I have a question about rebuilding top end on my 1980 L48.
Let me start from the beginning.

I have had my 1980 for five years now and it was pretty trouble free for now. Ever since I had the car it always used to burn oil; however I used to top it up regularly and promised myself that one day I will sort it out.

Few weeks ago it started to misfire and I have decided to do something about it.

I have posted a question about compression check and quickly learned that it could be sticky valves or worn rings or.... and the best way to find out is to take the heads of and see what lies beneath.

Well I did not fancy this so I have opted out for second best: basic checks like timing....
This was the time when I found out more about my engine.

The specs. is this:
1980 L48 with Holly 4160 carb, Offenhouser 360*intake, Comp.Cams roller rockers with 1.52 stamped in to them, dual valve springs and quiet possibly non stock cam.
I have tried to adjust the timing to bring the all in by 3000RPM; however with the current high RPM setup it seemed pointless.

Determined not to give up I remembered that I was given the original aluminium intake with the car when I bought it and decided to replace the Offenhouser 360* intake with my original intake which would lower my RPM to bring my timing to more usable 3000 RPM. Yes?
Wrong: Holly 4160 does not fit to 1980 aluminium intake and I need either a new intake or Rochester carb.

To put the final nail in to the coffin my car failed annual emission check in such a spectacular way that no amount of tweaking with the idle and mixture adjustments screws could bring my Hydrocarbons level down from 2400 to required 1200 to pass the emissions.

So here I am exactly where I did not want to be filled with optimism and high hopes.
I am stripping the engine!!! [Well just the heads hopefully]

I have followed the Haynes and Chilton’s Manual to the letter and now I need to ask few questions, hope you do not mined.

Before I started I have drained the coolant from the radiator and when I took some of the bolts off from the lower part of the heads under the spark plugs I had quiet a lot of coolant poring from the head bolts and some of the coolant leaked in to the cylinder bore which I have quickly moped out. {Was this meant to happen?}
Just noticed that the block water jackets are still filled up wit coolant especially at the rear side of the engine {the engine sites on an angle higher at the radiator side and lowered towards the gearbox} Should I lift the rear end of the car to drain the rest of the coolant?

I have inspected the Intake and Exhaust valves throe the Runners and what I can see so far there is a lot of carbon deposit under the valves and on the stems of the valves.
I have read a lot of articles about the 462624 heads and everyone seem to be in same opinion that they are only good for paper weights.?
Should I overhaul them or should I just replace them with some aftermarket heads and be done with it once and for all?

How do I check for cylinder bore wear?

ANY input gladly received.
Thank you
C3Paul
P.S. Pictures to come tommorow

 

Lets take this in small bits...

When removing the head bolts, having coolant run out is normal. The head bolts go into the water jacket, therefore when a bolt is removed, the coolant comes out. To remove the coolant from the block, there are drain plugs just above the oil pan on the side of the block, but they're not easy to get to - it is easier to siphon the coolant out, but that doesn't get the sediment which has settled in to the bottom of the water jacket. To get spilled coolant out of the cylinder bore, I like to use a vacuum cleaner nozzle to suck it out - does a better job.

The Quadrajet is a better carb, and will have better economy and lower emission than a square bore Holley. Performance wise, I love my Q-Jet - I've got a 12.10 best in the 1/4 with a 406 small block, however, the stock manifold is not very good. I'm using an Edelbrock Performer RPM (pn 7104).

Cylinder bore wear can be measured with a bore gauge, or if not available, look for cross hatching still visible (good condition), or the appearance of a ridge at the top of the piston ring travel (not good).

Heads? The new technology aluminum heads are awesome and well worth the cost, IMO.

 

Checking the cross hatching and the ridge at the top of the cylinder is a good starting point also turn the engine so the piston is all the way down in the cylinder and make a careful inspection for vertical scratches. This could indicate a bad or cracked ring and we know what that means. Your coolant concerns are nothing to worry about! Just clean it out, oil up the walls and change the oil before starting. NOW I will give you some install tips, DO NOT have any oil on the head and deck surfaces when installing new heads. Also use sealer on all the head bolt threads so water doesn't creep past and get in your oil! New heads are the hottest ticket if you can afford them. Vortex is the next pick and then a pre 71 head with a smaller chamber is the cheapest way to go with a bump in compression Carb is easy to buy an addapter plate or go with a Quadrajet. Good Luck

 

I am taking my heads to a machine shop on Munday, but before I do that here are some pictures of them as well as engine block.
What do you thing?

