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:

Can too little compression for a camshaft cause engine heating

Post by topradman » Sun Oct 15, 2017 11:03 pm

Ok, yeah it's me and still fighting a heating problem. 461 BBC, GM iron open chamber oval port casting #14092359. I cannot find any info on chamber cc's for this head anywhere and engine is assembled. Has flat tops w/only 2 intake valve reliefs per piston, gaskets 0.027 thick x 4.320 hole size. If chambers are around 113cc @ zero deck height I guesstimate CR around 8.9:1 but if chambers are around 118cc, maybe 8.4:1 CR. Nearest I can tell from trying to degree the cam w/engine assembled in the car ( using pushrods for measuring and has hydraulic lifters so don't totally trust readings to be on the dime ) specs are about 109 lobe separation, about 229 @ 0.050 intake/exhaust duration , 0.544 valve lift intake/exhaust which specs out pretty close to a Lunati 10110424 camshaft.

These small open chambered oval heads #14092359 still have 2.06 intake/1.72 exhaust valves. Question being, with this potentially low CR ( chamber cc ??? ), could this camshaft cause this engine to struggle getting exhaust out of the cylinder head or have possible valve intake events that could encourage an overheating problem at sustained cruise rpms of around 2600 or so?

I can jack up the ignition timing to around 44 btcd base (!!!) and get her to cool down wonderfully at 2600 rpm sitting in the shop but do not want to drive her this way. I advanced the CAM timing up 4 degrees and backed the ignition timing back to 16, then 14, then 12 btdc but it didn't help much so I have the cam timing back to straight up now and after going through the in the car degree process, the afore mentioned cam specs are what I came up with for straight up cam timing.

Thoughts on this cam for this engine with potential low CR causing heat??
Anyone know for sure what cc this head chamber is?? ( looked everywhere for hours )

moparjohan
New Member
New Member
Posts: 7
Joined: Thu Feb 24, 2011 5:37 am

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

Post by moparjohan » Mon Oct 16, 2017 2:55 am

You will need all the ignition timing you could get!
You have a big port, and a "slow" combustion chambers, the slow burn rate will make the engine run hot.
I would lock out the distributor and run it att 40deg.

Johan

kimosabi
Member
Member
Posts: 134
Joined: Sat Feb 22, 2014 5:01 pm

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

Post by kimosabi » Mon Oct 16, 2017 5:00 am

44 initial puts you around 60 total? Like Johan posted, lock the distributor. If it cools down "beatifully" on idle with 44 degrees you know you're in the ballpark somewhere.

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 9:12 am

Than I assume if this was a 10-10.5:1 CR motor I would not be having this problem?

DaveMcLain
Guru
Guru
Posts: 2671
Joined: Thu Jan 06, 2011 8:57 am

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

Post by DaveMcLain » Mon Oct 16, 2017 10:07 am

Most of the time when you have low compression and the engine isn't cammed correctly you'll have a very high EGT to deal with. It'll want to cook the headers, plug wires etc and sometimes it can make the engine run hotter than it would with higher compression and or the right cam, yes. With lower compression there is more heat later in the power cycle of the engine so you expose more cylinder wall to that heat and you also have more heat when you open the exhaust valve to dump it. Adding a bunch of timing won't necessarily help all that much but it might get the EGT down a little.

Walter R. Malik
Guru
Guru
Posts: 3400
Joined: Tue Jul 24, 2012 11:15 am
Location: Roseville, Michigan (just north of Detroit)
Contact:

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

Post by Walter R. Malik » Mon Oct 16, 2017 10:31 am

topradman wrote:
Mon Oct 16, 2017 9:12 am
Than I assume if this was a 10-10.5:1 CR motor I would not be having this problem?
Probably less of the problem.
Using a fuel with lower octane and faster burn time will help a little.
http://www.rmcompetition.com
Specialty engine building at its finest.

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 10:51 am

Ok, so with this combination, ANY exhaust restriction would aggravate the problem more as well I assume? We just found some home made conical shaped exhaust cones stuffed in the back side of the exhaust tips and the mufflers have what looks like the spiral type ( like an auger bit ) inserts with a 1" tube through the middle.

This vehicle gets super high under hood temps when throttled up. Headers are coated and coating still looks good. They are shorty type and design is more like a 4 into one manifold with center dump.

This engine will boil gas in the bowls at only a 205F engine temp and that is with an air gap manifold, 1/2" phenolic spacer and a stainless heat shield!

I put an air tube on the carb to get induction air from about 5 ft away from the carb while running in the shop and it made no difference so I wonder about reversion heat, possibly because of the perfect storm of slow burn configuration, cam choice, stupid homemade conical exhaust inserts, spiral insert muffler choice, etc....??

