318 LA rebuild after losing a valve seat

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Righty Tighty

Righty Tighty

Blame it on the dog
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Hey all, I'm starting this thread as a follow up to my "Pieces of steel in cylinder???" thread. To summarize, I was having overheating problems in my 71 Scamp with a 318 LA, stock build. I repaired the coolant leaks, and upon trying to fire it up, wouldn't start. Plugs were smashed, pulled the heads, and found chunks of hardened steel in all 8 cylinders. Turns out I dropped a valve seat.

The thread got pretty long and there was some really terrific discussion/advice given. Well, now it's time to start puttin' her back together. I'd like to document this for anyone interested and who perhaps may be in the same situation one day. Also, I'd like anyone with wisdom/suggestions/advice to please feel free to chime in. This is the first engine I've rebuilt, and I want to do it RIGHT. I'm on a bit of a budget, so I can't exactly go with the most expensive parts, but I also understand there probably aren't areas where I should skimp.

Here's where I currently stand: block is honed and painted, new crankshaft/bearings, rods have been checked (one was out of round), new H814CP pistons, new cam/bearings, high flow water pump, high flow oil pump, 302 heads w/ 901 springs, double roller timing set, Edelbrock 2176 intake, Edelbrock 1406 carb.

In the next week or so, I'll be installing the pistons and plastigauging the crank journals. The photos are a dry fit of what i have so far. I've since painted the heads to match the block.

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Righty Tighty said:
Hey all, I'm starting this thread as a follow up to my "Pieces of steel in cylinder???" thread. To summarize, I was having overheating problems in my 71 Scamp with a 318 LA, stock build. I repaired the coolant leaks, and upon trying to fire it up, wouldn't start. Plugs were smashed, pulled the heads, and found chunks of hardened steel in all 8 cylinders. Turns out I dropped a valve seat.

The thread got pretty long and there was some really terrific discussion/advice given. Well, now it's time to start puttin' her back together. I'd like to document this for anyone interested and who perhaps may be in the same situation one day. Also, I'd like anyone with wisdom/suggestions/advice to please feel free to chime in. This is the first engine I've rebuilt, and I want to do it RIGHT. I'm on a bit of a budget, so I can't exactly go with the most expensive parts, but I also understand there probably aren't areas where I should skimp.

Here's where I currently stand: block is honed and painted, new crankshaft/bearings, rods have been checked (one was out of round), new H814CP pistons, new cam/bearings, high flow water pump, high flow oil pump, 302 heads w/ 901 springs, double roller timing set, Edelbrock 2176 intake, Edelbrock 1406 carb.

In the next week or so, I'll be installing the pistons and plastigauging the crank journals. The photos are a dry fit of what i have so far. I've since painted the heads to match the block.

View attachment 1715405367 View attachment 1715405368
Click to expand...
Looking good. I hope all works out well for you.
 
Righty Tighty said:
Hey all, I'm starting this thread as a follow up to my "Pieces of steel in cylinder???" thread. To summarize, I was having overheating problems in my 71 Scamp with a 318 LA, stock build. I repaired the coolant leaks, and upon trying to fire it up, wouldn't start. Plugs were smashed, pulled the heads, and found chunks of hardened steel in all 8 cylinders. Turns out I dropped a valve seat.

The thread got pretty long and there was some really terrific discussion/advice given. Well, now it's time to start puttin' her back together. I'd like to document this for anyone interested and who perhaps may be in the same situation one day. Also, I'd like anyone with wisdom/suggestions/advice to please feel free to chime in. This is the first engine I've rebuilt, and I want to do it RIGHT. I'm on a bit of a budget, so I can't exactly go with the most expensive parts, but I also understand there probably aren't areas where I should skimp.

Here's where I currently stand: block is honed and painted, new crankshaft/bearings, rods have been checked (one was out of round), new H814CP pistons, new cam/bearings, high flow water pump, high flow oil pump, 302 heads w/ 901 springs, double roller timing set, Edelbrock 2176 intake, Edelbrock 1406 carb.

In the next week or so, I'll be installing the pistons and plastigauging the crank journals. The photos are a dry fit of what i have so far. I've since painted the heads to match the block.

