new cam

i want to revive my old renix. Its in an 87 laredo. Read an article in JP about upgrading cams. Has any one done this? Tips? Gains? How do you get the old lifters out to replace them? What can be done with the valves as long as your engine is half way apart? Thanks alot for your advice/experience.

Do the cam last if at all. More gains are gotten by a port matched head, a bored TB, a decent air intake tube, header and cat back exhaust. I have all these mods and more and still run the stock cam. Upgrading the cam on a 4.0 with out having the rest of the motor beathing in and out well is just a waste of money. And the nice thing about all these mods, is when you need to rebuild or put a stroker together they all go back on no need to buy something new. Dont beleive everything you read in the mags, the manufacturers pay good money for that little infomercial they have you reading....

couldn't you take a strong magnet and get the lifters out that way. You can take head off and have it rebuilt or do a swap to a HO head. If you have the time to have the XJ down Just take the head to a local machine shop and have them go through it (cheapist way around here) And you should notice a big difference doing that and the cam.

First, the head has to come off to access the lifters - that was one of the things we beat around on "strokers" about redesigning the head, and someone apparently listened (since the new HESCO/Patriot head has oversize pushrod bores to pass the lifters.) There's no way around this - if you have to take the lifters out, you have to pull the head. So, may as well get head work done.

Second - especially on RENIX, the main impediment to making power comes from the cylinder head itself. You'll get more out of opening up the ports and cleaning up the surfaces of them than you'd get out of a cam - and if you do take the time to clean the ports up properly, you'll get more out of the cam.

In fact, I daresay you'd get more benefit (swapping a single part) out of changing the #2686 (RENIX) head for a later variation - say, a #7120 head and intake. In 1991, the #7120 head featured raised intake runners, which reduced the angle that the intake charge had to turn (slightly) and allowed it to maintain airflow - which makes the head breathe better.

I'd honestly like to see a "cross-draft" head done for the AMC242, but I'd probably end up having to design that myself. I have yet to see flow numbers for the new aluminum head, but I am reasonably certain that the only AMC head that flows worse than the RENIX head would be for an earlier AMC I6 - probably the 199/232...

5-90

ported head seems to be a bit expensive for me. I would do it myself but dont want to run the risk of fing it up. Forgot to mention with the new cam i will be replacing header and everything behind it, along with T.B. and a better air intake.

thanks Jon- what about the timing sys. You had told me to replace that while i had it apart- can you recomend parts/ products?
thanks

That's all well and good - but the main bottleneck you're going to run into is the intake ports in the RENIX head.

If you do some searching, Standard Abrasives has a good writeup on a DIY port/polish job - it's minor, compared to working with an actual flowbench - but it's a good starting point, and it's geared toward the novice.

If you can't find it on the Standard Abrasives site, I think BillAVista has it mirrored on his Pirate section - check there. I need to get a copy myself for the WiP site, anyhow...

5-90

i searched and found a post from you on that standart DIY kit- i thought you said it was too easy for the novice to F-up. What about the timing? Leave it as is or replace while i have it out?

http://www.compperformancegroupstores.com/store/graphics/00000002/K-Kit.jpg

what do you think of this one?

I've had good luck with Comp Cams - although I've run cam data that I've been able to find so far (a collection of forty or so bumpsticks...) and I like the Blue Racer stick - I think it's part number WG5121. Killer low-end torque...

It's worth noting, tho, that most of these cams aren't listed as being compatible with electronically-controlled engine. I have yet to find out specifically why - but since the AMC199/232/242/258 all work from a "common casting," (many internals interchange - most notably the cam and crankshaft...) it may be that they were designed for older vehicles and haven't been updated - or tested with the updates - yet. I do intend to write the various manufacturers and find out - perhaps it's just a "standard disclaimer" relative to emissions-controlled vehicles (most of which are computer-controlled as well.)

If you do decide to clean up the head, that will help your cam make even more power. If you decide to have it done at a shop, I'd appreciate before and after flowbench reports (which should be part and parcel of having a machine shop clean up your head anyhow - that's how they know what they're doing, and how they know when they've done all they can.)

I'm honestly not trying to dissuade you - it's your money! I'd just like to see you get as much out of your money as you can - why make an additional 10 pound-feet for $200, when you can make 12-15? Even cleaning up the head on your own will help - and, if possible, I'd still like to see flowbench numbers on that job as well.

5-90

Just my opinion.......
Side by side and price for price, I would rather run my well hogged out, polished, port matched Renix head with chevy valves, and Extruded Honed Renix intake and bored TB than going to a newer head and having to get a new intake, do theThrottle Body work and match the exhaust.

(unless I don't understand and the "ports are not that different with the new head and that you can use your renix intake and exhaust, and if that truley is the case, I would like to see flow numbers of the difference in heads if anyones got them.)
I know my build goes against some peoples ways of looking at newer jeep parts to make perfromance, When I do the stroker this winter, I plan on keeping the renix head and just go another step up on injectors.

The RENIX intake can be matched up to the HO head - and the other way around - but it takes some work.

As I recall, the intake ports were raised (starting with the #7120 head in 1991) about 5/8" to reduce the angle entering the head. This results in a bit less disturbance to the airflow, and therefore increases flow through the port.

I've seen a writeup or two on making the RENIX intake fit the HO head, but I don't have any to hand. And, until I get an HO head of my own, I can't look into the subject any further (I have a RENIX intake lying about, and a couple of RENIX heads, tho...)

This is why the intake ports are the bottleneck in RENIX - because of the fairly sharp angle that the intake air charge has to go through in order to enter the cylinder head. This is also why the HO heads breathe better in stock trim - because the angle was reduced.

I haven't yet had a chance to section one of the RENIX heads in order to see what can be done about this, tho...

5-90

5-90 said:

The RENIX intake can be matched up to the HO head - and the other way around - but it takes some work.

As I recall, the intake ports were raised (starting with the #7120 head in 1991) about 5/8" to reduce the angle entering the head. This results in a bit less disturbance to the airflow, and therefore increases flow through the port.

I've seen a writeup or two on making the RENIX intake fit the HO head, but I don't have any to hand. And, until I get an HO head of my own, I can't look into the subject any further (I have a RENIX intake lying about, and a couple of RENIX heads, tho...)

This is why the intake ports are the bottleneck in RENIX - because of the fairly sharp angle that the intake air charge has to go through in order to enter the cylinder head. This is also why the HO heads breathe better in stock trim - because the angle was reduced.

I haven't yet had a chance to section one of the RENIX heads in order to see what can be done about this, tho...

5-90

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Thanks for the info, I was always a bit confused how if the ports were 5/8" off how is it matched up. My head flows very well. As for that "sharp turn" into the intake, it can be smoothed out rather nicely, And with the portts matched exactly,every intake polished well, and the slightly larger valves. The thing flows. Wish i would have put it on a flow bench since when I did it I had access to one... But as everyone else on here rates things, the mod gave me great butt dyno....LOL