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71 Chevelle SS clone - 8.1L Swap

tRustyK5 said:
Blueprint sells a standard deck stroker short block BBC that comes out at 598 cid. Safe to assume there is enough room in there...
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The 598 is still a short deck same exact external dimensions as a regular 454. I really want one but I would need a very large gas tank to feed it. Look up Engine Masters on Motor Trend. They did a budget build and a full build on them. Even the budget build made massive torque.
 
Truckman4life said:
The 598 is still a short deck same exact external dimensions as a regular 454. I really want one but I would need a very large gas tank to feed it. Look up Engine Masters on Motor Trend. They did a budget build and a full build on them. Even the budget build made massive torque.
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I have the MTOD subscription and am an "Engine Masters" junkie. lol. With good Dart heads, Brodix intake, 1250 dominator and a pretty sane cam it made 875 hp at 6400 rpm and a shade over 800 ft/lbs of torque. Dave Frieburger was the guy that convinced Blueprint to build and offer that 598 short block...

Being standard deck makes swapping one into the place of a dead 454 super easy. Everything swaps over. $6000 isn't chump change, but it isn't unobtanium money either.
 
After sitting down to price out both repairing and modifying the 454 vs installing an 8.1L I came to the conclusion that the cost would be fairly similar for both options. I know the haters don't like the 8.1L engines, but I am going to be very happy with one and that's all that really matters ultimately. I bought the whole truck that has the cheaper 8.1L in it this morning. I figure that after parting the rest out, I may come very close to getting the full purchase amount for the truck back, or I may even turn a small profit on it.

I've ordered up a custom oil pan designed specifically for putting an 8.1L into an A body chassis. I'll take the engine down to a semi-local fabricator who can modify the intake manifold and oil fill pipe for me to solve the hood clearance issues. I still need to track down some medium duty or g van type accessory brackets to solve the power steering vs steering box clearance issues. I am hoping to re-use the existing exhaust, but I budgeted for new headers and modifying the piping to fit plus adding in new O2 sensor bungs. I plan to install hi-flow cat converters and an EVAP system to help the car smell a little bit better. I'll need new 90 degree ceramic spark plug wires on each cylinder to help them survive the heat from the headers as well.

Not going to be a cheap swap, nor is it going to get done fast. I'll start with tearing the donor apart and getting the engine cleaned up, swapping the oil pan on and replacing the cam sensor with the 04+ version and getting the intake done. I'll tear the 454 out after the 8.1L is more or less ready to go in sometime next year.
 
Its definitely a valve issue. Either the intake or exhaust valve isn't sealing properly. No change in compression adding a teaspoon of oil which would usually help seal up ring issues. Or there is a hole in the piston, which I kind of doubt based on the fact that it is making any compression at all.

I'll sell the 454 locally after I am ready to pull it out. I don't plan on driving the car until the 8.1L is in, but I still want it mobile to move it around as needed so I can get in and out of my shop.
 
Russell said:
Its definitely a valve issue. Either the intake or exhaust valve isn't sealing properly. No change in compression adding a teaspoon of oil which would usually help seal up ring issues. Or there is a hole in the piston, which I kind of doubt based on the fact that it is making any compression at all.

I'll sell the 454 locally after I am ready to pull it out. I don't plan on driving the car until the 8.1L is in, but I still want it mobile to move it around as needed so I can get in and out of my shop.
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A way I like to figure out where the problem is, is put 50 - 100 psi of air pressure in the spark plug hole using the compression gauge hose, and then listen to where the air is leaking out, the exhaust, the intake/throttle, or the breather/valve cover. Make sure the valves are supposed to be closed, sometimes the air pressure will move the piston to the point where the valves open up, be aware of that, or just take the rocker arms off that cylinder to be sure.

Then you'll know whether it's the bottom end or the heads. If it's in the heads, then heads, cam, and intake would make it a strong runner, especially with the potentially higher compression with a smaller chamber. At least then you'll know if/when you sell it.
 
Midas well swap the 4l80 in as well and fire that stick in the bush seeing as you have a complete donor vehicle eh.
 
The donor has an allison. Ain't no way that trans will fit in an A body without some major surgery lol

I plan to keep the muncie. I will need to grab an internally balanced flywheel and a hydraulic clutch but it should bolt right up otherwise. I might swap a magnum 6 speed in sometime down the road.
 
Russell said:
After sitting down to price out both repairing and modifying the 454 vs installing an 8.1L I came to the conclusion that the cost would be fairly similar for both options. I know the haters don't like the 8.1L engines, but I am going to be very happy with one and that's all that really matters ultimately. I bought the whole truck that has the cheaper 8.1L in it this morning. I figure that after parting the rest out, I may come very close to getting the full purchase amount for the truck back, or I may even turn a small profit on it.

I've ordered up a custom oil pan designed specifically for putting an 8.1L into an A body chassis. I'll take the engine down to a semi-local fabricator who can modify the intake manifold and oil fill pipe for me to solve the hood clearance issues. I still need to track down some medium duty or g van type accessory brackets to solve the power steering vs steering box clearance issues. I am hoping to re-use the existing exhaust, but I budgeted for new headers and modifying the piping to fit plus adding in new O2 sensor bungs. I plan to install hi-flow cat converters and an EVAP system to help the car smell a little bit better. I'll need new 90 degree ceramic spark plug wires on each cylinder to help them survive the heat from the headers as well.

