Streetable L-88????

[Rex T.]

I have a 427 engine built to L-88 specs by TRACO, the well-known high performance machine shop from the 60s and 70s. I would like to put this engine in a street-driven car (1967 Corvette).......................the problem is with the compression ratio................11.9 to 1 with closed chamber aluminum heads and a wild roller camshaft. I was considering changing the camshaft to something a little milder, but all the camshaft companies say I will have difficulty creating enough vacuum to properly operate the power brakes, if I retain the high compression. The pistons are a real nice set of Arias hung on Carillo rods, so I am somewhat reluctant to do much to them (but I am open to suggestions). I would like to hear some options on how to best make this engine a more streetable unit, and by streetable I mean one that will be driven to local car cruises and small shows and just basically around town or on the country back roads. I want something that has a lot of power up to 5500 - 6000 RPM and makes some noise through a set of Stahl headers feeding into factory side exhaust. As always, thanks in advance for your help and suggestions. Rex #8089

[William C.]

Re: Streetable L-88????

cut the domes slightly and open the chamber a little to help breating and drop the compression, use the 427-435 hp cam and you will scare yourself when you stand on it

[Clem Z.]

Re: Streetable L-88????

the quick fix would be install a set of open chamber aluminum heads to lower the CR without taking the bottom end apart and you will even gain HP with the lower CR because of the better flowing of the open chambers,about 35 HP. if you do not want to go the aluminum head route use GM CI open chamber ones.

[Norris W.]

Re: Streetable L-88????

First of all, I don't think the change to open chamber heads is going to offset the horsepower loss of the lowered compression, and I'm sure you're also aware that big camshafts and low compression frequently produce a pig that doesn't do anything right. I've got two cars that I drive to cruises regularly that might interest you. (in addition to several 435's used the same way) One is a first design 69 L88, closed chamber heads, 12.5:1 compression, built exactly to factory specs. The second is a 69 Camaro with an LS7 crate motor, which of course has the open chamber heads, 12:1 compression and the more radical 2nd design L88/ZL1/LS7 camshaft. All these cars run flawlessly, even in traffic, but require race gas. (the L88 wants to heat up a little without the shroud) The L88 is fine in the brake vacuum department, but the Camaro is weak after the initial activation each time it's pressed, and I'm not sure it isn't as much a booster problem as weak vacuum. In any case, an auxilary electric vacuum pump is a good alternative for good brake performance with any camshaft you choose to run. If you like the Traco motor as is, throw the pump on and get a drum of good gas and let it rip.

[Clem Z.]

Re: Streetable L-88????

there was a dyno test done back in the 70s by one of the car magazine , a 427 BB 12.5:1 aluminum closed chamber heads vs the same engine just switching to the OC alumium and the engine made 35 more HP even thought the CR was lowered. we ran a L-88 powered drag race car back then, we got a set of early sand cast OC heads to replace the CC ones and nothing else was changed and the car was faster. the car was even faster after we installed the proper pistons to get the CR back.

[Norris W.]

Re: Streetable L-88????

The only thing I can say is that it's contrary to my experiences over the years with numerous open and closed chamber engines. The argument would seem to imply that a 71 LS6 Corvette should have MORE horsepower than the 70 LS6 engine, since the engines are very similar except for the open/closed chamber heads and perhaps some very small additional loss of compression. I did at one time own a 71 Corvette that someone had put a set of 70 LS6 pistons and cyl heads on (cast iron from a Chevelle) I don't recall the camshaft, and am not even sure if I ever knew what it was, but the car went from 13's to 14's when I stuck a set of open chamber heads back on it. One other example that may or may not be exactly parallel is a 540 that's in my boat. One reason that this seems a good barometer is the fact that it's operated at full throttle for long periods, with the RPM limited only by it's ability to pull the load. This engine has a solid lifter Crane camshaft that's a little more radical than the ZL1/LS7. We were having difficulty running marina available pump gas without detonation, given it's 10 & change compression ratio. Bolting on a set of open chamber heads resulted in a loss of over 300 RPM's at WOT. (approx 5% of the normal 5500 WOT RPM) A subsequent change to a lower octane fuel (straight super unleaded) after the existing tank of race gas/super unleaded was exhausted seemed to cause no additional change in performance, either positive or negative.

[Clem Z.]

Re: Streetable L-88????

with drag car we had to change gears because the engine would make power past 7500 rpm were before it ran out of wind at under 7000. the OC heads move the power curve up and you must gear accordingly. with closed exhaust on a street machine i do not not think you could tell the difference in power either up or down in the CR. i have a 510 OC blower boat engine running at 8.5 CR with 7 # of boost on pump gas,92 octane,and that equals better than 10+ CR and i have found that a little change in props make a big difference in performance even with close to 800 HP. just changing the cup in the prop tooks him from 103 to 107 MPH using a GPS to check the speed. we try to keep the RPM in the 6000 range. the boat owner has gone thru dozen different prop configurations to get where he is at now as he started out at about 100 MPH. happy boating!!