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C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Torque Build 350 Centered Around FIRST TPI

 
Old 05-13-2019, 01:06 PM
  #21  
jonbonez
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A 420 - 450 hp range motor in a C4 is that perfect line scenario of getting your cake and eating it too. The car is already so incredibly light. Get your traction part of the formula down and you have an insanely fast car. It's amazing to see how horsepower to weight ratios truly affect end results than a single number of RWHP does. 300 lbs is the difference between a 12.8 and a 13.2 at the 1/4 mile with a vehicle pushing 300 RWHP. A 300RWHP C4 could keep up with a 2019 Mustang GT until the last two or so seconds of the track.
Maybe at the end of the day, it's cheaper to just go ahead and get the bigger block that still allows a FIRST TPI intake. I.E. maybe a 400 or 383. But can't turn down a 427 if I know a way to bolt up a TPI to it.
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Old 05-13-2019, 05:33 PM
  #22  
84 4+3
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Originally Posted by jonbonez View Post
A 420 - 450 hp range motor in a C4 is that perfect line scenario of getting your cake and eating it too. The car is already so incredibly light. Get your traction part of the formula down and you have an insanely fast car. It's amazing to see how horsepower to weight ratios truly affect end results than a single number of RWHP does. 300 lbs is the difference between a 12.8 and a 13.2 at the 1/4 mile with a vehicle pushing 300 RWHP. A 300RWHP C4 could keep up with a 2019 Mustang GT until the last two or so seconds of the track.
Maybe at the end of the day, it's cheaper to just go ahead and get the bigger block that still allows a FIRST TPI intake. I.E. maybe a 400 or 383. But can't turn down a 427 if I know a way to bolt up a TPI to it.
When I do eventually decide if I want to do a crossfire build (it'll happen...) That is the area I was shooting for. I figure if I build shooting for 500 hp I'll end up around 450. It would be an incredibly fun car either way... not that it isn't already.
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Old 05-13-2019, 09:52 PM
  #23  
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Originally Posted by obijohnkenobe View Post
Here's the problem with a ton of low-RPM torque... how are you going to get it to the ground?
My car is a manual, so I'm not concerned about making a ton of low end torque. My thoughts on using the stock heads and intake is to keep cost down and start with a good foundation.

I agree that too many people get focused on that max hp number rather than power to weight. I think 400to 450 would be the most I'd want.
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Old 05-14-2019, 10:53 AM
  #24  
ctmccloskey
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You really need to consider rebuilding the entire engine to get reliability. The bottom end is probably the most critical part of a performance engine.

Many years ago I started a build using my 427 Big Block. The blocks machining was all done and the inside was painted with Glyptal sealing the pores of the Cast iron block. I started looking for a Crankshaft to use in my build and I went through 11 cranks before I found one that would pass the magnaflux testing. These were FORGED crankshafts and the first 10 all had little tiny cracks in them. I bought the best crank I could afford and used a kit from Comp Cams to build my valve-train. The Rods I bought were a new set and even those were magnafluxed to be sure I was okay. I have Forged Pistons on my Forged Rods on my Forged Crankshaft. This bottom end was balanced at 7000 rpm and it works great 26 years later. I am using 12.25-1 Compression with cast Iron GM heads (3931063, 100.3cc's) that use the Closed Chamber design. The closed chambers were chosen for their resistance to detonating even with higher compression. The combination I chose was my idea to make lots of power. It works very well and pushes my little 1968 C3 down the road quickly. The problem is like mentioned before, what good is the power if you can't get it to the ground? My 1968 will spin the tires half way down the quarter mile track if you let it. It looks impressive and sounds awesome but spinning tires are useless, try some good slicks and then your differential, transmission and half shafts will start breaking, ask me how I know?

Just because you have Forged Pistons doesn't mean your car is ready for making more power. If the 140,000 mile bottom end is "weak" you will soon find out after installing the engine. If it were my car I would seriously think about using a 4 bolt main block and build it using quality forged parts.

Build the engine the right way even if it takes more time. Rushing on an engine can lead to a expensive disaster and ruined parts. Take your time and do it right the first time, build the whole engine at once, adding new heads to a old high mileage block sounds like a recipe for disaster, In my humble opinion of course. I spent a year building my 427 the way I wanted it. I have a spare 350 Lt-1 with the double hump heads (Camel-hump) in my garage. I stuck it in my C3 while the 427 was coming together and kept on driving my C3 for the whole year. The LT-1 engine was able to get 21 mpg with my 3.36 rear-end and my Muncie 4 Speed. I had a buddy who had a real live 1970 LT-1 and my poor little 350 outran him every time and he had the 4.11 rear in his car.

