demetri

I have a 68 Imperial, and I have the following mods made:

The 906 heads get the 2.18 and 1.81 valves, and a mild porting.

The cam is the 0.477 intake lift from Mopar Performance.

Compression increased a bit, by may be 0.4.

Stock (low rise) exhaust manifolds remain. I am not interested in over 5000 rpm. Dual exhaust with 2.25" pipes and turbo mufflers.

I hope to get about 15-20% over the stock HP rating (which is about 330-350 net ...). So, may be ... 400 hp at the flywheel?

Comments?

demetri

Forgot to mention. I had a 750 cfm AFB on there (copy from Ederblock) that the engine builder thinks its junk. Should I ask him to rebuild this, or get a different carburetor? My other Imperial has an 850 cfm rochester, which I am not happy with its reliability, but at WOT, the 440 seems to do real nice.

moe7404

your Ederblock carb needs two things. 1. a good old fashion overhaul. 2. Ederblock doesnt know how to jet a AFB. when you rebuild it set the float level to 5/16, stock setting is 7/32. this will get the fuel to flow faster. but if it flows fuel out the main discharge at idle, go back to 7/32. and to jet it right use the rod that has the smallest step from power to cruse steps. then change ONLY the rod OR jet NEVER change both at the same time. best to adjust the rod first. then start changing the jets. a little is alot, as much as.003 " can make a change. the jets do NOT have to be instaled tight, just two fingers is all you need. during the jet changing you might be able to leave the two screws in the middle out. this will make changing the jets faster. allso use rags on the heads over the openings in the top of the heads, lest all your small screws get ate up by the head.

demetri

Thanks, I will transfer this info to the mechanic (car not in my care right now ...). It may be a bit tough breaking in the new cam while adjusting the carburetor though [?].

Forgot to mention, I also have a CH4B intake (I am sure that has not much to do with the carb adjustment, but it may be related to the final result).

moe7404

the Ederblock settings will be fine to breaking in the engine. then start setting the carb. quide line for adjusting the carb. 1. make only one change at a time. 2. give each change time to work 3. keep good records on the changes.

John Van

Demetri, A '68 imperial is a heavy car. You might be better off to change the rear end gear ratio to 3.23 or better if you are looking for better performance. Just my .02 worth.

also you might like this link:
http://www.imperialclub.com/YearByYe...tors/index.htm

good luck, john

Mr.4spd

If it were mine, I'd go with 2.5" pipes with an X crossover and three chamber Flowmasters. Not loud at all and a large performance gain over 2.25" and turbos. Nice choice on cam, not too hairy.

demetri

Thanks for suggestions and comments.

The Imperial weighs about 5200 pounds, and with the 2.94 and high profile 235/15's, it will not be a 1/4 mile racer for sure (may be I will get a 15.8 at 95 or 98, and will be still on 2nd gear at the end). But that's not what this car is for. I am more interested in high speed cruising, and high speed acceleration. The 3.23 will compromise that. Now, unfortunately, I am not sure if they even make tires that can handle these types of speed, but in American roads, you cannot go too fast for too long anyway.

My other Imperial has been clocked from 20-100 in about 17.5-18 seconds, which is not too bad. That has probably a cam "upgrade" and its stock 2.25 dual exhaust, but everything else is stock.

As for exhaust ... when more funds exist, we will consider revising the exhaust. Right now, that's what the car has on it.

RacerHog

You need some El Mirage...

Skwerly

I run the eddy 1411 on my 440 and it is super smooth.

TVLynn

As long as your tires are not 30 years old they should be fine. 3.23 gears would make a big difference and not compromise it a lot./... still 125+ you could still break any speed limit. 15.8 would be more like 80 mph 98 would be low 14's

demetri

The 3.23 with these big tires will probably hit about 135 at 5000 rpm (have not done the calculations, but that should be close), and gas mileage will drop. But you will be doing about 4000 at 100. The 2.94 is doing about 3300 at a true 100. Its all a compromise, obviously. If this was a racer or traffic light road warrior, the 3.23 would have been a worthwhile compromise. Plus .... The 2.94 is already there! Who knows, if I have more money to kill in the future, may be I will try the 3.23. Better yet, a 3.55 with one of these overdrive gearboxes behind the transmission.

