Carb'd 4.6 Questions

[Wombat Ranger]

Hi.

My stroker build started out as a simple rear main seal replacement. Bearing was grooved. I figured why put it back together, it's got 225k on it (4.2) and it already has a hard time starting. Picked up a 4.0 core for $100. Turns out nothing was good on it, hoping the lifter bores are okay so I can use the block. Pulled the peujoke and sold it for 3 times what I paid for the ax15 that is going in, pulled the motor and found the worst cam timing gear I have ever seen. This thing will slice your finger open in a heartbeat. Timing chain had a full 3/4" of slack on both sides if I pinched it with my fingers. I don't blame it for being a hard starter. I'd owned the jeep for about a month at this point by the way.

Anyway. My questions are probably the same ones that every newb to these motors asks, so my apologies in advance. I just need a little clarification. Been doing a lot of reading but it mostly all is focused around efi motors. I am gonna be running a carb. Initially the stock 4.2 carter (GASP!). Once I removed all 30 miles of vacuum crap from it I didnt have a single problem with it. I plan on a MC2100 eventually though. Also, purpose of this build is torque. My YJ is gonna be my daily driver once this motor is in, but it's built to wheel. So driveable with manners included, but I am rarely gonna be past 2 grand in this thing. I need it to not blow up at 4500 if the occasion finds me, but that's not the purpose here.

I keep reading a lot of threads about cam choice and I really just keep coming up with nothing. Motor is a '91 HO and the head I am building is also a '91 HO, but like I said nothing was good in my block. So I can't use the stock HO cam. Mopar purple cam? I like that it come as a kit, it's affordable, and it's mopar brand. If it's really just not enough cam for a 4.6 though, that's that. Should I do anything with valve springs? I read the cam problems people have are a lot of the time due to stupid heavy springs. Next question is deck height. Can I just leave it alone? I wanna run junk gas and not have to worry. But I also don't wanna be stupid. Speaking of stupid, I have a head gasket that has been installed but never run. Can I use it? Any help is appreciated.

Parts list so far
258 crank polished stock size
258 rods
4.0 block nothing done yet but a hot tank
4.0 HO head being built with bronze guides, minor port, grind, mill, seals & springs
.030 over Speed Pro Hypereutectic pistons
Moly rings
King main bearings
King rod bearings
Sealed power cam bearings
Sealed power high volume oil pump
Freeze plugs water pump blah blah blah

Thanks folks.

[Wombat Ranger]

Or how about this cam?

http://www.summitracing.com/parts/cca-c ... /make/jeep

[SilverXJ]

That cam will be fine. You may also want the 68-231-4 which has better top end power. Personally I would look at other options than Comp. There are many better companies out there. Isky, Clay Smith, Jones Cams, and Lunati to name a few.

Can't give you an opinion on the carb other than I would go EFI.

[Wombat Ranger]

Thanks for the reply.

I work at a diesel performance shop and my boss (owner) is adament that I will be best off with a re-grind of the OEM cam. I trust him as he has built a lot of high performance motors, gas and diesel. So I am thinking I will go that route to start with. If it ends up no good then I will change it later.

I am going carburated for the simplicity of it, and affordability. Mostly I don't want to deal with the swap. That may change in the future but for now it's gonna be carb'd.

Anyone got anything to say about the rest of my questions?

[Cheromaniac]

Motor is a '91 HO and the head I am building is also a '91 HO, but like I said nothing was good in my block. So I can't use the stock HO cam. Mopar purple cam? I like that it come as a kit, it's affordable, and it's mopar brand. If it's really just not enough cam for a 4.6 though, that's that. Should I do anything with valve springs? I read the cam problems people have are a lot of the time due to stupid heavy springs. Next question is deck height. Can I just leave it alone? I wanna run junk gas and not have to worry. But I also don't wanna be stupid. Speaking of stupid, I have a head gasket that has been installed but never run. Can I use it? Any help is appreciated.

There's nothing wrong with using the stock (or a stock replacement) cam in a 4.6 stroker. You'd have to settle for a few less HP than you'd get with an aftermarket cam but at least you'd have the peace of mind of bulletproof reliability especially since you can use stock (or Mopar Performance stock replacement) valve springs. I'm living proof that you can build a "poor man's" stroker and still kick ass.
I left my quench as it was (0.088") without decking the block/head to keep the CR fairly modest (9.25:1) and I can run the engine on regular gas.
As for the head gasket, you could probably reuse it if it's the new multilayer steel type. Just spray a thin layer of copper gasket sealer on each side and it'll be fine.

