440 Engine Diagnostic?

[gumshoestu]

Ok, before I ask my tune-up question, please read my Mopar's particulars: I have a custom 440 in a '71 Road Runner. The engine was taken from a '73 Imperial and rebuilt/modified for my B-Body. It was bored .30 over with forged, domed, TRW pistons achieving what I estimate (I say estimate, because I'm not positive, but that's an educated guess) at a 10.35:1 compression ratio. It has a Competition-brand camshaft, part #21-306-4, which has a 470 lift and 270/224 duration @0.50 (this cam was recommended by the manufacturer as an excellent replacement for the 440); I'm running an Edelbrock, dual-plane manifold and a matching 750cc carburetor. It has a new, Mopar, factory, electronic distributor with a Gold Box (yes, I know, not necessary, but I went with the Gold Box module because I got a good deal on it); and I'm running Hedmann headers. My 727 Torque-flite has a 2225 r.p.m. stall converter and a B&M shift kit. I've got a 3.55:1 Sure-Grip, 8-3/4-inch, stock rear-end in the car.
I am trying to get this car to run as good as it possibly can. I have received a lot of advice, most of which I have tried Ñ with some success.... that said, here's my question:
Is there any point in taking my car to a good, reputable, auto repair shop with modern diagnostic computers to analize the engine, to determine if it is running as good as possible? Do the dianostic computers for "regular" cars help much with modified engines? My car runs good, but I have this sinking feeling that I'm just not getting all I can out of this engine. What are my options

[Jetstar]

A diagnostic center cant help you.You need a good shop with an engine dynometer to acurately tell how much power u have and what the power curve is.Then,the car can be adjusted and tuned to get optimum results. Things Such as jetting,timeing,and advance curve,when set up properly will get u the best resultsand performance.Things like vehicle weight,gearing and such will effect the driveability and performance .

[gumshoestu]

Ok, a dynomometer it is then...are we talking about something unique and rare or will the dynomometer at the AAA center Ñ I'm a AAA member is why I ask Ñ in my neighborhood be able to tell me what I want to know?
I have seen advertisements for a local shop/center for "dyno" testing of Ford Mustangs...would they be equipped to hel

[6 packin]

They can give you a idea how well its running sure? But without a baseline, how would they compare, and to what? A good timing light how to red plugs and a carb tuning guide well do just as well. I bet you have more compression than that maybe over 11:1 with dome pistons. The gold box was not ment to run longer than a minute or so at a time. It to hot, to run on the street, trade it for a crome box. The converter is killing your package. The cam is ok. That kinda compression, you will need a bigger cam to help bleed some of that off. Like around .240 Dur at .050 lift. I would be suprised if you can run pump gas at all, and still have a good timing advance curve. Asuming you have iron heads.

[gumshoestu]

Yes, I know I probably have more than 10.35:1 compression. I was basing that number/figure on the combustion chamber size on the stock iron heads on this motor. The engine, as I said before, is from a '73 Imperial, and we belive the combustion chamber is 78cc, and since the block was not decked when it was "cleaned up" and there wasn't any head work performed, then we thought it had about 10.35:1 squeeze. But I have never been able to get this car to run well. I can't use the vacuum advance at all or the engine backfires terribly in park and "falls on it's face" while driving. So, I have the vacuum advance "closed off." I have tried many combinations of fuels, including a 50/50 mix of 110-octane racing fuel and 93 octane premium pump gas. It runs "o.k." like that, but never like I expected this "torque monster" to run.
I currently have the timing curve set from 14-degrees advanced at idle (about 850 r.p.m.) and it progresses to about 32-degress at 3,500 r.p.m. through 4,500 r.p.m. I had set it initially much higher at idle, but, of course it always pinged terribly unless I ran the racing fuel/pump gas mix. Now I run 93-octane pump gas and add a bottle of NOS Race Formula, and it runs "just o.k." I fully expected this car to run harder Ñ much harder.
Do you recommend removing the stall converter and putting in the stock converter, or a different stall converter? Should I put a "bigger" cam in there (such as one with a 240 lift), and would that fix the timing/compression problems?
I have been advised to pull the engine apart and put some 9:1 flat-tops in there and that would solve everything, do you agree? I would like to find a cheaper fix that an engine break-down. Cams are reasonably cheap and so are converters. Please provide some advice.
Stu Barnhil

