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Discussion Starter #1 (Edited)
How do I tell if my pistons are stock or aftermarket? Due to the casting number being at the distributor hole I think it's an early 67 400 which I believe had the 17 degree valve angle. I'm putting new edelbrock heads on which are 14 degrees. The way I understand it is that if I have aftermarket pistons the new 14 degree valves should clear the pistons. Am I on the right track? The heads I took off have 2.11 and 1.77 valves. Thanks. 20180430_111058_1525125102270.jpg
 

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Best reasonably priced pistons are the Speed Pro L2262F forged pistons, in the bore size you need.

Most cheap 400 rebuilds in recent years have used the cheap "8-eyebrow" cast pistons. They have valve reliefs for early & late heads.

https://www.summitracing.com/parts/slp-411np30/overview/make/pontiac

The SP pistons will have the part # stamped/etched on the tops.

https://www.summitracing.com/parts/slp-l2262f30

So, if you have either of these type pistons, they are easy to ID.

The pistons in the pic you posted are definitely for the older type heads. The reliefs are closer together than on pistons for the later type heads.

This pic of an 8-eyebrow piston, shows the difference in the valve reliefs for early & late heads.
 

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Discussion Starter #3
Thanks BigD. I attached a Pic of the pistons I currently have and was hoping to identify them. I'm hoping they will work with my build. I'm hoping to not have to by new ones.
 

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If it is a 400CI with "670" heads, it is the 14 degree valves, screw-in rocker studs, and big valves. The early 400CI in '67 that used the "143" head still used the 20 degree valves. These would have been found on the full size cars and had the smaller valves. These heads were then replaced sometime in mid year-ish with the "061" head that had the 14 degree valves & the larger valves. Both big car heads used press-in studs.

However, the pistons appear to be the Sealed Power 389 cast pistons in matching them up. Take a look here: https://www.summitracing.com/parts/slp-288p30/applications

Pontiac 400CI pistons have different valve notches in the piston tops to accommodate the larger valves which were moved inward towards the centerline of the cylinder bores along with the 14 degree angle of the valve. Here is a Sealed Power 400CI piston top: https://www.jegs.com/i/Sealed-Power/844/L2262F/10002/-1?CAWELAID=230006180035904595&CAGPSPN=pla&CAAGID=44693592161&CATCI=pla-224372728631&CATARGETID=230006180039218637&cadevice=c&gclid=EAIaIQobChMIws269Y3j2gIVSx6GCh0jJQLUEAQYAyABEgJXdvD_BwE

Realize you are going with the aluminum heads, just get the correct 400CI pistons for your build and you will be OK.

The following is just out of curiosity - you are 100% sure it is a 400CI? Now if you have the "061" heads with big valves, they are very good heads to work with.

My opinion - I have not seen what an early 400CI piston top looks like using the "143" 20 degree heads, but assume the piston may have resembled the 389 valve notching. However, it is very possible that 389CI .060" (which would be the standard bore size of a 400CI), or even .090" (400CI .030" over) pistons were used to match the earlier 400 "143" heads OR you have 389CI heads on your 400 block and the pistons were used so they could be used. What throws this out the window is that you said you have the large valve heads so............what heads did your 400CI have? :thumbsup:
 

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Discussion Starter #5
The block casting is 86133 which I've found to only be associated with a 67 400 and it has 3 freeze plugs per side which I've read are only on 67 and up. As far as the current heads I believe or was told they are #16 . Either way if I'm understanding you correctly, if it has big valves then it could only mean that they are 14 degrees so my edelbrock heads should fit without any modifications??
 

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The block casting is 86133 which I've found to only be associated with a 67 400 and it has 3 freeze plugs per side which I've read are only on 67 and up. As far as the current heads I believe or was told they are [URL=http://www.gtoforum.com/usertag.php?do=list&action=hash&hash=16]#16 [/URL] . Either way if I'm understanding you correctly, if it has big valves then it could only mean that they are 14 degrees so my edelbrock heads should fit without any modifications??

I take it you are new to Pontiac's? Yes, 9786133 is the block casting number for 1967 400's. Look for the 2-letter block code which will ID what the block came out of, not that it is of big importance other then simply knowing.

The #16 heads are most likely 1968 heads, but, they can be confirmed by the casting date found just below the rocker arm cover. They should also have screw-in rocker arm studs. If not, they are not 1968.

nasty64: "if it has big valves then it could only mean that they are 14 degrees so my edelbrock heads should fit without any modifications??"

PJ: "Realize you are going with the aluminum heads, just get the correct 400CI pistons for your build and you will be OK."

NOTHING fits without checking clearances, so never assume, BUT the Edelbrock's should work fine. Never used them, but I believe you will also need the matching head bolts to go with those heads.

I highly suggest you take advantage of the "Search" feature of this site in the upper right and surf through the many engine questions & builds to get a better handle on what you are attempting to build. Pontiac's are not built like Chevy engines so they have a little different approach. Build for torque, not horsepower. Match parts. Pick an RPM you want your engine to be its best for you, and then select all your parts around that.
 
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