My 70 LT-1 engine build begins - several pictures

[Steve F.]

I thought a few of you may enjoy some pictures of the 70 LT-1 engine I am building. I bought a 70 LT-1 roadster a few years back knowing that much of the engine had been changed out. I have spent some time looking for the parts to build the correct engine for the car and that has been an experience. I would say around 90% of the "LT-1 engines" and parts I have looked at had nothing to do with an LT-1. A few years ago I came across an LT-1 short block built in late 1970 that was intact and never built. In researching it I came across a couple of threads here on this forum where folks had discussed it back around 5+ years ago. I ended up buying it out of LA which is ironic as it had spent much of its life two states away from me in MA. I have waited until I rounded up other parts I needed to start the build and the first thing we did was to tear it down to be sure of what we had and look at the condition. You will see in the pictures it is what I had hoped - a 70 LT-1.
Let me say that I realize this is a CE block and will never be the car's original engine. I also know that I could build a stronger engine for less money using today's technology. I just want my 70 to be like it was in its day. I am never going to have the car judged and I know I will make some compromises along the way but I do want it as close to the original as I can make it.

I will add pictures of the other parts as it starts to come together.

The marker numbers are from us measuring everything to see what we have. This is as we found it before we cleaned it up. Also putting on new bearings and rings.
Steve

[Timothy B.]

Re: My 70 LT-1 engine build begins - several pictures

Steve,

Everything looks to be in V/G condition, has the block been decked? I would reuse as much as possible even the camshaft if it checks out and you kept the lifters in line with the hole they came from. Are those pistons/rods full floating? Don't remove any material from the crankshaft, just a light polish at home with some 4 or 600 wet paper.

[Alan S.]

Re: My 70 LT-1 engine build begins - several pictures

Hi Steve,
LT-!
There is actually something quite 'beautiful' about those pictures. The word 'sculpture' comes to mind.
It's amazing what those parts do when assembled, and the legend they have made.
Regards,
Alan

[Steve F.]

Re: My 70 LT-1 engine build begins - several pictures

The short block is as it came from GM with nothing done to any of the parts. We took the block off the crate and dismantled it to check it - the engine has never been assembled beyond its short block form so the only wear is from some turning by hand over the years. We plan to take the glaze off the cylinder walls and change the bearings and rings but that is all that needs to be done. We even debated on the rings but they have been sitting in the same position for 42 years so we decided to change them as a precaution. The block has the CE stamping and it does not need to be decked.The parts will be cleaned and used. While the engine isn't the one my car was born with it is as close to what it had originally as we can get it.

I have pictures of the caps and others of the pistons I will post along with the other LT-1 specific parts going together. I have done several engines but I agree there is something beautiful about these 40 year old pieces that have never been run. Seeing the block clock and thinking about the folks that made this originally is interesting to me. I am excited to hear it finally run.

[Duke W.]

Re: My 70 LT-1 engine build begins - several pictures

Did you measured the deck clearances on all eight before you disassembled the short block? If not you should do it when its reassembled. Then you can compute the true CR with the OE .018" thick gasket, and adjust it as necessary to achieve your target CR. BTW, what is your target CR?

What heads are you using? ...good opportunity to massage them if you want to maximize top end power.

Duke

[Timothy B.]

Re: My 70 LT-1 engine build begins - several pictures

Steve,

Why are you changing those good GM bearings and rings that have never been used..

[Steve F.]

Re: My 70 LT-1 engine build begins - several pictures

I am using a set of 70 LT-1 202 heads built in June of 70 for a CR of 11-1. I am the first to say I know I could get better engineered pieces but that isn't the goal. I also have a 72 LT-1 motor that we just finished and "upgraded" many of the pieces including the heads. For this build I want it like it was in 70 for the most part. I say this as some parts, like the ignition amp will be upgraded and I am still missing some pieces like the AIR system.

As for changing the bearings and rings the machine shop thought this was the safest step and if needed they will be replaced with GM parts. We will be checking the originals to see if they can be reused but a few of the rings were "stuck" in place and we want to be sure there are no burrs or spots where any rust may effect them.

[Duke W.]

Re: My 70 LT-1 engine build begins - several pictures

It's very unlikely that this engine will be "11:1" - more like 10.5 depending on deck clearance. I would recommend not exceeding 10.5, which should be achievable with proper head gasket selection, even if the decks aren't high.

See the Fall 2009 Corvette Restorer "Compression Ratio Explained". It's not that hard to make the measurements and hit the target. Anything else is just guessing, and typical "engine builder" advice to use thick head gaskets will usually leave torque, power, and fuel economy on the table.

If the bearings pass a visual inspection, I would not hesistate to reuse them. Those Morraine 400 bearings are better than what the aftermarket offers today, IMO.

A light hone and new rings makes sense, especially since a couple might have been stuck.

Duke

[Steve F.]

Re: My 70 LT-1 engine build begins - several pictures

I probably should be more explicit in my descriptions. I am not trying to build it to a particular CR rather I am trying to build it as it was built in 1970 and GM called it 11-1. The person doing the machine work also said it would likely be closer to 10.5 and we will not do anything to try for that extra .5. My goal is not to "improve" it or try to make it more HP. We are discussing head gaskets now as he does suggest using the thicker gasket although I do not think that will happen. I am waiting to see if the heads will continue to be stock after their rebuild.

I also agree on the bearings and we will try and clean them up as they have some grease that has dried over the years - you can see some of it in the picture of the cam above. If they appear good then we use them but if they have any scratches then we will replace them.

[Duke W.]

Re: My 70 LT-1 engine build begins - several pictures

The "way GM built it" varied considerably, and the big variable was deck height. They can be up to .015" above the nominal 9.025", which would be reflected in a deck clearance of .040", rather than the nominal .025".

Sometimes the deck heights are close to nominal, and I don't recall ever seeing one low (assuming the original Flint machining). Even if the deck is nominal the actual compression ratio will be less than 11:1, and it will be lower by about 0.3 or each .010" of deck height above nominal. And the same applies to head gasket thickness. The OE gasket was .018" thick, and the closest to this is the Felpro 1094, which is .015" thick. If one deck is more than .005" different than the other, one can use different head gasket thicknesses on each side to minimize the CR spread, which can easily exceed 0.5 side, to side.

What I am suggesting is don't leave this big variable to chance. You have an easy opportunity to "manage" it within the wide range that these engines were built, and it's easy to do by taking the requisite measurements and running them through the compression ratio calculator. Anything else is just guessing!

Read the article in the Fall 2009 Corvette Restorer, and I suggest you make a photocopy and give it to whoever will assemble your engine.

Duke