Technical too short exhaust will result in warped valves ?

I don't plan on doing this but I'm just curious. I don't hear this anymore as I did years ago. The subject never comes up . The theory was, after shutting off a hot engine after racing etc one had to cap the exhaust ends off to prevent cold air/temp from hitting the valves,that this might warp the valves if you did'nt. Question for you racers , Is this still a issue ?? Gene

 

I'd really like to see some input on this as well. I think it's an "old wives tale", but when I raced my dirt modified with a hemi (the engine in my avatar), we had a set of plugs made that we put into the headers right after we shut it down. I really don't think i made any difference, but it made us feel like "real racers".

 

Never happen .

 

Nope!....

 

No...

 

Ran dirt late models and modifieds for 25+ years, never capped a header, never warped a valve.

In high school (the early/mid '70's) you jumped out and stuffed rags in the end of the headers when you parked in the lot with open headers in the morning. I think it was so you could let everyone know you:
1. really had headers
2. were serious about your car
3.knew what the experts did with their race engines

Don't think it makes a bit of difference.
SPark

 

Don't think so , never seen those guys at Reno run up and cap the exhausts on those P-51's after a race. But ...I always heard to run an engine with no manifolds right out of the heads it could. But who would do that? lol. Lippy

 

Nope. That is one of those persistent myths, like 010 blocks having a high nickel content.

It was never an issue, ever. Piston-driven aircraft have been routinely flown at 40,000-feet, where the temperature is about -40°F to -70°F, often with exhaust systems that are 8"-16" long.

 

seen many a dirt modifieds with flames coming out straight out of 6 inch pipes right out of the exhaust ports and never saw or heard of anything but a piston hitting a valve warping or bending one.

 

NOPE

 

It's one of those things we always read or heard but with some of those short pipes around dirt tracks it may have been more about keeping foreign objects out of the pipes than blocking off cold air.

 

Injector stacks... That's a different story ..
Kids throwing rocks and stuff ..

 

But they don't shut down at 40.000 feet to suck that cold air in....

LynnW

 

Shorter than optimum pipes might take some low-end torque away, depending on the set up.

 

Was some truth to it way back in the days before modern valve materials were developed... nothing to worry about these days.

 

How do you spell..."wives tale"..?

The cover is to keep dirt, rocks, gravel out while towing back to the pit area.

Mike

 

Never heard of Warping Valves but I have Heard it will Speed the Flow up own the Exhaust Gases and that could be a Problem if Scavenging is Figured in the Cam Overlap.

 

Sure they do. There are may examples of stall, and restart at altitude, with no damage to the valves.

 

I don't know if the headers on my HA/GR are classed as too short. In 8 years of racing it I haven't warped a valve. Can't say the same for the driver.

 

Not sure on the spell'in but......I thank it starts with a B!!
6sally6

 

My Dad ran the flathead in his '51 Ford Crestliner circle track car with NO exhaust pipes, just straight out of the block. Never ever had valve problems. He ran it 6000 rpm every Saturday night.

Dave

 

Always heard that when I was in HS. Thought it was true but there is a bunch of stuff I "knew" back then that turned out to be total BS.

 

Even my brother the tool, knows better than that.

 

I,m quite old.. 50's and early 60's I do have pictures and memories especially at the drag strip with the pipes capped off after runs. I wonder if one of you didn,t touch on it, that valves back then were not of the excellent alloys of today. Just my 2 cents.. Gene

 

Well, they might. But then warped valves is the least of their worries!

 

In the 60's the fuel cars would pull the plugs and let the hot engine "windmill" back to the pits. Theory was that it would hammer the valves straight again by beating them on the seats

 

....

 

Same catagory as "self abuse will make you go blind".

 

Back in the early 60s we ran a hobby stock on a quarter mile oval. We ran no pipes, no manifold, just out of the heads. They never warped valves

 

I had a good friend who subscribed to this theory. He also insisted that running a manual transmission behind a motor than had previously had an automatic would soon have the rods knocking, and installing a four barrel intake and carb would also do the same, especially if a person used an Elderbrock intake. He also insisted that Plastigaged was to be left behind when used, another friend believed him.