Not going to be a cheap swap, nor is it going to get done fast. I'll start with tearing the donor apart and getting the engine cleaned up, swapping the oil pan on and replacing the cam sensor with the 04+ version and getting the intake done. I'll tear the 454 out after the 8.1L is more or less ready to go in sometime next year.
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Your money, your ride, your choice ultimately. But that being said I'm a fan of a 8.1 Chevelle. 425-450 lb/ft of torque (net) depending on the exhaust and minor tuning is better than what the net rating of a 71/72 LS5 or LS6. It will be OEM reliable and still put you in the seat. Carry on dude!
 
Reading everyone's motor opinions is comical to me :D

Should be cool and unique with the 8.1. And I love that body style Chevelle. It's actually my overall favorite Chevelle and am still hopeful I can own one someday.

I mistakenly tried to ask for people's opinions on the interwebs about my motor choice when I was going to swap an 8.1 into my crew cab. And I got pretty much the same responses you have received here. A few had good things to say about it, while a bunch were chomping at the bits to tell me how much of a wrong decision it was, others said the motor sucked, bad aftermarket support, poor fuel economy, my brother in law had one a while ago and I drove it and it sucked, bla bla bla. And I decided after looking at everything, that it would fit my needs perfectly and decided to do it anyways. And I'm so glad I didn't listen to those idiots. I couldn't be happier with my 8.1 in my truck for my needs. Everyone loves to think that all people around them have the same opinions about this stuff as they do (or in their mind they think they're an expert) and therefore want to hear their opinion (which is one reason why I keep going further and further away from forum sites as time goes on). And that's why, don't listen to anyone but yourself. Do what you want with your vehicle. I would have been happy to see you build the 454 or do an 8.1. Either way, I just think that's a bad A car that you'll make even better than the day you bought it. And in the end, I approve of that (y)
 
Kay86K5 said:
Reading everyone's motor opinions is comical to me :D

Should be cool and unique with the 8.1. And I love that body style Chevelle. It's actually my overall favorite Chevelle and am still hopeful I can own one someday.

I mistakenly tried to ask for people's opinions on the interwebs about my motor choice when I was going to swap an 8.1 into my crew cab. And I got pretty much the same responses you have received here. A few had good things to say about it, while a bunch were chomping at the bits to tell me how much of a wrong decision it was, others said the motor sucked, bad aftermarket support, poor fuel economy, my brother in law had one a while ago and I drove it and it sucked, bla bla bla. And I decided after looking at everything, that it would fit my needs perfectly and decided to do it anyways. And I'm so glad I didn't listen to those idiots. I couldn't be happier with my 8.1 in my truck for my needs. Everyone loves to think that all people around them have the same opinions about this stuff as they do (or in their mind they think they're an expert) and therefore want to hear their opinion (which is one reason why I keep going further and further away from forum sites as time goes on). And that's why, don't listen to anyone but yourself. Do what you want with your vehicle. I would have been happy to see you build the 454 or do an 8.1. Either way, I just think that's a bad A car that you'll make even better than the day you bought it. And in the end, I approve of that (y)
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I usually ask for opinions just so I can get feedback on things I might have missed, but by the time I am ready to ask for opinions I already have made my decision and just looking for something that I missed in my research.
I don't believe everyone needs the same thing, and that's what made my computer business so successful in the 90's and early 2000's because I was not trying to sell everybody the same top of the line fastest biggest computer of the day but taylormade a setup to the specific need of the client.
 
I had a customer at the parts store who had a '71 Chevelle that was his grandmothers...his grandfather bought it new for her,and he special ordered it with some unusual options..

He opted for a 250 six,a 4 speed manual transmission,and a 3:73 rear diff...a drive train I'd never seen factory before..car was a medium metallic green color,with a black vinyl top.

The car was still mint when I saw it in the 80's,the grandmother had the seats covered from day one with that plastic bubble wrap stuff, and I rode in it a few times,it was still pretty peppy with the 4 speed!--car had about 50K on it....also it was a 2 door,which the grandmother didn't care much for--her grandson who she gave the car to after his grandfather passed away said "I think he ordered it for himself--not me!.."I'd have liked an automatic much better,and 4 doors!"..she admitted her husband drove it a lot more often than she did,despite having a pickup truck of his own..

Everyone who saw the car at cruise nights would say "Dude--you need to put a 454 in this--!..but he refused to change anything--he said at first he felt the car was underpowered,but he learned that the six made its highest torque at very low rpm's and winding it out didn't gain you much as far as acceleration,and he often got 16+ mph with it..I often wonder whatever became of that car..
 
Donor truck arrived tonight! Fired it up when I got home and about jumped out of my skin. Thing definitely has a hole in the exhaust, damn thing is loud haha! Sounded right mean!

It will be a while before I have the time to pull the engine out. I did order up a new vortec 7.4L throttle body to put on it and figured out what I need to do to reprogram the 8.1L base tune for mechanical throttle vs electric. Pretty straight forward in efilive.
 
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