I am doing a body off restoration on my 70 lt1 vert.
I would like to have engine checked and rebuilt to original. Could some tell me where i could find the specs for a 70 lt1.
Thanks,
Nelson007

 

Nelson, best place would be the AMA specifications:

http://gmheritagecenter.com/docs/gm-...t-Corvette.pdf

 

If your block is original, let me be the first to scream DO NOT DECK THE BLOCK!!!!! Make sure you tell that to the engine shop about 20 times and then get it in writing.

A valve job, ported heads and you'll have a nice running engine.

 

I have the 71 Lt1. The question is do you want an okay running motor or a great running motor? The biggest draw back is the 60's technology solid lifter cam and springs.

I went for the balanced and blue printed 355 ci with a Crane solid lifter cam 238/248 with 1.6 roller rockers. Manley race flow stainless valves. Lighter weight forged pistons. It will leave the stock motored vettes behind and still beat them on MPG.

The only external thing that you can see when I lift my hood is nice ceramic coated hooker headers. The real choice is do you want to brag about having a NCRS top flight poor running vette or a fun performance Vette that you use and keep?

 

I just rebuilt my LT-1 engine. I went a bit overboard, but I would agree with the previous statements.

For some reason, folks LOVE to deck blocks and machine surfaces. DON'T!!! Seldom is it needed. And in the case of an LT-1, you run the risk of messing up your compression ratio even worse than the stock 11:1.

Personally, I'd stay with solid lifters out of nostalgia. And I would keep the forged crank.

I replaced my rods with a set of Eagle Forged, full floating, with 7/16 cap bolt bottoms. Good purchase. Takes a lot of variables out of the bottom end.

The stock heads are fine, pretty good even, especially if you're sticking with a stock-ish cam.

If you need to replace the pistons, go with Speed Pro...the 'new' TRW. Again, nostalgia. I was able to keep my original TRW pistons, which made me happy for some reason.

I'd ABSOLUTELY and without hesitation go with a FULL ROLLER SOLID LIFTER cam. You can either match the original profile or go a little more aggressive. Your choice. It would please the NCRS folks to have it sound SOMETHING like the original LT-1 cam. And that's not a bad cam anyway. I used Comp, but there are other brands.

Personally, I'd run a Rev Kit too...inexpensive insurance for a high-RPM solid roller with no real downside. Probably not necessary in a sub-0.500 lift cam, but nobody has given me a negative to running one.

Full balance is a no-brainer. New valves...Manley rocks, but there are others too...is also a no-brainer.

Of course, the other little things like a new Cloyes timing gearset, a new Schuman oil pump, and whatever other little upgrades you can fit in there.

With all those little things boiled together, you'll be 100% solid to 7k RPM that puts out a REAL 400 hp at the crank. And if you keep your intake, timing cover, balancer (new, of course) and other external bits, you will have a stock appearing (but fast and bulletproof) engine.

To fit the new non-cup rockers under the stock valve covers, you may need to trim away the drip rails. If I did that, I'd probably buy another set of covers so I didn't carve into my original ones.

Not that I JUST went through this or anything...

 

When you say a real 400 hp at the crank, are the numbers the results from a dyno. If so, could you post the results.
Thanks Bob

 

Thank Guys for all the information.
I definitely would not have it blocked. I am trying to keep the engine as stock as I can. The engine only had 32k miles on it and was running strong. I am trying to build this one to be judged. The car had set for about 20 years. The only thing the previous did was change the headers and ignition. I found the correct ignition and correct headers at Carlisle. The frame had some bad rust problems and was also able to find a new frame for the car. I have all the paint stripped off the car. Now doing projects that I can do inside, it’s too cold outdoors.
Here is a links showing some of my progress.
Nelson 007

http://s1060.photobucket.com/user/ns...?sort=3&page=1

 

Undergoing NCRS judging? I still wouldn't build a 70 LT-1 to original specifications. I would use a better quality connecting rod, use Mahle pistons and port the cylinder heads fitting them with far superior stainless steel valves (Manley only please!) The poster who said rarely do blocks need decking does not build motors for a living, in the machine shop I work out of it is very common for old 350 blocks to be out of square 0.020" from front to back as the cast iron takes a set after many hot/cold cycles. It is always a question of value on whether to deck or not, if it is an original motor, no I probably wouldn't deck it but, realize you are not then going to do a proper job of "blueprinting" the motor back to production line specifications, it may result in a motor that dosen't run quite as smooth, last as long between rebuilds, or make as much power as a properly built motor would.

