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350 valve carbon.....

2K views 22 replies 5 participants last post by  Rodnit 
#1 ·
I'm going thru a qt of oil every 600 miles. My intake gaskets are leaking and replacing them as we speak. It is my understanding that the leaking can cause a vacuum in the valley and the intake valves can suck up the oil and burn it. Nothing ever comes out the exhaust to indicate burning oil. Not even on startup.

Since I have the intake off I took a looksy at the valves. Notice the oily carbon buildup and discoloration of the stems. I'm linking to 4 valves, all 8 are the same.

Is this being caused by the leaky intake gaskets, valve seals, or possibly a combination of both? Or, is there another issue?

I haven't pulled the heads.

If you click on the pick once to enlarge them, then click again, it really makes them big. It was tough getting decent pix....

Thanks,
Rodnit
 

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#2 ·
Your right about it being a combination of both leaky intake gaskets and leaky valvestem seals...along with a third very, very likely additional problem of totally worn out valve guides, valve stems, and valve seats.

Very common issue with any Chevy small block head from the smog era with over 75,000 miles on them. Just flat worn out.

Thing is, the heads you have are sooooo poor from a performance standpoint it is a total waste of money to rebuild them....you could get into aftermarket aluminum budget heads or aftermarket Iron heads for what it will cost to rebuild you old small valve, huge chamber, low compression, poor airflow-ing, SMOGGER heads.
 
#6 ·
Your right about it being a combination of both leaky intake gaskets and leaky valvestem seals...along with a third very, very likely additional problem of totally worn out valve guides, valve stems, and valve seats.

Very common issue with any Chevy small block head from the smog era with over 75,000 miles on them. Just flat worn out.

Thing is, the heads you have are sooooo poor from a performance standpoint it is a total waste of money to rebuild them....you could get into aftermarket aluminum budget heads or aftermarket Iron heads for what it will cost to rebuild you old small valve, huge chamber, low compression, poor airflow-ing, SMOGGER heads.
Recommendation on which heads to look at? Thanks.....

Replacing the intake gasket didn't solve the oil consumption issue...... Rolled the dice and lost...... The motor was supposed to have only a few miles on a rebuild... Wrong.....
 
#3 · (Edited)
Crud. I was afraid of that, but, in a way it gives me an excuse to get decent heads. I need input tho. What I have now is a mild build, supposedly. No specs on anything. Performer intake. Sounds like a mild cam, no specs again. TH350 with Hurst Promatic 2. Has some giddy up when I shift manually. Not so much when I don't, pretty flat. No kickdown linkage. Not sure what converter is in in it. All I know it shifts really quick when I don't get on it....

I would like to get Edel Al heads. Can't afford them at this time. Putting in a composite deck. So, I'm on a budget.

Can you use a roller setup w/o a roller cam?

Is replacing the rods and lifters a good assumption to do now too?

Links to some setups that would be nite and day to what I have now? Keeping most bang for the buck in mind.

Noticed the rockers that aren't trying to open a valve have some movement which moves the rod too. I know the #1 exhaust is way too loose. It rattles around good. It's been a loooong time since I tore into a motor.

Also, I have aftermarket mounting plates for my A/C and alt. Any issue with new heads?

Adding a pic of the last bit of antifreeze that came out. I don't think it's oil, just shot....

Thanks.........
 

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#5 ·
I understand these heads are boat anchors when it comes to performance. But just curious, if these heads were shot why are they so clean? Wouldn't they be all sludged up? I plan on removing them in the next couple days to take a deeper looksy......
 

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#11 · (Edited)
If the machine shop only knurled the guides, and didn't actually replace them or install a guide liner in them, knurling last just a few thousand miles at best and the guides are back to worn out.
Knurling is the cheapest method, and quickly done... most places no longer do it but a lot of smaller shops will still cut this corner.

That Fel-Pro Perma-Torque Blue gasket is the wrong gasket to be using with an aluminum intake, it is meant only for the expansion rate of an iron intake bolted to iron heads. The aluminum intake expands more when hot and needs a gasket with better elastic rebound characteristics. The correct gasket is the Fel-Pro Printo-Seal, it's a fiber gasket with an embossed silicone bead around each port. Mr Gasket and Edelbrock seal a similar gasket set.
 
#9 ·
On a budget, these are copies of the Dart Pro 1 Platinum 200cc, best deal on the bare castings. Imported, but real good quality :
SBC Small Block Chevy Straight Plug Aluminum Cylinder Head Set 64cc 2.02/1.60 | eBay Straight plug

NEW SET SBC Small Block Chevy Angle Plug Aluminum Cylinder Heads 64cc 2.02/1.6 | eBay Angle plug

Get the assembly parts to finish them here:
Chev SB Head Improvement Kits Just choose the 2.02"/1.6" valve kit that has the spring requirements to match your intended cam.

Angle plug often doesn't clear the headers unless they specifically state that they will clear angle plug heads.

Want them fully assembled?? Best deals are here:
SBC CHEVY 350 383 406 427 64CC/200CC ALUMINUM HEADS HYD FLAT TAPPET - WPM-S-272 | eBay
or here:
SBC CHEVY 327 350 383 NKB-200cc ALUMINUM HEADS 64cc STRAIGHT PLUG NKB-272 | eBay
Both of these sources have valvespring options available.

