The Stovebolt Site Forums The Shop Area Engine Shop Hotter Rear Cylinders

235 with 2x1 intake, fentons and 2" pipes with 22" smithys under the cab and turn downs before the rear tires.

I noticed when warming up, the rear of my 235 always seems hotter than the front.
The rear header's pipe and exhaust is hotter and the rear carb also feels hotter.
I thought after complete warm-up and some driving the temp across the cylinders would equalize but never checked it.
Then last week, a friend who used to build harleys and hot rods, told me straight 6s always have hotter rear cylinders even when fully warmed up and running.
- I wonder how hot straight 8s must get back there?
Also explains why the temp sender is in the top rear, I guess.

To get better fuel economy and performance, shall I bother experimenting with....
* a smaller jet for the front carb (or larger on the rear)
* cooler spark plugs at least on cylinder 5 and 6, maybe even 4
* 1/8 - 1/4" smaller diameter exhaust pipe for front cylinders 1-3

I got hydraulic lifters on this one, but go with solids on my next project.
* With solid lifters should one compensate lash for rear valves and maybe even have the rear cam lobes also grind to compensate - how much, if at all?

I'm curious what more experience inliners think and if tweaking would make a difference or just create problems and a loss of time and funds.
Thanks!

The old Chevy 6's are notorious for building up crud in the rear cylinder water jacket at the bottom.Open the drain cock,or remove the plug on the rear lower left side of the block.If clean coolant flows out,good.If nothing flows out,the usual case,it's time to flush it out.

Good tip - Did that many years ago. Lots of build-up I remember, as you say.
Replaced the freeze plugs and installed a vintage coolant filter in place of the drain valve. Cleaned the filter many times since. Both coolant and oil passages are very clean in this engine and it runs beautiful.

This isn't a problem or anything.
Just noticed the difference in temperature and figured ideally one would have to compensate for rich and lean cylinders as fuel vapors burn more efficiently when hotter.

Just curious if anybody experimented with this or if the difference between cylinder temps is insignificant or I'm missing something.

Another problem is the fuel distribution. First and last cylinders run lean, therefor warmer. But that doesn't explain your problem.

I've never taken the temp of the exhaust manifold, and haven't noticed any difference. But I've only been working on these engines for over 40 years, so I haven't experienced everything on them.

On the road again,
As with any engine its all about the plugs. What do they look like will tell you everything you need to know about the health of your engine. Compare the ground strap on each plug. If you have the 2x1's jetted correctly it will be clean 1/2 way down. Any more towards the base where it attaches = too lean and therfore too hot. I'm sure you've noticed that with 235's and 2x1's less timing will help it "run" as you are getting better fuel distribution. 2x1's will generally require smaller jets and smaller jets will lean it making it run hotter. So check the ground strap for correct jetting. And try Re-setting your points to .014. Happy motoring.

I also wondered about that but all 6 plugs are clean and appear to be in the right heat range.
I use AC R45S and replaced them about a year ago, last time.

If I go down one size on the carb jets I get hesitation when accelerating.

It's possible that these engines warm up a little sooner in the rear.
But I have never noticed signs of uneven cylinder temps when fully warmed up - driving it every day since the mid 90s.

I like learning and listening and sometimes take a more experienced person's advice as gospel and go with it for a while until I can confirm or dismiss it.

Glad I asked around while it all was just a thought.

Thanks for all the helpful advice, as always...