318 Head job - Valve Springs?

polosteve · Post by **polosteve** » Sat May 06, 17 10:08 am

Hi All,

Did 300 miles in my latest project over easter to find oil leaking on the outside of the block at the head gasket. Its a 68 318, hydraulic tappets. Two of the cylinders were slack on compression anyway so I have taken the heads off. New exhaust valves are on their way, via rock auto so I can get it to the machine shop.

I would like to replace all of the valve springs. The book I'm using (HP Books - How to rebuild small block Mopar engines) Says that valve springs for 68-86 318 should be 2" free height, and it gives their spec. The HP book nor the A100 shop manual mention anything about the springs for the exhaust or intake valves being different sizes or specifications.

However rock autos online catalog and Stateside Autos seem to think that there are two different sizes when you have hydraulic lifters?

(But that with mechanical lifters the exact same valve springs are used for both exhaust and intake valves.)

Anybody got any knowledge on rebuilding a stock 318?

Question - Are the valve springs for Exhaust and Intake valves different sizes or the same for my 68?

Pretty new to this mechanic stuff, go easy on me with terminology.

Cheers

David Murray · Post by **David Murray** » Sat May 06, 17 10:36 am

I believe that if you have original 68 heads that spring sizes will be the same. I've heard that some late truck heads had different sizes as the exhaust has a rotating retainer setup and a shorter spring to compensate. I guess that's why you are seeing different length springs as an option on Rock Auto.

Pete · Post by **Pete** » Sat May 06, 17 10:38 am

Slightly off topic, but did you check for correct lifter / cam operation before you pulled the heads off?

Blue · Post by **Blue** » Sat May 06, 17 1:14 pm

Yes I've had a pair of these later heads with the rotators, the earlier heads all had he same length springs. You know straight away which ones your dealing with, the exhaust spring is about 1/4" shorter than the intake spring on the rotator heads.

polosteve · Post by **polosteve** » Sat May 06, 17 7:15 pm

Thanks chaps - That has helped a lot, they are all pretty much the same size. There is one freak longer one... When I took it apart 15 of the valves were shimmed..one was not, the freak long one.

One thing I have noticed that the rocker shaft have notches, well both notches were at the rear of the engine. According to the manual this is not correct, the left bank notch should have been at the front. Cannot of helped

The reason for the poor compression, was down to two exhaust valves on the passenger side bank having worn into the valve seat a lot. The valve guides being very loose.

I don't think anything is "wrong" I assume it has done a lot of miles (I could be wrong). The aim of this is so that I can use the van for the summer, in the long run the bottom end may need attention. It is a completely stock 318 with a tiny 2bbl, slow camper van stuff.

Slightly off topic, but did you check for correct lifter / cam operation before you pulled the heads off?

No, I assume I might regret that?

DaveB · Post by **DaveB** » Thu May 11, 17 10:12 pm

put a new set of springs in,real steel,about Â£30,
check spring seat to retainer height,use shims to make them all the same.
spring installed height should be 1.650",unless seats are cut very deep.

spring installed height is important,1.650" should give a spring pressure of 100lbs,ok on a stocker.

if unsure,get your machine shop to do it

polosteve · Post by **polosteve** » Fri May 12, 17 9:59 pm

Thanks Dave,

Have read up on measuring installed spring height, I will give it a go.

I ordered all new springs as well.

Ta