v864 hp upgrades?

[CadiJeff]

thanks LOL
but I still want to know if anyone has/is tried/trying improving on the 386 or are we just debating thoery and speculation? apeman, you seem to have the most experience on this engine of people that have spoken up, have you tried working with one? if so what results +/- or neutral have been shown.
this engine is no northstar, wich is pretty much a maxed out design, and people still make minor gains, but I would think something would help the poor ol 368.

[The Ape Man]

YOU just improved it by making it into a 386! I've done plenty with all the other displacement Cadillac engines in this family but always thought the 368 did it's job quite well in stock form. My 1980 gets excellent mileage on the highway. The thing still has the factory idle adjustment plugs in place.

[CadiJeff]

if it were only that easy! LOL
well then perhaps you could answer a question that has been driving me crazy....where does the other end of the 3rd gear switch wire go and which one(color) is it? I'd really like to get the v864 operational again.

[CadiJeff]

alternately, would the heads from a v864 work on a 425 block? the bore diameters are fairly close, would there be a piston clearance issue? obviously compression would be higher but by how much?

[CadiJeff]

oh and how do you reach the friggin no 7 spark plug, my arm is too big

[burnrubber]

According to JW at Torque Inc. ( www.cadillachighperformance.com) the earlier intake manifolds will do quite a bit performance wise for the 425s and 368s as will the exhaust manifolds. Cut the center divider out of the intake and round off the edges going into the runners and run a 3/4" or 1" carb spacer and you'll see an even bigger improvement.

[CadiJeff]

hhmmmmm, where is this covered on that site?

[The Ape Man]

#7 plug can be removed using a snap-on swivel spark plug socket driven by a Craftsman 3/8 drive flat ratchet. Piece of cake.
Get a schematic and check out the 3rd switch wiring. It goes directly from the ECM to the plug on the transmission. Inside the transmission is a normally open oil pressure idiot lamp switch which pigtails over to a 2 spade connector on the side of the trans just above the pan flange area.
You could backprobe (right at the ECM connector) with a high impedance Ohmmeter to see if you get a connection to ground when the trans shifts into 3rd.
There were also PROMS retrofitted at the dealershit that eliminated the modulated displacement creature feature. Your car might have one of these.

[CadiJeff]

would the prom still allow for the ecm solenoid diagnostics to be run? because the diags still work perfectly. I have back checked the wire as best I can and it looks completely intact. how would I I.D. the different prom? should I try to acquire a known good one?

[The Ape Man]

The diagnostics should be no different with the replacement PROM. Backprobe the wire with a meter as mentioned to be sure. Visual is not enough. Anyone with older snap-on scanner books will have a list of GM PROMS from that era. Maybe there are other ways to tell too. I'd look to ebay for spare parts. It might take a while though.

[Scraped Knuckles]

Some performance-fuel mileage upgrades for the V864 that have been overlooked are CNG or LPG conversion, multiple spark discharge MSD ignition systems, longer duration cam ( avoid high lift cams and variable duration lifters), send the throttlebody to a tuner shop to be rebuilt and modified for higher CFM (Turbocity?), make fuel injector spacers improve performance without raising throttlebody like the more common throttlebody spacers (aftermarket GM TBI injector spacers might work), add a adjustable fuel pressure regulator, maybe a two stage one designed for NOS, lower pressure for 4 cyl higher pressure for all 8, purchase or make your own adapter plates for using big block Chevy headers on Caddy engine and for fwd Caddies buy a BB Chevy custom header kit and weld your own. If you have the money rebuild the engine, zero deck the pistons and use moly rings or gapless rings, 3 angle valve job do your own mild port and polish on the heads (buy a how to video or research it on the web if you haven't done it before). Just remember these are low revving street engines that need good manifold vacuum and low idle speed. I've heard rumors that 3.8 ltr turbo V6 Buick Rivieras had lower gear ratio(higher numerically) diff's with same transaxle to engine bolt pattern for you FWD guys, and the 91 Fleetwood Brougham with the 5.7 ltr V8 and towing package had 3.73-1 positraction rear ends (the drop in highway MPG is worth the improved acceleration and city MPG, and higher top speed).