Help, I am going insane thinking about highflo cats! | Ford Explorer - Ford Ranger Forums - Serious Explorations
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Help, I am going insane thinking about highflo cats!


Well-Known Member
February 1, 2000
Reaction score
City, State
Chicago, IL
Year, Model & Trim Level
94 Sport
I am replacing my muffler and going with a Flowmaster 40 series. I am also planning to to run duals from the muffler back. The only problem I have is finding a good high flo cat to put on as well. I might as well have the muffler shop put it all on at once. I did a search on high flo cats but it didn't lead me to any conclusions. I know I have two cats (or you can consider it one (with two bodies)) do I need to replace them both or go with only one. What kind should I get. I already have Borla headers so a high flo cat and a Flowmaster muffler would be one bad a$$ exhaust system.

Please help! I feel like I am going around in circles and there is no end to it.

O yeah! I don't know if anybody has heard of Fair muffler shops, but I am going to get my exhaust done there. Does anyone know if they would have high flo cats.

Thanks in advance, I really need help.

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Definitely change the cat!

I put in a high flo catalytic in my 92' after having the dual for a long time and I think I got more horsepower from putting in the high flo cat than when I got the duals. So I agree you should do it all in one shot, its definitely be cheaper in labor now that your getting the rest of the system installed. I found mine over the internet in one of the performance products companies, but I can't remember the name. It was under $100 though, when I get home I'll look for the receipt and post the name. If you do a search for Catalytics on the board you might find my original post asking the same question (that was a long time ago)and other websites that offer the same product. The only thing I suggest after having it for more than a year is to remove or reinforce the covers on the cat. Just as it happened with my factory cat the covers on this one have started to loosen up and are rattling :( The problem is they only spot weld the galvanized cover on every corner, with time the spot welds come loose and the damn thing rattles like crazy. Their is a cover on each side, I guess its to prolong the life of the cat. So maybe reinforcing it is a better Idea. I'm hardheaded so I removed mine. If needed I'll give you the name of the Company I bought it from, they gave me excellent customer service. But rest assure that it will help if you change the cat. Some people might disagree but when you really need to put the pedal to the metal you'll notice the difference.


You may want to look into Random Technology, Dead Link Removed I just disposed of the link this morning, so i dug it back out. If I was going to repalce the cat, I would go with them.


I purchased a Pro-Flow Cat from Summit Racing around 2 years back for $79. It definitely flowed better than stock and you can expect around a 5hp gain at the most. Its worth it for the money.

remembered where I bought it.

Hey Rich,
I remembered now I bought my High flow through:
look under exhaust and you'll see the Cats. They are a little more expensive than what other people in the board are saying they got theirs for so you may want to shop around. The good thing about this brand "dynomax" is that they come in a lot of different sizes. To answer your first question that nobody (including myself)touched on. The one High flo that you buy will replace the two that the truck has from factory.

Hope this helps,

buyer beware...

High flow cats seems to be draped in mystery. Many manufacturers make good products but are bad about labeling them. This can leave you questioning what you are really getting. If you truly want a performance hi-flow cat, go with a reputable performance shop. You will pay the "performance price".
Some exhaust shops will sell you a high flow cat that is nothing more than a stock cat that has been "tinkered with". This can be as little as putting a cat on that was not designed for your vehicle to actually breaking them through with a rod.
Also, If you have emissions testing, you may get stung with a single body + make-up pipe setup on a visual inspection.
High flow aftermarket bolt-in replacements with two cat bodies are available but can be expensive.($250+)
As luck would have it, I happen to have one that I would sell for $100 + shipping. It is a year old and was taken off a built up 91 Explorer that was sold. It is in good condition, no rust or dents. It does not say Hi-flow or even a brand name on it but I can send you a picture of it if you are interested.

id have to agree with bigham on the random technology catalytic converters. their monolith cats are supposed to be able to see light through them, which means it probably flows pretty good. there was an article about them in the july issue of four wheeler. hope this helps

Rich -
forgot to mention. The Pro Flow cat that I picked up from Summit is the dual cat just like the stock cat.

Thanks for everybodies help. I decided to go ahead and get a high flo cat. But I still got a couple more questions. When the shop replaces the cats will they have to fabricate a longer pipe with a O2 sensor hole in it. Plus what should I pay for the cat itself. Please give me some price ranges. Please don't stop with the information.

Please don't stop with the type(brand) of cat I should get.

Thanks again, This is a great website!

Mike, got a part #?

I'd like to check that deal out. I know it was two years ago, but I just did a search for cats at Summit's website and all I got was a "universal CATCO Converter" for $80.99. That is a single unit that must be fitted. Maybe they have more in their print catalog but here and now Pro-Flow is not listed as a brand they carry.
Here is a link to the site where the cat I'm selling was originally purchased:

It is item 3. The direct fit Hi-Flow replacemant.$241.55
Note that items 1 and 2 are front and rear units and are both required to meet emissions standards.

[Edited by wabbit on 06-23-2000 at 12:07 AM]

The above link doesn't seem to work. Probably because it includes a sequential search criteria for a 91 Explorer 4.0LV6.
If so inclined, try and look up Hi-Flow cats for your vehicle...

Alright, I must have pulled the price out of a hat b/c I just looked at my receipt 12/10/97 and realized that I actually paid $141.69 for the cat, but even though - its still a better price than some have been quoted. Like I mentioned earlier its a "PRO-FLOW" high flow cat. I have been pleased with it so far and its emission legal (2 cats and not gutted). Oh, almost forgot - the part number for the cat is PFP-5186 from Summit Racing (800) 230-3030.

I have a Catco dual body design hi-flow cat sitting in the garage. I bought it from Summit Racing, and the price was roughly $115 with shipping/handling. One of these days, I'm going to get environmental and put it on in place of the gutted one I have now.

hi flow cats

do hi flow cats change the sound of your exhaust is the perfomance increas noticable

The cats really don't change the tone of the exhaust - they are more in line with reduce emissions, while the muffler's main job is to reduce the exhaust tone. I changed my cat converter and did not notice any notice in tone.

As far as performance goes, you will notice some improvement in acceleration, but don't go in with high expectations. The only way to achieve a really noticeable performance gain with the cat is to gut it - personally, I don't agree with it though b/c its harms the environment and its illegal.