turbokinetic

Hey guys. I have a thread going on in the DIY-PROM area for the TBI conversion on this car. I have had a lot of problems with the build. Some of it is the nature of the build, and some of it has been hard luck.

This is a friend's car, and as such I don't know all of its history. He purchased it and the engine started to fail immediately.

The car is a 67 Camaro RS/SS with 350 4-bolt. The engine is a 70's era engine. Heads are Bowtie iron heads. Fuel system is large bore TBI (from

I fully dismantled and did a basic overhaul on the engine with new seals and bearings and rings etc.

My friend wanted a roller cam engine, so we ordered a Comp Cams 260XFI-HR-13 cam and lifters kit; along with the recommended beehive valvesprings, timing chain set, and other parts. The car has 1.6 roller rockers as required by the cam setup.

The heads were in bad need of valveguides. I took them to a specialist who remanufactures heads. They replaced the guides with new cast iron guides, as well as installed valveguide seals. They also installed the Comp Cams beehive springs, set to 1.8" installed height.

I have been trying to get this car to run right for a week now. The first problem was a bad aftermarket distributor. After changing this for an original style unit, the engine started to run well. I was almost through with the tune, when it developed a high RPM miss, that progressively got worse. Finally it ended in a seized valve, mangled pushrod, and piston-valve collision.

I took out the seized valve and found heavy metal transfer and galling on both sides of the stem. Also taken out two other valves and found out that the stems are starting to score and gall.

A good friend of mine says that probably the valvestems and guides were not lubricated when they were assembled; or that the stem to guide clearance was too tight.

I am going to take the heads to another shop and get their opinion, but any insight here would be very much appreciated.

This is the seized valvestem after driving it out with a punch:


The valveguide:


This valve had not got stuck, but it was not looking too good:


The assembled valvespring and guide seal:


I don't understand how any oil gets down past this type of guide seal. It is a solid rubber lip seal with garter spring. It is virtually air tight around the stem. The guides are iron and as far as I can tell, they have no porosity or other way for oil to get to the stem. The original valveguide seals were a hard white Teflon material that was not as tight and positive of a seal.

Has anyone seen this kind of failure before? The engine has about 40 miles on it, and a few (3 or 4) WOT pulls in 3rd gear. The final failure of the valve happened after 10 miles of steady-state 1800 RPM cruising on the highway.

When assembling the engine, I checked that the rocker tip was rolling in as narrow of a band as possible, and it was in the center of the stem tip.

Sincerely,
David

Tuned Performance

iTrader: (92)

your buddys right, looks like the guide was knurled ;(

turbokinetic

Yes it was definitely knurled. The knurling doesn't extend all the way down to the bottom of the guide, either. Wonder if that lower area with no knurling was the cause of the seizure?

Tuned Performance

iTrader: (92)

Knurling just cuts threads in a worn out guide, The clearance should have been checked and adjusted. I hate knurling band aide fixes. You might as well try taking the heads back to the rebuilder and see if the own up and will press in a few guides and hone them. And request the springs/shims are labeled so you can put them back on.

turbokinetic

What's interesting is, these guides are new. The original ones were damaged at the top area where the guide seal installs. They are brand-new and knurled.

I wonder if they were supposed to be reamed to size after pressing in and that step was omitted, or the reamer was worn.

The heads are on the way back to the shop by way of my friend. I am going to be going off to work for about 2 weeks before I can work on this again.

sofakingdom

iTrader: (1)

Not sure how "new cast-iron guides" could POSSIBLY be considered A Good Idea.

Have bronze inserts installed in them.

Cast-iron guides require a certain amount of oil to lube them. You can't "pre-lube" them, they have to have it continually. Positive seals like that are well and widely known by all who know what they're doing, to NOT be a good match to cast-iron guides, therefore.

Bronze is self-lubricating to a great extent: if wear occurs, the bronze powder that results, IS a lubricant, thus preventing (or at least, minimizing) continued wear.

Here's what you need. http://www.cylinderheadsupply.com/va...de-liners.html

Good replacement valves for an application like yours, aren't too terribly $$$$; http://www.summitracing.com/parts/man-10766-8/overview/ and http://www.summitracing.com/parts/man-10765-8/overview/ are a good choice. Inserts, plus those, plus Teflon seals (FAR longer-lasting than rubber) such as http://www.summitracing.com/parts/cca-503-16/overview/ or http://www.summitracing.com/parts/cca-510-16/overview/ depending on your guide OD, will fix this situation right up and make everything better than new.

turbokinetic

Thanks for the information. You're the second person (one IRL here at my place) to say essentially the same thing. I thought I was doing the right thing having these heads rebuilt at a specialist but I guess not. Makes me feel kind of stupid now.

When I saw the failure I wondered about the wisdom of the positive seals. I should have questioned that when receiving the heads from the shop. But we all know that hindsight is 20-20. At the time I had no reason to question the underlying quality of the job or to disassemble the heads to look.

I've had a friend who worked at a local machine shop who did all my Buick V6 heads. He always installed the liners into the guides and there was never a problem. He moved to another state unfortunately.

Sincerely,
David

turbokinetic

Got a small update on this car today! It lives again! We got the heads back on, with bronze valveguides and all new valves.

Here is a short video of it going together and the startup.... along with a little safety info.