The Stupid Engine Questions Thread

[HotWheelsBurban]

Yeah, I remember you going through that. My mistake, I was referring to TBI trucks.

Well, the oil pressure sending unit going out, did inadvertently lead to getting the long crank/hot start issues rectified.
When it went bad, the "check gauges" light was coming on at idle and low RPM, and I knew it had good oil pressure (no noise!).

 

[1997]

what's the recommended 5.7 TBI head bolt procedure, clean and re-use or replace with new?
1995 GMC.
thx.

 

[PlayingWithTBI]

what's the recommended 5.7 TBI head bolt procedure, clean and re-use or replace with new?
1995 GMC.

When I went to aluminum heads from the old 193 cast iron ones, I bought a set of head bolts from Summit Racing, not ARP since I'm not running high compression. I used a thread chaser (not a tap) and put thread sealant on all bolts' threads (since they go into the water jacket) and assembly lube on the heads. YMMV

 

[Erik the Awful]

I'm running 9.7:1 in WCJr, and I just pulled the original bolts, cleaned them, and reinstalled them. They're not torque-to-yield.

That brings to mind a funny story - I hope you'll abide. A couple years back my race team took our BMW 325 to Barber Motorsports Park. On test-n-tune day a valvespring broke. The driver shut it down fast, and the valve barely tapped the piston. We found a spare head, but couldn't get a head gasket in Alabama on a Saturday. We got the head off, and the existing head gasket came off intact. The head bolts are torque-to-yield and we didn't have a spare set. We discovered the spare head didn't match, so we took a single valve and valvespring from the motor and swapped them into the original head. We fogged copper gasket spray all over the gasket and reassembled. Since we were scared of torquing the TTY bolts to their yield point a second time, we torqued them 10 ft/lbs shy of spec. We got it back together around 2 am. The next morning (a few hours later) we fired it up and it sounded nice! We left the cap off the radiator as it warmed up so we could keep an eye on the coolant. It was a good thing because as soon as the thermostat opened we saw chocolate milkshake in the radiator. That was the end of our racing weekend, and the cars were just lining up on the start grid. Now we carry a spare head gasket and TTY bolts.

 

[1997]

thanks for the explanation.
not that i'm cheap, just not sure of the quality of the bolts i'd be getting new.
i'll re-use then.

 

[stutaeng]

I've been watching this YT Chanel called Myvintageiron. Guy is really good, talks facts, explains things and best: no drama.

Anyways, one of the series of the SBC rebuild (he's got a TBI and a Vortec series) he says it's perfectly fine to re-use the head bolts. Just note the different lengths (there's 3 different lengths.)

They do recommend you use a thread restorer (chaser) for cleaning the threads; it's less likely to remove metal from the threads. But many folks just use a thread tap & die set.

 

[1997]

found the issue, still ran fine, no coolant loss, no regular blown head gasket symptoms ..... except temp guage rocketed to max temp in about 5min's, thermostat opened, back to normal. Repeat a few times, then good to go.

thoughts, #1 looks ok, 3,5,7 funky, most likely just head gasket or warped head or cracked head? Thx.

 

[stutaeng]

Don't the first 3 exhaust valves look "too" clean? Or are they white? What did the spark plugs look like?

 

[PlayingWithTBI]

#1 looks ok, 3,5,7 funky, most likely just head gasket or warped head or cracked head? Thx.

Or - all of the above? You're definitely burning something other than a normal air/fuel mixture. Time for a magnetic particle test (AKA Magnaflux). Or, new heads...

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Damn, prices have gone up!

 

[1997]

Don't the first 3 exhaust valves look "too" clean? Or are they white? What did the spark plugs look like?

they are pretty white and very clean. Plugs looked good, except 5, it was white like it was burning lean.