Modifying Big Block Chevy Valve guides for Modern seals & More lift
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- čas přidán 3. 06. 2022
- Recently I was performing a camshaft swap in a 396 BBC. I was moving away from a Hydraulic Flat-Tappet camshaft that had .550” gross lift to a Solid Roller camshaft that had nearly .650” gross lift.
This engine was running a set of ported stock iron heads, casting# 3931063 . These heads were still equipped with the original valve guides. These valve guides were presenting two significant issues that were preventing the use of the newer camshaft that had significantly more lift.
The first problem was that I needed to upgrade my valve springs to accommodate this new camshaft. I was going from the stock style single valve springs with a damper to dual valve springs with a damper. The valve stem seals that I was running were a soft rubber outer body with a Teflon sealing section that ran against the valve stem. These seals just slid over the stock, unmodified valve guide. Now these were sufficient with the OEM sized springs, but with the new dual springs the inner diameter of the spring set was smaller than the outside diameter of the valve seal. So I had to find a valve seal solution with a smaller OD diameter.
The second problem that I encountered was that with the OEM valve guides, specifically their total height was too tall. With the nearly .100” more lift the bottom of the valve keeper/retainer would make contact with the top of the valve guide well before max lift. Aftermarket heads, whether aluminum or iron have much shorter valve guides for this exact reason.
Many manufacturers sell valve guide cutters, that advertise the ability to cut down the Outside diameter of the valve guide. Now that is only 1 of my 2 issues. I was unable to find a clear, close image of a cutter, and no supporting information that outlined IF these cutters would also reduce the height of the guide in the process.
I decided to take the chance and order the pilot and cutter that I needed for my dimensions. Once I received the items I was able to see that it did indeed have a cutting blade to address the height of the valve guide.
I did not have access to a mill, or even drill press so I was limited to cutting down these valve guides with a hand drill.
It did take a fair amount of calculating and measuring on the needed clearance for the keeper to valve seal at max lift. DO NOT FORGET TO ACCOUNT TO THE VALVE STEM SEAL!!.
The cutter was very easy to use, and I was able to cut down all 16 of my guides with ease. The cutter did not indicate that it was getting dull or struggling at all. I was very cautious on keeping my drill speed very slow to not overheat the cutter.
This simple tool setup rectified both of my problems, which allowed me to run a significantly upgraded camshaft.
Now during this process I did stumble upon the realization that most all of the “stock’ish” or mild camshafts for the Big Block Chevy all have no more than .550” lift. Most all available flat tappet cams do not run more than this .550’ max lift. I am presuming that this is due to the fact that the manufactures are accounting for the limitation of the stock valve guides.
So in short these cutters will easily allow you to run a superior valve seal, and will also open up a whole new whelm of possibilities in terns of camshaft selection.
The Items that I used for this project were source from Summit Racing. Links are below:
COMP Cams 4734 - COMP Cams Arbor/Pilot
www.summitracing.com/parts/cc...
COMP Cams 4715 - COMP Cams Valve Guide Cutting Tool
www.summitracing.com/parts/cc...
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#ratmotor #bigblockchevy #454 #427 #496 #402 #bbc #chevy #bigblock #musclecar #horsepower - Auta a dopravní prostředky
This is my exact same problem after having new guilds installed , which the machine shop ( 30 miles away and always too busy to call ) had forgot or didn't know to cut the guilds down for me and I didn't think to ask when picking them up after 3 months of waiting for them to be machined...I'd rather spend the money on a tool rather than go back and wait another week or 2 or 3 , just to get the guilds cut down.....Thank you for this video.
Oh, and by the way , the guild is sticking up off the spring perch 3/4 of an inch......I should have realized when i picked them up , I did think it was odd but was too happy to pay and get the hell out of there.
Scott. I am glad that the video helped you out. Sorry to hear about your struggles with the machine shop. Unfortianly I know the feeling, as I have been in many similar situations in the past. Good Machine shops are getting harder and harder to come by.
~ Nick
Im doing a 454 build. I was just looking google for max valve lift stock 454. Wow people all over the place with no definite answers. So i got fed up decide to check for myself. I took spring off and put retainer on with locks. I checked the clearance below retainer to top of seal and i got .660 clearance. And thats the lowest part of retainer in the center that drops down a bit further than the actual spring surface. So technically you could run .650 lift (and spare .010) and not bottom out on the seal. Now as far as spring height and coil bind, i sqished the spring in my vise starting at the installed height to full coil bind and got .585 difference. These are stock 454 springs. Now i dont know everything about springs but i would guess its not a good idea to max out the valve springs. As they only have so much resistance strength per pressure? My calculation would be borderline safe to run a .525 lift cam. I've read blogs online where people say they've run .550- 600 lift cams with no issues. But i find that skeptical. So.... if this helps anyone.. thought I'd throw my 2 cents in. 👍
Very good information. I appreciate you sharing it.