View attachment 1715405367 View attachment 1715405368
Click to expand...
sounds like a good start. only other tip I have is to get an engine brush kit for like 30 bucks, clean and reclean every passage way, even if it has been dipped and flushed. and check and re-check cam bearings to make sure the holes are lined up enough.
 
dukeboy_318 said:
sounds like a good start. only other tip I have is to get an engine brush kit for like 30 bucks, clean and reclean every passage way, even if it has been dipped and flushed. and check and re-check cam bearings to make sure the holes are lined up enough.
Click to expand...

Thanks for the tip, I’ll do that.
 
As a first timer I would read up on rear main seal install/problems and break in procedures. That being said cam/lifter selection? Be careful so many garbage products in this area especially hydraulic lifter failures. Look into Rhodes lifters
USA made, I have not read of any problems (some don't like the noise)
 
66jim said:
As a first timer I would read up on rear main seal install/problems and break in procedures. That being said cam/lifter selection? Be careful so many garbage products in this area especially hydraulic lifter failures. Look into Rhodes lifters
USA made, I have not read of any problems (some don't like the noise)
Click to expand...

I went with the Lunati .454/475 lift, 256/272 duration cam and lifter kit.
 
good choice
dbl check all your spring heights, locators, stem seals for clearance to keepers- etc
read the threads about drilling the front plugs- I do to vent trapped air/ foam
I also do the main thrust mods and drill the thrust for pressure oiling especially if with a stick
 
I missed that
good choice - best for off the shelf cam
well maybe 248 MP
tell 4geardeamon in decent cam thread
 
Well, finally had some time to get some work done on the block. Chased the threads and cleaned it one last time before installing the mains and crank. Then moved on to the pistons. Would ya know it, I screwed up and bought the wrong rings. The Sealed Power H814CP pistons call for a 5/32” wiper, not a 3/16”.

As a first time builder, I really want to thank this forum and especially krazykuda for his build tutorial. Also Pete’s Garage on YouTube has been incredibly helpful. I’ll post updates as they happen.
7631D50E-A95A-453D-99A2-47AB2B78AF84.jpeg
 
what's your piston down the hole depth with those pistons
I'm thinking thin Mr Gasket
what do you figure you CR will turn out to be
I use the KB pistons but I'm prejudiced
 
Not sure yet, is there a way to determine that without the pistons installed? My biggest concern is since I didn’t buy pistons with reliefs and a cam with more lift, that I may have an issue with the exhaust valve contacting the piston. What are your thoughts?
 
That’s great news. And I just learned they’re called eyebrows, thanks for that!
 
On the KB SBM pistons, the eyebrows are about 5cc a pair. Which on a 318, drops your 8/1 compression engine to 7.64.
If you can get away with just one eyebrow at say 2cc, then your 8/1 drops only to 7.85 ; That comes to .2 of a point compression gain from the usual; the magic of math!
On a 318, Every cc counts; and each .010 of head gasket is ~2.15cc, and every 1* of later closing intake valve hurts her to the tune of more than 1psi of cranking cylinder pressure. And at a starting point of ~130 or so psi, it's easy to get into the death-spiral of falling pressure. Which makes the lower rpm lazy. Which costs you; engine efficiency, a hi-stall TC, and probably a performance rear gear. So it behooves you, in the interest of driving satisfaction, to keep the total chamber volume as small as possible. This goes double for fuel economy because low pressure is a factor of poor fuel efficiency.
 
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Righty Tighty said:
Not sure yet, is there a way to determine that without the pistons installed? My biggest concern is since I didn’t buy pistons with reliefs and a cam with more lift, that I may have an issue with the exhaust valve contacting the piston. What are your thoughts?
Click to expand...

The lift is not the issue. It's the duration. It's the "when" and "how long" the valve is open. Not "how much".
 
Thanks RRR. I’m getting a better understanding of the workings, just have to play it in slow motion in my head over and over. I need more exposure so that the numbers make more sense.
 
on the flat top SP pistons
Compression Height (in): 1.755 in.
KB's are 1.810
.055 different and KB's have valve reliefs
or a dome and valve reliefs
so if you use the SP pistons use the .028 Mr gasket
what heads did you say you had?
 
I’ve got the 302 casting 318 heads. I haven’t had them run on this block yet, I bought them as replacements for the stock 318s I ruined as a result of wrecking the motor.
 
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