Be careful, there is a very similar looking casting from SpeedMaster/ProComp that is not nearly as good quality.

A little farther up the quality scale, but still an imported casting is ProMaxx, it is a nice head. Summit carries them.

Want an American casting, the ProFiler is the best as-cast.
https://www.profilerperformance.com/176-sbc-23-degree-heads.html
 
#10 ·
Appreciate all the info, eric. It has what looks to be an older performer intake. The cast writing looks older than the newer ones, not that it matters.. The block was used from '69-'79....

When it comes to how the motor was built, I have zippo paperwork. No idea what I got except smog heads and the al intake. I was told it was a "mild" build. I believe it....
 
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#13 · (Edited)
No idea on on anything. The odo read 2k. I'm sure it had been disconnected since when I drove around 55, the speedo read 75. Racked the odo up quick. They used a GPS for a speedo that I still use....

Don't have the cash for a total rebuild.....

Didn't replace replace valve seals/guides....

Pulled plugs a couple years ago, they were all a very dark caramel. Replaced them. I'm attaching pix of 1 plug from today. It hasn't run since Oct. Haven't dove into this project yet.

If the machine shop only knurled the guides, and didn't actually replace them or install a guide liner in them, knurling last just a few thousand miles at best and the guides are back to worn out.
Knurling is the cheapest method, and quickly done... most places no longer do it but a lot of smaller shops will still cut this corner.

That Fel-Pro Perma-Torque Blue gasket is the wrong gasket to be using with an aluminum intake, it is meant only for the expansion rate of an iron intake bolted to iron heads. The aluminum intake expands more when hot and needs a gasket with better elastic rebound characteristics. The correct gasket is the Fel-Pro Printo-Seal, it's a fiber gasket with an embossed silicone bead around each port. Mr Gasket and Edelbrock seal a similar gasket set.
I replaced those old gaskets with these, printoseal:
https://www.summitracing.com/search?SortBy=BestKeywordMatch&SortOrder=Ascending&keyword=fel-1256

Last time I did a compression check a couple years ago. I read 180-200....

Oh yeah, this baby is getting plenty of top end lubrication. You might jst as well pull the heads since your already half way there and do a valve and guide job on 'em.
Bogie
Pull the intake last year. Didn't pull the heads since I knew the intake was leaking. Didn't fix the issue. In hindsight, I should have pulled the heads too....

This car was bought unfinished at an auction. Original owner lost the car with his business. The guy I bought it from had someone finish it, including paint. He had it for 2 years. I verified it all thru a guy that my father knows who knows the car. Even said the previous owner paid $16k at auction and put $8k into it....... I believe he drove from N Mn to BTT 50's car show a couple times and parked it. Most people who see it comment on a fresh build......
 

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#14 · (Edited)
I think that's what I'm going to do and cross my fingers, replace the seals. If anymore work needs to be done on the head, then I'll replace the heads since they're not big on performance.

Those heads are the same heads ericnova recommended, I believe. And probably the ones I would buy...... Providing everything else looks good if I pull them....

I'm really not sure if those are the same plugs I was using b/4 I changed the intake gasket..... Might as well change those too while I'm at it...

Is there one seal better than the other? Would you have a link to Summit, or someplace else?

Thanks, Rodnit
 
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#19 ·
If those are 882 open chamber heads they like a lot of timing and you normally reach the knock level before the motor reaches its power peak. Because of the slow open chambers need more timing than modern heart shaped chambers.

Hope this helps.
I believe the heads are 991 with the 3970010 block...... Found a thread with the same setup....

http://www.hotrodders.com/forum/3970010-block-3998991-heads-low-compression-motor-138756.html

As far as valve seals, I narrowed it down to these:

https://www.summitracing.com/search...ch&SortOrder=Ascending&keyword=350 valve seal

Looks like I need to find the size of the valve stem.

I'm a Summit guy.........:)
 
#15 ·
Boy did this thread get buried. Sorry for the less than prompt response.

I do appreciate the advice on the heads and other info.

I don't remember the total timing. I believe the initial is set to 20 deg. I set it as high as I can w/o pinging. I haven't run it yet this year.

As far as doing the seals, how much air pressure should I use to keep the valves in place?

No doubt, if those heads need to come off for any reason, they will be replaced with al......
 
#16 ·
95-100 lbs would do the job nicely. Another method is nylon rope to feed into the cylinder. THis works well but it a bit slower in the car.

I'd do a leak down test and see what the rings look like. That's a good way of testing the wear and would give you a real good indicator of the overall good condition. It's just more info for you to decide what you can and want to do.
 
#20 ·
Thanks for the valve size verification.

That's what I'll do, pull the covers and and see what I can see. If I need to, I'll pull a spring and pull the seal........

If I need to pull the heads, they will be swapped for aluminum. Not going to go thru all the work only to reinstall those sub-par heads.....
 
#21 · (Edited)
I can't believe how old this thread is and I still haven't replaced the valve seals. I didn't run it last year and want to replace the seals this year b4 I move it.

I could have sworn someone mentioned what size valve stem I have, maybe the post was removed? Can someone give me a heads up on the size? It would be much appreciated. I have Summits site open as we speak and ready to order.....

Thanks........

Edit: 11/32 ?
 
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