[hchris6360]

I would think more than 10.35 to 1. It sounds like you're using the same pistons that I am using in my 440. I have the 906 heads and I surfaced the block so I have .020 deck clearance and took another .010 from the heads. A normal 440 has about .050 deck clearance from the factory. My engine is 13.75 to 1 and I use racing fuel. I also use the steel shim gaskets to get that. Sounds to me like you way more compression than you think. A lot depends on your heads. Did you cc the heads or are you just estimating. My 906 heads were over 80cc and most of the later heads are even larger. But if that is where you are at with your heads I would think the flat tops would help.

[gumshoestu]

Ok, assuming my factory heads (according to my mechanic he did nothing to them but clean them up) are 80 cc or larger, and my compression is really as much as 13.0:1, and I do not want to change the pistons, then what are my options? Will a bigger cam make it run better? If I go back to the factory torque converter, how will that affect idle speed and general "driveability?" I would like to find a solution other than changing the pistons.
Do you know of any way to effectively measure compression ratio after the engine is assembled? I would love to verify it for certain, to know where I stand.
On the subject of timing, I said I run a curve of about 14-degrees advanced at idle (850 r.p.m.) and it progresses smoothly to 32-degrees at I think 3,500 r.p.m. and maintains that setting through about 4,500 r.p.m., does that sound right?
If I just resolve myself to mix my fuel, should I still return to a factory torque converter and go with the bigger cam? And if I do return to running a 50/50 mix of racing fuel and premium pump gas, should I increase my timing to say, something approaching 28-degrees? I had one local Mopar enthusiast/expert set my timing at 30-degrees. He seemed to think it was common to set it that high.
All of the conflicting advice I have received has me wondering if I can ever get this set-up to run well regradless of what I do, short of going to lower compression ratio pistons?!

[hchris6360]

You said that the engine has always pinged, so my first concern is has there been any damage done to the pistons. Pull the heads and check the pistons and heads. Have you done a compression test. My engine will make 185 to 190 pounds of compression. This is at 5000 feet of altitude. Lower altitude will of course make more compression. Also the choice of cam will affect the cranking pressure. I am using the .590 purple cam from mopar. I used to use the .557 purple cam and it had 205 pounds @ cranking. Less overlap makes more cranking pressure. That doesn't mean a bigger cam will solve your problem it just means the smaller cam fills the engine better when cranking. You might try using thicker head gaskets to reduce your cr but I am afraid you have over built the engine and racing fuel is the only answer, or replacing your pistons.

[amxauto-x]

If you are going to replace the cam then it wouldn't be that much more work to pull the heads and get the chambers CC'd. Then you can measure the cylinders for the piston to deck height. Then you can figure the real ratio. Then you can take out the pistons and get the tops cut to get a street compression ration of 9.5 to 10 to 1. I presume you will be pulling the engine to replace the cam. So the piston checking work should be a breeze.

I'd keep that cam [that's close to what I have in my 390 AMX] and check the heads and compression ratio anyway. My compression ratio is 9.67 to 1.

What do you mean "factory" converter? The 1500 rpm stall speed one? Na, you'll need one in the 3,000 rpm range with a hotter cam. With that cam a converter in the range of 2800 would work for the street with those gears, [same as my gears, 4 spd, but I need a wide ratio gear box to get off the line at the stoplights better.] , but 3,000 wouldn't hurt.

