Looking for Input on boring 6.9 to 7.3

[bronco78idi]

My 1978 Bronco Build

Hi all,

I am looking for some input. I am building a 6.9 for my bronco. The heads are back from the machine shop and the crank is polished and ready for balancing.

I am about ready to drop the engine block off to start that process however I trying to figure out if I should bore the block out to 7.3 or leave stock and just replace the sleeves with new 6.9.

Oh, my goal. Mild street performance and git er done off-roading. I am not looking at turning 5ooo rpm, just get me around.

If you look at my blog http://bronco78idi.blogspot.com you will see all the info on the bronco and see the project move forward.

I am having a hard time finding parts like larger or baffled oil pans, high flow oil pumps, better injectors..etc has anyone found these parts?

Thank for any help

 

[boosted power]

I'm sure the more knowledgeable will chime in maybe tomorrow.

First and foremost, if you want more power you're going to have to turbocharge. I see that you are planning to do so, and that's good. The most reasonable approach to making mild power with these motors seems to be: Start with a quality forced induction system, and then make sure it gets plenty of fuel. Mel on this board is the source for a better fuel pump (Moose Pump), otherwise I'm sure there are diesel shops out there that can custom tune/build one for a small fortune. Injector options are more limited, but seem to be less critical. It is generally accepted that the factory BB codes are the best.

As far as the oiling system goes, you're not going to find anything because these motors don't normally have oil temperature problems. It's got lots of oil capacity (+1 extra quart if you use a powerstroke oil filter), and doesn't turn alot of RPMs. I think the only people who have lubrication problems are tow trucks or county trucks that spend an extraordinary amount of their lives idling.

Just remember, it's not a SBF. There isn't much aftermarket support for these engines, and they don't make a ton of power. Their redeeming qualities are that they are cheap, plentiful, and rugged without being completely gutless.

*EDIT* Oh and to answer your first question, the displacement difference between a 6.9 and a 7.3 really isn't going to make much difference when you are using forced induction anyways. Personally I would rather leave the cylinder walls as thick as possible.

 

[hesutton]

I would not make that 6.9 a 7.3. 7.3's have issues with cavitation, and you don't need that headache. The 6.9 would be fine and as stated, the is no significant power difference between the two. A turbo is your friend with these IDI's. As far as injectors, without a modified IP, modified injectors aren't going to help much. Mel (Agnem is his handle here) can hook you up with some quality fuel parts--------- Moose pump and Moose injectors if you are so inclined, but again, you'd need a turbo 1st.

Cool project by the way............... and Welcome to OB!

Heath

 

[icanfixall]

Welcome to the forum. Please don't bore the 6. yo 7.3. That will ruin the block. If you want a 7.3 build one but boreing out a 6.9 to 7.3 is about a 110 thousands over bore.. Not good at all. Then you will surely have head gasket issues useing the 7/16 head bolts. Now building your engine like you want is not a bad thing. Just ask questions here before doing "stuff". Typ4 (RUSS) offers a great torquer cam that many have installed along with a turbo... Never a bad return on doing this. As posted, Mel is the person to talk to about pumps and injectors. Nobody makes a high volume oil pump and the stock oil pump is generally thought to be a better pump than the Melling after market pump. These oil pumps push 17 gallond per minute at 3000 rpm. The water pumps are doing 34 gallons at the same rpm. Installing a Banks wastegated sidewinder turbo will wake up your engine plenty. Adding a hypermax intercooler will just add to that. You will need to modify the intake hat so it fits the turbo or modify the turbo outlet to fit the hat. Banks never offered an intercooler... Sad to say too. Machine work on the block is important to get all the hp thats lost due to internal drag. When you removed the bearings from the crank did you see some side wear that went thru the babbit. If that was a rod bearing that cylinder is bored off center to the crank. Needs to be fixed. If the mains showed wear like that the main webs are bored crooked and it needs to be line honed or bored. Then balancing the rotating parts will give more lost hp. Decking the block so all the pistons are the same height is important too. These blocks run with the pistons as much as 31 thousands up out of the block. I'm not seeing the usefullness of a baffeled oil pan but thats probably something for the offroading you want to do. A larger oil pan is not going to add anything to the engine. These engines push large volumes of oil at low pressures because they only turn 3800 or so rpm. Now if it was a sbc turning 8000 or above rpm then yes.. A better than stock oil pump is needed. I have an oil temp gauge on my oil pan. I installed it so I would know what the temps are. Usually the oil temp is only about 10 or 15 degrees above the coolant temps. Untill your really working the engine. Then 260 can be reached or slightly more. I can tell you at 330+ degrees oil temps things begin to stick like pistons to cylinder walss and the world crashes in on you faster than you can pull over....

