GM had reprocessed the head manufacturing line to harden the valve seats more than a year ahead of the unleaded fuel decree. They saw this requirement coming and wanted to get ahead of it, in case it would adversely affect warranty of vehicles already on the road.

So, this 'improvement' occurred some significant time before 1971. And, as mentioned, if you are not pounding that engine hard through most of its life, there is NO issue, anyway.

 

Just a thought here. Those performance small blocks were designed to use a bit of oil when raced to make sure they were lubricated....set up a little loose for race conditions and heat. They all blew a little smoke, especially when shifted. If I was you I would start with a good compression test and a tune up paying attention to the PCV scavenging system in particular, spark plug color and heat range. Talk to an old time performance mechanic before you start blowing a bundle on it. With a rebuild, you may end up with more problems than a little smoke.

BUT....if you want a clean running small block you better count on more non original parts, ones designed to run tighter and cleaner, (with modern oil and gas) like a roller setup, flat tops, new valve job with different type of seals, etc,etc. Some guys are even putting in cat converters for a cleaner exhaust and smell.

 

No, what I'm saying is that there IS a difference and if you're replacing the rods, the cost difference is nearly zero so it is silly to not even consider doing it. Next you'll be telling me there is no friction reduction through the use of roller lifters/rockers.

Honestly, I appreciate this comment. It demonstrates how outrageously belligerent your posts can be in this forum. I had "taken a break" for a couple months from posting for no reason other than you and a couple others bashing my posts instead of giving the OP honest opinions about your experiences.

I can't believe I take time out of my work to actually participate debating the point. I'm all about a good discussion, but if you review this thread, it is very obvious that I am being singled out for criticism after trying to make honest points based on my personal and recent experience on a nearly identical engine to the OP's.

Best of luck to the OP. You have an awesome engine and starting point for a real peice of jewelry. Consider a few tasteful upgrades while you have the engine apart...that was my only point.

Thank you, Mr. Bashcroft, for relieving me of any interest I had in this forum. I'll be back when I have a problem, but believe I won't even attempt to be "helpful" anymore. I think this will be my last post for a very, very long time.

Sincerely,

Keithinspace

 

floating pins are good for saving time & effort during rebuild/freshening.

pressed pins tend to put stress into piston pin bosses during install ... and especially during removal... there are ways to reduce strees depending on technique ... but typical auto machine shop presson-press off procedure stresses sides of piston skirts.

 

That's the only thing they're good for.

During install, no. The proper way to install them is to heat the small end of the rod. The pins can then be pushed in with zero resistance.

During removal, who cares. If you're removing them, they're junk anyway.

 

How much money is involved in having the motor completely rebuilt--by a good performance shop?? Ball park for a complete job including appropriate parts.

I have a 71 LT-1 with 86k miles--the problem is--who knows if this is 89K or 189K or if the odometer didn't work for several years and maybe its 125K.

I am not a mechanic but it seems that if you're going to go to the trouble of pulling the engine and replacing "some" parts wouldn't it just make more sense to do a complete rebuild--assuming you have the money?

I have worked on the car and it is 99% original except for magnaflow mufflers and bilstein shocks (which are painted and have decals to look like original). No one can see inside the motor so who cares if it has original pistons, valves, cam, etc--if the motor blows up then you may replace the head or block and now it's really not original.

I only have questions--not the answers.

 

Anywhere from $1000 to $10,000. You need to ask your engine builder.

I agree, but there are many people here who think that their odometer doesn't lie.

Do it right the first time and you won't be doing it again some time down the road.

 

i think 120k miles is possible but i doubt 189k, pretty hard to get to that mileage with an engine of that era. as long as the crank and rods check out , then a rebuild with new pistons should get you set up. i would recommend pistons that take a modern ring package. they have made great improvements in that area , and it is worth taking advantage of.

 

Having JUST gone through this, I can offer some input.

My LT-1 engine had numerous small issues, but none were fatal. "A 9 out of 10 as a starting point" was my engine builder's opinion.

I kept my crank (straightened and ground), my pistons, my oil pan, my aluminum Winter's intake and...that's about it.

New Eagle full-floating rods, new 200 CC heads custom-assembled with 0.100 long valves, new chain, gears, and cover, new dampner, new Comp cam, solid roller lifters, and pushrods, new roller rockers, new oil pump and pickup, new Stewarts aluminum water pump. New rings, bearings, and all the other stuff, obviously.

All balanced and professionally assembled.

500+ hp is probably a little optimistic, but I'm HEAVY into the 400's definitely. Scary sounding engine and built to withstand about anything.

For the engine build and all associated parts, I'm into it right at $5,200.

You probably have a piston expense that I did NOT have in my rebuild...based on my cylinder wall wear, bearing wear, and other things, my engine builder thinks my engine had around 10k miles on it. 20k at most. The engine codes as an over-the-counter LT-1 replacement engine purchased from GM in 1976 to 1978. Interesting story, anyway.

Valve covers were $200.

A new Centerforce clutch is $350.

I already had a new QuickFuel carb and Holley fuel pump...~$800.

I also had previously put a new complete MSD ignition system on the car earlier in the summer...~$1,000.

I've decided to swap out the oil pan to a nice Moroso unit for $350.

