318 LA rebuild after losing a valve seat

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Not to worry about it, Righty.

You are some where in the vicinity of 8.5:1 to 9:1. That's all we need to know. Get her together and get her running.
 
Just looked up Stock 1971 Scamp 318 compression ratio:

8.6: 1 Compression Ratio

With the closed chamber heads, and they were milled .010 ths

You are getting closer to 9:1 cr.

So far, so good !
 
righty
we need the distence at tdc how far down are they?
I think you do need to know how to compute R
 
I'm going to get some final numbers after I've got the degree wheel installed, but some rough measurements I got were ~3.380 @ BDC and .085 @ TDC. Bore was exactly 3.950. I did notice some differences of about .005 depending on where I was on the piston when measuring depth. Is that normal? They are just flat top pistons with no reliefs cut.
 
post 118
FUNNY but it's a learning experience
righty find out where the piston mfg wants you to measure them
everywhere else will be wrong
 
Wyrmrider said:
post 118
FUNNY but it's a learning experience
righty find out where the piston mfg wants you to measure them
everywhere else will be wrong
Click to expand...

Thanks, I'll reach out to Sealed Power.

I think I missed the joke in 118...
 
Per the FME catalog, H814CP has a compression height of 1.755". With a standard LA deck height of 9.600, these will be about .067" in the hole. So the OP's .085" number at/near TDC is believable and may be a bit low. The deck looks unmilled in the OP's pix. You are not going to find any higher compression height with any stock cast 318 replacement piston in current production. We've all been looking for several years now!

With the standard Felpro head gaskets in their kits, that is PN 8553PT, .050" compressed thickness.

Typical 302 chamber volume stock is 62-63 cc.

These numbers all together gives a static CR of 8.44.

Published CR numbers from all the mfrs in this era were all .5 to .75 points 'optimistic' so that is not a good reference point.

Dynamic CR with his cam installed as the mfr intends (108 ICL) works out to 7.0.... very close to stock 318 DCR. So low RPM torque will approximate a stock 318 and mid to high RPM will be significantly better with the cam change.

Decking and piston changes seem out of the question at this point. Milling heads and a thinner head gasket would increase SCR and DCR by:
  • 0.15-0.2 points with the Felpro 1008 at .039" thick
  • 0.35 points with the Mr Gasket 1121G
0.25 points will be noticeable in low to mid RPM torque and throttle response. So the thin head gasket seems desirable. But some here have reported sealing issues with that 1121G head gasket, and I suspect that is due to the deck and heads not being flat enough. The heads look like they have been milled but the deck has not been milled so may or may not be good and flat.

IMHO, I vote to proceed as is. The cam selection is fortunately good for this lower static CR setup, and I think the OP should move on and get it running and drive his car. Good learning going on here.

I am a big advocate for high static CR on the street but the design selections have been made and backing up sure seems like a waste of time and parts and effort. Going to a significantly higher CR now would require a piston change and a crank re-balance.
 
Thanks ^^^^^ 8.5 C.R. is fine for what Righty has going on here.

Getting a fresh build on the shortblock and heads is a huge improvement for a nice running engine too.
 
Found TDC using a dial indicator, and #1 is sitting .077 down @ TDC. I couldn't quite figure out how to find BDC accurately.

Also installed the checking springs and used the checking rod to determine my pushrod length using rumblefish's method (install checking rod and extend it until the lifter is depressed .050. I found that length to be 7.125. The stock rods I was running with the stock setup were 7.5. I put one in with clay on the piston just to see what would happen, and I don't think I got 1/4 turn before the valve bottomed out.

I'll be shopping for some 7.125 pushrods.
 
Righty Tighty said:
Found TDC using a dial indicator, and #1 is sitting .077 down @ TDC. I couldn't quite figure out how to find BDC accurately.

Also installed the checking springs and used the checking rod to determine my pushrod length using rumblefish's method (install checking rod and extend it until the lifter is depressed .050. I found that length to be 7.125. The stock rods I was running with the stock setup were 7.5. I put one in with clay on the piston just to see what would happen, and I don't think I got 1/4 turn before the valve bottomed out.

I'll be shopping for some 7.125 pushrods.
Click to expand...