[Wombat Ranger]

Thanks for the reply. The block needed love to get into spec, so they ended up decking it the minimum amount to get it flat. No big deal. They are doing the bore, deck, align hone, cam bearings, resizing the rods, freeze plugs, and assembling the rotating assembly for $500 cash. This is all labor cost as I brought all the parts to them. Still seemed like a really good deal to me.

My head gasket is a fel-pro, not a steel multi-layer. I will probably just replace it. This build started with me being told that the 4.0 long block I bought had a fresh (under 5000 miles) .030 over on it, and that my head was freshly rebuilt too. So I was trying to keep it super cheap. Now I am almost $2000 into it including poly motor mounts, header, etc. Shoot just last night I ordered 4wd hardware's HEI kit. At this point I may as well just buy a new head gasket since its gonna be an all new motor. Since my deck height is gonna be quite a ways above the piston at tdc do I need to worry about head gasket bore size?


This has turned out to be an expensive rear main seal replacement.

[Wombat Ranger]

I am still in the dark about head gasket bore size if anyone can give me a pointer.

[Cheromaniac]

I am still in the dark about head gasket bore size if anyone can give me a pointer.

It's 4.0".

[Wombat Ranger]

Not what I was looking for, but thanks anyway. I was able to find my answer elsewhere.

[Wombat Ranger]

There's nothing wrong with using the stock (or a stock replacement) cam in a 4.6 stroker. You'd have to settle for a few less HP than you'd get with an aftermarket cam but at least you'd have the peace of mind of bulletproof reliability especially since you can use stock (or Mopar Performance stock replacement) valve springs. I'm living proof that you can build a "poor man's" stroker and still kick ass.
I left my quench as it was (0.088") without decking the block/head to keep the CR fairly modest (9.25:1) and I can run the engine on regular gas.
As for the head gasket, you could probably reuse it if it's the new multilayer steel type. Just spray a thin layer of copper gasket sealer on each side and it'll be fine.

Mmkay so the engine is done and went in the Jeep today. Then someone started talking to me about quench and I thought I messed up real big, as it is looking like .091" if my numbers are right. Static comp ratio at just under 9.6:1. I thought I was screwed until I saw that you are running high quench and not having issues. Am I going to be okay or is the motor gonna pre-det itself to death? I am hoping to fire it tomorrow if I get it all ready. I would love to at least break in the cam. Which by the way the cam I ended up using is a stock reground HO cam, with a bit more lift and duration to give a nice torque curve starting real low and progressing through the whole range.

Thanks.

[Cheromaniac]

Then someone started talking to me about quench and I thought I messed up real big, as it is looking like .091" if my numbers are right. Static comp ratio at just under 9.6:1.

Your numbers will be pretty close. Just run some 91 octane fuel initially and see how it goes.

[Wombat Ranger]

Thanks. I will report back. Kicking myself for not going with a zero deck now that I know a little more about it. Oh well.

[Wombat Ranger]

I have been trying to fire it up yesterday and today. I have distributor timing set correctly. Getting general behavior of a motor that is not timed properly.

Yanked my timing cover apart today. Cuz all I am getting is backfires. I even caught the carb on fire today. Woohoo.




Obviously the crank and cam are lined up. However I was under the impression that when these marks are lined up the motor is supposed to be at TDC#1 comp stroke. I am nowhere near that. I am almost (maybe even exactly) on Cyl #2 TDC comp. Does anyone have any insight for me?

[SilverXJ]

You won't be at TDC on the compression stroke on #1 when the timing set is dot to dot. However, while it is dot to dot, it appears you have used the adjustable timing set incorrectly. It appears that your crank key is on the left notch, which is not where it should be for straight up cam install. Too much counter clockwise. That key should be more or less pointing straight up. This is where the crank should be:

[Wombat Ranger]

It appears you have used the adjustable timing set incorrectly.

It appears that I am an idiot.


I thought that I was supposed to use the dot that was 180* from the keyway, not the one right next to it. I wonder why I thought that. Well a major goal of this project was to learn, that's what I am doing. Thanks so much for your help! That completely explains my problem.