I have a blown head gasket on the 350 sbc in my 51 Chevy. I am trying to decide if I should have the heads machined flat, or if I should try to find some aluminum heads. The motor is from an 88 Suburban with 68k miles. Money is the biggest factor and I am not familiar with costs to get machining done. If I get a set of used heads though, I may have to get them machined anyway. Thoughts?
not sure the cost out your way.. but i just had a set of heads for a v6 windstar checked for crackes and re-surfaced for 125.00 last week..
Just because you blew a head gasket doesn't mean they are warpped. Have you checked them with a straight edge?
is it that obvious if they are warped? I dont really have anything thats super straight. Maybe I can find a peice of glass.
First question you should ask yourself is what is your budget, then ask yourself what do your want to do? Do you just want a little bit more squeeze? your cam whats in it or are you changing it. I mean bottom line is most shops will charge a pretty penny to completely redo a set of heads. that includes guide liners if the guides are worn a couple valves replaced those that are under spec, installing hardened exhaust seats, machine for pc seals, install screw in rocker studs with guide plates, and setting the new springs, resurfacing, shot peening and magnafluxing. I mean a trip like that puts you upwards of 700-900 bucks. For that you could get a new set of assembled iron eq heads for that. and if you put a nice new set of heads on you might as well do the cam, and, and, and. this process gets out of control for me. OR if its a relatively mild motor near stock or with a small cam with flat top or stock dished pistons, I would just pull the heads off wash them up, put a new set of mild springs on (the summit spring and retainer set is $57 right now), lap the valves (while checking to see that none of the guides are too wobbly), get the heads minimally resurfaced ($60-70 at most shops), and put them back on with a set of felpro steel shim gaskets (q7733sh1 $20 for the pair) to get your extra squeeze, readjust everything back up and call it good to go.
The motor is an 88, so I wont need hardened seats. Its bone stock with 68k limes on it. Its only 7.5:1 compression, so I would like to get them shaved a bit. My buddy can reassemble them and set them up for me for free. Then I would like to put the steel gaskets and a small cam in, noting to crazy though since I have a 2:43 rear end and a stock converter. They may not need to be machined at all, but I figure with a blown head gasket, they probably should be.
It wont be obvious and I wouldn't use glass to check it. If you clean the surface real good, a decent machine shop in your area can check them for warpage and tell you if they really need surfacing.
My all time favorite baby cam for a mild 350 with iron heads is a comp xtreme energy hyd flat, ground on a 108 LCA degreed in at 104 intake centerline. It sound awesome, makes great torque and pulls 13 inches of vacuum. Whats not to love but i mean you can pick whatever you want.
I'm not sure where in so-cal you are, but I'm having work done on my motor at www.perfectengine.com They are in LA, near downtown. They might be able to give you a quote over the phone for machining your heads. They seemed very knowledgble to me when I talked to them.
A nice straight edge and some feeler gauges are a good way to check for flatness. Both are relatively inexpensive and a good addition to the tool collection. As far as the tolerance on flatness...better ask someone else.
To be honest, don't assume that the head gasket 'blew' because the head is warped. Most older engines I've seen with leaky head gaskets is because the head gasket corroded through. In most cases, shops just plane all of them that come through the door as a feel-good preventative measure for the customer....and I'm sure to add a few $$$ to the bill. Also some shops now instead of the dip tank, are using a ultra-high tempature oven to basically cremate any gunk on/in the head to clean it. Then we'd check and tell the customer the head is warped and needed to be re-surfaced. What wouldn't be warped after being subjected to such heat? Now, in retirement I have a old 60's era Sioux valve tooling (seat grinding and valve resurfacing) and do my own.
Why do you have such low compression? You shuld have 8.3 or more for that engine. Whe you take the intake manifold off see if you have a roller cam ready block. You might want to upgade the cam if you do have it roller ready.
Unless you are building a monster take your stock heads and have them faced. Its not real expensive. Trick heads are a big investment for one unless you are serious about going fast.
Just replace the head gaskets (both of them) with a regular Felpro type (composite not steel shim) and put it back together (after making sure the head isn't excessively warped or cracked). The composite gaskets will compensate for some warpage. There is no way your compression is that low to begin with. If you want cheap, that is the way to do it. Put the key back in a drive it. I really doubt you want a "cam" in it with only 2.43 gears and a stock convertor. As for converting it to roller, make sure the lifter bores accept factory roller lifters ... some of the "factory roller" blocks won't work because of odd lifter bores.
most iron heads wont warp unless you run them for a while after you blow the gasket. aluminum heads eat the material between the cylinders when they blow the gaskets. i definetly sugest steel shim head gaskets with copper coat, its the only thing i run on my small blocks.
I agree with him. Check the heads to see if they are actually warped or not or have them checked and get a set of good FelPro composite head gaskets that will seal. Unless I was building a motor specifically to race and needed the compression ratio to be just right on the money I'd shy away from the steel shim gaskets. And laying the head on a sheet of glass or other flat surface won't accomplish anything you need to use a good straight edge and feeler gauge and check it with the straight edge across the surface of the head in several different angles.
Are we sure the head gasket is blown and not the intake leaking. I have seen more intake leaks than blown head gaskets. Just asking.
i have checked heads by holding a straight edge on them and holding them up to the sun, kinda redneck, but if i were you i'd have them milled down to raise my compresion ratio, .030 should be ok and not effect your intake fitting properly, i wouldnt use a steel gasket now days but then i have in the past.
I got a quote yesterday for them. It included a magnaflux, hot tank, machining and a 3 angle valve job. $240 I will call around more today to see what other prices are around...
You might get a better deal with a set of exchange heads, but $240 isn't that bad. Most older non-chain auto parts stores provide this service. I've gotten many sets of heads and crank regrinds that were good to go off the shelf. Bob
$240 would be good around here, I suspect it's even better for So-Cal. I wouldn't go with exchange heads. Too many pieces of shit turned in a cores.
I went to a shop that a few of my buddies recommended and know the owner. Got the head gone thru for $120. Its nice to know people who know people!
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