Is my 350 on the outs?

[tommy3horse]

Hi folks, owned my truck for 2 years, rebuilt the turbo 350 when I got it and tuned the 350 and been having a blast. On Monday I ran a local errand. Along the way she started "missing", running like it had a vacuum leak. I checked the vac sources from the intake and replaced all hoses and nipples. Still running like crap.
Today I pulled the plugs and #7 was black and wet. Wires are newer and seem fine. Cap and rotor newer, HEI. I pulled off the radiator cap for grins and found a brown frothy mess.
Head gasket or intake gasket? BTW, I go thru a lot of oil, like a quart every200 miles or less, but no smoke...even at startup. Thinking it may be sucking oil thru the intake somewhere via a bad gasket? Help

Alum intake
76 block

Thanks,
Tom

[TwoFiftyShifter]

Sounds like a possible bad head gasket. A quart in 200 miles is quite a bit of oil. Brown coolant is a telltale sign I would think.

[tommy3horse]

No doubt I gotta pull it apart. But then I have 882's and with them off it will be hard to ignore a valve job, seals in addition to having them milled flat, so like many of us, I am at the crossroads of the future of my truck...cheap out now, pay later or find a decent set of heads elsewhere?

Tom

[Marshy]

Vortec heads?

[geezer#99]

Flat cam!!!
Pop off the valve cover and watch the rockers for correct movement.

Brown crap in the rad might just be from a low coolant/water ratio.

[LongBox]

Is the brown crap in the rad kind of like a gel? If so, you got a mixture of oil and coolant. Lots of possible causes,none of them nice to think about. Could be head gasket, cracked block or head, leaky intake gasket.

Have you done a compression test? That's the start of the diagnostic process. Can also have the rad "wanded", which tells whether there is combustion gases in the coolant system.

[cleszkie]

What does your oil look like? If it looks like a frothy chocolate milkshake, then you have more work ahead of you than just replacing head gaskets and coolant.

[tommy3horse]

Oil looks fresh, no milky to it. I pulled the valve cover to see if the valve train was doing its thing. They look like soldiers, working as they should, quiet too. The #7 plug was black and wet, so to appease my inner child, I swapped it with another good one, still not firing.
I don't have a way to check my compression, but I need to, thanks Longbox.
Have I missed anything?

[Marshy]

Maybe your local auto parts store have a compression gauge you can use with a deposit. (Lend a tool)

[tommy3horse]

Ok, got off early today and gonna wheel the truck into the shop and begin the tear-down of the top end of the motor. Will let everyone know what I find with pics. I have a significant issue and not going to do a compression test...can't repair whatever it is from the outside anyway.

[tommy3horse]

Got it apart last night, dropped them at the machine shop first thing. They called, the head in question is toast, cracked. Vortecs here I come...?

[LongBox]

Based on what I know from driving my 98 5.7 Vortec, you are going to like the change. More power (Lots!), and better mileage. Are you going to try putting in an Fuel Injection system?

[Marshy]

Originally Posted by tommy3horse

Got it apart last night, dropped them at the machine shop first thing. They called, the head in question is toast, cracked. Vortecs here I come...?

Do it!

[tommy3horse]

Thanks Marshy and Longbox for the encouragement. No, fuel inj is not in the future here, but from an economical standpoint, it's a great idea. Marshy, you went through the same project, but I think yours went quite a bit further. Piston tops are incredibly clean and no ridge. The slugs are dished, but not too big. What kind of compression Can I expect...roughly, if I go with the Vortecs? I do have reason to believe the bottom end is up to it, oil pressure is great.

Tom

[Marshy]

Originally Posted by tommy3horse

Thanks Marshy and Longbox for the encouragement. No, fuel inj is not in the future here, but from an economical standpoint, it's a great idea. Marshy, you went through the same project, but I think yours went quite a bit further. Piston tops are incredibly clean and no ridge. The slugs are dished, but not too big. What kind of compression Can I expect...roughly, if I go with the Vortecs? I do have reason to believe the bottom end is up to it, oil pressure is great.

