Anyone have a Renix Stroker?

Hey guys, I am thinking of building a budget stroker like Dr Dyno, but haven't heard of many people using the Renix engine as a base. I called a Jeep shop and asked a couple of questions but I don't think the guy knew what he was talking about. He said you can't build a stroker with the older style head, you MUST use a high output head. He also said a stock cam would work fine with it as well, which may be true, but you would have so much unlocked potential... Anyway, what all is involved in building a cheap stroker with the Renix engine and computer system, as I have an 87 Cherokee that is in need of a HP boost. I am working with my father on this and he is weary of doing this for 2 very good reasons. First, some may recall some of my posts from a while back saying that I attempted to rebuild the engine with a Crane 753901 cam with the recommended lifters and springs, but in the end, due to some bad advice from a mechanic, the engine was destroyed within 1 hour of its break-in. Well, the engine is back out and ready to be re-built (AGAIN!!) and this time I still want more power, but my dad doesn't want to run the risk of having another catastrophe, as we can't afford any more time or money on this car. The other reason is I start college soon and I really don't want to shell out the dough for premium gas for now on. If you have any advice, I would greatly appreciate it!

karter74 said:

I called a Jeep shop and asked a couple of questions but I don't think the guy knew what he was talking about. He said you can't build a stroker with the older style head, you MUST use a high output head

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Definately stay away from that SPOBI spewing jiffy lube flunky....

Serious about a stroker? Go to the strokers group on yahoo and do a lot of research....

There are a lot of combinations, all revolving around the 258 crank (or an expensive custom) with all sorts of block/head/cam/rod/piston combos.
It pretty much revolves around your budget... Oh and by the way... Figure on going over budget once ya get started

I've got 10k+ on my 4.7L stroker based on the Renix computer. The Renix is really preferable on a stroker due to the ping sensor.

I second the yahoo strokers group. I pieced my stroker together myself and I have never been happier with an engine. The torque is a pleasure to drive and I have to work at not getting tickets. For a mixed use vehicle, I would stick with the stock head, maybe only cleaning up casting flashes and maybe port matching. It is true that the older head does not flow as well as the new head, but nobody ever tells you about the fact that the head restriction will aid you low end torque. Porting a head for low rpm use is for the most part a waste. That doesn't mean it shouldn't flow and that headers aren't a good thing on a stroker, but you need to pick what rpms you want your power at. If you want it at 4,000rpms, you don't want a stroker. By 4,000 rpms, your power will start to fall off.

The key on a stroker is to get your compression ratio up without getting ping. The secret is to deck the block to get the quench height in an acceptable range. I'm running around 9.6 and get no ping on regular gas. Do your research but be careful of who you listen to. Lots of web idiots go spouting a lot of bull about strokers. You need to find people who have actually built more than one motor in their life and actually built and driven a stroker.

old man, I see you're the President of the Colorado chapter, as it turns out, I am staying in Colorado for the summer. Perhaps we could chat about this, as I called a place called F N Jeep Parts (719-634-0666) and a guy said he would sell me a used set of rods and a crank from a 258 for $50. What I want to do is use as much OEM stuff as possible. I would get the Sealed Power 677CP pistons, but I don't really know what cam to run if I do this. I was looking at the Isky Cam 13325/26 at www.iskycams.com but didn't really know the way to go. By modifying all of this, what length pushrods did you use, can you get away with stock? You say you have a CR of 9.6 running on regular gas, by regular you mean 85 octane here in CO (or 87 when you're farther south, no oxygenation there) I have a set of Crane cams springs that were recommended for the 753901, but the spring height is different than the stock height and in order to achieve what Crane recommends, I would have to mill the seats, which I don't want to do. Can you give me a good (and cheap) base set up that I would need in order to convince my dad that this is a do-able project and he doesn't have to worry about the engine failing like it did before? Thanks!

