HIT 18 PSI TODAY!!!!

[dyoung14]

As the title says it all, i was comming home climming the 7% grade mountain and i thought hey its like 30 degrees outside so i mashed down on the ole idi and i got to watch the boost climb to 18 and almost touch 19psi i wish i could get higher i normally only see 15-16

Oh yea its a 83 low compression engine, with re-used headbolts and brand new gaskets heads torqued to 80FTLBS holds 15+ PSI DAILY! at 5PSI of oil pressure at idle and 25 sometimes 30 going down the road at highway speeds

 

[icanfixall]

Your a true test bed for these motors.... Glad to see you still on the road. Just think what you can do with a newly rebuilt motor with a few extras added....

 

[rhkcommander]

I'm glad your pushing these motors and posting the results. With PSI up there I have hope yet

also, package is ready n should be enroute monday

 

[dyoung14]

Your a true test bed for these motors.... Glad to see you still on the road. Just think what you can do with a newly rebuilt motor with a few extras added....

It would be pretty awesome if i had more fuel im sure i could pass 20 psi, then my head gaskets would probly let go, as of right now i make my max boost absolutely smoke free

 

[dyoung14]

I'm glad your pushing these motors and posting the results. With PSI up there I have hope yet

also, package is ready n should be enroute monday

Good cause i really need it, I didnt think the truck was gonna start last night at my girl friends house, and it still has to start this morning and take me to work but its 25 degrees outside

 

[rhkcommander]

Its cleaned up and ready to go. Should work great it worked when I pulled it so I kept it as a spare from back when I had hard to start days (later to find out it was just bad batteries AND air intrusion )

Also, get some wobble 1/4" extensions if you dont got some already, makes it pretty darn easy to pop the starters off n' on

 

[dyoung14]

Its cleaned up and ready to go. Should work great it worked when I pulled it so I kept it as a spare from back when I had hard to start days (later to find out it was just bad batteries AND air intrusion )

Also, get some wobble 1/4" extensions if you dont got some already, makes it pretty darn easy to pop the starters off n' on

Sounds great

 

[Rot Box]

The piston tops are shorter giving a lower CR on the earlier motors correct?

 

[Worstenemy453]

Could someone take the 83 pistons and use them in a 86 block ?

 

[Diesel JD]

I was thinking that the 83 A motors actually had different heads and that was the reason for the lower compression. I'm thinking the reduction in compression was slight and could probably be duplicated by shaving the pistons withing safe limits according to Mahle. Those guys told Gary how much you could chop off before it starts to potentially cause problems with the top ring. I don't remember how much that was, it was not a large amount, but anything could be significant where the starting CR is 21.5:1

 

[dyoung14]

I dont remeber if its the pistons or the heads that give different compression,

But i can tell you my engine has been rebuilt and it had .020 pistons put in, not sure if they are different than factory, and not sure about the heads either, i could tell they look fairly clean so i dont know if they were bought new or just re done, so the engine may not be low compression anymore or it may be, or it may be even lower,

83 model compression= 20.7:1

 

[Black dawg]

what did your pyro say at 18 psi?

 

[The Warden]

I was thinking that the 83 A motors actually had different heads and that was the reason for the lower compression. I'm thinking the reduction in compression was slight and could probably be duplicated by shaving the pistons withing safe limits according to Mahle. Those guys told Gary how much you could chop off before it starts to potentially cause problems with the top ring. I don't remember how much that was, it was not a large amount, but anything could be significant where the starting CR is 21.5:1

This is going off the "6.9 Liter Diesel Engine Update" series of pdf's that were scanned from a Ford publication printed in October 1985. I don't remember who scanned these in (might have been Travis or Heath?), but it seems like I'm the only one who saved a copy and remembers that this publication exists I'd take screen shots of the pages and post them as images or simply post the .pdf files, but I'm worried about getting in trouble over copyright issues.

According to this publication, the differences between the A engine and the B engine are in the piston, precombustion chamber, cylinder head, and exhaust valve. The compression ratio on the A engine is 20.7:1, which was upped to 21.5:1 on the B engine.

The pistons are different in the following ways:

• A engine piston height (top of the piston to center of the pin) is 1.9435 inches.
• B engine piston height is 1.9465 inches.
• A engine piston combustion chamber cavity is 4.5 cubic centimeters
• B engine piston combustion chamber cavity is 6.6 cubic centimeters

The combustion chamber cavity was altered to match the different precombustion chamber.

The precombustion chambers are different in the following ways:

• A engine precups have an overall volume of 21.89 cubic centimeters
• B engine precups have an overall volume of 17.43 cubic centimeters
• A engine precup throats are 0.270" wide
• B engine precup throats are 0.245" wide (which necessitated the design differences in the combustion cavity)
• A engine precup top opening (where it goes into the head) inside diameter's 1.240"
• B engine precup top opening inside diameter's 1.144" (outside diameter's the same)

If I'm reading this correctly, the heads were altered in that the precombustion chamber that's not part of the insert (i.e. where the glow plug and injector tip go in) was reduced in size, but it doesn't specify how much. The exhaust valve on the B engine was made slightly thinner (from 0.020" to 0.017") to clear the taller piston.

Hope this helps a bit...I really wish I could post the .pdf file

 

[dyoung14]

what did your pyro say at 18 psi?

I havent installed my pyro yet, im going to this week, then i will find out the EGT numbers and post them

 

[david85]

Warden, wasn't it the 7.3 IDI that had 21.5:1 and the B model 6.9 that had 22.5:1?

I think it was 20thou that was the safe limit to mill the stock pistons down if I remember right. Although there are pistons available that move the pin higher up by 10 thou in case of having to resurface the deck.

Sure wish I could see boost numbers like that....