675 v 920 home porting

-
V

vghoon

Well-Known Member
Joined
Oct 4, 2013
Messages
72
Reaction score
30
Location
nsw australia
I have a 318 ,904, 3.23 diff gears in a valiant coupe here in aus that's just a fun cruiser.
+030, ldb4 intake, voodoo 701 cam, edelbrock 500, currently has 675 heads decked .050 & cranking psi is 165, and is a fun package to drive, From memory the 675 heads on the car are at about the 63cc mark.
Do I start home porting the decked 675 heads or 920 heads as I still have to buy & put hardened seats in the 920 heads to start with before anything else?
The goal is to home port as the Thread has inspired me.

20191230_165118.jpg
 
I haven’t messed with(modified or flowed) either of those heads in close to 30 years.
But, from what I can remember.......the 920 head(that’s the 67 closed chamber head, right?) is the best flowing as cast 318 head.
 
vghoon said:
I have a 318 ,904, 3.23 diff gears in a valiant coupe here in aus that's just a fun cruiser.
+030, ldb4 intake, voodoo 701 cam, edelbrock 500, currently has 675 heads decked .050 & cranking psi is 165, and is a fun package to drive, From memory the 675 heads on the car are at about the 63cc mark.
Do I start home porting the decked 675 heads or 920 heads as I still have to buy & put hardened seats in the 920 heads to start with before anything else?
The goal is to home port as the Thread has inspired me.

View attachment 1715528100
Click to expand...
That's really your choice ,if you're looking to just swap heads on in a day...but if you don't mind tearing it apart the ones you have , porting them re lap the valves back on the seats they came off of...n then put them together and stick'em back on motor...that's a great plan. 920 head are around 66-67cc
675 are around 68... so the 675 is smaller after the milling you had done.
Closed chamber or not wont matter much if the piston is a mile away from it, no quench.
 
From my research they both flow similar to each other std, the closed chamber head should be between 57 to 63cc
the open chamber head is 64cc shaved already.
 
vghoon said:
From my research they both flow similar to each other std, the closed chamber head should be between 57 to 63cc
the open chamber head is 64cc shaved already.
Click to expand...
there are a lot of conflicting numbers out there but the pair I pulled off of a 66 Coronet of 920 heads that already had hardened seats so they've already had a surface and a valve job before ,and guides ,most certainly didn't get larger... so they could have been near the same.
Only heads that have ever been what was stated was 360 j heads @72cc ,318 '302' heads @64cc and 906 heads at 88 or whatever.. lol the 318 open heads are right around 68cc and the early closed chamber versions were only a couple cc smaller.
I've cc'd them to know... and anymore I really dont care what anyone thinks or wishes they were..I trust my own eyes.
 
vghoon said:
I have a 318 ,904, 3.23 diff gears in a valiant coupe here in aus that's just a fun cruiser.
+030, ldb4 intake, voodoo 701 cam, edelbrock 500, currently has 675 heads decked .050 & cranking psi is 165, and is a fun package to drive, From memory the 675 heads on the car are at about the 63cc mark.
Do I start home porting the decked 675 heads or 920 heads as I still have to buy & put hardened seats in the 920 heads to start with before anything else?
The goal is to home port as the Thread has inspired me.

View attachment 1715528100
Click to expand...

That's a beautiful VF Coupe.

Just use the 675's. Work out how far your pistons are down the bore and mill the heads a little to get the comp up a little more. If it were me I'd aim for 185 psi on premium 98

There's a VF sedan here in Sydney that the owner tells me he has a 318 with 11-1 comp on premium and runs 12.7's.

Keep us posted on how it turns out.
 
Hysteric said:
That's a beautiful VF Coupe.

Just use the 675's. Work out how far your pistons are down the bore and mill the heads a little to get the comp up a little more. If it were me I'd aim for 185 psi on premium 98

There's a VF sedan here in Sydney that the owner tells me he has a 318 with 11-1 comp on premium and runs 12.7's.

Keep us posted on how it turns out.
Click to expand...
I like your thinking on the cranking, you're more familiar with regions fuel n I didnt catch on.... 98 octane? Oh fk yeah, 185psi and with room to breathe..
 
What size valve are you thinking?
 
You must log in or register to reply here.
-

Back
Top