96 Blk/Red LT4

Kevova

Trans Am is heavier than a Corvette by roughly 400 lb. It has more drag because it has more downforce. That big wing in the back hurts fuel economy although it does look cool. They use different transmissions using different ratios. although both have.5 od in 6th.

cv67

You wont feel a damned bit of difference there is nothing special about the vortec head over the LT1, nothing. You ask questions get the proper answer then argue its wrong. Some people call that an Askhole


This thread

Phoenix'97

I said awhile back that this started from my research into the cast iron heads for the LT1. They flow better than the aluminum LT1 heads despite the weight penalty so I figured instead of spending the money to mild port my aluminum heads, it may be worth it to get cast iron heads which have more endurance. My aluminum head on the driver's side now suffers from a stripped header bolt hole requiring a larger bolt to secure the header. If the material was cast iron, it would not have stripped. So, there are some minor advantages to having iron heads. The other argument that wins me over is winter time warm up. Okay, aluminum can transfer heat to the coolant faster but in frigid cold isn't the heat dissipation of the aluminum head helping to keep it cooler as opposed to heat retaining iron which will then eventually transfer that higher heat to the coolant? Honestly, I guess it depends on how you look at it. If they sell special coating for aluminum head combustion chambers to retain more heat for complete combustion, mimicking iron heads, then I have to think there is some good with iron as head material.

With regards to compression, if you are using fuel that is higher in octane level, pre-ignition won't be a problem when using iron heads and everyone on this forum jokes about it but I plan on using Iso-Butanol to fuel my own car in the future, and it is rated at 102 octane. So, even if I do have compression bumped up by using a thin head gasket, it shouldn't be a problem and furthermore I have the reverse-flow coolant set-up to help keep pre-ignition at bay. Newer cars today don't use reverse-flow cooling that I know of, and if they have turbos then they need aluminum heads.

Okay, you do have a point here and this is what I wanted to hear from someone.

Phoenix'97

I have a manual and I prefer to cruise below 2000 RPM. I can't drive the car at 1000 RPM but 1500 RPM doesn't seem to lug the engine. This is why my goal is to increase low end and mid-range torque since this is where my engine spends most of it's time. The B-Body LT1 cam may be the most ideal but I am still eyeballing the ZZ4 if it is an "improved" B-Body LT1 cam of sorts.

With regards to 4.11 gears, this is a trade-off I am not willing to make. I don't want to trade up highway mileage for the chance to improve city mileage by multiplying torque if that is what is going on. This is why my philosophy is to bump up low end torque instead of trying to multiply it with rear gear ratio. I want to keep my mileage rating, not trade-off mileage rating.

Space387

Iron heads will take longer to come up to temp. As I mentioned in my last post comparing the all iron L98 in my corvette to my Aluminum head LT1 in my Firebird. Did you know the only iron heads built for the LT1 that match the aluminum heads are found on the cop cars. They built them assuming the cars would spend a lot of time idle and heat soaked.

Your tuning and computer enrichment is also directly tied to coolant temp during the warm up phase. The engine burns more fuel until roughly 130F. I have spent the last 8 years tuning my firebirds(all iron 3.4l v6 and the LT1) and trust me with just a little time behind the computer you can probably get all of your gains with out ever turning a wrench. Also on the Fbody LT1 a good set of long tubes has been shown to net an extra 2-3 mpg and +25hp give or take.

For the cost of a tuning cable and a wide band I promis you will get better results than 2-3k spent on heads. Besides if you learn on gas where tuning is easier you will be ready for tuning your iso-butanol.

Last thing I forgot. I daily my camed, ported untuned LT1 with a 3.73 rear and average 22mpg. It could be better I just haven't had the time to work on the fuel table. Running 92 octane on a stock timing table with the compression bumped to 11:1. Yes my engine is built to make power through 6k but rarely sees it.

To conclude I feel you are trying to reinvent the wheel. Right now it's very round and you are just starting over with a square instead of polishing what you have.

