Rebuilding 308 2V cylinder heads

I recently posted a thread in the 348/355 forum that walked through the valve guide replacement I was doing on a pair of 355 heads. I got a lot of positive response by people who appreciated the information and the pictures. I'm just finishing a pair of 308 heads and thought I'd share the project on here.
These got the full deal including new valve guides, porting, custom valves, and new exhaust seats to accommodate the new exhaust valves.
The new guides are manganese bronze. The valves are stainless and the intake is 2mm oversized while the exhaust is 1 mm smaller (which is why I needed a new valve seat with a smaller inside diameter). The only reason I would go to a smaller exhaust valve is to insure the valves don't interfere with each other as they are already close and they open toward one another. Even with the smaller valve I was able to increase the flow in the exhaust port. The intake valve is 2mm larger than stock and has a 30 degree face rather than the stock 45. 30 degree seats flow more air at low lift and with stock cams these heads only have a little over .300" valve lift. I'm not going to publish my flow numbers on here but I can provide it to anyone who's really interested. We're expecting around a 20 H.P. increase.

If we decide to replace valve springs and upgrade to titanium retainers, the bill on these heads will be right at $3850 for parts and labor and will be ready to bolt on the engine before they leave the shop. The job will take a little less than 2 weeks from the time I received them.
There's more info on my website: www.FerrariPerformance.com
Enjoy!
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You mean to break the heads lose from the block? Yes, I've heard they're really on there. The first pair of these I ever worked on, the owner drove a wedge between the intake manifold and head to get it off... I had to weld and resurface the intake side of both heads to repair the damage he caused. Fortunately he figured that out before he did the same thing to the deck. He built some sort of puller to get the heads off. Them must be some sticky head gaskets! LOL

 

that's a relative question... too small for what? A bigger valve almost always moves more air and this head is pretty poorly designed IMO. It is after all 30 year old technology. Our knowledge of port design has come a long, long way in just the last 20 years. Increasing the valve size does move more air, which in turn increases volumetric efficiency, which increases cylinder pressure, which increases torque which is converted to horse power with rpm. As for the exhaust valve, even with the smaller seat I was able to crease the flow by being able to use a 3 angle valve job rather than the stock single angle, and the smaller seat also allowed for some reshaping to be done. An optimal exhaust will flow around 70% of what the intake does. In stock form these flow around 78% (because the intake is weak). After I've gotten an increase on the intake side, the exhaust still flows around 78%.
So, is the stock valve too small? Well, these cars run pretty good in stock form... but aren't we all trying to always go just a little bit faster? LOL
I just bought a 96 Chevy one-ton dually crew cab pick up and the engine is having issues. I'm afraid the heads may need to come off. If they do, the first thing I'm doing is installing larger valves and porting them.

I just hit the edit button so I could add this last little thing... increasing valve size does NOT kill bottom-end torque, increasing port volume does... two totally different things. That is widely misunderstood.

 

I've been working on getting titanium retainers for the 308 that will fit the stock spring. I'm also working on putting together an aftermarket spring, ti-retainer, and spring seat package but am not there yet.
Below are the finished pics of Ben's heads with some close up shots of the titanium retainers and one of the stock steel retainer. The ti is less than half the weight and equally as strong.
Enjoy the pics!
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It seems like the stock springs coil bind at about .460" lift and I don't remember seat pressure but 90 lbs rings a bell. Sorry, I write this stuff down so I don't have to remember it and I'm not at the shop where all the paperwork is. If you need to know for sure, feel free to call me during the day at the shop 503 390 8875 or email me from my site: www.FerrariPerformance.com
As far as how high to rev with stock springs and cam.... when the numbers on your tach turn red, I'd quit.
There is a considerable amount of mis-match between the head and intake manifold. I don't know that it really hurts anything but it can't possibly help. I have done some flow testing in that area on other applications and there has to be quite a large mis-match for it to show up. Still, it's nice to have a smooth transition. Here're a few shots:
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Hey Sean... did I speak with you on the phone today? 110 and 250 should still be safe. There is way more danger in a valve bouncing on the seat at closing if the springs are too light, than having it "beat" the valve seat from too much presure. The ramps on the cam lobes keep it from closing too hard. (if that's a concern you can set the lash a little on the tight side for a softer closing.) However, if it bounces it will destroy the valve face. This may be apples and oranges, but I have a flat tappet Chevrolet drag race engine running 155 lbs seat and 420 open on a solid flat tappet right now... granted it runs 1/4 mile at a time but it has two full seasons and is showing no wear. I think your'e probably safe as long as you keep it under 140 seat and 300 open and with a valvetrain this light you shouldn't need to even approach those numbers. As long as everything is "happy" a little extra pressure shouldn't cause exessive wear. As far as what cams.... I just run what people send me.... other than that I don't get into that end of it. does that help at all?