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Discussion Starter · #1 ·
I have a stock 1991 Z28 305 TPI engine that I'm putting in my '57 Chevy pickup.
I am going to keep the internals of the engine bone stock and am going to use a set of repro Corvette 2 1/2" ramhorn exhaust manifolds with it. I intend on setting it up with a 2 1/4" dual exhaust system and turbo mufflers.

My question is whether I would see any benefit from an H pipe in this particular setup. It wouldn't be that hard or expensive but I don't want to waste time and money if it would make no difference.

Thoughts will be appreciated.

Just for interest,
Here's the mock-up of the install:
After I get everything fitted I'm going to remove it all and do a cab-off restoration.

 

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In my opinion there is only one good reason for not installing one - more work. The reasons for installing one are many : it is the best place for you put your O2 sensor, otherwise you should run two; exhaust balance; sounds better, less exhaust vibration, etc....

I've done it once and will never leave them seperated again. It wasn't that much more work and the benefits definitely outweighed the time it took to hook them together.

Looks like a nice build - good luck:)
 

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the sound is preferred by most people.
2 1/4 is quite small for any exhaust system
The 'H' pipe is a good addition for balance and sound.

This is what I used to design and build the exhaust for my 5.0 moderately warmed over engine. Sorry the table looks confusing so I also added the link:

"Quick and Dirty Exhaust System Math

Easy Way To Estimate: Your intake system needs to flow 1.5 CFM per engine horsepower, and your exhaust system needs to flow 2.2 CFM per engine horsepower.

Good Way To Estimate: Take engine RPM x engine displacement, then divide by two. This is the intake volume. Use this same volume of air for the exhaust system, but then correct for thermal expansion (you need to know exhaust temps to figure things out).

Exhaust Pipe Size Estimate: A good section of straight pipe will flow about 115 CFM per square inch of area. Here’s a quick table that shows how many CFM each common pipe size will flow, as well as the estimated max horsepower for each pipe size:
Pipe Diameter (inches) Pipe Area (in2) Total CFM (est.) Max HP Per Pipe Max HP For A Dual Pipe System
1 1/2 1.48 171 78 155
1 5/8 1.77 203 92 185
1 3/4 2.07 239 108 217
2 2.76 318 144 289
2 1/4 3.55 408 185 371
2 1/2 4.43 509 232 463
2 3/4 5.41 622 283 566
3 6.49 747 339 679
3 1/4 7.67 882 401 802
3 1/2 8.95 1029 468 935

NOTE: These numbers are just estimates. All pipes are assumed to be 16 gauge steel.

The table above is probably over-estimating pipe size, but you can see that a 400 hp vehicle with a dual exhaust system only needs 2 1/4 – 2 1/2 inch pipes. Anything larger is overkill." How To Calculate Muffler Size and Exhaust Pipe Diameter | Exhaust Videos
 

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RE:I.C.,,,QUOTE;
Here’s a quick table that shows how many CFM each common pipe size will flow, as well as the estimated max horsepower for each pipe size:

what about that stupid muffler in the system and all the non mandrel bent pipes?
2 1/4 exhaust is likely too small for a 283 if you use mufflers or bend the pipes
 

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Discussion Starter · #6 ·
RE:I.C.,,,QUOTE;
Here’s a quick table that shows how many CFM each common pipe size will flow, as well as the estimated max horsepower for each pipe size:
what about that stupid muffler in the system and all the non mandrel bent pipes?
2 1/4 exhaust is likely too small for a 283 if you use mufflers or bend the pipes
Since this is a truck, I don't need tail pipes. I'll just put on short turn-downs on the back of the mufflers. The exhaust pipes will only have one 90 turn coming down from the manifolds. I could get a mandrel bend for this one.
The other thing is that this is a 305 TPI and is a low rpm engine. Probably around a 5000 rpm redline. My experience with TPI engines is that the shift point on full acceleration is best at about 4,800.
 

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You will need a higher shift point than 4800rpm.

A cross over, balance or H-pipe will give you a mellower, quieter sound and will only bolsgter low rpm torque with no power improvements. The TPI engines are not short on torque.

2 1/4" is more than big enough, esp. for a stock 305. The IROC TPI exhauist manifolds had 2 1/4" exhaust manifold exits which were larger than other Fbody manifolds. The 2 1/2" Ramshorns are overkill.

The TPI 305 all else equal will have a higher power/torque band than a 350. All depends on which stock cam your 305 cam with. The auto cams were wheezy, the 305 manual would run with the 350's.
The 1985 IROCZ TPI 305 would cetainly be limited with 4800rpm WOT shiftpoints.

The TPI 305 will work excellently in your application. Your truck wouuld look pretty cool with a TPI/dual filter air intake system that the Chev's used. WHat yoiu are using is just fine though, plus you are running SPeed density that dont run those horribly restrictive 85-90 MAF's.

I had a manual trans TPI 305 installed in my 1984 reg cab longbox GMC truck. With 3.08 gears and 315/70/15(33") tires it woudl run low 17's trapping in only 2nd gear, but running 84mph. Same trap speed as the stock 454 SS trucks.
Stock 1985 IROC Z auto would run [email protected]

peace
Hog
 

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Discussion Starter · #10 ·
Thanks Hog.

I'm building this truck for my wife to do errands with. I want it to be a good smooth running truck for her and I thought the 305 TPI would be perfect for that. I found the engine/700R4 transmission on craigslist. It was in a creampuff '91 Z28 with 63K miles and I got to hear it run before it was removed.
My wife has no interest in hotrodding the truck. She just wants it to run well and be dependable. It had the original 3 on the tree and a 235 6 cylinder in it but she would just not drive it without power steering and A/C.