84 4+3

Yea I went through the heat transfer rates already... but somehow the negledgible amount of airflow in a relatively sealed engine bay is enough to cause the aluminium heads to take longer to heat up...

Polo Vert

You're all full of ****!!!!! **** on Vortec heads! You want cheap, efficient, low end power out of a 350 Chevy? Here is your answer......http://www.alliedmotorparts.com/87-9...nder-head.html

Small 58cc chambers to bump up your compression ratio. Small, yet adequate runners for increased airflow velocity all the way to your 5000 rpm threshold. Torque central, boys! You jackwagons can thank me later!!!!

Space387

Polo hate to rain on his parade but the stock heads he has are 54cc chambers. So just about any head is a loss of compression

Phoenix'97

My uncle was a police officer who drove in the old LT1 Caprice cruisers. I am not sure if they were offering police only performance packages back then but knowing that the iron heads flowed better and in combination with the B-Body camshaft, I think the patrol cars were adequate for the work. I don't know of any complaints of these cars at that time. Even then, I struggle to see the problems with using iron heads on my car when they proved themselves on the Caprice, Impala, Fleetwood, and Roadmaster for daily driving. Plus, I love how you can't strip the header bolts or spark plug holes in iron heads unlike in aluminum heads. I just experienced one stripped bolt on my driver head and I fear for other bolts that may be just sitting but not holding down the header.

Maybe I am trying to reinvent the wheel here. I am just trying to see what options I have, figuring out what needs to be done to give me what I seek, and then having a decent game plan to execute come the day this car spends time in a shop for a full "Overhaulin". I really feel that the TPI intake will be beneficial in the set-up I have in mind. Now that I am reconsidering the L31 Vortec heads, I am back to where I was.

I still have a hard time believing that long tube headers will help increase fuel economy but I have been proven wrong before in my assumptions. Even then, my car sits low and the exhaust system is going to need rerouting if I wish to use dual cats and then I need shorter long tubes so that the flanges don't run the risk of bottoming out if the car sinks into a pothole.

Phoenix'97

I just discovered this and wanted to share.


John Lingenfelter on Modifying Small-Block Chevy Engines: High Performance ...



John Lingenfelter on Modifying Small-Block Chevy Engines: High Performance ...


https://books.google.com/books?id=GUC52-afG5EC&pg=PA75&lpg=PA75&dq=iron+cylinder +heads+during+winter+warm+up&source=bl&o ts=H0-SAmbE-r&sig=j-JNJlUOhSpyWANUgIzJRL4s2r8&hl=en&sa=X&ved =0ahUKEwjCje_QpYDbAhXpxlkKHceyBBAQ6AEITz AH#v=onepage&q=iron%20cylinder%20heads%2 0during%20winter%20warm%20up&f=false

pologreen1

I have to say I have NEVER seen someone put so much thought and energy in to focusing on such small gains (intentional limited gains), even for hypotheticals.

You are working your brain and everybody's here 100x harder, than just throwing on real performance heads cam and gears, to be happy with over 100 HP+ gain and 100+tQ.

I just don't get what you are after?

Can you simply and only list what your desired results are and then let people pick away at a solution for each?

Phoenix'97

Okay, let me try...

1. Improve low and mid-range torque as much as possible up to 5000 RPM.
2. EPA rated fuel economy can not be reduced from the modifications.
3. Must maintain factory rear gear ratio.

Where do we go from here? So far I am thinking I am back to the B-Body set-up, cast iron heads and the camshaft or maybe I can better enjoy the ZZ4 camshaft. However, if I am not restricted by lift from the Vortec head, why not jump to the Crane 227 or a Lloyd Elliot sleeper cam? However, I am still irked because the TPI intake can help to peak the torque curve that is generated from the combination of other parts and my goal is to maximize the torque as much as possible up to 5000 RPM.

MatthewMiller

Yeah, if only one of us earlier had thought to point out that there are other options for improved low-lift flow that are better than stock L31 heads...

