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It just keeps getting better with my new burb LOL

Re: All right got the first tank and a MPG figure Ideas

If that convertor is the flat style, it is pellets and very restrictive. It is about 2' long and 1' wide and 2"-3" thick, and that bastard weighs about 50lbs. I replaced mine with a CATCO high flow from summit and a flowmaster exhaust kit and it made quite a difference in power, not sure about MPG but it could not have hurt it. My exhaust was the 3" stock with a HUGE turbo muffler (about 3' long) and it was holding the power back. Also I have a 350, so imagine how much that 454 is being choked down! You need a good quality high flow muffler with alot of volume, not just a regular performance muffler. Flowmaster makes big block 70series muffler for that application (5"x10"x22"case) and then get a direct replacement high flow cat, you will not be upset with that upgrade.
 
Re: All right got the first tank and a MPG figure Ideas

So how much was the cat? I hang on a camper board as well and a lot of the folks with 454 campers speak highly of the banks set up. Some claim a 1-2 mpg increase and big power improvements.
 
Re: All right got the first tank and a MPG figure Ideas

What would the FI do if ther wasn't a cat? My local laws I don't need emmisions inspections because I'm over 8500 GVWR.
While I like staying in compliance well anyway.
What would the FI do without the restriction of the cat. Would it throw off the O2 sensor and throw codes?
 
Re: All right got the first tank and a MPG figure Ideas

The cat was $107 from www.summitracing.com. I think the engine would have no problems w/o a convertor on it. Get a section of 3" pipe cut for the correct length and expanded on each end an try it out. The convertor slips on, on both ends and you clamp it down tight. I was thinking of doing that, but my inspection is due next month and I did not want to test my luck.

The key is to get the right amount of back pressure and flow, so you still have bottom end torque and it is open enough to help your MPG.
 
Re: All right got the first tank and a MPG figure Ideas

Thanks. Let me think about how far I want to push the envelope. I might run a test pipe for a Day or too so I can see the improvement and see if I trip any lights or run into any fuel mixture problems.
 
Re: All right got the first tank and a MPG figure Ideas

you wont throw any codes with no cat. The O2 sensor is before it. It will be really loud and smell pretty bad though
 
Re: All right got the first tank and a MPG figure Ideas

I know the cooling issue has been covered before, but if everything else is original, what about the radiator?

You know GM didn't let it leave the factory heating up that hot (to my knowledge) so as you suspect, and I tend to agree, somethign thats been changed is the culprit.

I'm more inclined to believe its the radiator though, or at least a bunch of junk wedged in front of either one, because the radiator is so often overlooked for maintenance.

Of course, guess I'm spoiled, within 5 miles of my house I have a radiator shop that will flow test your radiator for free if you pull it and bring it in.
 
Re: All right got the first tank and a MPG figure Ideas

[ QUOTE ]
you wont throw any codes with no cat. The O2 sensor is before it. It will be really loud and smell pretty bad though

[/ QUOTE ]

Uhhhhhhh I'm just curious why it "would smell pretty bad"....I just want to know why it will smell any different. I have to hear this answer.

/forums/images/graemlins/rotfl.gif
 
Re: All right got the first tank and a MPG figure Ideas

well, it wont smell bad...i happen to like the smell of exhaust, but it will smell a lot richer...the cat takes a lot of stuff out of the exhaust. I took mine off and it smelled a lot different...
 
Re: All right got the first tank and a MPG figure Ideas

Well part of that is because for what ever reason the mixture is off. My 75 with carb that NEVER had cats doesn't "smell" any different to me then my 88 FI burb does. My 79 Blazer I just sold passed the sniffer at the emmisions check with no cats.
Cats don't do much for a properly tuned engine. Properly tuned they run clean enough to pass the sniffer. Cats are for vehicles that are not properly maintained.. It may not be so far out that you have any real driveability problems but it is out none the less.
Now why you FI vehicle smelld different IS a concern. What may happen is it chages the O2 reading with the incresed flow and that is a very real concern for me and why I'm hesitant with what I may do in reguards to this restrictive cat that is actually lowereing my performance and fuel economy..
 
