Stroker Questions

alexgalexg

New member
I have been dealing with some pretty substantial problems with my 1998 jeep xj 4.0 recently. The engine pings unless I use premium fuel and is all around just very knocky.

You can catch up on all this along with hearing the knock on my recent thread (over my head in problems)
https://r.tapatalk.com/shareLink?url=https://www.naxja.org/forum/showthread.php?t=1149570&share_tid=1149570&share_fid=13728&share_type=t

I am still waiting to get my hands on the fancy 8k reader in order to troubleshoot what's going of with my engine but depending on what happens I may just replace the engine all together.

I was going to go with the stock 4.0 but the way it downshifts on steep hills due to that widely spaced 4 speed automatic has bothered me for years. Want more torque. Was thinking about a stroker.

If you guys have any recommendations for reman stock 4.0 or 4.7l engines please share here!

I just ask that they be quality
Paint wont flake off in 2 years, engine will actually last and from a legit company

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old_man

NAXJA Member
NAXJA Member
Before you go and drop some serious money and start replacing parts, run a can of BG44K through the fuel system (~$20). It will clean the injectors and remove carbon. Don't cheap out and use the STP or other brands. Try NAPA first. It is for "professional" use and most chain stores do not sell it. If you can't find it, run a couple of bottles of Chevron Techron.

But before doing that, pull the plugs and take pictures and post them up.

After running the BG do a vacuum check and report back the results.

I have 200k+ on the Renix stroker I built.
 

RCP Phx

New member
If you guys have any recommendations for reman stock 4.0 or 4.7l engines please share here!
I just ask that they be quality
Paint wont flake off in 2 years, engine will actually last and from a legit company
The only catch to that is price. Good motors are built, not bought! I "built" my stroker for 5k, a Golen will run you 5k but you only get half the motor!
 

sidewaysstarion

Coffee Drinker
NAXJA Member
Chapter BOD
The only catch to that is price. Good motors are built, not bought! I "built" my stroker for 5k, a Golen will run you 5k but you only get half the motor!
Yeah, I have a golen 4.6 stroker that I've been redoing fixing all of their factory mistakes, like having the pistons set 0.045 in the hole and the crank having enough end play to measure with a yard stick.
 

alexgalexg

New member
Alright so consensus on stroker engines is that I need to steal a recipe from one of you kind people if I choose to go that route and have a machine shop handle the rest.

Not sure how possible that will be due to the copious amount of engine knock I have I dont know if the crank will be without significant wear.

What about stock 4.0 engines. Are those the same? All junk?

And in response to old man:
I run seafoam fairly often. Did a cylinder head In December and pistons were golden and clear i can link a youtube vid if you need a visual. I can still get what you mentioned and run it through though if you feel seafoam is not good enough.

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old_man

NAXJA Member
NAXJA Member
Alright so consensus on stroker engines is that I need to steal a recipe from one of you kind people if I choose to go that route and have a machine shop handle the rest.

Not sure how possible that will be due to the copious amount of engine knock I have I dont know if the crank will be without significant wear.

What about stock 4.0 engines. Are those the same? All junk?

And in response to old man:
I run seafoam fairly often. Did a cylinder head In December and pistons were golden and clear i can link a youtube vid if you need a visual. I can still get what you mentioned and run it through though if you feel seafoam is not good enough.

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Ping or detonation (worse) can have multiple causes. It is either caused by excess carbon buildup that glows when hot and causes predetonation of the mixture, or by running too lean which leads to high combustion temps.

BG can address several possible causes and is well worth the time and money. I run a can every 10k miles on every vehicle I own. It removes carbon deposits, addressing predetonation. It cleans clogged injectors which can cause it to run lean in one or more cylinders, hence the request to see images of the spark plugs for signs of running too lean.

Ping can also be caused by timing that is advanced too far. That is rarely the problem with electronic ignitions since the timing is ECU controlled.

A vacuum leak can cause one or more cylinders to run too lean and cause ping, hence the request to do a vacuum check.

Mixtures can be wrong based upon a sensor feeding bad data to the ECU, such as a MAP, temp, O2. Sensors can read wrong due to failure or things like a leaky exhaust manifold due to bad gaskets or the more common crack.

Running lean can be caused by low fuel pressure.
 

old_man

NAXJA Member
NAXJA Member
looking back at the thread, you initially called it ping, now you are calling it knock. There is big difference.

