[YJ_and_Corey]

400HP pump gas friendly 4.5L stroker (now with dyno numbers)

Gentlemen,

I am in the process of building a new motor for my Junk. If you feel the urge to flame me for not being "hardcore enough" let me know and I'll delete this post and go away. I may have some previously unseen shite to throw down here however, so be patient. I'll record progress, and hopefully finish with a dyno run after install.

Waiting on a red star to post pics. Not much to see yet, block dropped off for a tanking, bore and hone this morning.

---------------------------------

I have been playing with turbo charging on the 4.0L for some time (and with 4.2 and 4.0L performance as well), but always with stock compression and stroke. The gains have been great, especially with the use of certain dual pattern cams, head work, and free-flowing exhaust and intake. On ODB1 vehicles, detonation has never been an issue with proper fueling via 2 bar MAP sensors and enhanced fuel pressure with upsized injectors.

However, the sustainable limit for forced aspiration on a fairly stock engine has seemingly proved to be about 6.5 lbs giving 260-275 at the crank. Much more than that and heads start to crack on the exhaust seats. I have experienced this, and some pretty knowledgeable I6 gurus concur with me on my power ceiling.

So, how do I make more power than this in a sustainable fashion? Like they say - there is no replacement for displacement.

The goals were to run pump gas (~88/89 octane in Canada), at 8lbs of boost, and hit 400 crank ponies reliably. The secondary goal was to finally build myself a turbo specific, "4.0L rodded" stroker I6.

Based on the build plan, my primary goal should be very possible.

Here are the specs, parts ordered today:

93 block @ 0.30 overbore. ARP studs. 91 head.

1988 YJ 4.2L crank, balanced. Used for turbo specific engine due to lower rotating mass ( only 4 counterweights) - should spool faster then heavier, older 4.2 cranks or stock 4.0L crank.

As yet to be determined cam (spec'd for turbo apps).
Crane 96803 springs and 99278-12 lifters
Mopar retainers and locks, silicon bronze guides and neoprene seals.
Stock valves used, with valve seats milled out and hardened diesel engine valve seats pressed in.
(Oversize valves have proven to have negligible gains in I6 forced aspiration applications, I have been informed)

Hesco custom 8.0:1 forged chromoly stroker pistons, on Hesco shotpeened/magnafluxed and weight balanced custom machined 4.0L rods. Plasma-moly ring set.

The 8.0:1 CR will allow regular pump gas to be used, as well as gulp some serious air at 8.0lbs boost.

This engine will also run a progressive methanol injection kit, which is already installed on my Turbo YJ. However, the nozzle size and flowrate will be upsized significantly with this latest engine rendition.

Will post pics and info as project proceeds.

 

[YJ_and_Corey]

Pics

Here are the pieces, from "croaker" to "stroker". Here's the lightweight 4.2L crank.

The donor 4.0 was pretty skanky, blew this one up 2 years ago. Rod bearings were so shot it was "eating" the tips of the spark plugs.

 

[MC]

You forgot to add custom rods, head o-ringing, block o-ringing and prayers that the stock cast crank will hold up

 

[YJ_and_Corey]

You forgot to add custom rods, head o-ringing, block o-ringing and prayers that the stock cast crank will hold up

I'm running 6lbs now at 8.8:1, and it's very stable. So are many others doing the same. It could run this way for years, recent leakdown and compression tests verify this.

My cylinder pressures will be appproximately the same with the new motor. And due to the whole "equal but opposite forces" thing, turbo charging isn't all that hard on a crank in the sub 10lb range. Christ, you can buy aftermarket turbo kits for many new domestic vehicles that come set at 7.5lbs.

And I've held 7.5lbs on a MOPAR head gasket, with no leaks at all. When we pushed the rig I've got now "to the limit" it held just fine. Even running on the verge of overheating under full sustained boost, no head gasket issues.

So please, explain yourself.

 

[Sillyneck]

very cool. can't wait to see how it works for you. Just for shitzngiggles how much do you think/know you're spending on the whole build? I'm not going to ask "why not an (insert favorite v8 here)" like so many people will. I like innovative different ideas myself!

Gotta get some vid up w/ sound after you get it together... I built a little rat rod for a customer w/ an I6 that supposedly had 300hp. (felt like 100 ) but it had a super nasty cam and sounded very very cool!

 

[PedalMesh]

You forgot to add custom rods, head o-ringing, block o-ringing and prayers that the stock cast crank will hold up

From what I have been reading on the subject (don't have a turbo or blower yet, just doin' some research), using a copper or aluminum "o-ring" to help contain the cylinder compression is not really a common upgrade when running LESS than 12 lbs boost.

Why you would suggest the extra machining cost to have this done for 8lbs boost?

 

[MC]

You can obtain 400hp through stroking and turbo. The stock rods cant handle much in the way of power at all. I have seen more rods sticking out of oil pans on 4.7ltr strokers, 258's and 4.0's after modifications are done. I mention O-ringing because of the head bolt placement and the surface area the head takes up. Keep i mind when your talking about hp in a strait six your also talking RPM. This may be a unpopular opinion but when your dealing with a reciprocating mass as heavy as a strait six and pushing 66hp on each rod with boost...man I really think your askign for trouble based on this same advice to two others who ended up with a rod sticking outside their oil pan.

