Piston dish volume 27.5cc
Head gasket volume 8.2cc
Deck clearance volume 2.4cc
Bore size 3.905"
Displacement 4587cc

I think your estimate of 260hp at the crank is reasonable so your stock fuel pump will do fine. Since I use a rule of thumb of 0.1lb/HR injector flow per HP for the Jeep I6, you need injectors that flow 26lb/HR at 49psi fuel pressure. Therefore your existing injectors are 10% too small and I suggest you go with these:

Bosch 0280155849 24.5lb/hr @ 43.5psi (same as Ford XF1E-A5B)

Another problem is your axle gearing. It's obvious your Jeep is an AX15 manual but the combination of 3.07 axle gears and 31" tires now makes it too tall. Normally I'd recommend 4.10 axle gears with 31" tires on a Jeep 4.0 but since you have the extra torque of a stroker, 3.55 axle gears would be ideally suited. You could either regear your existing axles or pull the stock axles from an AW4 automatic Jeep where 3.55s were standard.

As for the Flowkooler water pump, I went through two and each one lasted 60k miles. My original stock water pump had lasted 112k miles so you can see where I'm going with my recommendation.

I ran a HV oil pump in my stroker without any problem at all. Oil pressure was 60psi on cold start up but once the engine was hot, it was 25psi at idle and 50psi above 2000rpm.
1992 XJ 4.6 I6 - 5MT - Stroker build-up, Stroker "recipes" Sold
1995 Mustang GT - 4AT - Modded Sold
2006 Mustang GT - 5MT - Modded Midlife Crisis Car :mrgreen:
Russ Pottenger
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Joined: August 15th, 2009, 1:27 am
Stroker Displacement: 4.7
Vehicle Year: 2000
Vehicle Make: Jeep
Vehicle Model: Cherokee

Re: My Build and Performance

Post by Russ Pottenger »

Only thing that I will add is to be sure to double check your static compression ratio.

Aluminum heads will dissipate faster. This allows for higher Compression ratios. As a general rule I advise running a full point of compression more with a aluminum cylinder head. For example if you were planning on running 9.5:1 with a cast iron head I’d recommend running a static compression ratio of 10.5:1 with your Edelbrock head.

With a tight piston quench and my Edelbrock piston dish were running static compression ratios of 10.8:1 to 11.0:1 on 91 octane without any problems
elbaldo3
Posts: 2
Joined: March 31st, 2021, 7:01 am
Stroker Displacement: 4.6
Vehicle Year: 1999
Vehicle Make: Jeep
Vehicle Model: TJ
Location: Austin, TX

Re: My Build and Performance

Post by elbaldo3 »

Thanks you all for replying to my post.

I obviously made some error in entering my numbers. I guess I should have talked to Russ while I was in the planning stage!
I did neglect to mention the Jeep is an early 99 Wrangler with single coil pack.
It’s my understanding that there are two Johnson lifter companies. Toplineauto.com (Hylift Johnson) is located in Muskegon and has been around for over 70 years. The “S” lifters I selected sounded like a better way to go over OEM since I don’t plan on revs over 4500rpm the lifters provide full cam profile to the valves from idle on (At least that’s what I was told & sold) they were pricey little buggers!

So if my dynamic compression is in lower to mid nines, with the Edelbrock head, is my static compression going to be too low? If so what effects will that have on engine tuning and longevity?

I have a Dana 44 out of a Rubicon with factory 4:10’s I’m planning to install in coming weeks and will regear the D30 upfront. Sounds like it will be blast to drive when installed...maybe not on wet pavement though.

When those tires are burnt up I plan to upgrade to 33’s. What would my estimated gear ratio be going that route?

Thanks again for your time guys! I’m sure most if not all of this info can be found on the site with a little digging but I’m writing this as I’m sitting on a plane with a mask on wishing I had taken a sleep aid 30 min ago.
User avatar
Cheromaniac
I live here
I live here
Posts: 3180
Joined: March 8th, 2008, 12:58 pm
Stroker Displacement: 4563cc
Vehicle Year: 1992
Vehicle Make: Jeep
Vehicle Model: Cherokee
Location: Cyprus
Contact:

Re: My Build and Performance

Post by Cheromaniac »

I agree that you could easily run a higher static compression ratio, and I suggest you talk to Russ about getting a set of pistons with a smaller dish volume. His pistons are also slightly taller than the Keith Blacks you were planning to use so you wouldn't need to deck the block, saving you that cost. A full point CR increase from 9.2:1 to 10.2:1 would give you an extra 10hp, and I'd estimate the dynamic CR to be around the mid 8's.
Heavier, taller 33" tires will add more rolling resistance and aerodynamic drag so the 4.10 axle gear would be a great choice. Just remember to change the speedo gear in the transmission output shaft extension housing to compensate for the changes in tire diameter and axle ratio.
1992 XJ 4.6 I6 - 5MT - Stroker build-up, Stroker "recipes" Sold
1995 Mustang GT - 4AT - Modded Sold
2006 Mustang GT - 5MT - Modded Midlife Crisis Car :mrgreen:
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