Can too little compression for a camshaft cause engine heating

General engine tech -- Drag Racing to Circle Track

Moderator: Team

Post Reply
topradman
Member
Member
Posts: 129
Joined: Fri Aug 02, 2013 8:12 pm
Location: Kansas
Contact:

Re: Can too little compression for a camshaft cause engine heating

Post by topradman » Mon Oct 16, 2017 2:50 pm

travis wrote:
Mon Oct 16, 2017 2:35 pm
Does it have vacuum advance? Have you done a cranking compression check (it sounds like this would tell you a lot in this situation)? Have you verified TDC on the balancer is correct? Basic stuff I know but sometimes the little things can kick your ass.
Have you tried dropping the pipes and see what difference open headers will make? Severe exhaust restriction can certainly cause overheating too. How does it idle and drive? Does it feel off or really down on power?
It does have vacuum advance. Cranking compression test needs done again as my guys didn't do it properly ( in my opinion ). Balancer is correct ( has big counter weight, typical 454 ). I am so far beyond "basic" it's unreal ( see "41 Willy's 468 overheats" thread ).

Am going to button engine back up and drive with open exhaust tomorrow or this afternoon. Idles great, driving has a slight rpm vibration but cannot find any obvious cause ( reversion? ). Flex plate looks correct ( 454 w/big weight, typical ), balancer good, pistons in correct direction, not the converter ( ran w/converter disconnected ), does it in Park so not driveline. Power doesn't seem great for a big engine but it isn't noticeably lagging, no flat spots in acceleration so AFR not real lean anyway. It' does feel off but that was with cam degreed +4 and I am putting that back where it was. With oil pan off, bottom of rods would make it appear that at least a balance was "attempted"?

Either way, with the slow burn set up ( low CR + this cam shaft ), just want to get it to cool better with rpm.

FYI, radiator new and over sized, new and perfect/correct w/p, plenty of fuel to the carb, plenty of fan and well shrouded.

The cam/compression ratio combo is what I am down to having to fight based on earlier posts. I have removed all exhaust restrictions but just gotta get her back together for another test drive. I cannot improve on the engine internals at this juncture so am trying to overcome the combo that it has now.

Any thoughts on ignition upgrade that would help speed up the "burn" in the chamber? Has MSD distributor w/vacuum adv ( not points ) and just a typical looking "Blaster" coil.

topradman
Member
Member
Posts: 129
Joined: Fri Aug 02, 2013 8:12 pm
Location: Kansas
Contact:

Re: Can too little compression for a camshaft cause engine heating

Post by topradman » Mon Oct 16, 2017 2:55 pm

Zmechanic wrote:
Mon Oct 16, 2017 2:44 pm
PackardV8 wrote:
Mon Oct 16, 2017 11:48 am
Lacking that and in the vehicle, start with a name brand hand held IR temp gun to get more information as to EGTs at the header inlet.
Imho, for serious EGT readings, I'd stick to a thermocouple. IR guns can have all kinds of emissivity issues.
AGREE! Temp differences to some degree if surfaces are same/same but readings you know are not right on a regular basis as far as "correct" readings.

travis
Pro
Pro
Posts: 236
Joined: Sun Mar 15, 2009 5:31 am

Re: Can too little compression for a camshaft cause engine heating

Post by travis » Mon Oct 16, 2017 3:11 pm

Crank the timing up and drive it...it will tell you if there is too much advance or not (kicks back against the starter, pops back thru the carb, etc). Don't fixate on the number just yet. If you haven't verified that TDC and the timing tab/balancer relationship are correct, then what may look like 44* advanced might be actually be 20*.

The very first cam install I did was approximately 1000 years ago...installed a comp cams 260h in my trucks 307sbc that had 76cc 350 heads on it...for a total of about 7.75-1 compression. I did it in the truck on the side of the road out of necessity...I ended up installing it 1 tooth advanced by mistake. It had exactly the same issues your describing...overheating, super hot intake, boiling fuel in the carb, etc.

topradman
Member
Member
Posts: 129
Joined: Fri Aug 02, 2013 8:12 pm
Location: Kansas
Contact:

Re: Can too little compression for a camshaft cause engine heating

Post by topradman » Mon Oct 16, 2017 3:43 pm

travis wrote:
Mon Oct 16, 2017 3:11 pm
Crank the timing up and drive it...it will tell you if there is too much advance or not (kicks back against the starter, pops back thru the carb, etc). Don't fixate on the number just yet. If you haven't verified that TDC and the timing tab/balancer relationship are correct, then what may look like 44* advanced might be actually be 20*.
Unfortunately, not going to be something simple like that. Balancer is verified w/TDC, cam is fully degreed to know what's in it ( that's all 16 lobes btw ), not a tooth off. I am going to crank the timing up and drive it though.