Yeah, I've told him that before, too.

Told him that before, too. Multiple times. But he "read it somewhere" so we all must be wrong!

You do realize that the torque and power peak-rpms we've been discussing are only at full-throttle, right? When you're just trundling around the roads going to the grocery store or school at a very low throttle opening, your torque peak is nowhere near 3500rpm (or whatever you think it would be with L31 heads and a TPI intake). It's probably below 1000rpms - that is to say, at low throttle openings you can't physically run your 350cid engine low enough to be anywhere close to the torque peak at that throttle setting.

Phoenix'97

It is very hard to tell what you are discussing. At times it sounds like race oriented performance and other times I get suggestions that get me to think a little bit. This is why I am asking "stupid" questions as threads.

My interest is increasing torque numbers from what my stock LT1 F-body cam is getting currently with aluminum heads and my factory rear gear ratio. My choices seem to be narrowed down to the B-body LT1 camshaft or the ZZ4, unless a custom grind will be the best choice, something superior to the B-body LT1 camshaft if one can be made. Then, I am still very interested in getting a TPI intake on my LT1. The vortec heads would have made it easier but now I am back to my original plan, find a way to get the factory TPI base to work on my LT1 heads or maybe find someone who can make the base for me. When there is a will there is a way.

Tom400CFI

The rest of us have known about exhaust crossover passages for decades. What are you "sharing"? What is the point?

I don't get your erection over the "B-body cam". Have you seen a dyno sheet somewhere that shows it to be a low RPM TOWAK MONSTAH? I haven't, but I bet that it makes just under 300 lb-ft of torque at 1000 RPM....about the same as any other same era 5.7L V8.

BTW; Remember in your other thread, where I told you about a car I had that got 24 mpg with a 305, then later got 24 mpg w/a 400? Just asking because you keep shitting this out of your mouth:
Even though I gave you a real world example of one that didn't. So instead, you'd rather:
This has been a closer look!



.

MatthewMiller

Your questions aren't what makes you stupid. Your insistence that we all are wrong is what makes you stupid.

Why does your peak torque at WOT matter to you? It has nothing to do with your goals of improved mileage.

confab

What is the advantage of keeping the bottom of the LT1 and trashing the top?

The ignition?

Tom400CFI

Best sentence in this thread.

X2. Especially when your LT1 bottom is a worn out/thrashed/rebuild bottom end. Hard to tell which is your case b/c you've claimed all of the above.

Phoenix'97

My insistence? Where? This is YOUR IMPRESSION. I have never said that you all were wrong but I did question your statements. The way you like to joke, how can I not question and challenge your comments?


I am not talking about peak torque at WOT. I am talking about a torque curve that peaks within a given RPM range. Have you been reading my comments properly? I bet not.



I have no use for top end power. The way I shift during hard acceleration I rev up to 5000 RPM. This is why I want my torque curve to be optimized for this specific band and this is why the TPI intake is such a good fit.

That post is more for my reference but the iron heads have a provision to help them warm up faster during winter time. Either way, I am sold on the iron heads for my LT1 and for the LT1 those iron heads will flow better anyways than my aluminum.

Nope, but I trust the fact that a camshaft designed to move a 4500 pound car has to be of an advantage to a lighter 3200 pound car. The B-body LT1 cars had more restrictive exhaust systems which limited their full performance potential. Had the exhaust been upgraded they would have enjoyed similar power numbers to their higher performance F and Y body counterparts. So, I don't stand to lose much by swapping in a B-Body LT1 camshaft, and RV/Tow cams are known to be fuel economy cams.

Yeah, and I don't believe a joker. I don't believe your numbers, I think they are deliberately bloated for joke purposes and for guys who build high performance cars I seriously doubt that you accurately record your every fill-up and average your fuel mileage like I do. It does help to indicate possible mechanical problems when your economy takes a crap all of a sudden, I must add.


This has been a closer look!