v864 hp upgrades?

[CadiJeff]

couple of questions to get more efficiency out of the 368.
would any of the older intake manifolds fit on the v864 for better flow?
obvioulsy better flowing exhaust..... better flowing exhaust manifolds?
would the tbi from say, a 4.5 fit, work and flow better?
any thing else along these lines?

[CadiJeff]

wow! I think I hear crickets chirping!

[davesdeville]

I don't know about the intake port sizing on the 368 so I couldn't tell you if an older intake manifold would work well. 68-76 exhaust manifolds should be worth a little bit, if only for the lack of clearancing for that bolt... You know what would be good though? A 500/472 or heck even a 425.

[The Ape Man]

The earlier intake and exhaust will bolt up but port sizes are much different. There also won't be anyplace for the Oh-2 sensor and the Y-pipe is larger on the older models. Chances of removing all the exhaust manifold bolts on a vehicle this old are nil. Some will break. If you really want to do this then go with headers and have an O2 bung installed.
Easiest way to wake this car up is with a higher numerical rear axle gear ratio and positraction. Gas mileage will go into the crapper though. An overdrive transmission will cure that but would take a long time to pay for itself.

[CadiJeff]

the thing is I am trying not to impact fuel efficiency negatively, thats why I am only looking to make whats there flow better, and you can't tell me that a 6.0L engine can't make more than 145hp. the big air/fuel flow issue is in the intake manifold due to the upflow design(kinda counter intuitive isn't it?) IIRC the older manifolds were at least on a flat plane. and throttle body with larger bores would help air flow as well. I think the engine could be capable of 200hp easily with out negativly impacting fuel efficiency in any serious way. The point is to make the V864 system operate more powerfully so as to make it more effective on the highway.

[The Ape Man]

That engine is designed to lug a 3800+ pound car along and get just about 20 miles to the gallon on the highway. Sure, you can make it into a gofast machine but you will become a member of the freinds of OPEC club. By the time you get it to move, the money and time spent will most likely exceed what would would be spent in equipment to install an older Cadillac engine with factory big car hauling torque.
The name of the game for economy with a large engine is to maximize manifold vacuum while cruising. Most gofast happy bolt on stuff shifts the torque curve higher in the RPM range thus lowering vacuum at cruise. The older manifolds have a long uphill situation and weigh 57 Lbs. The olde manifold carbonator flange will not mate with the existing '81 throttle body either. No free lunch.
Beware of information from anyone selling stuff claiming to work better than what generous motors could come up with. Most of this stuff has serious drawbacks.

[CadiJeff]

I wouldn't be opposed to modifying an intake to accomidate tbi (prefferably a more free flowing tbi) as I stated above all I want to do is maximize what the engine makes on the fuel it uses. even the old guru admitted that the engine was capable of more if the restriction points were freed up and thats what I want to do. I am not after a go fast gas hog, if that were all I wanted I would put in a 472/500, olds 455 or a chevy engine

[The Ape Man]

If your 368 is in good shape and tune then it is about as efficient as it will ever get. The design is well thought out. The stuff that you call restriction points is there on purpose. Larger ports in the intake might allow for more full throttle power but will certainly lower part throttle response. BTW larger Cadillac engines will deliver excellent gas mileage in this car. The name of the game is vehicle weight, gearing and vehicle airflow. Have fun.

[I~LUV~Caddys8792]

What kind of mileage does the V8-6-4 give you? I thought I'd heard something like 13/20 or so....

[CadiJeff]

(v864 currently didabled) I average 17 (per the comp) but when actually moving in-town it is around 13-15, highway varies dramatically by speed upwards of 25 @55mph but only 17 @ 65mph and 15 @ 75mph (this car needs overdrive bad)

apeman, you can't tell me with a straight face that an intake manifold with runners that flow uphill are more efficient than even a flat plane design. I used to have it on good authority that this design was used because of a percieved hood clearance issue involving the tbi unit, and it is a problem as it causes some (more than usual) of the fuel vapor to settle on the runner walls, not to mention the natural resistance the air/fuel has due to an unnecessary direction change. then there is the exhaust.....

[The Ape Man]

My face is straight.

[CadiJeff]

so one of us is insane then? LOL
and there is no hope because the general laws of physics and every engineering concept I have ever learned is wrong?

the smaller intake plenem in the 368 alone dictates a loss
hhhhhmmmmm
it makes no sense that freeing up the engines air/fuel/exhaust flow would do nothing to help the engine.

has anyone actually tried to make the 368 more efficient or does every one give up and drop in an older cadi or olds motor

tell me, is my logic flawed, or are all 81 368's subject to some weird quantum fluctuation that dissaffects them from the laws of physics?

[The Ape Man]

Yes, your logic needs more work. Sounds like several concepts are being interchanged here. The most efficient engine is one with a wide open throttle. Obviously a 368 cannot be driven at highway speeds with a wide open throttle because it is too large. If the engine were shrunk to just large enough to haul the car then your thinking might apply. Removing obstructions in the airflow will only serve to slow down said airflow while cruising. The uphill manifold doesn't add up to much of a problem with throttle body setups. It WAS an issue with the carbonated engines. They did not idle too well. Above idle they worked just as well as anything else and they were much better on gas. If Cadillac had already manufactured engines with larger "more efficient" ports (as you propose to install) then why did they bother to re-tool and make those evil small port 8/6/4 parts??? A lot of engineering went into that manifold design. It also had the capability of playing into only 4 cylinders without starving any.
Taking your idea of intake restrictions toward the absurd: I suppose that big block Chevys should also all have large ports for better efficiency also. Ever work on a Boss 302 or a 4 barrel 351 Cleveland?

[CadiJeff]

I never said anything about the intake ports being too small but as I stated the intake was designed as an up flow model due to a hood clearance issue it had nothing to do with and intentional engineering concept. if the engine is as good as it gets then why does the 80 carbed version make better numbers? as an electronics technician I can expertly tell you that the computers available back then were more than capable of actively controlling the fuel better than a carb (with the exception of an expert tune that would not last), yet the 80 still made better numbers.

[The Ape Man]

Horsepower numbers in American automobiles are not accurate. At one time they fooled with them for insurance reasons. Later numbers fudging might have been some marketing idea of perceived economy. The years we are talking about included gas lines and gasoline priced higher than currently adjusted (for inflation) prices. Advertised horsepower is just what it says. I'd put my money on an '81 verses an 80 any day in a drag race. I currently own an '80 368 and have owned several 8/6/4 cars. The throttle body equipped car runs much better hands down. It isn't as reliable as the carbonated model though. I fully agree that engine management had plenty of computing capability back then. Problems these cars had were not related to the functionality of the ECM.
Congratulations on being an expert electronics technician.