Precats and mech ?'s...what are they?

[jhauschild]

I have a few quick questions. one in regards to the precat malfunction thing. What and where are they.? Under the heat shield.? I am replacing the down pipe and regular cat. Do I need to replace the header.? And whether or not it's there, what would the first sign of problems related be.? I do have a cold knock on the coolant pump side of the engine. May be normal for all that I know. I am used to big block v8's and ten cylinders. Another question. Years ago my parents had a 88 Corolla Fx, The car rocked. I wish my Parents would have kept it. I blew the doors off of a 73 Nova sparking a modified 350ci once. Anyhow it needed the valves adjusted periodically. Is this so with the Spyders power plant? Sorry for the rambled questions. Thanks..

[jhauschild]

Might as well throw this in with the other ? . Can the 1ZZ-FE be squeezed for more power.? Stroking it, Boring out, cam changes.? Remember, I am used to the whole V8 and big block world.

[lbridges]

The pre-cats are contained in the widened section of the exhaust manifold and can be found under the heat shield that is right in your face when you open the hood.

The issue is that the catalytic material is retained in place by a ceramic matrix top and bottom of the widened chamber I wrote about above. Either end can go and cause trouble. If the bottom goes the material is flushed out into the main cat and causes problems like a stopped up muffler (along with the added heat etc.). If the top goes the engine (during valve overlap periods) can suck the catalytic material back into the engine and score the cylinder walls.

In any case, replacement of the header, or 'de-gutting' the pre-cat will remove the potential - why not sleep better at night and get rid of them. It will technically be illegal for any shop to do, but it's really only an ULEV vehicle thing - removal makes you a regular emissions legal vehicle.

The cold knock is not the pre-cats. Their symptoms are either failure to rev freely (bottom falling out) or excessive oil consumption (top breaking up). It's relatively easy to inspect the top - simply pull the two O2 sensors and take a peek.

Valve adjustments are done with via replacement stainless steel shims. It's not a periodic maintenance item like it would be on an old-school Chevy with solid lifters.

There are NA power adds for 1ZZ, such as you ask about, but the cost/benefit factor is not very good. I suggest you take a look through the MonkeyWrench Racing site to get some ideas. The most cost effective AND reliable solution is to do a 2ZZ swap. But of course, for big power numbers you will need to turn to FI - either via a supercharger or turbo, both of which reduce reliability. I believe MonekyWrench achieved 500hp out of a well massaged 1ZZ with turbo.

[jhauschild]

Thank you for always being informative.

[lbridges]

Originally Posted by jhauschild

Thank you for always being informative.

You only say that because you haven't seen my smart a$$ side.

On a more serious note....I previously owned a '91 MKII MR2, which was a very nice car but there were a lot of them. Then, after handing it down to my daughter, I picked up a Subaru SVX - which had sales in the US of about 15,000 units over a 5 year run (sound familiar?). As a result I think those of us with low production number cars need to stick together, or die on the vine.

BTW, you're welcome.

[knifesmith]

Alright, the wife left me and now I finally have time to get into this car. WOOT!!! I heard about the precat issues and want to make sure that if I replace the header I will get rid of both right? I think the lower p-cats blew already so I am stuck driving the 89 4runner. Believe me I am still stoked to have one of those also.

[supunna_picta]

Switching to an aftermarket header will remove the OEM header that has pre-cats built in. This leaves you with the regular cat which doesn't have any issues.