[6 packin]

You need to post the casting number on your heads, also try to dig up the piston part numbers too. Call the machinest or whatever. TRW/Speed Pro makes several diff dome pistons for the 440 Mopar. Go Here and look at the pistons, they have the pice also. Maybe you can remeber the part number or som thing.

www.summitracing.com
Find that out and you can get head gaskets that will taylor the dersied compression you want. The timing you run sound like optimal street timing too 14 deg intial, 32 deg total, ditching the vacum advance is no biggy, Alot of times I do it also. They built Mucho mechanical advance in factory distributors.

[amxauto-x]

By the way, what does N with ~ over the top mean?

[bj96droppedram]

AMX auto, My best guess would be "and"

[gumshoestu]

Ok, I'll speak with my mechanic, who is also my friend, and see if he can recall the CC size, and the exact piston specs. I've been down this road with him once before when I couldn't get it to run as strong as I expected from the start...
My main reason for wanting to get away from running race gas, other than the expense, is the availability. It's only available at one station in my area and it's a thirty minute drive; then you gotta put the gas in separate containers, and...yada, yada... you all know the rest. If the stuff was available locally and you could put it right in the car, then I wouldn't care, but, that's not the reality.
It's looking like I'll just have to break down and put some flat tops in the damn thing after all. But I'll get back to you with those specs.
As for the stall, I was refering to the "factory" converter I took out of the 727 when I rebuilt the transmission. I am unsure of it's "speed..."
Thanks for the info. so far guys...I'll get back ro this thread.
Stu

[pcb1]

Okay, flat tops are the way to go. I'm running 11:1 on 91 octane 50/50 with 110 and 1 bottle of boost. No Ping! Stock stall of 2000, so no scream off the line, but mid range is a monster & I'm not parnoid about getting on it.
You have too much compression (13:1), but not lift, for the street with street fuel. Blend it or blow it. Are you automatic or shift? Easy to overrev either way. Major $$$ if you do. Go to the county airport & fill up with aviation fuel. Cost less, burns cleaner!

[beepbeepsrule]

Get a Chrome box and replace the Gold box just for reliability. If you have enough fundage to use a dyno then spend some of it on the Chrome box. The Gold is a dragrace piece, not meant to run for very long periods of time.

This is a very general statement, but one of the main reasons for going with higher compression is to run a large cam for lots of power at the higher RPMs. Cams that big have a lot of overlap and the bottom end of the powerband is soggy. Higher CR keeps the bottom end of the power band alive. So, one of the requirements (or "fixes") for a higher compression ratio engine is a large overlap cam.

You will probably need an MSD or other type of CD ignition also to make sure the plugs light off correctly each time. Combustion chamber mix in a higher CR engine is harder to ignite.

Assuming that the reference lines on the balancer are correct the engine would want 34-36 degrees total advance for maximum power. This would require VP or other racing type fuel as it would be set on "Kill". Going with a 30-32 degree total advance number would let you run on 50/50 MAYBE. 13 to 1 CR with iron heads is pretty high for the street.

[Geezer]

In the "FWIW" area.. the so called octane boosters are pretty much worthless.. About all they do is crud up the plugs and the combustion chambers w/ a nasty orange/brown powder.

If you look at their ads, they say some BS like "gain 4 points of octane", yadda, yadda. What the real deal is, the 4 points is:
You begin with 93 and think adding 4 points is now 97.. NOT. it's 93 plus .4, for a "wondrous" total of 93.4... Hardly worth the price and aggravation...BTDT, in many turbo and hi comp troubleshooting sessions....

Back to working on my HEMI!!!

[ehostler]

If the heads are open chamber heads, they are closer to 88cc - 90cc (if they have not been milled). Even then, based on domed pistons, you have too much compression and not enough cam.

Send the distributor to Don at FBO system and let him properly tune the advance in it.

Get that gold box out of there. Replace with either a Jacobs ignition system or an MSD box.

[renee]

Domed pistons will produce better flame travel and faster burn, therefore less ignition advance is needed. Timing initial setting and advance need to be tweaked (usually the vacuum canister itself is adjustable). Good Luck