Overheating BBC 468 Pro Street Willy's Coupe

[topradman]

Topradman-

Wow is right. Please don't let that stop you from giving us an update.

Thanks rp930, no way will I not update when finished and running! Heads should go on tomorrow so will have results soon!

[topradman]

Here are photos and part numbers of the new gaskets and a photo comparison of a parallel flow versus the hybrid series flow gasket design I came up with. Heads are going back on now. GEN V 4 bolt block, MARK IV cylinder heads. Results coming soon!

[rp930]

I guess we’ll never know...

[topradman]

Ok, has been very busy at the shop so getting back to this overheater! Installed the new Cometic gaskets, reassembled with an air gap manifold to help with the car boiling over. Drove around town for an hour at cruise speeds and temp was great! Take it on the high
way and as per usual, it took longer but.... the temp began to climb. Ambient was around 95F. After 20 miles it was at about 205F and if it would stay there, that would be fine, however, it continued to climb until carb boiled over fuel ( that is with an air gap manifold, 1/2" phenolic spacer and a heat shield!!). Under hood temps are way up there! Sooooo. We surmise that basically, we may not be moving enough coolant at higher rpms as Meziere "55gpm" electric is static on coolant movement.

Installed serpentine drive with the best of the best Meziere belt driven water pump claiming "7-8 gpm more off idle than any competitor". I figured this would raise my idle engine temps a bit as I am sure no belt driven pump at idle will keep up with the Meziere electric but was willing to trade off some idle temps for better upper rpm cooling. After install, indeed the idle temps went up a bit, maybe 8F. I roll into the throttle and as I expected, the temps begin to go down which is normal, HOWEVER, it only drops about 2-3 degrees on the gauge and again, will slowly start to climb if 2200 or so, rpm is maintained. This is driving or setting still.

I wondered if the under hood temps were killing this build so I took a 90 degree x 5" elbow and tube and installed it on the carb. The induction air was now being pulled in from 3 ft. in front of the fenders and hood is open... same result!! Put a fan in front of the car to try and blow the heat out from under the hood some ( not going through the radiator ) and this was with the induction tube still in place. No change!!

Is it possible that retarded camshaft timing could be the culprit?? The car seems to run good, has plenty of get up and go. No flat spots on acceleration that I can sense. I am adding a video that shows manifold vacuum in relationship to rpm. I would think that as throttle is rolled open that vacuum would drop and it seems very strange that it acts like ported vacuum to me?? The carb is a new Quick Fuel 780 vacuum secondary carb.

All other potential problems I can think of have been addressed??? WTF!!!!

( I hope the attachment will load as a video ok?)

Does the vacuum correspondence to rpm seem normal to you guys??

[shoedoos]

Not that it helps, I wouldn't wish your predicament on my worst enemy....

[topradman]

https://www.facebook.com/10000593590894 ... 330960685/ Ok, seems like this short cut to FB might work for the video.
Doesn't the vacuum seem odd being manifold vacuum on how it behaves with rpm. Seems like it acts as though it was ported vacuum rather than manifold.

Could this indicate incorrect CAM timing?

[superpursuit]

Could it be that the airflow and heat just can't exit the engine bay or not sufficiently? Some mods may be necessary to accomplish this. I think your carby percolating certainly points to this.

[BigBlockMopar]

No worky on the FB link. Have to be member of their little group it seems.
YouTube always works for everyone.

Id the spring present on lower radiator hose?

I could agree with hot air no being able to leave the cramped engine bay.
A low front air dam might help on the highway like mentioned earlier. Creates a low pressure area behind it which help draw out hot air so fresh can enter through the grille more easily.

Maybe talk the owner into lovering the hood to vent air?

[topradman]

Ok, finally figured out how to upload video to Youtube for a short cut.... what a pain.... https://www.youtube.com/watch?v=C0stHfzlsYM
Try this and give me some feedback please. Does this act normal for manifold vacuum or could it indicate retarded CAM timing?

[rp930]

Vacuum looks normal. I would tend to agree with airflow out of the engine compartment.

[topradman]

Ok, just fired this dude back up, unhooked vacuum advance and set timing for highest manifold vacuum to see what happens. Have not run the car very long today, just enough to reset timing. Highest manifold vacuum at idle is 14 in/hg but that is with base timing at 45btdc!! Sooo... what do you all think. You hear about balancers being wrong but honestly, in 43 years of screwing around with old cars ( Grandpa gave me a 57 chevy when I was 12. Could only drive it around in the orchard and back and forth to my grandpas on dirt roads, lol ) I have never run into an incorrect balancer ever. Balancer ring is tight on the center and looks like oem GM.

The engine on this car has always had a slight vibration to it. I realize the 454 is externally balanced but is the timing mark different between it and other BBCS?

[BigBlockMopar]

How much advance does the vacuum-advance pull?
Say you put timing at 20° and then connect vacuum advance, where will timing end up?
Is the vacuum source on manifold vacuum or ported vacuum?

[topradman]

I haven't reattached the vacuum advance yet but with base timing 45 degrees btdc, the vacuum would add about 10 and the advance weights would add about 10-12 more so total would be 65-67 which is WAY too much.. unless the balancer is wrong or the cam timing is wrong. I think I need to remove the balancer to examine and if nothing wrong is found, remove the timing cover and start looking at cam timing. What are your thoughts?

I am a firm believer in manifold vacuum for advance.

[Old as Dirt]

What is idle rpm? Could the idle be high enough that the weak springs are allowing the extra advance and the weights not returning home?
What vacuum can? and only 10 degrees @ the crank is only 5 degrees at the distributor.. sure?
BBC's will tolerate around 52 degrees total @ cruise..
Think I would be around 26-28 degrees initial, 10 degrees max for centrifugal and 12-14 vacuum.. and make sure the vac can unloads when you romp on it so the timing goes back to 34-36 under a good load..

[BigBlockMopar]

< I got treed. Was typing while Old posted >

Intake vacuum is good imo. Makes for a cooler running engine, unless the cam is too wild.

I went through the topic but didn't see any advance numbers posted at first glance.

How much initial was the engine running on, during the video for instance?
Seemed like a very low engine vacuum at idle.
Was the vacuum advance connected?

Can you adjust more advance in the vacuum?
How about giving it 20° initial for a try, so it will (safely?) max at around 32° mechanical.
And idle with 30° or more with vacuum connected.