gg4uk

What kind of piston to valve clearance does a stock 350 with stock Vortec heads have? I made the mistake of installing my heads with the Fel-Pro 1094 (0.015) before I checked my piston to valve clearance. Several on FB have told me that I don't have any issue. However, I am not sure. Yes, I can pull it apart.

Stock Vortec 906 heads. I am wanting to follow the build that Cutters on Youtube has suggested. This package will provide will yield a 0.530 lift with NO machining.
Sum-174002 Pro LS6 Springs
Comp Cams 787 Retainers
Competition Products VTO4134 Lock Height: + 0.030"
Fel-Pro SS 72861 Seals
Howards Cams CL 110245 (Advertised Duration 278/284, Lift .500/.510)

This package provides 0.530 Intake lift.

Does anyone know if my piston to valve clearance could be a problem others have told me that I don't have an issue? I don't have the lite valve springs where I can measure with a dial indicator.

ironwill

Any time non-stock valve train components are installed, the valve-to-piston clearance must be verified. Valve spring coil bind as well as spring retainer-to-guide clearance must also be checked.

Obtaining a dial indicator/base and some light valve springs will prove to be far cheaper than finding out too late that proper clearances were not present.

skinny z

There are too many variables to predict with any accuracy. Any misinformation means contact.
Examples of these variables lie in the "stock 350" mentioned. How stock? Pistons are down how far? My stock 350 (NIB from 1979) was quickly modified with different pistons. Still though they were the typical factory .030" down. That helps in the P to V clearance.
But if the block ahs been decked anytime in it's history, then those values change. Same with the piston choice.
FTR, I've run up to .575" lift, with a piston down .014" and an .026" gasket. Cam was also installed with a 102° intake centre line. Even so, with the cam advanced that, the intake clearance was still better than the .080" recommended. I determined this with checking springs and a degree wheel.

Your best bet would be to pop off a couple of springs, replace them with checking springs and determine the P to V that way. If you have an accurately degreed dampener, there's no need for a degree wheel. This is certainly easier than pulling a head and using clay. Unless of course it's still on an engine stand with no intake.

By the way, how do you get a net .530" lift from a .500" - .510" cam? You didn't specify if you were using a 1.6 ratio rocker, which at .500" would yield .530".

sofakingdom

iTrader: (1)

Max valve lift occurs when the pistons are at about halfway down in the bore. Middle of int stroke, middle of exh stroke.

Therefore P-V clearance is not directly associated with "max lift".

Where interference DOES occur, is when the piston is at TDC, at the point where the exh valve is closing, and the int valve is opening. Lift at that point is usually pretty small. The exception is with LARGE duration cams, which of course hold the exh open longer and open the int sooner; THAT'S what causes interference. Also, weird cam timing installation; if the cam is advanced, int clearance decreases, and if retarded, exh clearance is lost.

It's EXTREMELY unlikely that your combo will cause trouble, as moderate as it is; both lift and duration. Never hurts to check though.

You can get suitable "lite" springs at any hardware store. Not rocket science.

skinny z

To the OP.
I can't say I ever discount what Mr. Kingdom has to say. Experience says he's "been there and done that". So take that as a reference.
FTR: The measurements you're after, should you decide to measure, are that at 10° BTDC and 10° ATDC. Exhaust clearance at .100" and intake clearance at .080" respectively. Those are minimums from a variety of sources.
Something of note: Having the proper clearances doesn't excuse you from valve to piston contact. I can probably give a date stamp to the time where an enthusiastic burnout, for the benefit of my neighbours kid, led to two bent exhaust valves. Stock (Vortec) valve springs were the culprit (besides my right foot) and it was a lesson learned.

Beeman

I wonder how well .015 steel shim head gaskets will work over time with Vortec heads?

sofakingdom

iTrader: (1)

Probably a 100% failure rate, same as with any other heads

AlkyIROC

All the responses are correct. There\s no way to guess if there is enough clearance. So many factors will determine how much clearance you have, not just lift numbers.

On the intake stroke, the intake valve is chasing the piston as the piston moves down into the cylinder. On the exhaust stroke, the exhaust valve is moving away from the piston as the piston is moving up into the cylinder. These are where piston to valve clearance issues take place. Lift, duration, advanced or retarded cam position all affect how much clearance you will have.

The best way to check is by using lightweight checking springs, only need a pair, and some modeling clay. A thin skim on the piston top in the valve relief areas. Put the head back on. Torque to spec. Install pushrods etc for that hole, Rotate the engine by had 2 full revolutions then pull the head back off to see the valve imprint in the clay.

Rule of thumb is minimum 0.080" clearance on the intake and 0.100" on the exhaust. You can advance or retard the camshaft to change clearance if it falls below those minimums.

A different way of checking can be done but it takes a bit more effort. You still need some lightweight checking springs but also a dial gauge. Install the gauge on the spring retainer. Rotate the crankshaft about 10* and push down on the valve to see how much clearance it has. Helps to have a degree wheel. As long as you stay above the minimums during full rotation, you will have enough clearance.

Also as mentioned above, when the valve is at full lift, make sure the springs are not in bind and make sure the bottom of the retainer isn't touching the top of the valve guide/seal.

There's a difference between building an engine and assembling an engine. Very little is a simple bolt on.

gg4uk

My apology for the confusion.
I meant the valve have .530 lift on the intake side. The exhaust has much more but I don't have the numbers with me.

As it turns out my machine shop called yesterday because the springs are too light for the cam.
Closed they are at 92 pounds but need 135
Open they are 260 and need 360

So I had to order a new head gasket anyway. I will be able to measure my piston to valve clearance now with out any worry.

AlkyIROC

Ewww. 92 pounds on the seat with 0.530 lift. That will definitely cause some valve float.

The cam in my BBC has 0.833/0.809 lift and my triple springs have around 300 pounds on the seats.