But for now, back to reality. Funds are limited, and the project already went over-budget.

The reason why I expect a mismatch between the trap time and speed is because the car will lose a lot of time off the line, due to the 2.94 and stock converter. But once the engine hits 3000 rpm on first gear, it should start pushing real hard.

jimiheadstone

If you have not done your exhaust yet look for a pair of 440 magnum exhaust manifolds!!!! Man will you notice a difference. A couple of years back i had a 67 chrysler 300, a friend of mine sold me a 440 six pack motor which had a cam but i had to add a holly 850 double pumper.
i put it in, The car when done looked like the bat mobile. I ran the stock manifolds originally, the car ran what i thought was good, then i put in the 440 magnum exhaust manifolds, the car flew and off the line too, felt like it gained 50 hp. It had 2.5 inch exhaust with an x pipe.originally I was running 2:73 gears. the car flew, changed the pumpkin to a 3:23 posi it roared, then i found 3:55 gears and the ****** was a track car.
and it had a/c too

The exhaust manifold and 3:55 gears got the car to 100 2.5 seconds faster from what i remember. the car was over 5200 lbs with 17" wheels

demetri

Nice car, sounds like you no longer have it. Curious: Did you replace the manifolds BEFORE any changes on the differential ratio? Because, if you changed exhaust manifolds simultaneously with the rear end ratio, may have been hard to see which mod does what.

I considered the HP manifolds, and I almost bought a pair on ebay. But it looked like I would have to change the pipes too (fits 2.5", I had 2.25" pipes), and I did not want to go through the expense. I was also not certain about the real benefit of these manifolds, especially given that I am not interested at over 5000 rpm, given how this car is geared.

Here is the benefit of the tall gearing. You can hear the driver reading out loud the engine rpm. With a 3.23, you would be at much higher rpm.

jimiheadstone

I changed the Manifolds first, then I changed the gears,
Your right it did rev higher but with the power of the 6 pack motor High speed was not an issue at all.

Skwerly

Gearing definitely changes things. I actually went to steep in my Jeep Cherokee. Course, that’s off-road but it’s the same idea. I went up to 35s and plugged in a 4.88 gearset--woops. Didn’t need to go that deep. I miss my 3.55s.

demetri

Update. Car has not been delivered yet, but may be real soon. The cost may not be that bad.

One small concern. The previous cam had gone flat in a few lobes, probably due to weak (old) valve springs. There is some chance that I may have problems again. I asked to add extra ZDP oil additive, and I have a big magnet on the oil filter. I hope that minimizes chances of same problems repeating (if they do, at least the heads are rebuilt, and may be I can replace the cam myself, but not looking forward to that). Any suggestions on the oil filter? Should I replace it after a couple of hundred miles? I think once we get to summer and the temperatures start rising again, I will switch back to the 15w50 Mobil 1, but right now we have dynasaur 10w30.

I expect this car will be a blast to drive on the freeway, if it all works well.

Skwerly

pretty cheap just to get a comp cams 256h for it. nice low end torque and works well with stock gearing and converter.

RacerHog

Wix Filters
5W30 Motor Oil
Castrol in all my street stuff...
Moblie 1 in all my racing builds..
UNLESS THE CAM MFG says something else!!!!!

