Hello engine expert,

I need help. I'm doing a frame off on my 1977 and now I'm reassembling everything on my new frame.

The engine was sitting outside my garage for the last 5 months. I had a cover on top of it but, I had not reinstalled the air cleaner bowl. So I cleaned and painted the engine and everything that comes with it (see pictures). Allot of hard work and time but very satisfying. Before putting back the body, I decided to do a compression test. This is when I realized that bit of water pass through the cover and got inside the engine, not a good thing I know. I removed the water, blasted air through the cylinder. And put a bit of oil in those cylinders to moist the seal. It did increase compression. The passenger side of the engine (cylinder 2,4,6,8) are all around 130. However the driver side (Cylinder 1,3,5,7) are at 110, 100, 80 and 80. What could cause this? I don't want to tear up the engine..too expensive. Can I run with it and maybe after a while things will get better:-)

 

A compression test on a cold engine that has been in storage as you stated is not very meaningful. The numbers are not indicative of a problem. Put the engine in the chassis, stick a radiator in front of it, hook it up, and start it up - it's easy to do. Let it warm up, and then do either a comp test, or better yet, a leakdown test on it. It would take you half a Saturday and 6 good Canadian beers to mount it and fire it up with some jumper wires - worth the minimal amount of time it would take to do. Make any decisions based on that relevant data.


Lars

 

If your motor is stock and has no performance improvements then you have nothing to loose just buying a GM crate motor "Hecho in Mexico" to replace it - less than $2000. Otherwise your gambling with your time and labor you can make that old motor work. Don't you think your frame off car deserves a new motor? That or re-ring and re-bearing with a valve job on the stock motor while out of the car.

 

Thanks gents.

Lars, yes it was cold and not running for 5 months, so I will do as you say and hope for the best. Sorry for my ignorance but what is a leak-down test?

I want to keep the numbers matching so the worst solution would be to do a completed rebuild of the engine.

 

Cardo0 -
Keep in mind that Denis is in Canada, where things are not as cheap or easy as doing things here south of the border...

Denis -
A leak-down test is a method of evaluating engine "health" by blowing a known pressure of air into each cylinder and measuring the amount of leakage present in each cylinder. The leakage can be isolated to valves or rings, and provides a quantifiable measurement independent of the engine's compression ratio and cam duration (which will affect a normal compression test).

You can see the process here (there are many other You-Tube videos out there - check out a few of them and you will get the idea):
The video indicates that a leakdown less than 20% is in the "acceptable" range, but I would say that the "good" number is 15% or less - if you are below 15% leakdown on all cylinders, you have a good, serviceable engine. Obviously, if you're over 20% on any cylinder, you need to bite the bullet and do some work...

The video shows the guy doing the leakdown at TDC. I have found this is not always the best idea: Putting the piston at TDC with 100 psi of air injected into the cylinder will usually result in the piston being forcefully pushed down to the bottom of its stroke, which will open the exhaust valve (a 4-inch bore Chevy 350 has a piston surface area of 12.56 square inches - when you put 100 psi across 12.56 square inches, you are applying a total force of 1,256 pounds to the top of the piston, and it will be pushed down...). To avoid this situation, I like to pull the valve covers, remove the rockers arms, remove all spark plugs, and then do the leakdown, just allowing the pressure to push the pistons down to the bottom of their stroke.

Summit Racing sells some reasonably priced and good leakdown testers with instructions. Summit ships to Canada:
https://www.summitracing.com/parts/otc-5609
https://www.summitracing.com/parts/wmr-w89729

The numbers provided by a leakdown test (after having run the engine) will provide you with the real data you need to determine the health of the engine, and whether or not to spend time & money on a rebuild.


Lars

 

Well if the OP is unable to do diagnostic leakdown test or not ready to rebuild the motor he has I will assume that even in Canada there are rebuilt GEN I sbc motors at reasonable prices. Just about any auto parts store should have a L48 replacement on the shelf.. I see ATK does business in Canada. Ya know with all the vendors for rebuilt GEN I motors I'm kind'a favoring just replacing an 40 year old motor with new/rebuilt and even more so for those on a learning curve rebuilding motors. And a good rebuild replacement would hardy slow his (OP) progress getting the car back together. Often these days I see more of a benefit of replacing the sbc motor with new or rebuilt rather than dealing with machine shops and parts vendors for correct parts.

I will agree a leakdown test would be a great diagnostic for the health of the motor. Not trying to discourage self reliance but a quality rebuild or new crate motor can even be less expensive for many owners like when you consider the car has just had a frame off rebuild and the original motor is suspect. Heck any 40 year old motor is kind'a suspect to me. Just my 2 cents.

 

and they ain't < $2000 any more; recently, all GM/chev crates went up
-add-
GM has quite recently moved crate engine Machining & Assembly to Springfield MO USA

 

Great points and great suggestions. I will finish the frame off, should be done in couple of weeks. I will do the leakdown test and keep you guys posted with my progress.