Re: All right got the first tank and a MPG figure Ideas

I've run a 93 with headers and no cat, and it smelled fine and ran great. I don't want to be caught without a cat on my 95, so I had a custom single outlet 3" exhaust bent up for under $400, and that included a flowmaster delta flow as well as a new high flow cat. It wasn't a big improvement, but it did make a noticable difference.
 
Re: All right got the first tank and a MPG figure Ideas

Yeah That's my worry. like I said since my truck is over 8500lb I'm not required to test it. But it is a restrictive bead style converter. I'm sure that better flowing would improve MPG and performance. When the 79 finnaly did get cats put on it it did take out some performance but MPG wasn't checked. that vehicle rarely was a few miles from home. WIthout the cats on straight hwy I was getting a little over 13. I DD this burb and if I could get 2 mpg even spending $100 on the converter it would pay for the upgrade in a couple months. My bigest concern with no cat is noise. Cats cut the volume a LOT. That 79 had 40 series flow masters on it and when it didn't have cats it droaned horribly on the hwy. when the cats were put back on it was much quieter going down the road and they stayed on for mostly that reason. They were cheap cats so the flow was not great. If I can find a QUIET free flowing muffler then that's what I want. This is the family ride and will be pulling a camper and hauiling the kids long distance and I want QUIET. LOL.
 
Re: Shocks? What shocks?

Did the shocks tonight and fuel filter.

Hahaha almost no resitance on the old shocks under compression. I extended them and put my full weight on them and they just slammed to full compress. /forums/images/graemlins/blush.gif

It was all I could do to get the gas shocks on. I had to lay under the fronts and shove them up. Not fun with a broken finger LOL.

Took it for a quick spin around the block and a VERY noticable improvement. Truck is much more stable and responsive to steering inputs. Seemed to cure all of the spazzing out the truck did if you hit a bump while cornering. Took a lot of the cornering under braking dive out. See if I feel sea sick after the ride to work in the morning. /forums/images/graemlins/rotfl.gif

Threw a new fuel filter on as well. See if it helps with the serge.
I hope it cures it. if not it's time to start testing eveything. That's the last of the simple stuff unless I find a bad vac line to the Map sensor.
 
Re: All right got the first tank and a MPG figure Ideas

[ QUOTE ]
If I can find a QUIET free flowing muffler then that's what I want. This is the family ride and will be pulling a camper and hauiling the kids long distance and I want QUIET. LOL.

[/ QUOTE ]

Grim...I have a MagnaFlow exhaust on my /forums/images/graemlins/k5.gif. I chose it becasue at the time it was our family vehicle and I wanted both performance and quiet. My muffler guy said they flow as well, if not better than Flowmasters and the sound is a nice quiet tone without much resonance. /forums/images/graemlins/thumb.gif
 
Re: All right got the first tank and a MPG figure Ideas

Thanks for the tip. I'll check into them.

Had to say these Bilstiein shocks are AWSOME!
Rides great now, really improved the handling.
 
Re: All right got the first tank and a MPG figure Ideas

This is a 2wd, right?

I don't run a cat on my '87 with TBI. No issues at all.

3" exhaust is probably enough. If I were you though, I'd look into some headers. They'd probably make a massive improvement on a big block. You can keep the 3" single or go dual. I personally would go dual exhaust on a big block as even a 3" single isn't really enough. I'd put 3" duals on it if you can get someone to bend it.

Mufflers it's your option, just put them as close to the rear of the vehicle as possible.
 
Re: All right got the first tank and a MPG figure Ideas

Yep 2wd.

I'm really beginning to think I have a cat thats at least partly plugged. Both exhast manifold gaskets are blown, I have a heat up problem at idle with A/C on and I have this serge. All could be explained by pluged converter. The flow out the tail pipe doesn't seem all that great. No Hiss you sometimes hear but I really don't think I'm getting good flow.
 
Re: All right got the first tank and a MPG figure Ideas

Grimy...food for thought...living in emissions test required for registration states all my life and working in the field...i have noticed a trend of 10 years being the end of a cats usable days....you can also do the back psi test also...

DW /forums/images/graemlins/usaflag.gif
 
Re: All right got the first tank and a MPG figure Ideas

How is that done?

I think I'll hit my local exhaust place and have them make me a "Test pipe" and see if it comes alive. I plan to replace the exhaust manifold gaskets this weekend but I sure would be pissed to find the cat's bad after the fact and blow them out again.
 
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