TVLynn

Are you in the USA ? If you are planning to run 125-150 mph on the highways ?? I hope you get arrested !!!

demetri

Which auto part supply store sells the Wix? Do you think I should replace the filter quickly, or let it sit there for a few hundred miles? I read somewhere that the Castrol still has ZDP, which means it is a good candidate for the cam early life (car leaks a bit of oil from the rear main, so I can add the Castrol). The reason why I like the Mobil 1 is the following. These engines are 7.2 liters (or I think 7.4 in this case, this is bored 30 over some time in the distant past) and holds only 5 quarts of oil, and has no oil cooler. One would expect that in an extended WOT run, the oil will get very-very hot. Especially in the summer. The 15w50 synthetic will hold its viscosity much better, even if it gets a bit hotter than a 10w30 (that might actually be good, as all water/fuel in the oil will evaporate faster, which means you can let the oil stay there for a long time). So, after I am confident that the cam is out of its dangerous early life, I will divert back to that oil.

However, if one drives his car with only short high load, then may be you don't need that fancy oil.

No Lynn, I don't really drive that fast, its all hypothetical!

RacerHog

You my have to call around.... Or you can use Napa Gold, it is a re-boxed Wix filter.

I guess you could use what you have for break in oil for now???

Sounds like you might want to look into Amsoil or Texas Refinery (Pro-Spec) Products.

I'll be waiting for your results on your oil findings.... There is all kinds of stuff out on the market for you to play with..

Keep us posted...

demetri

OK, will check into NAPA. But lets find out what type of filter I have on it now. (may be I will have the car next week).

On the oil ... I have been using Mobil 1 on that 440 (before the weak springs took out the cam lobes) and on the other 440. I have driven both cars hard, but that does not really prove anything. There is really no mineral oil that can maintain viscosity at high temperature like synthetics, but that still does not prove whether the synthetic is really essential or not.

Anyway, for the first few hundred miles, the mineral stays in, may be topped of by Castrol 10w40.

RacerHog

Well.. All I can say at this point, is I am sure the type of oil is not your problem.

Weak Springs??? Sounds like you may need to check and or change your springs more often.

demetri

I do not know what the history of this engine was before I got it. It appears that somebody had rebuilt it in the past, but did not replace the valve springs. The probably car sat for a long time too. When I got it, it ran great, and I did not hesitate to rev it all the way to 5K. Apparently, the stretched timing chain gave the car good upper end. Eventually, the engine started missing at over 4500, and I had no clue at the time as to why. Eventually, it got worse and worse, and the rpm at which it would not run good kept on going down. In the same time, I had some fuel starvation issues, which confused me further. When we finally figured out that the springs may be getting weak, it was too late, the cam was already flat. But the good side of this is .... the car is now getting a larger cam and head work!

May be the lesson is, if one gets an old car that suspects is still with original engine, best to replace the valve springs anyway.

I agree, even a poor oil selection will probably not cause such a catastrophic engine. But a good oil choice could decrease wear with long term benefits. Problem is, it is impossible to confirm with certainty what the real benefit of the better oil really is. But ... it makes you feel good about it!

RacerHog

Not so true....Oils are not just Oils...They must have good values for protection. That you will learn when you start doing oil annuluses of oils and its values...
Anyhow...Just food for thought... Good luck.. Hope all goes good with the build....

Keep us posted & see you at the races

demetri

There is no end to the oil discussion, but what I meant is that the cheapest oil you can buy today is better than the best oil you could get in 1968.

RacerHog

Kendall, Justice Brothers, Wynn's, STP, OR Redline were the good ones back in the day....
Torco was for rear ends... I still use it today....

But you are rite...Oil has come a long long way...

demetri

Some progress. I heard the engine running last week, and it sounded good. I could not drive the car, b/c the transmission was leaking big time. I do not want to refill it, b/c if I do not do a full rebuilt, I want to use as much the old fluid as possible (they told me that an old transmission will do better if you don't change its oil).

One small problem I have is that the accelerator pump is no longer working (AFB 750, from Ederblock). By looking at an AVS sitting around, looks like the accelerator pump is external and easy to replace. yes? Where can one buy one?

May be next week the car will be on the road.

RacerHog

Get one of Johns Street transmissions and you will be happy.
http://coperacingtrans.com/

For the Carb Stuff... You can get it from these guys...
http://carbkitsource.com/

Just my 2 cents