Thread: Compression is too high on my '71 460 Lincoln...

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Originally Posted by Itoldyouso

That didn't sit well with me either, the part about the builder being so secretive. Aren't you the guy who paid the tab? When I take my engines to the machine shop I specify exactly what I want done and he is my employee at that point, your situation is no different. Just doesn't make any sense to me. I would he at his door step with some very serious questions for this guy. Even if Keith Black built your engine he would tell you all the specs and parts used......this isn't voodoo!

Don

Have you seen the used car commercial ,where the customer brings the witch doctor with him to the car lot....he tells the salesman that if he does not get a good deal the witch doctor is gunna shrink his head.........

Like Shawnlee said, determine what the fuel/air ratio is first. It's the easiest thing to change if the motor is lean.

With the ratio dialed in, if it still pings, take another compression reading on all cylinders with the motor warmed, throttle blades wired full-open and coil wire disconnected.

Crane Cams recommends no more than about 165 psi on a street motor with good pump gas: here's their verbage:
"In very basic terms, the more cylinder pressure we make the more power the engine will produce. But look out for the fuel! Today's pump gas is too volatile and cannot tolerate high compression ratio (above 10.5:1) and high cylinder pressure (above approximately 165 PSI) without risking detonation. Fuel octane boosters or expensive racing gasoline will be necessary if too much cylinder pressure is generated."

I suspect, like Tango said, you're around 11.0:1 at this point and in my opinion, you have no choice but to change some parts if you are limited to pump gas. Bigger chambers from '73-up heads will do it. A longer cam will also do it, but will move the operating range of the motor higher in the rpm band and may require better valve springs, a looser converter and shorter gears. What's happening is that the intake valve is closing too soon and trapping too much mixture for the static compression ratio. A longer cam will move that point to later in the cycle and bleed off some of the compression. You can also change the intake closing point with the cam you have now by retarding it in relation to the crank. This will extend the closing point and bleed off some compression at the expense of power at the low end.

I'm not a fan of using thicker or multiple head gaskets to lower compression because it changes or negates squish (piston to cylinder head clearance with the piston at top dead center). A tight squish (0.035" to 0.045") will go a long ways in reducing the tendency of the motor to detonate with a higher static compression ratio. A case in point is the '72 cylinder heads which were open chamber (no squish) and contributed to detonation so badly that Ford discontinued them after only one year of production.

Thank you all so much for your replys, and the sharing of your knowledge. The problem with the builder is that I was stupid for not having a written estimate of the cost of his work, and realizing 3/4 of the way in that the guy was a thief as well.

He said that he would pull my old motor, rebuild a core 460 for me, and put it back in the car for a thousand dollars, or less. This involved my helping out with some of the grunt labor to reduce cost. After a YEAR AND A HALF and numerous little things that made me rethink his stated motor-building experience, he presented me with a $2600 bill.

3/4 of the way I was dropping of some parts for him at his shop, and while standing around waiting for him, I noticed a hood scoop that looked a lot like mine sitting in the bed of his pickup. It had been in my trunk.

Sure enough, it was.

I retrieved it and put back in the trunk. I didn't want to confront him over it because my motor was sitting on his workbench in pieces. It wasn't until I finally got the car home that I realized that he had stolen my 5-volume factory 71 Lincoln manual set that was in the trunk too.

I did go back at him over that, but he totally denied taking them. The argument got heated, and he finally called the Police to get me to leave. The cops were sympathetic because I wasn't the first irate customer this shmo has had, but I couldn't prove anything.

So now there is no contact between us and no info coming either. I am going to take the advice given here and start out with new updated motor performance stats, and go from there. Thanks again.

Originally Posted by 71LincolnCoupe

Thank you all so much for your replys, and the sharing of your knowledge. The problem with the builder is that I was stupid for not having a written estimate of the cost of his work, and realizing 3/4 of the way in that the guy was a thief as well.

He said that he would pull my old motor, rebuild a core 460 for me, and put it back in the car for a thousand dollars, or less. This involved my helping out with some of the grunt labor to reduce cost. After a YEAR AND A HALF and numerous little things that made me rethink his stated motor-building experience, he presented me with a $2600 bill.

3/4 of the way I was dropping of some parts for him at his shop, and while standing around waiting for him, I noticed a hood scoop that looked a lot like mine sitting in the bed of his pickup. It had been in my trunk.

Sure enough, it was.

I retrieved it and put back in the trunk. I didn't want to confront him over it because my motor was sitting on his workbench in pieces. It wasn't until I finally got the car home that I realized that he had stolen my 5-volume factory 71 Lincoln manual set that was in the trunk too.

I did go back at him over that, but he totally denied taking them. The argument got heated, and he finally called the Police to get me to leave. The cops were sympathetic because I wasn't the first irate customer this shmo has had, but I couldn't prove anything.

So now there is no contact between us and no info coming either. I am going to take the advice given here and start out with new updated motor performance stats, and go from there. Thanks again.

well i hope you didn't pay his $2600 bill when he quoted you $1000 an stole your stuff.