Enjoy your Corvette for all it is worth! Build the engine of your dreams just do the entire engine at one time and you will be happier in the long run!

Best Regards,
Chris
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Old 05-16-2019, 12:27 AM
  #25  
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Thatís weird this thread was started. I have been talking to Ken at FIRST because I plan on getting a first intake and then getting either edelbrock e street heads or afr 180 or 190 heads and a cam to put in sometime. This is in an 85 too. I donít know what cam yet but I would rather keep flat tappet so not much needs changed and Iím hoping this will get around 400 hp at the crank. I hope to have enough saved up by the end of next year to buy everything and start installing it. Iíve heard the first really performs similar to a superram intake and I think the first looks a lot better.
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Old 05-17-2019, 01:37 AM
  #26  
jonbonez
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Originally Posted by ctmccloskey View Post
You really need to consider rebuilding the entire engine to get reliability. The bottom end is probably the most critical part of a performance engine.

Many years ago I started a build using my 427 Big Block. The blocks machining was all done and the inside was painted with Glyptal sealing the pores of the Cast iron block. I started looking for a Crankshaft to use in my build and I went through 11 cranks before I found one that would pass the magnaflux testing. These were FORGED crankshafts and the first 10 all had little tiny cracks in them. I bought the best crank I could afford and used a kit from Comp Cams to build my valve-train. The Rods I bought were a new set and even those were magnafluxed to be sure I was okay. I have Forged Pistons on my Forged Rods on my Forged Crankshaft. This bottom end was balanced at 7000 rpm and it works great 26 years later. I am using 12.25-1 Compression with cast Iron GM heads (3931063, 100.3cc's) that use the Closed Chamber design. The closed chambers were chosen for their resistance to detonating even with higher compression. The combination I chose was my idea to make lots of power. It works very well and pushes my little 1968 C3 down the road quickly. The problem is like mentioned before, what good is the power if you can't get it to the ground? My 1968 will spin the tires half way down the quarter mile track if you let it. It looks impressive and sounds awesome but spinning tires are useless, try some good slicks and then your differential, transmission and half shafts will start breaking, ask me how I know?

Just because you have Forged Pistons doesn't mean your car is ready for making more power. If the 140,000 mile bottom end is "weak" you will soon find out after installing the engine. If it were my car I would seriously think about using a 4 bolt main block and build it using quality forged parts.

Build the engine the right way even if it takes more time. Rushing on an engine can lead to a expensive disaster and ruined parts. Take your time and do it right the first time, build the whole engine at once, adding new heads to a old high mileage block sounds like a recipe for disaster, In my humble opinion of course. I spent a year building my 427 the way I wanted it. I have a spare 350 Lt-1 with the double hump heads (Camel-hump) in my garage. I stuck it in my C3 while the 427 was coming together and kept on driving my C3 for the whole year. The LT-1 engine was able to get 21 mpg with my 3.36 rear-end and my Muncie 4 Speed. I had a buddy who had a real live 1970 LT-1 and my poor little 350 outran him every time and he had the 4.11 rear in his car.

Enjoy your Corvette for all it is worth! Build the engine of your dreams just do the entire engine at one time and you will be happier in the long run!

Best Regards,
Chris
Did a little reading and this post was definitely a bit of a wake up call. Good wholesome story to be read from it. Definitely going to just enjoy the car and make the best of it's quality, I'll build the engine on the side with a whole new block and rotating assembly. Thanks for the awesome words, probably seems like nothing to you but definitely made me think and feel better about this project oddly enough.

Originally Posted by 85 CRVET View Post
Thatís weird this thread was started. I have been talking to Ken at FIRST because I plan on getting a first intake and then getting either edelbrock e street heads or afr 180 or 190 heads and a cam to put in sometime. This is in an 85 too. I donít know what cam yet but I would rather keep flat tappet so not much needs changed and Iím hoping this will get around 400 hp at the crank. I hope to have enough saved up by the end of next year to buy everything and start installing it. Iíve heard the first really performs similar to a superram intake and I think the first looks a lot better.
Awesome to see another '85, and also one looking into the FIRST intake. 400 rwhp is right where I like personally cause it's not too much and it keeps driveability. And yes, the FIRST looks awesome looking like a stock intake on steroids. Plus, superrams are hard to find, they work great, but I'd rather not have my power band up there if it's just a fun car I'll drive whenever I want. Good luck with your build too and hopefully you have all the fun doing it.
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