Rod knock is fairly common in older engines and is due to worn rod and crank bearings. The only way to see how bad things are is to drop the pan and check the bearings both visually and with plastigage.

If you catch it early enough, you can do a bearing replacement only and get by for a long time. Waiting too long can mean you will have to turn the crank and resize the rods, or in the worst case, you will throw a rod and the engine is worth the scrap value for the metal.
 

alexgalexg

New member
looking back at the thread, you initially called it ping, now you are calling it knock. There is big difference.

Rod knock is fairly common in older engines and is due to worn rod and crank bearings. The only way to see how bad things are is to drop the pan and check the bearings both visually and with plastigage.

If you catch it early enough, you can do a bearing replacement only and get by for a long time. Waiting too long can mean you will have to turn the crank and resize the rods, or in the worst case, you will throw a rod and the engine is worth the scrap value for the metal.
Oh no I have both ping and knock. I get ping when I dont use premium fuel. (Popcorns between 45 and 55 under heavy load) this is not normal I have 2 xjs and the other does not do this. They also shift at the same time. I also have knock. If you go to my thread "over my head in problems" you'll see a link to a youtube video. I film underneath the engine where the knock is extremely loud. This engine sounds like a diesel more often than not. Also has a late start.

I got my fuel trims looked at and they are normal so I dont have a lean burn. Last I checked I didnt have ghosting on the plugs either. I'm planning on pulling the plugs this week so I'll send a pic when I do for sure

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RCP Phx

New member
There is nothing wrong with most remanufactured motors. That said the problem with them is you don't know what your getting. I would accept cores to -.030" under, but would grind and resell to -.040" ! Same applies to heads and rods.
 

asymptonic

NAXJA Member
NAXJA Member
There is nothing wrong with most remanufactured motors. That said the problem with them is you don't know what your getting. I would accept cores to -.030" under, but would grind and resell to -.040" ! Same applies to heads and rods.

Obsessed about this with my own knock issue and went with a Jasper motor. I don't feel great about it, but couldn't afford the time it would take to pull the motor on my only vehicle and have it worked on in a local machinist. Jasper claims you can pay $50 for a specific bore, so I did, and asked for 0.030 over only but I have no way of verifying that's what I got without digging into it. So far so good bar an oil pressure problem that turned out to be a bad sender. Fingers crossed.



If I had the time I'd have had it remanned in a trusted machinist locally under my supervision, but in my case I couldn't do it. I still feel bad about it because I have no idea what motor I got in what condition and with what parts, something I wouldn't have worried about if I'd controlled it in a local rebuild.


Long story short, I'd say be sure you need a reman/rebuild first, and then lean towards a rebuild if you can help it.
 

old_man

NAXJA Member
NAXJA Member
To muddy the waters even further, lets add piston slap. It tends to be worse on strokers and is commonly mistaken for rod knock.
 

alexgalexg

New member
So my plan right now based on all this info is this.

I need to get my computer hooked up to one of those fancy 8k readers. This way I can see the timing and fuel trims. I also need to check the connection with my upstream 02 and run a compression test. This will help me diagnose that ping. If I can figure out and fix the ping I'll tackle the knock. I'll likely start with an oil pump and new bearings on the connecting rods. My cylinder walls look good so I'm not worried there.

If push comes to shove I'll fix the main brake line going from the master to the rear diff on my other xj and drive that while I pull the engine out of this and have a local machine shop handle the rest.

Was doing some thinking last night and between it being low miles, having a brand new head, push rod and rocker arm set and clean pistons it's probably better than whatever I'll get online.

I'd much prefer a stroker engine because the gearing in these jeeps is just awful and I could use the torque but this is my daily driver and I dont have time to play around with something that big if it's not for sure going to work and work reliably the first time.

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techno1154

NAXJA Member
NAXJA Member
To muddy the waters even further, lets add piston slap. It tends to be worse on strokers and is commonly mistaken for rod knock.
And I thought the replacement pistons would be ones that were not prone to piston slap.

My XJ seem to have some piston slap on warmup which tend to go away at operating temperature. Then again, I think gas from some stations seem to make it worse.
 

alexgalexg

New member
And I thought the replacement pistons would be ones that were not prone to piston slap.

My XJ seem to have some piston slap on warmup which tend to go away at operating temperature. Then again, I think gas from some stations seem to make it worse.
I have heard that shell gas has the most detergents so I go there to fill up. I dont notice any difference in knock between there and Cumberland farms although I notice you get better fuel economy from cumbys gas

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