I'm toying with the idea of replacing the Winter's intake with a newer Air Gap intake for $300.

So if you went absolutely nuts and didn't save ANY of your old stuff outside of the block and crank, you'd be closer to $8,500.

This is my engine installed:



And my car the very first day I pulled it out of the gararge...bear in mind that I've done ZERO tuning, so the idle is high and the needle valve on the secondaries was being grumpy, so it sounds MUCH better now...

http://s1245.photobucket.com/user/ke..._2236.mp4.html

 

Just curious: How could you reuse the LT-1 pistons if the block cylinders were remachined? And, if the bores were not re-machined during a $5K rebuild, why not?

 

The cylinder walls were in A-1 perfect condition. There were still original/factory hone marks in the walls. As I said, the entire engine, purchased new from a Chevrolet dealership between 1976 and 1978, had very few miles on it. I am 100% confident that the engine had never been rebuilt as evidenced by many factory internals including the GM factory plastic-tooth timing gear which was still in perfect condition (my 8 YO son has it in his room right now). The #2 main bearing went away in 1987 (from the heat evidence on that main cap and the main bearing date codes) but they replaced the bearings in the car, we think. If they DID remove the engine, they did NO other work...including rinsing the main bearing material from the drip corners of the heads. The collected '1987 failure' main bearing material was one of the reasons I pulled the engine in the first place.

My builder just resurfaced them and went with new rings.

Honestly, part of the decision in keeping the pistons was financial. Part of it was nostalgia...awesome TRW mini-dome pistons.

In large part, our attitude about the build was "put money where money is well spent" which meant saving money where the benefits were less tangible. There was absolutely nothing wrong with the pistons, but there was a lot of confidence and strength to be gained by new rods with 7/16" cap screws...

 

If you want originality all that matters is you got the original block and heads

If it were me go ahead and stroke it noone will know the difference except your butt meter!

Plenty of nice solid flat tappets out there that are easy on valvetrain pieces.

Mike Strak at CFM performance does a number on porting those old irons;very talented individual. Larger valves a +. Youll never go back to a 350 again

Your motor can still look 100% original and pick up rediculous amounts of power youll love it. Doubt it would lose 1 ounce of value in fact imo add to it.

 

If I needed to, for whatever reason, replace the CRANK...I would have stroked mine. Absolutely no question.

 

I would want to keep everything original that can be seen and replace all internal parts with new and probably better. I difinitely would keep the solid lifters, a radical/original specs cam, etc.

I know you can only bore out an engine so far (say .030)--then can you put in a sleeve. The main thing on these older cars is--they have to be numbers matching. If you bore it out .010 or .015--then I guess you could do it again but if .030 is needed can you put in a sleeve that can be bored again or removed next time??????

 

Yes, but that will get expensive. Last time I priced to sleeve a block was probably 15 years ago and it was $100 each cylinder.

 

Probably worth it if it is a "well-scored" car...meaning if it is otherwise original or the owner is taking a real run at judging. The percieved value of the car could be hurt more than the ~$1k investment if the block original to the car was no longer utilized.

If the car is a "driver" car with no additional attempt at originality, the expense of sleeving an original block would seem unwarranted...better to put that money toward a really nice core or a new block.

 

A different perspective - you have an LT-1 and the only meaningful thing that separates your car from a non LT-1 car is the engine. If you start changing all of these parts to "better" new parts you may indeed have a better built engine although you will no longer have an LT-1.

I agree with a previous poster that if you want to play with something different then do that and put your original engine to the side for later when you want to go put the car back to an LT-1.

I have three LT-1 engines that all have NOS GM short blocks. Two are 70 and one 72. While they are all CE blocks all are date correct with all original to the year LT-1 parts. The engine I have just completed for my 70 LT-1 was built with all number and date correct parts. While I know and agree that many of these parts are not the originals to my VIN number all of them were made for a 1970 LT-1 in 1970. Was it the cheapest way or the best built engine for the money - absolutely not. For me I wanted the experience of driving the car the way it was made.
When I want new car technology than I drive a new car. Just an alternative to consider.

 

I'm not trying to make 500hp just get it back to what it would have been originally. The carb, brake cylinder, intake, fuel pump, water pump, AIR system, transistor ignition, etc are all 100% original date coded and the car is almost ready for top flight judging but I'm not against using better than original pistons, valves, etc because no one can see that and it makes the car more reliable. Wouldn't mind having it closer to the 1970 LT-1 internally with higher compression, etc.

If you want a fast corvette buy a newer one--they will eat the the SB and BB engines from the 60's and 70's. I also have a 02 ZO6-WOW it screams.

 

I understand having a 'vintage' engine that is still in great condition. I have a '65 Pontiac Grand Prix with 60K miles and just 'refreshed' the engine and engine compartment. But, I did open up the engine...at least, far enough to check the condition of the block and internals. No bearing wear or gouging; still had wear-in finish on the cam lobes; no apparent wear in the cylinder bores.

So, it can happen. And it's nice when you get one like that. Congrats!

 

That makes your decisions REALLY easy...

Straighten and grind crank, new rods with 7/16" caps, new pistons, new timing gear, rebuilt heads, new cam.

The only real variable would be if you go full roller or flat tappet. And if you want to go a slightly more aggressive on the cam.