Dont get me wrong I am not negative about your build at all and I hope things work out perfect for you. I just posted a little cautionary tale and advice from those who have failed in the past.

 

[JEEPRZ]

My cylinder pressures will be appproximately the same with the new motor. And due to the whole "equal but opposite forces" thing, turbo charging isn't all that hard on a crank in the sub 10lb range.

There is no way your going to go from 275 HP to 400 HP with the same cylinder pressure.

I am not sure what you mean by equal but opposite forces in this context, but 400 HP is 400 HP. Thats three times what a factory crank was 'rated' with.

I am not saying you shouldnt go for it, just dont fool yourself with false logic.

 

[CTD NUT]

I assume the "chromoly stroker pistons" is a typo?

 

[NOSJunkie]

Not to hyjack but.. The Honda 3.5L v-tech will make 500 plus hp STOCK with just a turbo and adjustments to the fuel system (boost sensitive fuel press. reg.) DO NOT exceed 12PSI though..... I believe that is double the rated HP..

 

[tjmark]

Nice project. But this is no new thing.
I have had my 4.7 stroker blower combo for 2 years now. 9.3 to 1 compression with 6 lbs boost. No problems yet and i run 6 lbs boost at 5000 rpm. I will bump up my redline this year 500 to get more hp but i am pretty shure i'm over 400 hp. I have 258 707 casting rods and just 677cp pistons with major port and polish work. stock valves. Harlen sharp roller rockers and 200o pluss intake. 30 lb injectors. Runs fine on 91 octane no ping. I also run a intercooler.

I keept it low budget for a reason. I have under 2000 total in my blower stroker motor. Including the blower. I think to go all forged and cromoly parts you are way better off just going with a take out LS1.

 

[Jeepman14wheel]

That is all nice, but for the $$$ get a SBC or do what I did and get some real HP!!

 

[bnine]

Looks good Corey. I hope it works out good.

Its pretty obvious that you have the ability to go with SBC if you want to, but you are taking this route to do something unique and original with your rig.

Dont sweat the SBC fanboys that are to fuckin stunned to get that.

Carry on and keep us posted.

 

[krazeemofo]

The six is a great motor, unfortunetly it has its limits. What is your thinking behind trying to pull that kind of power out of it ie. what is the application. Maybe if I understood what you planned to do with it I would understand your choice. I am not flaming you.

 

[tjmark]

Looks good Corey. I hope it works out good.

Its pretty obvious that you have the ability to go with SBC if you want to, but you are taking this route to do something unique and original with your rig.

Dont sweat the SBC fanboys that are to fuckin stunned to get that.

Carry on and keep us posted.

If your refering to me being stuned?

Hard to belive since i have both a ls1 and a 4.7 stroker blower.



I have done it both ways and the Ls1 is by far cheeper to have, and be reliable than a straight 6.

This being said i still have the built stroker/blower in my tj It was unique to build a couple years ago but the novelity has worn off and heinsight shows the ls1 is better.

I also am not trying to deture you from building a jeep stroker blower combo.
It was a learning experience to me. I have a set of cromoly jeep rods if your looking for some. New in box. Keep us posted.

 

[mondtster]

very cool. can't wait to see how it works for you. Just for shitzngiggles how much do you think/know you're spending on the whole build? I'm not going to ask "why not an (insert favorite v8 here)" like so many people will. I like innovative different ideas myself!

I'll ask it... Why not a turbo v8? :flipoff2:

Anyway, the one nice thing about turbocharging is how relatively easy it is on parts as long as the motor is tuned properly. I have personally built and run turbo motors that have exceeded the limits that most people will tell you that the motor/parts are good for.

My real question though is why? I really don't think that a turbocharged motor would fit the type of application that most of the people on this board use their vehicles in due to the power band that a 'crawler would really be able to use properly. But that's just my opinion.

 

[tjmark]

A forced induction stroker is perfect for rock crawilng. Super low end and great top end.

 

[CTD NUT]

A forced induction stroker is perfect for rock crawilng. Super low end and great top end.

I would agree if it was supercharged.... a turbocharged stroker might be a bit more laggy on the very bottom than what some people prefer - the average hp isn't likely to be quite as high.

 

[YJ_and_Corey]

I assume the "chromoly stroker pistons" is a typo?

Well yes and no. When I ordered these:

http://www.hesco.us/shop.asp?action=details&inventoryID=44910&catId=7569

I noticed they were made out of 4032 aluminum, and I looked the alloy up - it has 1% chromium which I remembered thinking was odd, but a typo - no, a brain fart yes.

 

[YJ_and_Corey]

There is no way your going to go from 275 HP to 400 HP with the same cylinder pressure.

I am not sure what you mean by equal but opposite forces in this context, but 400 HP is 400 HP. Thats three times what a factory crank was 'rated' with.

I am not saying you shouldnt go for it, just dont fool yourself with false logic.

Ok, I disagree about false logic. The factory crank was rated for 200HP, or 190 anyways in a 4.0L. Is a 4.2L crank that much different metallurgically?

I'm talking 400 at the crank.

I can't prove to you that turbocharging isn't all that hard on a crank, but from the books I've read on the general subject of turbocharging - the crank and rods aren't being affected at the same rate as the power is being increased.

Without launching into a huge physics discussion, and noting that I respect your opinion, I am very sure that not only will my crank and semi-custom rods (read above) hold together, they will do so for years and years.