You can see the new power steering box I got in that photo. It is a CPP 400 series box. I've got the Ididit shift steering column too. I'm also going to put in power disc brakes (front only). I've already bought the Vintage Air A/C for it too.

Btw, here's the air filter that I'm going to use for it. It will fit inside the fender well behind the headlight really easy.





Here's the truck right after we got it for her:





Also just for interest, here's my Bel Air that I just completed last year. This one is my car so we're doing the truck to call hers. I'll try to make her truck just about as pretty.



 

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Thanks. It was a bunch of work.

Here's the day I brought it home in Sept. of '09: It was much more rough than the pickup is.





Same shot now:

Very nice shoebox, hopefully my Diamondback, will turn heads, but wont be as pretty as yours. I do have a pretty Belair though.
The diamondback was Dad's old "gasser/daily driver" which was well known back in the 60's with its 50 truck straight front axle and 365hp 327 crate engine.

This is my new, Dad's old car. Back in our family after a 30 year hiatus. Dad would have been proud that I got her back.



And the "pretty car".She was in a 1996 Chev Cavalier Superbowl commercial. And on the 1997 Snap On Calenday, March 1997. Snap On once lifted this car on top of 4 of their Tropical Turquoise tool boxes at a car show. It scored 994 out of 1000 points once and has scored its Platinum Certificate(970+ points) multiple times. One time Mom and Dad found a boat launch, 1 on the PAcific side and they dunked the back tires in the water, then drove cross-counbtry to teh Atlantic side and repeated the process. This was teh 1st Canadian Classic Chevrolet Club car to do this.

Dad bought the car back in 1991 down in Arizona. He trailered it back with the engine in the front seat, cast iron powerglide in the back seat. It arrived at our place in many different colours or primer/paint. Dad did a frame off resto doing ALL work except paint and the actual triple chroming, he polished all his own stainless. I remember wet sanding with 2000 grit sandpaper. My shoulder still hurts LOL. It's a driver and regularly beat trailered Belairs. Even the other "driven cars" that would stay at a hotel 25 miles from the show, then UNLOAD their DRIVEN CLASS CARS off of their TRAILERS and then DRIVE 25 MILES TO THE SHOW. This car would still win the class over them after being driven 500miles, 1000, 1500 miles one way. Mom and Dad regularly won the "Long Distance" awards in the car. Once I get all of their pictures converted to ZERO's and ONES (digital) I will post them for all to enjoy.




We just got her polished up as Mom is taking her to a show in the States at the end of June. She is taking another friedn of hers who also has recently lost her Husband. So the 2 girls are taking the car to the show, the both used to LOVE doing the shows in their old cars.

This is a "seamless" 1957 2 door hardtop frame that Dad didnt get to use. It's in great shape and was used in 5% of Chevs that year, its "supposed to be 80 lbs lighter than teh 2 pice frames and was used in the 1957 strippo 150 series Black Widow NASCAR's that used the Ramjet 283/283 hp engine with dual shocks at each corner, 6 lug hubs. I was going to sell it, but everyone that sees this frame, says I shoudl use it on the Diamondback. I may just do that. Its in great shape.





Roger 1, you have a beautiful car and that truck is an awesome platform. I wont comment on your family's appearance(we are ALL beautiful), but it's really nice to see that you and your Wife appear to love cars/trucks and each other very much, and that type of love IS beautiful. I remember my Mom and Dad posing for shots with their cars. I really miss that they cant do that anymore.

Take care!

peace
Hog
 

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Discussion Starter · #19 ·
Hogg,

Cool cars!

Sorry you just lost your Dad. That's cool you are keeping t he '57 up for your mom to continue going to shows in it.

There's kind of a story about my '55 too. The reason that's what I had to have is that I was born that year and my Dad bought a new 2 door 210 with a 265 that year too. He loved that car and always talked about it and how it would "skid" the tires (leave rubber). It's long gone though. He got hit hard in the quarter panel in '57 and chose to give it up and get a new '57 sitting on the lot. It was a 4 door Bel Air with a 6 cylinder and he just didn't like that car as well as the '55.

I wish he was around to see my '55. I know he would love it.
 

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Hogg,

Cool cars!

Sorry you just lost your Dad. That's cool you are keeping t he '57 up for your mom to continue going to shows in it.

There's kind of a story about my '55 too. The reason that's what I had to have is that I was born that year and my Dad bought a new 2 door 210 with a 265 that year too. He loved that car and always talked about it and how it would "skid" the tires (leave rubber). It's long gone though. He got hit hard in the quarter panel in '57 and chose to give it up and get a new '57 sitting on the lot. It was a 4 door Bel Air with a 6 cylinder and he just didn't like that car as well as the '55.

I wish he was around to see my '55. I know he would love it.
thanks, since we are sharing stories, I have quite the "personal" connection with the 57 in primer above. That was the car I was conceived in, so the story goes. Not sure if I beleive it though, since we all know our parents, never actually copulated, right? There must be a WHOLE LOT of immaculate conception going on in the world, lol.
My parents got married, bought property and built a house had my Brother and myself, car was sold. I still have the advertisment from the newspaper. It reads "1957 2-Door hardtop, Corvette 327, 4-speed, 4.11 gears, Stewart Warner gauges, bucket seats, $2200 OBO.
It sold for $1500 and that money went towards his new garage that he built on the same property that his house is on.

I really like the 55's as well. I think they are supposed to be a bit lighter than the 57's. Which is why they are the more popular "shoebox" for drag racing.
I really like the "Belair" floor mats in your '55. Where did you get those, if you dont mind me asking?

It's funny how our parents influence us. I'm a GM guy through and through, just like Dad was. He was a great guy and I miss him. Thanks for the condolences. I guarentee that your Dad is smiling that you have such a beautiful '55.

peace
Hog
 
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