 

Those are dished pistons but IDK how many cc's. Give some thought to World Products heads. They use all conventional (and therefore cheaper) manifolds, the vortec heads need dedicated manifolds. The W.P. heads allow for a larger cam with no machining too, and they flow almost as good.

 

I am taking my heads to the shop to check for any cracks and find out what condition thay are in, however if thay are OK I am thinking of cleaning the heads and the valves and put it all back together.

I undestand that it is dificult to judge the condition of the engine from pictures, but can someone have a look at the pictures and tell me a bit more about the block weather I need to do the rings as well, please?

if I need to take any more close up pictures of the cylinders I will be more than happy to do so.
Thank you

 

I have spoken to the Machine shop and the result is excellent.
No cracks, warpage or any other abnormal damage. All it needs doing is to regrind the valve seats and the valves and put it all back together.

I was asked to get hold of Valve seals. I have one of them in my hand it looks like a little black plastic/rubber o-ring. What is it and where can I get it?

My valve springs currently installed in the heads are dual springs. The springs do not have any markings on them and I do not know what pressure they are, so I can not check weather they are worn out or not. {I have Comp/Cams 1.52 roller rockers fitted in. Does this help with finding out more details about the springs?} I was told all they can do is to measure the free length of the springs and compare them against each other to see I they are any good. I am in two minds weather to put them back in or replace them with new ones. What do you thing?

And lastly:
When I bought my car it had 360* intake manifold fitted in and I do not want it. I have managed to get hold of replacement Dual Intake Manifold #14014432 with casted # 4/7/80/2 in it. Is this the casting date code? April 7th 1980? What is #2 and what does GM3F stand for casted under the #14014432?

Well, yet again. Thank you for all your help!!!!!

 

I don't doubt valves need to be reseated... I also expect a 28 year old sbc that's burning oil & fouling plugs to have a good bit of wear at valve stem-to-guide ... especially since shop is asking for seals ... make certain shop has measured that clearance-wear ... if excessive (and that'd be typical here) have shop install thinwall guide liners.

Chances are the rings also need replacing.

Put the heads back on with thin shim felpro p/n 1094 head gaskets to raise compression.

Have someone measure cam lobe lift on several lobes so you have a better idea what you're working with.

It's an L48 w/ dished pistons & L48 heads ... so it does not make much compression ... thus it cannot utilize more than a mild, small camshaft without street manners & drivability suffering greatly.

also ... suggest you find another machine shop ... one that can measure spring pressures ... that's not rocket science ... that's basic ... if they cannot do that basic procedure they may be less than brilliant elsewhere.

 

I know what you mean by saying about basic measuring and so on…
The problem is that the Small Block Chevy is not that common in the Europe so to find someone who is knowledgeable about these engines is rather hard.
To make it even more confusing all measurements are in inches and we are used to mm.
The shop guy is very helpful and really trying to help.
We have checked the valve guide clearance and it is within the required factory spec. so no need to change the valve guides.
Back to the valve stem seal
I see there is a choice of 11/32, 5/16, 3/8… Which ones do I need?

 

You need 11/32 seal. big blocks used 3/8 the 5/16 would be used on an aftermarket set of heads. The original O-ring valve seals are realy not very good
are you getting all your parts from the UK, or do you have the time to get stuff
from the major performance parts warehouses here in the US.

Heres an example of a good viton seal that pushes on to the valve guide requires no machining to the guide. part # S5325, www.competitionproducts.com.
stay away from the umbrella seals the oil and heat makes them hard and brittle
they end up cracking into pieces end up down in the pan, my fathers 72- 429 mercury came from the factory with umbrella seals this is what happened to it.

 

I am sure that you ALL must be sick and tired with my constant questions about this or that, but I really am learning and taking on board all your advice.

All parts will come from the USA and that’s why I am making sure that I order right parts as it is almost impossible and time consuming to exchange them.

I am very lucky to have 2004 Z16 as well as my 1980, so I can take as long as I need to put my 1980 right.

 

Everyone that looks at the forum learns something they did not know thats what its for. I don't claim to be an expert but I have worked on SB/BB since the early 70s I can help you get the right parts if you want to PM me, I will have to know what your shop is doing.