Just Snooping Around Under the Hood

[32witha409]

I had a small VC leak that I wanted to fix, so this evening I pulled the cover and here is what I found.
1147 heads, D3060 date code (makes me happy). Valve springs installed @ 1.761 and 142 pounds seat pressure and have a 279 lb./inch spring rate.
To I guess more evidence that the deck stamping is correct and this could have been a 335 horse.
Tomorrow I plan on doing some limited cam mapping, at least lobe lift measurements.
And of course some pictures.

 

[oldskydog]

What is the suffix code on your block and are these heads original to the engine?

 

[32witha409]

I don’t know if they are original to this block but certainly could be. Engine numbers

Front Pad: T0630FH
Date Code: F2160

 

[oldskydog]

I don’t know if they are original to this block but certainly could be. Engine numbers

Front Pad: T0630FH
Date Code: F2160

You have a 350 hp engine that was not called 350hp until the 61 model year but it was the exact same engine even though it was marketed as a 335 hp engine in late 1960.

http://www.348-409.com/forum/threads/1960-348-high-perf-engine-changes-tsb.27102/

 

[32witha409]

Very interesting and thanks Cecil, Your GM docs have been pinched and saved in my library.
The block, and heads date right I think, somewhat reasonable to date the engine with my Impala at late June 60 build date.

 

[Skip FIx]

Man that valve spring tester is fancier than my Rimac!

Map your lobes or total valve lift 10-15 degrees BTDC and ATDC as that is where V-P is the closest. You can use a light spring and a dial on the retainer then at each point push down the valve and see how much V-P at each spot.

 

[Gofish]

You have a 350 hp engine that was not called 350hp until the 61 model year but it was the exact same engine even though it was marketed as a 335 hp engine in late 1960.

http://www.348-409.com/forum/threads/1960-348-high-perf-engine-changes-tsb.27102/

Two years ago I met a man from Washington with a 1960 El Camino at a Palm Springs Cruising Association monthly show in Palm Springs, CA. He campaigned the car in the 1/4 mile when it was new and told me he would not have been competitive except he had the 350 HP 348, but it was badged a 335 HP. An interesting person with an interesting story and a great car. Maybe one of you on this forum!

 

[32witha409]

Mapped the TDC valve events on. Clearly the cam is advanced.

Intake
@10 ATDC .045 (would be worried if this valve was not opening) I checked this event several times just to make sure.
@ 15 ATDC .180
Exhaust
@10 BTDC .130
@15 BTDC .200

If we corect the 10* events for the intake and exhaust, this thing is close with the average at .088" P-V
Lobe lift is .310 on both. Can't find a match anywhere, show cars doesn't list anything. I'll dig through the Comp lobe catalog and see if anything jumps out at me.

My measuring springs after the reassembly process had started.

 

[32witha409]

Decided to have a look in to the cylinders, to see if there are any valve marks on the pistons, and to see what pistons are installed.
Look like a standard LP .030 pistons. Can anyone guess what the net compression ratio might be? Cylinder walls look great. No valve marks that I can find.
Photos. Sorry for the crappy image quality, I have a cheap endoscope camera.

 

[Don Jacks]

Those look like the cheap,cast 10.5-1 pistons.No doubt that they're cast.

 

[32witha409]

I thought they looked like 9.5 universal position slugs. Like rock auto sells. But with 1147 heads what would you estimate CR be? Given the lack of valve reliefs, they can’t be high compression units.

 

[Don Jacks]

Depending on the deck height and head gasket clearence,from 8.8 up maybe 9.1.The difference between the 379 and the 1147 as far as the cc area around the valves is maybe 2-3 cc's witch will translate to about .36 off a point with the 1147.It's likely got a very high quench clearence.Maybe I need glasses as I thought that I saw a valve notch for an intake valve in one of the pictures is why i said that they were 10.5's.

 

[32witha409]

Man that valve spring tester is fancier than my Rimac!

This was a non working QA piece from work that I knew I could repair, It cost me $50 and remove the shorted rechargeable internal battery. Super handy because I can zero the stroke measurement scale on the valve spring installed height gauge and compress the spring to the zero point. It gets used a lot.

 

[32witha409]

Another question to the collective mind of 348-409.com, should I reconstruct the coolant bypass on my Impala? The Impala, despite a very sanitary radiator 4 row copper and cooling system, seems to heat up quickly 215-220 after jumping on the freeway eventually cools down once the speeds mellow and the road levels off. Wondering is the coolant trapped behind the thermostat and not circulating through the bypass is causing issues with hot spots and or delayed thermostat opening? The PO blocked the bypass port on the water pump and the heater / bypass Tee fitting is missing.

I understand the purpose, but on my roadster, as soon as the thermostat would open, the water pump would become air locked. an the engine would go through odd thermal gyrations. The only thing that fixed it was to block the bypass and drill a couple of 1/8 holes in the thermostat. I'm running the mid height truck pump on it so it might have been more sensitive to trapping air.
I don't suspect this was a problem on production cars.

 

[Don Jacks]

I'd suggest drilling the thermostat like you did on the 32.If that fixes it,the you can either put the bypass back in,or simply leave it alone since it's fixed.

 

[32witha409]

Around town including blasting up a long high grad hill it sits around 180 even with 95+ degree temps.

 

[427John]

So at freeway speeds only?And it goes up quickly once you get to freeway speed?

 

[32witha409]

Here's what is seems to do, and stated above plus a bit more clarity.
"Around town including blasting up a long high grade hill it sits around 180 even with 95+ degree temps", head on to the freeway which from this on ramp is a slight up hill and while not sparing the spurs, accelerate to about 65-70 true, the temp stays steady at 180-185. Continue down the road for a few minutes more, look down and the temp is at 220. Throttle to maintain this speed on the slight incline is about 50% open on the center carb only. Hop of 3 miles later and it is tapering off to ~ 210, head back on the freeway and it recovers to 190 and continues to drop to 180 by the off ramp. Total drive both directions ~12 minutes on freeway, total drive including town driving ~ 25 minutes.

While I have just reintroduced the vacuum advance, the same thing occurred before. Total mechanical timing is 34 deg all in at 3000.

Carb main jetting verified at .060 in all 3 2g/2gc's which is basically stock. During the snooping around I did last weekend, I had the plugs out to ease rotating the engine while accomplishing cam measuring, they were very clean, I feel to clean, like super white lean. Ground electrodes showed a little heat.

 

[Don Jacks]

Yes,it's a little lean,but not that bad.This sounds like a water flow issue . Change[and drill] that thermostat as it's acting like one that's sticking.

 

[32witha409]

Will do, thanks Don!