The Stovebolt Site Forums The Shop Area Engine Shop 235 rebuild - what valve springs to use

A machine shop is rebuilding my 1954 truck 235 with the following non-1954 parts:

1. 1954 Corvette cam (a 261 cam)

2. higher compression "848" head - I forget the year

3. The 50-52 Powerglide 235 intake valves (1.94" dia. GM #3835519)

4. Small block exhaust valves, as spec'd below (I think)
Exhaust Valve
Head Diameter: 1.6
Stem Diameter: 11/32
Overall Length: 5.01
Tip Length: 0.25

The engine shop just called me and asked me what intake/exhaust springs I want them to use (car/truck 235 - what year).

Please give me advice - this is out of my little-league level of knowledge/abilities.

If I was doing the project I would find some specs on the 235 Corvette spring installed height and also the spring pressure, then I would check out the specs for valve springs for a 261. The other thing I would be concerned about would be the clearance between the bottom of the valve spring retainer and the top of the valve guide to make sure you have enough clearance.(learned the hard was on a LS-6 years ago) I'm sure Jerry will come along and have more specifics. Don

Thanks, Don,

I'll give them the specs for 261 valve springs. The shop has my 1954 Shop Manual - the 261 is in there.

Yes, I also home that Jerry and/or Dave (and others) offer information/suggestions/instructions - I hope it is simple enough for this shop not to get frustrated with me.

Sounds real similar to my 848 head rebuild plans, except mine is going back on a 235 block. (if the machine shop says they're servicable).
Been researching the same info and from what I've gathered from here, a few other webs sites and the vendor I plan on using for the parts the stock springs would work fine. Consensus was that stronger springs were only needed for the most radical cams/builds that see in excess of 5k rpm and may even cause premature wear on the cam lobes.

I never did come up w/the full specs on the Corvette 235 Blue Flame and would be highly interested in seeing them.
Dave

It is hard to find many spec's for a 261's, but I have compiled a list of spring pressures and installed heights from the GM Heritage Center on my BLOG

Always happy to waste my time...

Volfandt (Dave)
Mine is a 235 block : "A machine shop is rebuilding my 1954 truck 235 with the following non-1954 parts:" 235 head (and rocker arm assembly) and 261 cam.

Pre '68 Dave
What year/engine springs (intake/exhaust) should I ask them to use (they will get whatever I ask for).

Should I find out if it is a 56-58 or a 59-62 head?

Thank you,

I guess I will determine the year of the head and tell the rebuilder to get 261 intake and exhaust springs for that year?

Does the use of Powerglide intake valves and Small Block exhaust valves affect the choice of valve springs?

I do not see why valve choices would effect spring choice.
The installed height of the spring is what is important.
I don't think which spring you choose will make much differences.

Thanks, Dave,

The shop wants to know if I want
- 235 Corvette springs (1954, I suppose - the 261 cam started being used in mid-1954); or,
- 235 truck springs (what year); or,
- 261 truck springs (what year).

I have to tell them something. I could just date the head and go with 235 truck engine springs for that year (just to give them an answer)?

Why are there differences in spring pressures and heights for 56-58 vs 59-62?
- Valve rotators/caps?
- Different cam (did they go to the 261 cam)?
- Other?

Thanks,

I would match the spring specs. to the cam being used.

Pete

Thanks, Pete

261 - but, what year?

I might go for 261 springs for the year of the head.

It might not really matter, but I have to pick something?

I just spoke to the Shop. Before I could give them an answer about springs, they brought up the same points that Pre '68 Dave posted.

I am going to the Shop today to give them primer and paint, the harmonic balancer (they want to check balance?), and Dave's valve spring table with valve spring pressures and heights. I'll check the head casting date.

Thanks to all for the advice, suggestions, and questions.

What did you decide, and why?
Build done?
Happy with the results?

I think the builder used the springs that were used on 235 Corvettes that had a 261 cam.

We have not yet broken-in the engine.

Try Federal Mogul/Sealed Power VS424 for 235 hydraulic cam engines and 261 engines.

Try VS534 for 235 Stock solid cam engines.

I do remember finding comparable valve springs in my Comp Cams catalog. Buick 455 maybe?

Here's a link to 235/261 engine specs.

http://canadianmilitarypattern.com/1960%20235-261%20Engine%20Manual.htm

Valve spring selection on a non-high-performance engine is pretty simple. Pick a spring that doesn't "stack solid" at full valve opening and has enough seat pressure to prevent compression/combustion pressure leakage when the valve is seated. It's difficult to imagine a stovebolt engine operating at an RPM range where valve float would be an issue, and compression pressures sufficient to cause a leak past a seated valve are almost impossible due to the huge combustion chamber volume, even on an 848 head. I think the Corvette springs that match the cam would be an excellent choice, or pick any spring that comes close to the same specifications. A good valve seating job and proper guide clearance is probably a lot more important to good performance than getting picky about valve spring specifications.
Jerry

Valve spring concerns: Coil bind height, Seat pressure, Lifter weight, Pushrod weight, Rocker arm ratio, Valve weight, RPM range and limit. As each is critical, and non forgiving, you do need to know them. When you changed the intake valve size, you made a difference to the demand on the spring. That spring is the only thing that keeps the valve in time with the cam and piston. For practical reasons the difference is small and the engine is mostly stock. You will get by with the valve springs that have been recommended. I would Have the shop measure the height at full lift and keep around 0.060 left in the spring to prevent coil binding at the high end. The higher the RPM range the more critical these things become. Many engines that can turn around 6,000 RPM have 2 springs, one inside the other. Why 2? To prevent spring harmonics from allowing the valve to lose contact with the cam, otherwise known as valve float. Most commonly followed by contact with the piston. Rapid disassembly can follow. So to completely get the answer you need to do a lot of work. Most cam companies have done the work for you so I would use them for advice. With these things in mind, the advice from Hotrod is as good as it gets. Not a critique, just an old guy letting you know there are lots of things that Engineers do besides drive trains.