My opinion on solid rollers in street motors, unless your ready to pony up $800 for a set of bushed roller lifters DON'T DO IT! Needle bearing roller lifters will not live a long life in a street motor idling around at low oil pressures, even the NASCAR motor builders went through HELL trying to make roller lifters live 350 miles in the Truck and Busch (whatever they call it nowadays) classes and the top class still uses flat tappets (admittedly quite expensive ones on $3000 cam cores made from exotic tool steels.)

If your intersted in my builds, here are some youtube links:

70 LT-1 start-up:

 

My opinion on street building a LT-1 if your on a budget and my wifes lesson in whats inside a motor, I am a very fortunate man, I married a WINNER who take great interests in her Corvettes (the 70 LT-1 roadster is hers, I just get to drive on occassions and maintain it)

Lori gets lesson on lifters:
Lori gets lesson on valvetrains:
My good friend Dan owner of AEPM machine shop whose longterm friendship has made my successes in automobiles possible:

 

This is the final result 1970 LT-1 has been runnig great since 2009 when restoration was complete around 10K miles on rebuild at present time, has never been on the trailer since it was taken home from the initial completion and 1st place award at 2009 WSCC convention in Las Vegas. This Vette would be totally ridiculed by the NCRS crowd as it isn't "correct" or nummbers matching but, when I take it out for a drive it always gets great compliments from the general public and having owned a 54K mile "survivor" 1970 LT-1 coupe, I prefer a car that I can drive around in without feeling guilty for doing so.

LT-1 driveby:
Lt-1 run up to redline:

 

Most of that 0.020 was there from the day the block was broached by GM. If it hasn't caused any trouble in the last 40 years, it doesn't need to be 'fixed' now.

 

Mike your quite the expert on about every subject......please post up some photos or videos of your work......your dead wrong about a GM block being 0.020" out of square at time of machining at the Flint or Towananda engine plant. Until you show me your GM Quality or Engineering credentials and proof of company employment from the era our Vettes were made your spewing more of your key board BS here.

Having a set of cylinder block decks out of square by 0.020" especially if it's a worse case scenario can result in having to compromise ignition timing settings. This poster is rebuilding a 11:1 compression 370HP LT-1 not some 350 that shares it's components with an Impala Station wagon like your Vettes motor. There are more things to take into consideration when rebuilding a high performance engine than with low revving low compression power unit.

Mike please post some of your Corvette work I question if you have ever built a motor let alone operated machine equipment required to complete the process of rebuilding and I pretty much know a guy like you has never spent hours suffering away holding a 16000 RPM industrial die grinder in their hands in search of that extra "free" horsepower to be found by using such a tool.

 

The deck being .020" out front to back makes a 4cc chamber volume difference in the front hole compared to the back hole. That is a full 1/2 point of compression ratio difference. It also means a looser quench at one end which will make for less combustion efficiency and more sensitivity to detonation on that cylinder.

It is things like this that make the difference between a runner and a pooch!

 

Wow. Awesome comment. Thank you, Bob.

They say 370, I say 400 in so much as CONSERVATIVELY, a thorough friction reduction regimen through full roller valvetrain combined with full floating wrist pins, a little more cam, and quality valve job will give you 30 hp gains. Relative to where the factory said the engine was originally. And conservatively.

 

Pot calling the kettle black here.

Please go over to the NCRS site- you won't burst into flames I promise, and do some research. Many low time/mileage or zero time brand new blocks have been examined over the decades and found to have all sorts of deviations from 'perfection' that guys like you feel the need to 'correct'. The cylinder case broaching operation by nature is not the most precise way of doing things especially in an environment where a new engine was produced every six seconds.

I don't have my head in the sand and only look at what's directly in front of me. There's a ton of knowledge out there for the taking. Might help you with that chip on your shoulder too.

 

That 370HP rating was actually achieved using the old Z/28 L-76 Fuelly cam in the certification motor. The LT-1 cam installed in 1970 and later motors is a little tamer.