 

[Dieselcrawler]

No need for the oil pump or baffled pans. I run mine at ALL angles and she still runs like a champ. Also remember for off road you want reliable. Thats the reason I took the turbo off mine. One less thing to worry about.

 

[typ4]

there are 2 cams available over stock, mine for torque and another only if you have cut pistons. I would turbo it, there is nothing unreliable about a turbo, if you want a stock type turbo that builds boost lower in the rpm range I can mod the 093 ats or any of the others for that matter for more low speed boost, bore your 6.9 .020 over and balance it, I have a good line on stainless valves . pm me for other info, better yet email
[email protected]

also do not buy a new oil pump, use your old one, take the cover off and inspect for scratches. My brand new melling pump had **** clearances and I will put in my old IH one if the engine comes out for any reason.

 

[bronco78idi]

Thank all of you for the info. I dropped the engine off today and I am not going to make it a 7.3. I ordered Mahle pistons and I am having them sent to Swain Tech coating for the best coat they offer. I am going to look at the old oil pump and check it out and get back to you on what I find. The valve job is complete and I have to wait 2 weeks before I see the pistons. I will have pictures when I get them back.

Thanks again for the info I will keep you posted on the progress.

 

[icanfixall]

Why did you choose the Mahle pistons... Did you know they are the oem pistons for all the idi engines... Russ is the man for reworking most any turbo for getting all the smoke out of your engine... Just one more thing about building any idi engine. Buy a set of ARP studs. The 6.9 stock head bolts are marginal at best. Adding a turbo will stress the head gaskets to failure. This is from real world experiances here on this forum and several other forums. Its really cheap insurance when building an engine. Don't bother studding the bottom end. Thats well taken care of with the beefy 4 bolt mains. Only one owner has pushed the crank out of the bottom end and he was making some big hp. Probably upwards of 500 or 600 at the crank... I really didn't get the hp but it was big stuff. Some here may know what Ken was making.

 

[bronco78idi]

Hey all, its been a long time. I have been busy with life and my motor build has been slow. I am hoping to get back on track! Dropped off a few parts yesterday and the motor is close to being complete to bring home. I will be shooting a video in the next few days of the Harland Sharp roller rockers installed..
http://www.youtube.com/watch?v=BW52Ls32GW4

 

[riotwarrior]

Hey all, its been a long time. I have been busy with life and my motor build has been slow. I am hoping to get back on track! Dropped off a few parts yesterday and the motor is close to being complete to bring home. I will be shooting a video in the next few days of the Harland Sharp roller rockers installed..

Interesting build I must say, I'd sure like to know what the cost of roller rockers where as I am sure a few others here would as well, also do you have a part # for them?Now what cam did you go with? What all have you done to the engine?Looking forward to more on this!

 

[bronco78idi]

Here is the list of what I did to the engine.

Block
Line Board
Decked
Balanced Rotating
Cryo Rods, Piston Pins and Pistons (milled piston for balanced deck height prior to coatings)
Tri-Coated Pistons (seal Power)
Dry Film coated Main and Rod Bearings (Clevite 77)
Crank Nitrided
Total Seal Rings
R & D Stage 1 Cam

Heads
New Valves –Ceramic coated face
Intake Valves (Perfect Circle)
Exhaust Valve (Stellite)
Comp Cam 910 Springs
4 angle Valve grind
Harland Sharp Custom Roller Rockers
ARP Head Stud

Misc.
Victor Rienz Complete gasket set
R & D Custom Intake

You must be registered for see images attach

 

[bronco78idi]

The Harland Sharp are custom made at the cost of 800.00

 

[typ4]

Thats not bad.Contact info please for Harland Sharp.

 

[bronco78idi]

http://www.harlandsharp.com/Contact%20Us.html

Talk to Mike

 

[hce]

Are the rockers the same ratio as stock?