Valve stem to guide fitment

[Fischy]

Some interesting info for those buying valves.

When I went to Valley Head Northridge CA, to get a quality valve job the machinist mentioned that the SI (DOHC Neon) valves were too loose in the guides. (the Neon valves are stock intake and +1 exhaust)

Stock specs:
Guide bore- 5.98mm
Intake valve stem- 5.94mm
Exhaust valve stem- 5.91mm (almost .003" clearance!)

Dodge designed loose clearances into the valve stem/guide fit.

I happened to have a used set of 420A stainless valves (Ferrea brand)

The 420A valves are 35mm intake (srt-4 stock size), 29.5 exhaust (+1mm) and stock srt-4 length.

What I want to point out is the 420A valve stem diameters:
Intake valve stem- 5.96mm
Exhaust valve stem- 5.95mm

The stem to guide fit is better.

Buying 420A (Mitsubishi) aftermarket stainless valves seems to be a smart choice for our heads. I now have 10K miles on the odometer with these valves and all is well.

Of course, your head machinists opinion might vary.

Steve

[nemiro]

VERY interesting info! Do you have the complete specs on the 420a valves?

[Sota]

subscribed.

[Fischy]

Quote: Originally Posted by nemiro

VERY interesting info! Do you have the complete specs on the 420a valves?

One of the forum porting pros mentioned (1 year ago?) that the 420A valves were slightly different in length, but the amount was small enough that the hydraulic lashers would accommodate.

BUT...The question of the actual SRT-4/420A lengths needs to be answered by someone with recent firsthand knowledge.

Like the DOHC Neon valves, the 420A valves come with a single groove. I used the DOHC Neon spring retainers and locks and found them online for $50.

[a853rox]

Just so you know that .003" on the exhaust side is on par with the factory specs....

Intake
0.048 - 0.066mm (0.0018 - 0.0025in.)
Max. Allowable 0.076 mm (0.003 in.)
Service Limit 0.25 mm (0.010 in.)

Exhaust
0.0736 - 0.094mm (0.0029 - 0.0037in.)
Max. Allowable 0.101 mm (0.004 in.)
Service Limit 0.25 mm (0.010 in.)

Generally we hone for +.002-.0025" on the intake and +.0025-.003" on the exhaust when using bronze guide replacements.

$.02