~ Nick
Awesome! Thanks dude! I was in the same predicament with no answers after a shitload of searching. This video answered all my questions. Thanks again!!
My umbrella seals won't fit with dual valve springs. Options either use behive spring or cut valve stems. Beehive springs superior if possible (lighter) that's as far as iv got. Your vid has helped clear up a few things. Thanks 👍
Yes there are a lot of advantages to running the beehive springs. But I feel that the advantage to moving away from umbrella valve seals over to Viton, is far greater. Plus you then have the option to run either style of valve spring that you choose. It will really open up more options for you.
Can you put a link to the vocals you have for that job please?
I'm going to a hydraulic roller cam in my 402 Chevy and I'll be doing the whole deal also. Did you leave an additional measured clearance for the retainer and valve seal like an extra .010" or so? Thanks for sharing this video.
Yes. I did account for the seal, and retainer when I made my measurements.
~ Nick
You need some racer friends.
😂
How much of the oem guide did you end up machining off for adequate seal/retainer clearance in you application. I have a hyd roller .600" cam I plan to use on the same cast # head that you modified.
Thanks!
I did not measure the total amount of material that I removed. I was trying to leave as much guide left as possible, while gaining the clearance that I needed. It was a bit of trial and error, since I though I had it set just right, but then I needed to cut them down a little more due to the valve seals.
Great video, just what I needed to know. that arbor for the cutter what are the cutter end dimensions? Can I modify a old 3/8 valve to use as a arbor? TIA Steve
That is a very good idea to save some cash! I sold the tools a while back, so I am going off memory here. I do not see why you couldn't use an old valve stem as the arbor. As I recall there was nothing special about the arbor, other than the fact that it had 3 flat flanks machined onto the drill end for the chuck to grip onto.
~ Nick
@@AutoTechNick Thanks. I'm a WV Hillbilly living in New Zealand and I'm NOT paying 400.00 for the cutter and arbor. Even buying from jungle site or summit shipping is like 100 bucks. Thanks again
@@AutoTechNick yup I cut off a valve did a little fancey grinding and it worked great.
What tools do you use for cutting the valve guide in order to make more clearence for the lift? All the best
Pedro, here are the tools that I used to modify my guides:
COMP Cams 4734 - COMP Cams Arbor/Pilot
www.summitracing.com/parts/cca-4734
COMP Cams 4715 - COMP Cams Valve Guide Cutting Tool
www.summitracing.com/parts/cca-4715
~ Nick
@@AutoTechNick thanks bro! I make the same work in a 454.!!
I need to replace the seals in my 396, stock heads. I am not a fan of the rubber Umbrella sals, but cannot use the Viton seals without machining the guides. Where can I find the Seals with Teflon rings like you used?
Jack, if I remember correctly I got them from Summit, although I recall it taking a lot of searching.
~ Nick
I did all this and now I’m burning oil thinking it’s my seals haven’t opened up yet to check but all the signs point to that smoke on start up loss of power and burning oil lol
🤔 What type of seals did you end up using? I assume you had a good fit on the seal to guide, and valve stem?
~ Nick
Do the wiggle test. Pull the valve out about 1.5" and see if the valves move in the guide. If so, get bronze guides installed.
What's wrong with the umbrella guide seals?
Umbrella seals arnt nearly as effective as a positive type seal, since the ride with the valve. Oil can still get around them easily. But the biggest drawback is their diameter. The diameter limits your valve spring options, which can limit your camshaft selection.
~ Nick
@@AutoTechNick I only run flat tappet cams on my bbc and use a comp cams 911-16 single spring, that's as high a pressure you want to go with a flat tappet if you want any life from your cam.
I used to frequently run flat tappet cams. But with the ongoing quality issues from all manufacturers with the cam cores, wiping lobes on break in. I highly doubt that I will gamble on another one again. It is just too costly if you end up wiping a lobe.
~ Nick
@@AutoTechNick I've been running solid flat tappet cams since the 60s and never had one go flat. I guess I'm blessed.
@@joe-hp4nk Its been a recent development in the industry. I would say the frequency that it has been occurring has rapidly increased in the last 10-15 years. The old cams don’t have the same issue. Two of my engines are flat tappet, but the cams are from the late 90’s.
~ Nick
Get the grinder out.