Any thoughts on how to get a faster burn though ignition upgrade?

travis
Pro
Pro
Posts: 236
Joined: Sun Mar 15, 2009 5:31 am

Re: Can too little compression for a camshaft cause engine heating

Post by travis » Mon Oct 16, 2017 4:06 pm

What was the cranking compression numbers? How much idle vacuum?

Unless there is a physical problem with the existing ignition system, changing ignition systems is going to do little to nothing.

travis
Pro
Pro
Posts: 236
Joined: Sun Mar 15, 2009 5:31 am

Re: Can too little compression for a camshaft cause engine heating

Post by travis » Mon Oct 16, 2017 4:32 pm

I did a quick search on the 359 heads...they are later model 427T heads, probably 2.06/1.72 valves, and somewhere between 103-113cc chambers, so the compression shouldn't be too bad, unless the pistons are a mile in the hole.

topradman
Member
Member
Posts: 129
Joined: Fri Aug 02, 2013 8:12 pm
Location: Kansas
Contact:

Re: Can too little compression for a camshaft cause engine heating

Post by topradman » Mon Oct 16, 2017 4:43 pm

travis wrote:
Mon Oct 16, 2017 4:32 pm
I did a quick search on the 359 heads...they are later model 427T heads, probably 2.06/1.72 valves, and somewhere between 103-113cc chambers, so the compression shouldn't be too bad, unless the pistons are a mile in the hole.
I was actually assuming it was between 113 & 118 cc, maybe more? IF the deck height is zero, that puts me around 8.5-ish. I cannot find anyone who knows what those chambers cc to for positive. The cam seems to be spec for more around the 10:1 CR.

I knew they were little valves and off of 427 tall deck.

cuslog
Pro
Pro
Posts: 372
Joined: Tue Apr 13, 2010 9:08 pm
Location: BC, Canada

Re: Can too little compression for a camshaft cause engine heating

Post by cuslog » Mon Oct 16, 2017 9:34 pm

I recently helped a friend with a 350 sbc with a 6-71 blower on it. Headers were glowing red hot at idle, intake and blower were so hot the gas was boiling in the 2 carbs. Ignition timing was locked at 16 deg. Cranked it up to 32 deg. -- no more glowing headers but still running hot and very hot manifold -- still boiling the gas. Took it to the track next week, running full exhaust -- white smoke trailing out one side -- took exhaust off - no more white smoke and running cooler. Shake exhaust pipe, pound it on the ground --out comes a mouse nest and dead mice !
Not enough ign. timing can make them run hot, so can severe exhaust restrictions.

Geoff2
Expert
Expert
Posts: 581
Joined: Mon Nov 09, 2015 4:36 pm

Re: Can too little compression for a camshaft cause engine heating

Post by Geoff2 » Tue Oct 17, 2017 5:28 am

You have a few factors working against you, which all conspire to make for a hot running engine.

- low comp ratio. Two factors here. Bigger chamber, more surface area to absorb heat & put heat into the cooling system. Plus, low CR takes more time to burn, so metal is exposed to heat for longer time; double whammy!
- poor cam choice. Too much overlap, means engine does not make god low speed tq. Engine is not efficient at low/cruising rpms. Result is engine has to work harder, creates more heat.
- nowhere near enough ign timing. Low CR needs a looooooooot of initial timing to help the slow burn of LC & it needs a little more total timing as well. At cruise, a LC engine with the above poorly chosen cam may need as much as 55-60* of total timing: init + centri + vac adv = 60.

joe 90
Guru
Guru
Posts: 1991
Joined: Tue May 27, 2014 4:02 am
Location: The land of the long white cloud

Re: Can too little compression for a camshaft cause engine heating

Post by joe 90 » Tue Oct 17, 2017 6:16 am

My method was to get it warmed up, fiddle around with the static timing advance, idle mixture and idle air to give the best vacuum at the lowest RPM.
Then back off the timing slightly until the RPM begins to drop.


That's using guesswork with only a vacuum gauge and nothing else.


That gives a baseline for idle .
No point in doing anything else if it won't idle right.
Then you can put the timing light on it and see what it reads.

User avatar
MadBill
Guru
Guru
Posts: 12624
Joined: Tue Nov 15, 2005 10:41 am
Location: The Great White North

Re: Can too little compression for a camshaft cause engine heating

Post by MadBill » Tue Oct 17, 2017 4:26 pm

2X. That last step makes quite a difference to idle stability and load tolerance.
Felix, qui potuit rerum cognscere causas.

