340 build

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aaron68s

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Ok here's what I have came up with for my 72 duster, will it work do I need to tweek it?
Stock forged 72 short block std. stock piston
Ported J's 1.88 1.60 valves 995 springs heads milled .020
MP thin headgaskets
Comp XE284H
1.5 comp adjustable rockers
Airgap intake
750 double pumper
4spd 4.10 rear gear
 
aaron68s said:
Ok here's what I have came up with for my 72 duster, will it work do I need to tweek it?
Stock forged 72 short block std. stock piston
Ported J's 1.88 1.60 valves 995 springs heads milled .020
MP thin headgaskets
Comp XE284H
1.5 comp adjustable rockers
Airgap intake
750 double pumper
4spd 4.10 rear gear
Click to expand...

Nothing wrong jump's out at me Aaron. Pretty stout cam with your compression, but the 4 gear and 4.10 should handle that. Bet it'll be fun to drive :D.
 
OldmanRick said:
Nothing wrong jump's out at me Aaron. Pretty stout cam with your compression, but the 4 gear and 4.10 should handle that. Bet it'll be fun to drive :D.
Click to expand...

Shouldnt my compression be around 9.5-8 with .020 milled off the heads and a thin gasket? Do you think I will have clearance issues with that?
 
That's still pretty low compression for a bigger cam. I'm up at 11:1 with slightly less duration in my 390, and it makes great low end torque as a result.
 
aaron68s said:
Shouldnt my compression be around 9.5-8 with .020 milled off the heads and a thin gasket? Do you think I will have clearance issues with that?
Click to expand...

I doubt you'll have clearance issues, but you should check the P/V clearance after all the final numbers are in and depending where the cam is degreed to. The guides will probably be machined for a dual spring and the appropriate seals so i dont see a clearence issue there. Just looking at generic numbers, i think the 9.5 comp is easily obtained.
 
If you can swing some lighter KB hyper pistons that would be the way to go. Lighter pistons allow engine to rev faster resulting in a quicker car. Lighter pistons also reduce stress on rods, crank, and bearings. And you can get that compression up to where you need it. You would have to get it all balanced. Stock 340 pistons are super super heavy because of their size so lighter pistons make a huge difference in a 340 build. I don't know what your budget is though.
 
does somebody know the engine build date that the compression was dropped form 71 to 72 models? my CAR was built 10/12/71
 
Pill the heads and measure it up, cc The heads and do the math.
IMO. A 11-1 ratio with aluminum head and a 10-1 with iron heads is a limit that is generalized and safe for pump gas with most any cam/engine combo.

It will be pimp gas friendly a d run great. Tweaking it at this point would be costly. AKA: better pistons, 2.02 valves and better ones than stock. Like Ferra's. the list can go on and on.
 
rumblefish360 said:
Pill the heads and measure it up, cc The heads and do the math.
Click to expand...

The compression drop was not due to a change in heads it was because the compressing height of the pistons was decreased which made them ride lower in the bore.
 
340sFastback said:
The compression drop was not due to a change in heads it was because the compressing height of the pistons was decreased which made them ride lower in the bore.
Click to expand...

Never said that or hinted it as far as I see it. He did say, milled heads with a .020 gasket. Considering he doesn't know for sure the piston height due to possible year change(s) from high to low ratio's.

I did tell him to measure everything up so he knows for sure and go from there. OR he can shot the target in the dark.
 
aaron68s said:
Ok here's what I have came up with for my 72 duster, will it work do I need to tweek it?
Stock forged 72 short block std. stock piston
Ported J's 1.88 1.60 valves 995 springs heads milled .020
MP thin headgaskets
Comp XE284H
1.5 comp adjustable rockers
Airgap intake
750 double pumper
4spd 4.10 rear gear
Click to expand...
Are you going to have it Balanced?? or maybe it is already??
 
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