4.5L stroker, my first engine build

[specneon74]

A couple years ago I bought an XJ for $500 to tow the race car and winter beater duties. It starts and runs fine, but has low compression (90 psi cold) on cylinder number 1. With that in mind I've been hording parts for a cheap rebuild and after 18 months have the major components. At first I just wanted a replacement 4.0L with better stock components. Then I learned about strokers and found a 4.5L simple stroker recipe on this sight. Here's what I've got so far:

1999 XJ 4.0L short block (head cracked)
1999 XJ cylinder head 0331 (back from machine shop, magnafluxed, valve job, and flatness checked)
1990 YJ 258 I bought off craigslist. 4 counter weight crank.

I pulled both the 258 and the 4.0L apart yesterday and took the 258 crank and 4.0L block to the machine shop. The block and pistons looks pretty good. I can see cross-hatching in the bores so hopefully it will only need to be hot tanked (there was some mayo in the oil pan). The 258 was in worse shape and the crank journals have some minor grooves.

While I'm waiting for the parts to get back I'm trying to decide on a cam. I'm stuck between the comp 68-232-4, 68-231-4, and stock 1999. I'm on a budget, but figured I'd swap in a cheap cam while I've got everything else apart. Are the stock valve springs really not adequate for the comp cams? Do the stock valve retainers work with the Comp Cam valve spring (926-12)? I've found the cam, lifter, and timing chain kit for $205 at www.flatlanderracing.com. I can stomach paying $200, but if I have to shell out another $65 for valve springs I may just use the stock cam and replace the lifters and timing chain.

Thanks,
David

[dwg86]

The comp springs will not work with the stock retainers. Have your machine shop check the stock valve springs to see how much lift they can handle, I would also like to know .
I was never a fan of running an old cam in a new engine. I would be affraid the the taper on the lobe that causes the lifter to spin, might be worn down. That could cause the new lifters to wear.

Comp has some smaller cams that might be able to work with the stock valve springs. Part # 68-200-4: 206 [email protected]/.433 lift, and part# 68-201-4: 212 [email protected]/.447 lift. They will probably perform better than a stock cam also.

[SilverXJ]

I have a spare set of stock springs sitting around, which I really need to take to the machine stop and test they to see when they do in fact bind. What is the minimum space between coils necessary again? Now that I think of it all you need is a bench vise, caliper and two stout washers to get that measurement.

[dwg86]

I think have read .050 minimum clearance, but I will research again. The vise thing is a good idea. I have a set of springs that I can put in a vise and set to the installed hight @ 1.640. Then compress all the way and measure. Then subtract .050. I'll do that tomorrow.

[dwg86]

Comp cams web site says .060 min clearance between coils.

[SilverXJ]

The vise thing is a good idea. I have a set of springs that I can put in a vise and set to the installed hight @ 1.640. Then compress all the way and measure. Then subtract .050. I'll do that tomorrow.

I learned the vise method when Titan sent me some stock springs from something or other to install with a 68-231-4. The said they wouldn't bind, but they did. They thought the MP springs caused a failure on the cam that they broke in.

[dwg86]

I checked the stock valve springs out of a 7120 head. The coil binds at 1.130. Valves installed at 1.640. So 1.640-1.130=.510. .510-.060=.450. So it would seam the stock valves springs would be good to .450 lift with .060 coil clearance. Comp makes a couple of high energy cams that would be able to be used with the stock valve springs.
Comp part # 68-200-4 is [email protected]/.433 lift, and part# 68-201-4 is [email protected]/.447 lift. I think the 212 dur @ .050/.447 lift would be a pretty good cam. If someone wanted a higher lift/duration on the exhaust side, you could have one custom ground.

[dwg86]

Is there somewhere we can put the stock valve spring specs on this forum (coil bind, max lift). I know this question comes up alot.

[stroked'73]

Maybe the FAQ forum?

Just to add more info to the spring topic......
I tested a couple stock springs today - one from a 94 and one from an 89. I recorded the clearances for the rated .430" lift and for .485" lift - which is the max lift on the comp 231-4. Then I recorded coilbind. I used the retainer with a bolt thru and a large washer and nut on the bottom and tightened it to get the "valve lift" heights. I measured from the top of the bolt to the bottom of the nut and corrected the calipers to get 2" on the free height. (Both the springs measured 2".) Here's what I found:

Renix spring: @ .430" lift, .065" clearance
@ .485" lift, .030" clearance
coil bind @ 1.065"

H.O. spring: @ .430" lift, .050" clearance
@ .485" lift, .025" clearance
coil bind @ 1.090"

The renix spring had wider spaces between the top-middle coils, while the H.O spring was more uniform thru the middle. Since the springs don't compress exactly parallel, there is slightly larger spaces on one side of the spring than the other - I took my clearance measurements from the tighter side - including coil bind.
I don't know why the two springs measured slightly different - they should be the same spring for both motors. Maybe factory tolerances? The 94 springs have far less miles on them than the 89 ones. The 89 ones were also in my stroker with the comp cam for a while.