Thanks again,

 

It's a NEW Day; things changed including NAFTA which our President TRUMP negotiated into current USMCA
New info for 2020; popular crates were discontinued but now available again; instead of Mexico, Now USA. Of course they cost more $

 

I completely agree, if "the numbers" are not a concern. If you want a stock-type replacement engine, you can't beat the cost of a new GM crate engine with a full warranty to get a car up and running quickly, reliably, and with minimal cost. With parts and machine work (even discounting all your time) you can't rebuild your own engine for less than the cost of a GM crate.

If Denis's engine fails leakdown, he'd be best off stashing the original engine under his workbench and getting a GM crate. If all the numbers look good on the current engine, and it's not a "smoker" from bad valve seals/guides, I'd just run it and enjoy it.


Lars

 

The #s match may be worth something to you..honestly I bet most buyers could care less on a 77....if its new/rebuilt thats all that matters. Most wouldnt hesitate to not want a GM crate imo.
2200 I think for the base GM crate? Shame they cant be had for 1200 Id buy a couple.

 

That's why you simply take the numbers-matching engine and stash it under your workbench - the car becomes worth something if it has a new engine in it, yet is being offered with the original, running engine as a bonus...

Lars

 

~ $2200 today: That's the old universal equivalent to an L48 w/ 4 bolt main, cast iron crank, flat tappet cam & crappy heads. pn 12681429 fka 10067353

For another ~ $800-$900 today, you get an updated L31 (Above post) w/ Vortec heads, Roller cam-lifters & 4 bolt main, Forged steel crank, ready for mech fuel pump. pn 12691672 or 12691673 (only diff is x672 has HD Iconel exhaust seat inserts).

 

There's no end to sbc options. I didn't bother to price out a basic crate but the sbc has always been the best deal of any V8. I'd like to know what they ask for a ATK reman in Canada. I like ATK as they advertise better parts than stock and here in the states you can buy a reman ATK sbc for at least $500 less than a GM crate while AutoZone and others stock them. And to be realistic w/o performance mods that reman will do the same job reliably for less. Just want to give the OP something reasonably simple to consider rather than throw a bus load of options at him.

 

ATK reman = cheapest pistons w/ cheapest wide old fashioned rings, lotsa mix of whatever rods are on hand, and block overbored to limit so it can never be bored again, heads a mixup of used parts, and crank is almost certainly cast iron and block may or may not be 4 bolt main; some do Not have a finished fuel pump mount. BTW, atk has a sister company "Vege" operations headquartered in mexico.

GM's newer crates are All New parts w/ good pistons w/ good thin ringpak, forged steel crank now*, all are 4 bolt main now* and all now* have finished fuel pump mount. Now* GM crates machined & assembled in Springfield MO USA of globally sources parts.
*now = current production since JULY-AUGUST 2020.

-add-
and Every GM dealership in North America sells and services them and can service & expedite any claim against GM's very generous warranty. Thus any warranty issue that cannot be resolved at dealer can be adjudicated within Your local court.

 

I just ordered the Leakdown test tool (OTC5609) it's about $120 cnd, should have it early next week.

I guess I should of done this test before spending all that time cleaning and painting this engine. Oh well I guess this is part of the learning. I just check and the ATK 350 engine is over $4,000 cnd. Not cheap to say the least.

Keep you posted but you

Denis

 

Wouldnt be surprised if ATK makes them for Autozone they are pretty big.
Buying a GM is a plus due to the fact they are brand new noones messed with it before. I do like the 4 bolt block
Many including myself save the original engines may be a selling incentive. Will they ever get put back in who knows.

 

You make it sound like ATK is putting bad parts in their remans. In fact you more than stretched it. If it didn't have a fuel pump mount then it's not a correct replacement so thats BS. You wouldn't get substitute rods unless the originals were bad as it would only add to the cost of the reman - same for crank too. And the L48 came with a cast crank so what's the point? Who cares if it's overbored to the max - just a few more horsepower to me. Did you expect better rings and pistons than stock on a rebuild? Scroggin Dickey sells a new GM crate for $2900. Auto Zone sells their renamed ATK (as PROFormance VC42) for $2100 ($1700 + $410 core) and comes with a 4 year warranty. It's up to the buyer and just thought it would be something to help his project along.

I didn't post to start an argument of the quality of cheap sbc's. But you make it sound like ATK is selling junk - thats BS. ATK has a great high performance shop and is one of the largest engine reman companies in the world if not the largest.

 

Good morning,

Small question, do I need a 1977 engine or I can take any GM 350, 4 bolt main? what ever year? (btw what does 4 bolt mean?)

Denis

 

I really like this idea! So just so I'm clear on this; it doesn't really matter where the piston is in the cylinder so long as both the intake and exhaust valves are completely closed (which is done by removing the rocker arms which lets the springs close all the valves)? As to the determining where the air is leaking from (pistons rings or valves), you do that by just listening for where the air is escaping right?
Thanks in advance Lars.