Please feel free to contact me BC. I will need to go back through my records to get numbers for the Crane cam I am running. I am running the sealed power pistons and will see about the numbers for that as well. I have run it from sea level to 13,000 feet and run the cheapest local gas I can find. The secret is in getting the quench height correct. I am running a standard 4.2L crank and rods and decked the block around .025 if I remember correctly and I am running the thinner Mopar performance head gasket. I don't remember which springs I am running. I did check that they didn't bind when I built it. I am also running Ford Cobra 24# performance injectors and a set of Clifford headers.

Yeah, I would really appreciate as much info as you can give me, if I do go ahead and build the stroker, it needs to start right away. Can you explain what the quench height is? How do I know what the right height is for me? Also, are you still running stock pushrods?

Yes I am still running the stock pushrods.

Quench height is a bit tough to explain in words but I will try. Visualize the head. There is a pocket/cavity where the valves and spark plug reside. Notice that it isn't circular. It only covers a portion of the circle formed by the cylinder. The rest is simply flat. The quench height is the distance from this flat portion of the head and the top of the piston at the top of the stroke.

The way it works is that as the piston comes up and compresses the fuel/air, it heats up. If it heats up too much it ignites before the spark, and that is ping (pre ignition). The secret is that as the piston gets to the top, the fuel/air that is between the piston and the flat portion of the head, gets squished (nice tech term) out and causes turbulence in the bigger cavity, causing a cooling effect, thus preventing ping. If the distance is too great, you have little cooling You have to be careful not to cut this distance too much though, because with wear, temp variations, and carbon, the piston could contact the head. Lots of discussion has taken place on what the optimal numbers are. Right off hand I don't remember what I put the number at, but IIRR I set it to around .060 which includes the thin head gasket, but that may be off. Check the strokers group and do a search. I haven't been posting over there much for the last year, but there used to be some good tech on this.

karter74 said:

Hey guys, I am thinking of building a budget stroker like Dr Dyno, but haven't heard of many people using the Renix engine as a base. I called a Jeep shop and asked a couple of questions but I don't think the guy knew what he was talking about. He said you can't build a stroker with the older style head, you MUST use a high output head. He also said a stock cam would work fine with it as well, which may be true, but you would have so much unlocked potential... Anyway, what all is involved in building a cheap stroker with the Renix engine and computer system, as I have an 87 Cherokee that is in need of a HP boost. I am working with my father on this and he is weary of doing this for 2 very good reasons. First, some may recall some of my posts from a while back saying that I attempted to rebuild the engine with a Crane 753901 cam with the recommended lifters and springs, but in the end, due to some bad advice from a mechanic, the engine was destroyed within 1 hour of its break-in. Well, the engine is back out and ready to be re-built (AGAIN!!) and this time I still want more power, but my dad doesn't want to run the risk of having another catastrophe, as we can't afford any more time or money on this car. The other reason is I start college soon and I really don't want to shell out the dough for premium gas for now on. If you have any advice, I would greatly appreciate it!