That's pretty good on the piston height at TDC .077 ths. A lot of stock 318s are .140 ths and .160 ths below deck at TDC.
Good choice on pistons, not easy coming up with good one for a stock setting 318.
 
Righty Tighty said:
Found TDC using a dial indicator, and #1 is sitting .077 down @ TDC. I couldn't quite figure out how to find BDC accurately.
Click to expand...
Good work for confirming these 318 CH numbers. CR will now compute out about 0.15 lower but does not change the situation on the build. No need to find BDC unless you wanted to verify the stroke length.
 
Righty Tighty said:
Also installed the checking springs and used the checking rod to determine my pushrod length using rumblefish's method (install checking rod and extend it until the lifter is depressed .050. I found that length to be 7.125. The stock rods I was running with the stock setup were 7.5. I put one in with clay on the piston just to see what would happen, and I don't think I got 1/4 turn before the valve bottomed out.
Click to expand...
Just curious as to what rockers you have now.

And for sure the lifter(s) was(were) on the base circle? I.e., no lift on the lifters whatsoever for the pushrod being measured. I just want to make sure you were not doing something like checking the #1 lifters when at TDC and #1 at overlap... where the lifters are slightly lifted.
 
nm9stheham said:
Just curious as to what rockers you have now.

And for sure the lifter(s) was(were) on the base circle? I.e., no lift on the lifters whatsoever for the pushrod being measured. I just want to make sure you were not doing something like checking the #1 lifters when at TDC and #1 at overlap... where the lifters are slightly lifted.
Click to expand...

I have the stock stamped steel non-adjustable rockers on the shaft. I'll go back tomorrow and go through the procedure again, making sure I'm starting at base circle.

The installation card for the lifters said I should soak the lifters in oil, but I've seen videos that say to install them dry? I'm thinking I should be believing the manufacturer over some Joe making videos online.
 
Righty Tighty said:
I have the stock stamped steel non-adjustable rockers on the shaft. I'll go back tomorrow and go through the procedure again, making sure I'm starting at base circle.
Click to expand...
I answered you PM on the base circle question and valve overlap.

If you are using the same rockers as before, then a length change of 7.500" to 7.125" does not make sense.
  • They may change a bit with the individual heads, but I cannot think of anything in the 302 heads that is so different that the pushrods should change so much.
  • The cam might be a bit different in base circle, but really should not be anything like that.
  • The valve could be waaay too long but that would mean they are basically wrong.
  • Lifters very different? AMC's?
What am I not thinking of, guys?
 
OK if you soak them in oil then - without turning the motor over -install with moly break in lube- not wheel bearing grease etc
do the pressurize the oil with the drill and hex shaft
then turn the motor over at least TWICE with a breaker bar- NOT THE STARTER stopping every 45 degrees to let the springs bleed the lifters down
else you can bend pushrods and/or valves
other way is to coat with molly lube, do the pressure bit and fire it up and lett it rattle till the lifters adjust themselves
either way know where the dist is installed so the motor fires immediately
 
checking with the lifter bottomed out?
*
do you have any old lifters
take two apart and fill with solid with washers or whatever and retest intake and exhaust
or use a solid lifter (which may have a different seat height)
in fact you have to check and see if your new lifters have the same seat height as your old or stock lifters
all lifter heights changed around 1967 for example and the pushrod ball size changed too
DO NOT USE THE early lifter pushrod combination eventhough parts catalogs still show them
replace both
there are good reasons Ms Mopar upgraded
 
nm9stheham said:
I answered you PM on the base circle question and valve overlap.

If you are using the same rockers as before, then a length change of 7.500" to 7.125" does not make sense.
  • They may change a bit with the individual heads, but I cannot think of anything in the 302 heads that is so different that the pushrods should change so much.
  • The cam might be a bit different in base circle, but really should not be anything like that.
  • The valve could be waaay too long but that would mean they are basically wrong.
  • Lifters very different? AMC's?
What am I not thinking of, guys?
Click to expand...

OK GUYS, here is another stock component 1969 318 build with the 302 Heads, stock pistons, stock pushrods, stock stamped steel rockers, using the Mopar Performance 340 camshaft.

