186/2.02 head rebuild/worth it?

[robert leazenby]

I removed my heads, took them in for inspection and was floored at the estimate for a re-build. $960.00 for new intake valves, hardened exaust seats, new guids, new springs, three repaired intake manifold threads, and mounting bolt contact area re-surfacing. (Some of the casting has chipped away from incorrect torqueing, yada, yada.

This seems a little high but want to keep the original heads but don't know if I want that at all costs.

Does this price seem fair. I do know the guy is of great reputation and knows what he is doing. He tells me most of the cost is for labor.

[Jim T.]

Re: 186/2.02 head rebuild/worth it?

I don't know what year your car is Robert, or what you are going to use it for. If you are not going for max points on NCRS judging and really just like to drive and enjoy your Corvette I suggest a new set of heads from GM. The fast burn cast iron heads that I have read about improving the hp on a smallblock by about 30 are available from Pace and Scroggin Dicky for about $450. That is for two brand new heads. You will have to use a different intake, the bolt pattern is different for these heads.

[robert leazenby]

Re: 186/2.02 head rebuild/worth it?

my fault for not expanding more. the car is a 1970 350/370hp. Not planning on going for max points at this point but want to keep the LT-1 original. I know I can find cheaper heads, but was wondering if that price was reasonable for all the labor that they would take.

[Duke W.]

Re: 186/2.02 head rebuild/worth it?

If those are the original heads to your LT-1 I would go ahead and have them rebuilt; '70 LT-1s are rare and desireable i.e. valuable, and non-OEM heads might be considered sacrilege. From the price and the scope of work I suspect you are dealing with a quality shop, but you could get another estimate.

As far as the work is concerned you might consider going without the "hardened" exhaust valve seats. There have been reports of some coming dislodged, though if they are installed with the proper interference fit, they should not dislodge unless the car is severely overheated.

Unless you plan on racing it or towing a trailer, I don't think that valve seat recession will be an issue, but you could also run a bit of leaded racing gasoline for the first few thousand miles. That will provide some insurance.

I'd also suggest some pocket porting and port matching, which should yield at least five percent more top end power. I just hate to put together heads with that crude ridge above that valve left over from the original tool cut to rough form the valve seat!

Duke

[George J.]

Re: 186/2.02 head rebuild/worth it?

I do not know if these are the same heads as on my '65 fuelie, but if they are DO NOT try to put hardened valve seats in as you risk hitting the water jacket and creating a very expensive door stop. George #31887

[Bill#34162]

Re: 186/2.02 head rebuild/worth it?

I recently took the original 300 HP heads from my 70 to the machine shop. From your description it sounds like yours need roughly the same amount of work as mine do. The estimated price for mine was around $850.

[Wayne K.]

Re: 186/2.02 head rebuild/worth it?

I had about the same amount of work done by a respected shop here in WI on my 67 L79 heads and it cost $650. I went with the hardened exhaust seats as I wanted to run pump gas and that is what they suggested I do. I would work with your original heads if you know you have an original motor for the same reasons that Duke gave.

[robert leazenby]

To seat, or not to seat.

Thanks for all the input gentlemen. The guy has a great reputation and was recommended by another corvette guy. I think you can tell a lot about someone by their shop, not too many places you couldn't eat at his place. That's why I wanted to ask others instead of just taking my heads back and insulting him.

He showed me everything about my heads, what the specs called for and why he wanted to do what he said. He mentioned the risk of installing exaust seats, so I guess that is the only decision I've yet to make.

Could you share the pros and cons of the seats. I don't plan on racing the car except for the occasional mustang stop light to stop light. I never take the car to the 6500 red line, max usually about 5500 (very rarely). No trailer towing. (A hitch on the back of my car?, I had a hard time drilling a hole in the back of my duallie for a hitch)

I plan on putting in composite gaskets to lower the compression just a tad.

[Joe L.]

Re: To seat, or not to seat.

robert-----

If the heads are in good shape, I'd have them rebuilt. For quality work, I think that the price is about right, especially if you live in a relatively high cost urban area like I do (San Francisco Bay Area). A lot of work goes into all of the machining operations which you described. Usually, though, machine shops charge by each machining operation for the set of heads. So, you might want to get a breakdown of what the costs are for and see if you can live without some of the more expensive operations.

For one, the conversion to hardened valve seats might be better forgone. I like this conversion just as a matter of improved durability and complete restoration of the exhaust valve seats (which may have "receded" primarily as a result of several prior valve grindings). However, I think that it's awful risky with 2.02/1.60" valve heads. I don't think that the benefit is worth the combination of risk and cost. If the valve seats are in decent shape, I'd recommend just going with them as-is. I really don't think that you'll ever have any problems with the engine as a result of the use of unleaded gas. If it makes you feel better, you can use a concentrated, sodium-based lead substitute like Red Line or Alemite CD-2. These are convenient to use at about 2 oz per tankful. I don't really think that you need it, but if it makes you feel better, these substances DO work. However, it's really only necessary to use them in engines operated under high load, which yours is not.

You don't actually need all new valves assuming that yours are in good shape and up-to-spec, particularly with respect to the absence of valve stem wear. However, I'd probably go with all new, HIGH QUALITY stainless valves.

[robert leazenby]

Re: To seat, or not to seat.

I just spoke with the guy for about an hour. He measured my valve seat recession, which showed about a .050 recession. Meaning the seat would have to go the much farther in. He is now leaning against installing inserts.

He had quite a bit to say about the who leaded/unleaded gas thing. He is not so sure that unleaded would ever cause me problems as he has seen 60's era vehicles with 200,000+ miles which have been burning unleaded for 20 years with no problems.

In a nut shell, he stated if it was his car, he probably wouldn't chance the inserts because I would be fine without. He told me to keep an eye on exhaust valve lash (solid cam) to forsee any problems.

[Wayne K.]

Re: To seat, or not to seat.

Robert,

Good luck with your decission. I decided to go with the hardened seats on the exhaust as several of mine were hammered out from what my shop said was running unleaded gas. They said the lead acts as a cushion between the valve and the seat. Maybe I wasted money on the project and only hope I haven't created an upcoming one. Don't be afraid to take the LT-1 to 6500. I owned a 70 LT-1 roadster from 1972 to 1979. It had 4:11 gears and it pulled real nice up to 6500 in any gear. Have fun with your project and enjoy the driving experience.

[Duke W.]

Re: To seat, or not to seat.

I would recommend you pass on the exhaust seats. Have them ground to a width of at least .060". Also you should go through the calculations on what your actual CR is. This will be a function of measured deck clearance, chamber volume, head gasket thickness, and piston dome volume. Shoot for about 10 to 10.5:1, and you can machine off the piston dome if you have to.

If you did not see the lengthly discussion on valve lash, the bottom line is to set the lash at .021"/.026" COLD on the LT-1 cam. The inlet must be set 90 degrees ATC and the exhaust at 90 degrees BTC. If you adjust them at TDC the exhaust will be about .003" looser than your adjustment because the cam is still on the ramp. The inlet is on the clearance ramp at TDC, but just barely. By using the above algorithm, you can adjust two valves at each TDC postion.

The tighter than spec adjustment is because the real rocker ratio at the top of the ramp is about 1.37, not 1.5. Loose valves mean that the valve is slammed down on the seat at greater than ramp velocity and THAT will pound in the seats faster than if they valve is set down on the seat at clearance ramp.

I'll send you a file on valve adjustment.

Duke

[robert leazenby]

thanks much *NM*