The best HP With a factory Hi-Rise intake was indeed using a roller cam in a 0.030" over 355 cu/in LT-1 it made around 426HP on a very conservative dyno with Hooker Headers and mufflers attached. During a Corvette club dyno session in 2001 that same motor unseated the top HP levels of the happy new owner of a C5 Z06 with 373Rear Wheel HP. That being said, it would display lash problems at around 6K miles with the symptoms being opening of lash then the messy job of pulling the intake to swap out lifters with brinelled needle bearings of the Crane then Comp cams roller lifters. Spring pressures weren't excessive (160 lbs on the seat, 420 over the nose and the Comp lifters were fitted with a Rev Kit. Hydraulic roller lifters are great, they stay on the cam lobe solid rollers on the other hand lead a hard life, they are constantly being impacted and I won't do a street build of a solid roller motor unless I use something like an Isky EZ Roll, Crower is presently offering bushed rollers too and Comp had some last year at SEMA. If your running a solid roller I would advise you the pull your intake and check them at any sign of lash enlargement that you observe. Pull the lifters apply pressure to them and roll them across your fingertips, you will feel the roughness if the needles are going bad.

 

Was the 426hp achieved with accessories on it? You had mufflers installed, so are you talking Gross or Net?
You exceeded 373rwhp? That would be less than a 12% drivetrain loss? Am I missing something?

 

Only accessory was Edelbrock water pump with smaller diameter crank pulley and stock LT-1 deep groove pulleys. Like I said, the Dyno is conservative it is a Heenan Froude GH490 fifteen hundered HP water brake (google that dyno refrence) My buddies Dyno nummbers are way low compared to other engine shops but, at the track his stuff blows away the competition in series like USAC Silver Crown, Bonneville. You can see the Dyno set up at my friends shop in the Dicovery Channel series of the ACK Attack world landspeed record holding motorcycle, it was quite the event to reconfigure the engine dyno to mount the Bonneville Streemliner onto it, also pretty DAMN SCARY watching 14FT of final drive chain whip around at 12000 RPM.

My Vette ran an M-22 Muncie and 4:11 gears during the chassis dyno session, the operator who had only tuned C4/C5 Vettes at the time was quite surprised that a GEN1 small block could turn such numbers. He asked me....383? "NOPE! 0.030 over LT-1 355 cu/in motor a little warmed up over from stock" was my reply. Motor went 12.28@117MPH at the Drags and over 14K street miles before I lost a rod bearing at a high speed autocross. Right now, it sits in my garage waiting to get freshend up and put up for sale, no time right now.

Here is a photo of the dyno cell, your looking at about $400K worth of hardware/software here, Digilog controller, Depac 32 channel real time data acquistion and the master console behind a 4" thick bullet proof window. Look really hard and you can see the job my friend Bob inherited of an Austrailian Pro Stock 400 cu/in motor, it makes over 1150HP at around 10500RPM The job was at another shop many of the components wouldn't have been Bob's first choice to use in a build. Last year 2013 with a rookie team, this motor went 3rd fastest of all the racers in OZ this year Bob has the heads he wants the custom tunnel ram he developed(I could show you a picture but, then I would be banned from the shop for life and children of a lessor god like myself, often need help and advice from a guy like Bob) 2014 should be an interesting year down under, the season starts in MArch and there is much activity at Bobs shop right now (starting race was bumped up a month sooner than originally scheduled last year.)

 

I agree. All solid lifters do, but solid rollers have the added risk of a messy failure.

The rev kit helps a bit with the beating-upping. I am running a similar 160# seat pressure. After break in, I am setting the limiter to 6,500 RPM...maybe even 6,200...but plan on shifting at 6k.

We are running a very tight lash cam, also. We were setting the factory flat tapped at 0.040, if I remember. But my Comp setup is designed for 0.016/0.018. That, again, will help with the durability of the valvetrain.

Good advise, though. Keep a "black book" of lash and record all adjustments. That will tell you if something is going sideways on one valve or another...easier to pull a whole, but grumpy, lifter out of the engine than a lifter out of the top and THE REST of the lifter out of the oil pan...

 

Blocks dont have to be old to be off

Bought a brand new GM block in 2000 it was out by .002 at least right outta the crate;.003 on the other bank if I remember correct