Tom

Vortec heads are 64cc's. I estimated my compression to be 9.6:1 on my engine. I have stock bore and the stock Vortec dished pistons with 0.035 quench distance (20 deck clearance and 15 gasket thickness). I assumed the heads were actually 63cc in my calculation after a skim cut and assumed the pistons were 12cc dish. I don't know how accurate those numbers are but my engine runs good with a 206/212 @ 0.050 cam that has 0.480, 0.489 lift.

We would need to know your deck clearance, what gasket you will use and what dish volume your slugs are to determine conpression.

Its anyone's guess about your bottom end. How many miles are on it and when was the last time it was rebuilt and how was it treated since the last time it was apart is going to determine if it will last with the new heads. You are taking off 882 heads IIRC so you are picking up compression just by dropping the combustion chamber by 10cc's. Got pics of the piston tops?

[tommy3horse]

Best I could do...

[tommy3horse]

I pulled the entire top end off the motor and it revealed a lot of very worn parts. Timing chain loose, lifters coming apart and one even cupped on the bottom, and likely a wiped cam lobe.
Thought about it for the past two weeks, rebuild or buy a crate motor. This morning, I decided to order a GM crate 350 and got a great deal on a "new" 350.
Now to clean up the mess from the autopsy and ready the engine bay for the new motor.
Thanks for the replies,

Tom

[TwoFiftyShifter]

Good idea. Which motor did you pick?

[tommy3horse]

GM#10067353, 195 hp base motor, alledgably capable of 260hp with a decent intake and headers. Got it for a lil over $1300, free shipping.

[tommy3horse]

Hello, the motor arrived in only 8 days, including Thanksgiving there in the middle. Looks great...well on the outside. Busy weekend upcoming, will have pics of the install.

[Ken B]

I ordered the same engine for my 70 Longhorn and put it in this past May. I updated to a new Pertronix ignition with a new Edelbrock intake and carb. I won't run headers, too much of a headache. I do have dual exhaust with Flow Masters. Got the engine in and it fired up with the first bump of the key. Excellent oil pressure... It runs excellent and has plenty of balls. I have about 2500 miles on it now. I can and do drive it anywhere and everywhere. I don't want to say much else because I don't want to jinx myself... I do still have the original engine which at some point I will rebuild and reinstall..

[68Stepbed]

Originally Posted by tommy3horse

Hello, the motor arrived in only 8 days, including Thanksgiving there in the middle. Looks great...well on the outside. Busy weekend upcoming, will have pics of the install.

What carburetor do you plan to use on this? Everybody always thinks I'm crazy, but a 500 Holley 2bbl works like a charm on those engines!

[72bowtiestepper]

500 CFM is plenty for this crate 350 if used for everyday driving. If using a 4 barrel carb, I would not use more than a 600.....many people overcarb and it kills performance.

[lsversaw]

$1300 with free shipping is a stone bargain. Where did you buy it?

I know I'm in the minority, but I like the original Quadrajets. They are harder to rebuild and tune correctly, which is why I think some Holley guys don't like 'em, and parts and info are scarcer than for Holleys. But they are arguably deliver a better mixture over a wider RPM range, and I like to keep things original-ish unless there's a reason to change. And the next time you hear someone trash talk Quadrajets, just say "yeah, not one of those GM muscle cars of the 70's ever ran wortha sh1t". OK, end of rant. For more Quadrajet info, see http://www.cliffshighperformance.com/.

Great thread.

[tommy3horse]

Thanks, I have a Weiand "Steath" duel plane and and Edelbrock 600, using a lower pressure pump that should put out about 5.5 lbs. Of course long tubes and 40's, should sound decent. When the warranty expires, maybe Vortec heads and a hotter cam. I will have to see and feel this one first, I think my old 350 was ailing for awhile even tho is ran great and started right up, this one should make more power and use a hellava lot less oil.

Tom