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Old 04-18-2010, 09:17 PM
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hardened valve seats 1969 Firebird 350

I've recently bought a 1969 Firebird 350. I've been told that it has not been rebuilt. The car has probably put 1500 miles on the road since 1986. This engine stock had 9.2-1 compression. My friend and I have heard that hardened valve seats are a must for older engines running on todays gas. However, we don't hear many people talking about it or doing it. I was wondering, is it absolutley necessary? Why, specifically, must the valve seats be hardened. What happens if they are not hardened?

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Old 04-18-2010, 09:23 PM
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Quote:
Originally Posted by Gladis
I've recently bought a 1969 Firebird 350. I've been told that it has not been rebuilt. The car has probably put 1500 miles on the road since 1986. This engine stock had 9.2-1 compression. My friend and I have heard that hardened valve seats are a must for older engines running on todays gas. However, we don't hear many people talking about it or doing it. I was wondering, is it absolutley necessary? Why, specifically, must the valve seats be hardened. What happens if they are not hardened?
Not using hard seats allows them- over time- to erode, because there's no lead for lubricity. Hardened seats were introduced when the lead was removed to counter the loss of this lubricity.

However, if this is a weekend, or occasional use vehicle, you'll need to put a lot of weekends on it before there will be any appreciable wear.

I'd run it as is until such time that you decide to go in and rebuild the entire engine and deal w/the seat issue then.
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Old 04-18-2010, 09:35 PM
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when the lead was removed from our gas,people freeked and told of all the problems we were going to have. those problems never materialized.
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Old 04-18-2010, 10:12 PM
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Originally Posted by Sixguns
when the lead was removed from our gas,people freeked and told of all the problems we were going to have. those problems never materialized.
I agree, except that the problem of too much compression would cause detonation does happen with the low octane unleaded gasoline, but with 9.2:1 compression, you're almost perfect for pump gas. If you don't have a 4bbl on it , any Pontiac '65 to '71 manifold, from a 326, 350, 389, 400, 421, 428, or 455, will bolt right on, and you'll be surprised at how peppy that 350 can be!
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Old 04-18-2010, 10:33 PM
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I dealt with this alot on some of the stock type rebuilds and I will say after a seat cleanup to see just how bad they were, only a couple actually needed the seats done, only due to mileage that was on it, and I only replaced them because they wouldn't cleanup due to pitting. 99% of the time, I was able to do a valve job and the seats looked like new, so no need to spend the cutomer's money. This only happens with mileage while using unleaded fuel as it takes ALOT to warrant hardened seats. Most owners of older cars do not plan on driveing the car very often, unlike the old days where they were used as everyday drivers. Now they are driven on Sundays, and only when it is nice. At that rate, it would take 10+ years for the seats to even start failing from today's fuel. Drive it, enjoy it, and when it comes time to rebuild, have them inspected. If they cleanup with a cleanup valve job, I would leave them in. Incedentaly, the valves are usually the first to go, and odds are these will need to be replaced and are cheaper to do than hardened seats. I think there is just alot more hype than anything when guys say it MUST be done to run with today's fuel. Just not true.

PS 9.2 compression is just fine for pump fuel with iron heads and 93 octane fuel.

Last edited by Bad Influence Racing; 04-18-2010 at 10:42 PM.
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Old 04-18-2010, 10:42 PM
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I have actually been surprised already, I wasn't expecting much power from a 2bbl engine. The torque curve is fantastic for the specs, much better than a similarly built SBC.

thanks for the responses
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Old 04-18-2010, 11:30 PM
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Creech is right. I have done this alot on these stock engines. In addition to what I wrote to improve upon this, you can change some hard parts to gain a bit more umph. Gears, obv help a ton. You won't have to go real big, just enough. The 6 cyl cars actually come with more gear, as do the 2 speed cars. Something in the 3.23, along with the short stock type radialls works very well. On the engine, I have used the Carter mechanical pump, Swap out the timing chain to a double roller setup as the stock chain is often very cloppy which retards cam timing and changes ignition timing when it is worn. Next, we fo with a Edelbrock Performer intake, with a holley vacuum secondary carburetor, like a 650 street avenger as they have electric chokes for winter months. You can also add roller tip rockers, HEI ignition with MSD box and coil..all very minor stuff that greatly improves the output of the engine. The reason why they have a nicer torque curve than the SBC 350 is due to the stroke. They run the same 3.750" stroke as a 400, where the SBC is only 3.480". Enjoy your new ride.
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Old 04-18-2010, 11:43 PM
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I use to have a set of SBC 041 casting heads from 1968. They didn`t have the hardened seats and it was evident how the seats were being pounded out when I took the heads off to have new guides installed. Afterwards, I ran some stuff you can get at almost any parts store called "lead substitute"
When I later removed the heads and sold them the seats still looked the same and this was 20,000 miles later, so I knew the lead substitute worked somewhat. The only problem is, you have to run a bottle of it every fill up, and at close to 4 bucks a bottle it gets expensive, especially on a daily driver.
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