I recently got a 89 XJ, and it seems no one makes headers, throttle bodies, intakes, etc for anything older than 91.
Any reason why?
For the pre 91 guys, what have you done and are you happy with it?
I'm looking at Rustys cat back, intake and TB spacer..any reasons not to go with Rusty's stuff?
That's an easy one - the RENIX rigs (1987-1990 XJ/MJ w/AMC engine) were the "odd man out" for production. It was easier to get CARB approval for OBD-I and OBD-II parts than for pre-OBD parts, so they didn't bother (if they can't do a fifty-states legal street part, they generally don't bother. Unless the market is, they are sure, there - the CARB approval process is onerous and spendy.)
If you're willing to do a little fabricating
and the Air Police aren't a factor for you, you can open up your choices and increase parts availability - so let's look at a few things...
- Bored Throttle Body - while you can have an OEM RENIX throttle body bored, there's really no reason to do so. The OEM RENIX tbody will support airflow to feed even a stroker up around five litres displacement, so what of it? You will note an increase in part-throttle responsiveness, but that isn't an increase in power (has to do with flow dynamics, physics, and geometry.)
- Throttle Body Spacer - I'm not sure about these. As far as I'm concerned, the jury is still out on the potential benefits on the nominal increase in plenum volume obtained with a throttle body spacer plate. You'd get much more benefit from Helmholtz tuning and construction of an intake from whole cloth - but that's a major project.
- Headers - Are there true "equal length" headers out there for us? I need to check. However, the primary difference between 1987-1990 and 1991-1999 is the presence/absence of the EGR tube bung (deleted for 1991,) and the 2000-2006 headers are split 1/2/3 and 4/5/6 with two pre-cats on the thing. I believe the collector is in a different location between the 1987-1990 and 1991-1999 header, but don't hold me to that at the moment.
If the Air Police aren't a factor, the 242ci will run just fine without the EGR (and cleaner - I've got before/after test reports from a failed EGR valve on my 87!) but removal of the thing is still a violation of Federal "Clean Air" regulations (found in 49CFR, I think,) so it's still technically illegal. While I think the thing is a bad idea and useless on low-compression engines, I
do not and
can not advocate removal of the thing - even if it gets replaced with a more effective system (like a water/MeOH fogger setup.) You Have Been Warned (and I'm hoping that last statement will keep me from getting clobbered...)
An equal length tuned header will generally increase performance
within a certain RPM range, so it's best to make sure what it's tuned for before you buy it. Or, have one made to increase exhaust output around the torque peak of the engine combination (generally accepted as around 2800-3200rpm with stock bumpstick) and go with that. The custom piece will cost you more than a box part (unless you can talk several people into getting one - that will help spread the cost out over several parts, and you can always send buddies to that shop for parts...) but you'll net more benefit from it.
- Camshaft Swap - This is, dollar-for-dollar, one of the best things you can do to increase performance! The RENIX computer is highly adaptable, and generally sorts itself out with any cam you hand it. All of the later AMC sixes (199/232/258/242ci) share a common cam blank, so these are readily available. Select or design your header to complement your camshaft.
- Cylinder Head Swap - The RENIX head is known for being restrictive, and corrective actions are relatively minor in effect. Easiest to swap to a #7120 or #0630 head (1991-1995 or 1996-1999) and intake setup - you'll open things up with that swap more than you can using a flowbench. And, you can clean the head casting up and get even more flow out of it.
- Strokers. Pound for pound, this is pretty much the
ne plus ultra of performance mods for us. Get the reciprocating assembly out of a 258ci engine (for max benefit) or a 232ci engine (less benefit, but still an increase,) put on the 242ci pistons (they're larger,) and drop the whole thing in. Even a simple swap will still get you some 35-36ci displacement increase, and you'll notice the torque addition right away! This can be done alone or in combination with any of the other mods (if you take the block and have it bored, you'll get an even greater increase in displacement - meaning more torque. The torque is increased by the longer stroke and increased compression ratio... You may end up having to kick up to 89AKI fuel instead of 87 to get the full benefit, but it's worth it.)
There's nothing wrong with Rusty's parts, but opinions on his service vary. Search him up, read through the posts, take the appropriate grain of salt, and do what you feel is right.
shocked
member.
and we'll either decide it's good, brain out ways to improve what was done, or whatever. If any negative reports come back, they get accounted for as 'caveats' when I make my statements.