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There are several Renix-based strokers out there (they probably outnumber the HO-based strokers), so the guy at the Jeep shop definitely doesn't know what he's talking about.
You could indeed build a budget stroker similar to mine and use your Renix head instead. If you home port the Renix head, it'll flow nearly as well as a ported HO head so why not give it a go? Remember though that porting will only really boost torque above 3000rpm so if you hardly ever go above that rpm, you don't need to bother doing it. I do like to extend my engine to the 5250rpm rev-limiter every now and again so I ported mine. I've only taken my stroker up to 4500rpm so far but it's very strong up to that point.
You can even reuse your Crane 753901 cam if it's still OK but get new lifters. If the cam is trashed, the Isky 133125/26 is an excellent choice. Keep the CR somewhere around 9.2-9.3 (basically the same as my stroker) and it'll work great.
I assume you used Crane springs so if you're going to reuse these, you'll need to have 0.060" machined from the spring seats of your Renix head so that the springs will be at the correct 1.70" installed height. I used Mopar springs (1.64" installed height is same as OEM springs) to avoid doing this.
I don't think you need to get too hung up about the quench issue. The quench height of my stroker might be considered high at 0.088" (ideal is 0.040-0.060") but it doesn't ping even though it's 117*F outside. The only grade of fuel available here is 91 octane but I'm confident that my engine still wouldn't ping on 89. I did consider decking 0.010" from the block to reduce the quench and still keep the CR just below 9.5 but I didn't bother because I would have had to get the head-aligning dowel pins cut off to do it.
If you don't deck the block nor the head, you can use the stock pushrods even if you use a slightly thiner head gasket. If you remove a total of more than 0.010" from both surfaces and use a thinner head gasket, consider shimming the rocker arms to prevent the possibility of having excessive lifter preload.
_______________________________________________________
1992 XJ Laredo 4-dr - 4.6L I6 HO Stroker - 175k miles - AX15, NP231, D35c, D30
Estimated 261hp/322lbft, best 1/4 mile [email protected] before stroker install
Websites - Jeep 4.0 Performance, 4.6L Stroker Build-Up, Dino's Jeep Tricks

What lifters are you guys running in your stroker. Can I get away with stock ones with the Isky cam, or did you guys use Crane/Mopar lifters?

I have Crane lifters with my Crane cam, and you should also match your new lifters to the make of cam i.e. Isky cam, Isky lifters.

When I called Isky, the guy there said that if the engine is bone stock (which it is/may still be) he said that if I used OEM lifters, pushords, springs, they should work. Also, I think having a shop machine the spring seats is kind of expensive, so would it be that bad for me to just leave them as they are with the Crane springs?

Just as a side note, never run old lifters on a new cam and vice versa The surfaces work harden on both the cam and lifters together. You shouldn't even swap lifters to different lobes. It is a recipe for disaster.

But since I will require new lifters and cam, I don't think that should be a problem. Old_man, do you remember where you purchased your crank/rods? Were they local in a junkyard or were they already pulled in a shop? I am having a problem sourcing these parts, and the jeep shop that says they have them is only open from Tues-Fri. Thanks!

I picked up my set from 4x4UsedParts in Fort Collins Colorado. He charged me $100. I have picked up a second set from him for a buddy as well. He used to own/run??? Fort Collins 4x4 before it went to the yuppie mall crawler croud.

He as a web site and from there you can get his phone. He knows his shit and is extremely honest.

I called him and he said he could get a crank and rods for $150.....he said he's not sure the condition or if they would need to be turned. Any other ideas? BTW, you said to contact you by BC, what is BC? Right now I am in Estes Park, but will be leaving later this afternoon to go back to the Highlands Ranch area where I work. I would like to contact you so we can discuss this into further detail. Thanks!

Do you guys just look for injectors on eBay or do you know of a better souce than that? Since I need to start building pretty soon as soon as I get a hold of the crank and rods I will need the injectors soon after.

You'll get injectors cheaper on e-bay, especially Ford 24lb'ers, but you can also find them at http://www.fiveomotorsport.com

Do you guys run special lifters as well or do you go for the OEM type? Do I need special lifters with anti-pump up or can I get away without it. Also, I bought a crankshaft today and the guy said he can get me a set of rods probably by tomorrow. My father swears up and town that you MUST get the set of rods that came off that specific crank or it just won't work? I can see some logic in this, but is it really necessary to get matching rods? Can't you just hand the rods and the crank to a machine shop and tell them you want those rods on this crank?

you should have the rods reman'd anyway so they shoud be fine. For a stroker, high rpm anti-pump up lifters are not necessary, but remember, new lifters on a new cam.

I have 18K on my 89 with ported Renix head and 258 crank and rods. I am .102 down on quench height and get pinging at light throttle (automatic) but built it before quench height information was widely available. So stock 258 rods and crank will work with stock replacement pistons on 87 octane.