Those are pretty damn cheap valves. ~$8 each, in today's market, would give me serious doubts about their quality. Especially those prices for a "performance" valve.

 

Considering that you pay 5 times as much or more for good quality valves like Manley I would agree.

The $8 "performance" valve got ya.

 

Could be. They look like a decent valve but who knows they also have a race valve but considerably more. This 550hp deal. Peak hp at 6300

 

Qualfast valves are really cheap and soft
Also 1.710 will clip the bore if you don't relieve it

 

Typically valve bounce (float).
Any other pistons show anything?

 

Some marks on opposite bank. But I figured some garbage was thrown into intake. Maybe not. These are on 3-4 opposite bank.

 

Failure was on 6. This is number two opposite bank.

 

Trash will cross over into other cylinders for sure. Did you check to see if the exhaust valves are touching the side of the cylinders? This is an issue on 4.030 bores and 1.710 valves for sure.

 

You should also check to make sure all the other cylinders that have had trash in them havent pinched the top ring.

 

Thanks Jim. This is 400 block .030 there is some relief left on exh side. I cannot see anywhere the others were hitting wall. It split number 6 so will need sleeve. I do have another block we may use instead at any rate needs tore down. Everyone stepped up in this class so i have another recipe that was 650 hp with single 1050. Might go that way.

 

Ok well just give the cylinder a little rub and clear the valves. Probably just cheap valves. Rev is my go to valves and if you need something from the states just let me know , be glad to help.

 

I think I’ll replace Jim. See if we can fix head without much fooling around. Otherwise gotta head to wood shed for another.

 

Valve springs up to the task? Valve bounce with cheap valves?

 

We believe they are. I’ll recheck pressures on rest. Never know. We set high typically. Cam calls for 120/320 I think we are 160/380. I do have about 5 other engines out with these valves. Their still going so hard to say. One thing about these thinwalls. When something falls in usually cracks cylinders. 🥲🙈

 

REV guys, they are bullet proof.

 

Jim any idea what valves Ford Racing used in the Aluminum CJ Heads mine have the 2.20 Intake and 1.76 Exhaust Valves and were complete heads when i bought them?

 

When I see a broke exhaust valve, I usually think of valve float.

 

When it actually let go he was at about 1500 rpm. Driving slowly to mud pit. The rev limiter was set at 6800. If it was float you would think there would be some valve marks in other holes. There’s not. 🤷🏻
Thanks guys. We’ll do some more digging.

 

I had no other marks. It doesn't have to hit the piston, just bouncing on the seat will do it, plus a not so great valve, like speed pro

 

Sounds like some cheap valves cost you in the long run, DK, good luck fixing it.

 

Qualcast LLC

Heres more. Beats me. Lol. Thanks everyone. One good thing is we can ramp up a bit more.

 

Well guys i was wrong. Not qualfast valve these valves came with engine i had bought. We had taken these heads off and replaced with a set i had built. These heads we freshened up, ported and new springs to match cam. We checked all springs today all good. 🤷🏻

 

Their machining is better. Margins are close to identical valve to valve, however they are heavier and don't flow as well and they cost more.

 

Ferrea valves have enough material at the head to allow a decent back cut on the intake valves. The Manley BBC intakes don't have much material to back cut, so they are lighter.

 

A very out of round seat will cause fatigue in valve with it constantly hitting down trying to bend and eventually breaks.Check others with a good excentrimeter.

 

Might be the pic, but the surface just above the neck-down seems to have a very rough finish.

 

2 piece cheap valve?

 

Numbers on valve. 1403. O801. Only we thing we found. They are not the qualfast I usually use.

 

The most common problem that causes valves to break is the valve seats not being concentric with the valves. Concentricity must be checked and corrected when the valves are installed/ground. If the valve seats are not concentric the valve will contact the seat at different locations (angles), due to the fact that the valves rotate while running. This will cause the valves to bend very slightly and just like bending a piece of wire back and forth, the valve stem will eventually snap. Quality machine shops will always check valve concentricity before the heads leave the shop.

 

THAT.

 

Thanks guys. We are replacing valves and seats.

 

Make sure seat runout is checked .Many of the FAST machines do a poor job of machining seats round .