The stock 69 valve relief flat top pistons sit .040 ths. down in the hole.

.028 ths. head gaskets, 340 valve springs were installed after breaking in the cam.

All assembled and running, no interference issues with valves to piston tops what so ever. Runs out very nice and great performance.

Stock Mopar Valve Train:

318 3.jpg


318 4.jpg


318 5.jpg


318 6.jpg


318 8.jpg
 
nm9stheham said:
I answered you PM on the base circle question and valve overlap.

If you are using the same rockers as before, then a length change of 7.500" to 7.125" does not make sense.
  • They may change a bit with the individual heads, but I cannot think of anything in the 302 heads that is so different that the pushrods should change so much.
  • The cam might be a bit different in base circle, but really should not be anything like that.
  • The valve could be waaay too long but that would mean they are basically wrong.
  • Lifters very different? AMC's?
What am I not thinking of, guys?
Click to expand...

Thinking back, I don't think I had the cam at base circle. I'm going to revisit that tomorrow and see what I come up with.

I can't seem to find info online about stock lifter height in the 318 LA engines, only diameter. That said, I don't have my previous lifters to compare the current ones, I only know the new ones were included in the cam kit.

Also, one question I have is if the new pushrod length wouldn't be that different from stock, why would they contact the pistons so soon with so much spring travel left? I'm really hoping I'm not gonna have to cut reliefs.

Wyrmrider said:
in fact you have to check and see if your new lifters have the same seat height as your old or stock lifters
all lifter heights changed around 1967 for example and the pushrod ball size changed too
Click to expand...

How do I check for, or find, the seat height? I've tried the Lunati website to no avail. Do I just measure down to the pushrod seat?
 
NICE BUILD
post your compression when you get a chance

Righty-- you measure from the lifter face up and back down to the pushrod seat
you are not going to have to have valve interferece unless you got the cam installed with the centerline(s) way off
do you have a multiple keyway timing set for later tuning?
 
Wyrmrider said:
unless you got the cam installed with the centerline(s) way off
do you have a multiple keyway timing set for later tuning?
Click to expand...

I installed the cam with the timing dot at 12 o’clock, is there some other way I could’ve screwed it up? And yes, my timing set does have multiple keyways.
 
Righty Tighty said:
I installed the cam with the timing dot at 12 o’clock, is there some other way I could’ve screwed it up? And yes, my timing set does have multiple keyways.
Click to expand...

I would say you have your cam in right at the stock position, dots in line with each other at TCD on #1. Whether it be 6 & 12 (fires on #6) or 12 & 12 (fires on #1). If it is 6 cam & 12 crank, you just roll the crank around so it fires on #1 at TDC, then you drop in your distributor there pointing to distributor plug wire #1. Dots still in line with a straight edge.

Some folks advance or retard their cam installs by 4° so then the dots will not be in line at TDC. Best to keep your build at the stock setting.
 
Hmmmmmm..... I may see an issue on the cam timing. Look back at the 1st pix in post 118. It shows the cam dot at 6 o'clock. Both #1 and #6 cylinders should be at TDC in this situation; #6 cylinder is visible but its piston is nowhere close to being at TDC. Also, the crank key is not visible where it should be in this pix (around 1:30 o'clock when viewed from the front).

Back up OP, and set #1/#6 at TDC. Once that is done, then look to see if the dot on the cam is at either 6 or 12 o'clock. I suspect it will not be, based on this pix. However, you may have corrected this in-between times, but please re-check since the pushrod length check seems baffling.
 
Also the lengths of your push rods as compared with the above stock '69, 318, 302, 340 cam build. These stock pistons with the valve reliefs sit .040 in the hole.

Your Scamp 318 build with the flat top pistons sitting .077 in the hole.

Same same as far as valve to piston clearance is concerned, considering the valve relief pistons in comparison to your new flat tops.

Thinking you can use your stock length pushrods here.

Put a wad of plumber's putty on top of one of the pistons, bolt on on one head with head gasket just snug. Drop in a pair of solid lifters with the stock valve train, roll it over and see what you got for piston to valve clearance.

Valves not touching the pistons, that is a good thing . . .
 
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