I have a rebuilt 8ba but I didn’t replace the seats or valves. Do I need to run lead in the fuel. What will happen if I don’t? Who runs this motor without led and doesn’t have a problem? Sent from my iPhone using H.A.M.B.
With high spring seat-pressures you risk exhaust seat recession. I don't know what cam and springs that you have, but I doubt that you have anything high enough to worry in a flathead. If you are still worried about risk, than there are several brands of lead-substitute additives on the market such as CD2, Redline, Gunk
Easy... If you plan on driving it many miles, similar to a daily driver... then , no, a good idea, but not a requirement. If you plan on long trips or putting 8000/10,000 mile a year on the engine, then yes...I would. My last car did "not" have hard seats. I had to adjust the exhaust valves three times to every one time for the intake valves. This is first hand experience..! So at LEAST...plan on many more valve adjustments without hard seats..! Another thing to think about...adjusting the valves on an overhead engine (my car) was not a big deal. Are you prepared to be pulling the intake manifold off your engine every 3000 or 3500 miles..? Me...I'd say hard seats now, save the aggravation for something else..! Mike
It’s way too late to put in hard seats. So what I’m thinking. Is I will put in lead additive in but do half of the measurements since that stuff ain’t cheap. And that little bit should work ok. Sent from my iPhone using H.A.M.B.
Good point saltflats.....may not be cost effective for this op, but good makers like Manley's use stainless steel benefitting a higher specific heat spec (cooler valves)
Flatheads do not need high seat loads from the valve springs. Seat recession should not be a problem if the seat loads are low as they should be for a properly built flathead.
Put a million miles on regular seats and unleaded gas. I put hard seats when I built the last engine only cause it’s pushing 7k pounds unloaded.
I've been reading this, while I've been wondering the same thing about my SBC. It's all new, got the receipts from the machine shop when i got the car but it's never been ran much more than just the break in for the camshaft. It's got 1969 041 heads on it. New guides, springs, valves, locks, and retainers. The receipt shows "valve job". I called the number on the receipt and talked to the guy, he said he kinda remembers the job. I asked if he would've changed the valve seats and he said that if he did it would be on the receipt. Doesn't bother me that much, but it's stuck in the back of my mind. Figure I'll run the car this year and pull the heads this winter. Or should i not even worry about it?
I wouldn’t unless your working it hard. Lots of truck engines got hard seats in the leaded gas days cause of how hard they worked.
The story was, back when unleaded fuel first started being used in 74, that the non-hardened seats could deteriorate after about 75,000 miles of use with the unleaded fuel, and this would have been on a standard issue new or used car at the time. Keep in mind, at that time in history, very few cars made it to 100,000 miles, so we were not concerned with used cars lasting long enough for the valve seats to be an issue. We hammered the non-hardened valve seat motors real hard back in those days (graduated HS in 74) and valve seats were about the last thing in a motor we were concerned about. Currently, if I was rebuilding a motor I expected to last a long time, I'd put in the hardened seats, but if the motor was already together, I think I would consider taking a look at the heads in 50-60,000 miles, or running a lead substitute through it a few times a year. Gene
yes you can the old LP engines used stainless exhaust valves and valve rotators on standard seats. I simply add a pint of diesel or outboard motor oil to every ten gallons of gas and that works for me.
My Ot 402 big block engine someone before me had let some machine shop install hardened seats. and one came loose. popped the head off the exhaust valve knocked a hole in the cyl head, bent the rod . cracked the piston and cracked the cyl wall. all happened at a idle going down a hill. Nope I aint paying a machine shop to ruin my cyl heads.
Unless you are working it hard.... such as truck pulling 8,000+lbs trailer, marine use in a boat, or road race use, all of which add to the heat soak seen at the valve seat/valve margin contact area, Don't even worry about it. It was an overblown issue when everyone worried over the switch to unleaded gas in the 1970's, and it still is overly worried about by hotrodders.
The replacement seats are a press fit in the heads or block, there is a risk of the coming loose as already stated above. Are you willing to take the chance one comes out or the original seat, I would bet on the original seat everytime!
no you do not. Unless your 8BA was running on premium when it was new it was running on unleaded. The only leaded fuel back then was Ethyl (premium in todays lingo). If you are worried about it spend a buck on a can of Bardahl top oil and dump it in your fuel. It will cushion your valves well enough.
That hard steel seat expands and contracts at a different rate than the cast iron head. there is as great chance of it coming loose and destroying you engine. I had it happen to me. and have seen several other hard seat failures. So now you again have something for your brain to worry about. LOL
My machinist is third generation....I trust him and also never had an issue in my daily driven model A coupe for over a decade. Also have seats in my '36 knucklehead, no problems......
I run the no ethanol unleaded gas in all my old cars and have never had exhaust valve seat erosion problems, but they only get a couple of thousand miles a year. The ethanol is hard on the rubber parts in the fuel pumps and that's the only reason I run it.
Son had a mid 60's Volvo 4 cyl and the exhaust seats totally got eroded away from unleaded gas. It was amazing the motor kept running after repeated exhaust valve lash adjustments, as the valve receded into the head. Buick Nailheads seem to be ok w/o hardened seats; maybe better cast iron ingredients. In fact, have known of Nailheads being ruined by installing hardened, seats because it is easy to get into the water jackets.
I think the biggest problem [but not the only] was the 70's lean burn emission junk engines that made it tough on exh valves. Remember when the engines would deisil after the ign was turned off? That was funny or embarrassing. I have a '67 SBF that I built in '71. About 10:1 compression, ported 67 4v heads, big cam, 5" vac at idle..Stock replacement TRW valves, no hard seats, Drove it a few years, raced it [beat it pretty good] for three years, plus about 50k street since '78. As the lead disappeared from high test I mixed the the octains to get what ever lead I could. Last bunch of years [20+, I don't remember when lead stopped] I just run 93 or 91 no lead. In a pinch I have put 87 in. Every time I check the lash they are fine..I believe that when the tune is off problems are on..
All of the Chrysler product Lean Burn heads had hardened valve seats. In fact, every engine the auto factories built (at least in the USA) since about 1974 has hardened exhaust valve seats. The hardened valve seats came along with the unleaded fuel and the converters because of the higher exhaust temps. Gene
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