Happy is he who can discover the cause of things.

DaveMcLain
Guru
Guru
Posts: 2683
Joined: Thu Jan 06, 2011 8:57 am

Re: Can too little compression for a camshaft cause engine heating

Post by DaveMcLain » Tue Oct 17, 2017 4:41 pm

Geoff2 wrote:
Tue Oct 17, 2017 5:28 am
You have a few factors working against you, which all conspire to make for a hot running engine.

- low comp ratio. Two factors here. Bigger chamber, more surface area to absorb heat & put heat into the cooling system. Plus, low CR takes more time to burn, so metal is exposed to heat for longer time; double whammy!
- poor cam choice. Too much overlap, means engine does not make god low speed tq. Engine is not efficient at low/cruising rpms. Result is engine has to work harder, creates more heat.
- nowhere near enough ign timing. Low CR needs a looooooooot of initial timing to help the slow burn of LC & it needs a little more total timing as well. At cruise, a LC engine with the above poorly chosen cam may need as much as 55-60* of total timing: init + centri + vac adv = 60.
Most of the time the overlap isn't the problem its the opposite. Late intake closing and early exhaust opening are the problem especially at low speeds.

User avatar
amcenthusiast
Member
Member
Posts: 153
Joined: Mon Aug 15, 2016 10:56 am
Location: Central Texas
Contact:

Re: Can too little compression for a camshaft cause engine heating

Post by amcenthusiast » Tue Oct 17, 2017 5:56 pm

Get a Chilton's Repair Manual and follow the flow chart in the troubleshooting section.
XRV8 Race Parts > for AM's '56-'67 Rambler V8: http://amcramblermarlin.1colony.com/favorite_links.html

jeff swisher
Expert
Expert
Posts: 993
Joined: Wed May 23, 2007 11:13 am
Location: yukon ok.
Contact:

Re: Can too little compression for a camshaft cause engine heating

Post by jeff swisher » Tue Oct 17, 2017 6:02 pm

I have ran huge cams with low compression and never had your problems.

I did build a 60 over 350 that ran hot no matter what. 200-215 almost all the time.
I tried different fans and mechanical with electric pushers.

Radiator was a rebuilt 3 core copper brass Larger than factory.
It began leaking and I got a new one from the local parts store.

With the new one it ran 140 F I was amazed..Both of them looked to flow the same amount of water by looking into them with cap off.

So no more rebuilt ones for me.

I assume the fan blades are not all tucked inside the shroud..As you know you need some of the blade to be outside the shroud.

I seen a guy install reverse rotation pump on regular rotation fan.. spun the pump backwards.

I would resort to pulling the back of the water pump cover off and take a look.

Have you tried No thermostat? I boil my thermostats to check them and the flat washer area gets a hole or 3 drilled into it.
My 57 chevy runs warmer than I like down the highway at 85 MPH and I resorted to propping the rear of the hood open 1"

That fixed it. Could not expel the air that was being passed through the radiator with all the inner fenders and the newer style exhaust manifolds blocking the exit.

topradman
Member
Member
Posts: 129
Joined: Fri Aug 02, 2013 8:12 pm
Location: Kansas
Contact:

Re: Can too little compression for a camshaft cause engine heating

Post by topradman » Tue Oct 17, 2017 6:33 pm

MadBill wrote:
Tue Oct 17, 2017 4:26 pm
2X. That last step makes quite a difference to idle stability and load tolerance.
Ok, set base timing @21 btdc, w/mechanical all in 41 btdc @2850 rpm, add vacuum advance 60 btdc @2850 rpm. Holds 15" vacuum @ idle so idle timing 40 btdc. Engine does good for awhile. Ambient today is only 82F. Drive for about 23 miles and engine temp gets to about 190F, (recap, no thermostat so would've expected temp to hang much lower) turn around to come back, gets to 195F and boils fuel out of the carb again 2 times on the way back at 190-195F!!??? (recap, have Air Gap manifold so no crossover, 1/2" phenolic spacer + heat shield ) There was no detectible engine knock while driving. IF my LM2 was worth a damn ( locks up off and on regularly ) I would say light load cruise AFR runs about 11.5-12.5ish @ 60 mph around 2650 rpm. If I slow down to about 50 mph and just cruise, temp comes off a bit and AFR hangs around 12.5-13+. ( I am very disgusted with this brand new Innovate LM2 as much as the car itself! )

Thoughts????

Post Reply