Thoughts on exhaust aiding and abetting high under hood temps, thus higher engine temps?

This job has kicked my ass more so than any overheating problem I have ever dealt with!

PackardV8
Guru
Guru
Posts: 5030
Joined: Sun Jul 30, 2006 2:03 pm

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

Post by PackardV8 » Mon Oct 16, 2017 11:48 am

This job has kicked my ass more so than any overheating problem I have ever dealt with!
Like looking in a dark room, trying to find a black cat which isn't there.

Ideally would be to put it on an engine dyno with EGT readouts in each cylinder of the headers. 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.
I can jack up the ignition timing to around 44 btcd base (!!!) and get her to cool down wonderfully at 2600 rpm sitting in the shop but do not want to drive her this way.
Maybe it's trying to tell you something here and you aren't listening. But half here will tell you to lock it out at 40 and the other half will recommend taking the time to build in a centrifugal and vacuum curve which will give 50 - 55 degrees at level highway cruise, the way the OEMs do it with computers.
This engine will boil gas in the bowls at only a 205F engine temp and that is with an air gap manifold, 1/2" phenolic spacer and a stainless heat shield!
What's with that? Is there an exhaust heat crossover passage in the intake?
Jack Vines
Studebaker-Packard V8 Limited
Obsolete Engineering

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 12:05 pm

Like looking in a dark room, trying to find a black cat which isn't there
.

Good analogy!
Ideally would be to put it on an engine dyno with EGT readouts in each cylinder of the headers. 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.
There are about a million reasons I cannot do this as it is a customer car. If it were mine I would pull the engine immediately. Actually, if it were mine, this engine configuration would not be in this car at all, not with that CR or those heads! Since headers are coated, accurate egt's are very hard to surmise. I get temps of only around 500F with the coating and tight spots to try and get a good reading. Engine is packed in the engine compartment. Inner fenders prohibit a good shot at some of the cylinders.
Maybe it's trying to tell you something here and you aren't listening. But half here will tell you to lock it out at 40 and the other half will recommend taking the time to build in a centrifugal and vacuum curve which will give 50 - 55 degrees at level highway cruise, the way the OEMs do it with computers.
I am a big fan of mid to mild street motors running vacuum advance with dynamic responses for timing and have had great success in the past running vacuum advance on manifold vaccum.

There is no egr crossover as it has an Air Gap manifold so I have ruled that out. I still wonder about reversion with lazy combustion chamber and low CR. We are going to put the pan and timing cover back on, reset the rockers (again) and see how it behaves with the stupid home made conical exhaust inserts and the auger style mufflers removed. I may also go up a jet size on the primary circuit for mid throttle ( New Quick Fuel 780 VS carb ), then jack the timing back up and see how it drives and cools. Problem is, it's getting so late in the year that ambient is dropping so gets harder and harder to tell if we made much headway when we drive the car.

DaveMcLain
Guru
Guru
Posts: 2671
Joined: Thu Jan 06, 2011 8:57 am

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

Post by DaveMcLain » Mon Oct 16, 2017 12:11 pm

Maybe you should also check to make sure that the cam is really in time and not put in the engine lined up with the key on the bottom pulley.

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 12:37 pm

DaveMcLain wrote:
Mon Oct 16, 2017 12:11 pm
Maybe you should also check to make sure that the cam is really in time and not put in the engine lined up with the key on the bottom pulley.
Yeah, just degreed the whole cam yesterday ( all 16 lobes.... in the car ... pita! ) to see if there was anything wrong with the grind. Crank keyway is correct. Already tried to run the engine w/4 degrees advanced and it didn't run as good as it did straight up on the gear. Couldn't run as much timing either and did not help with cooling. Intake lobe center is 106 with gear located straight up ( no advance or retard, 3 keyway crank gear, no spacers or mods on the cam gear ) so I am putting it back like it was.

tresi
Member
Member
Posts: 167
Joined: Sun Mar 24, 2013 10:10 pm

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

Post by tresi » Mon Oct 16, 2017 2:23 pm

Let us know how pulling those cones and augers out work.

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 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?

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 2:38 pm

tresi wrote:
Mon Oct 16, 2017 2:23 pm
Let us know how pulling those cones and augers out work.
Oh trust me, I will post all my findings here as well as the "41 Willys overheats" thread. Nothing worse than reading 5 pages of a thread and then no fix ever posted at the end!!!

Zmechanic
Pro
Pro
Posts: 282
Joined: Wed Oct 24, 2012 9:33 am
Location: Austin, TX

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

Post by Zmechanic » 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.

Post Reply