Brown Truck Under the Knife Project - Engine

[6 Nebraska IDIs]

There's a stud hole and a machined surface for a copper or nylon gasket.

 

[sle2115]

ALL none adjustable valve train Ford engines get the tip of the valve ground. That's how you set the lifter preload. There is a standing height spec for them, you install the valve, measure standing height and then grind the tip. Look at any valve facing machine, you'll also see a straight grinding wheel on it usually with a tube or a place to vise the valve to grind the tip to the proper height. Just doing a valve job seats the valve deeper in the head, making the standing height taller, so you grind it.

.009 off them huh...seems like a lot, but if they needed it, you don't have much choice, which leaves the question that is hard to answer now, did they need it?

Looks like things are coming together nicely.

Just so you guys know, most machine shops will hot tank your engine parts for little to no money. We would have hot tanked that intake for $10 and it would have been much cleaner, we did valve covers, etc. Take about 5 to 10 minutes and you can do about all the sheet metal parts, intake, etc. together on most machines. I just had three sets of valve covers, two intakes and various other parts done (serpentine mounting brackets, etc.) and it cost me $20! I still get a little bit of a discount at the machine shop I used to work at, but it would probably have cost anyone off the street $25.

 

[dyoung14]

With the head shaved now that makes your compression ratio higher right?

 

[6 Nebraska IDIs]

That's a good idea bout the hot tank SLE. I'll have to try that on the next build. My normal machine shop builds only race motors and he didn't want to mess with these heads so I took them to this other guy. He's supposed to be the best diesel guy in town. But I wont ever be going back. I'll drive my stuff to Omaha and have a shop up there do it before I'll ever take anything back to this guy. Sorry, you don't take a job under the pretense it'll be finished for the customer within a week and then take nearly two months on it all the while promising every week that they'll be ready for pickup. I understand stuff happens, but all the whining and ******** the guy did when I picked them up, just helped solidify my decision. Then as I was leaving he said he just couldn't handle all the work and needed to get out of there. He had an entire shop full of stuff to work on for people and he said he was going to go on a cruise next week. ***? Never again.

Anyway thanks for explaining the valve stem grinding.
I really wish he hadn't taken that much off of these heads. I really see no reason for doing that. I asked him why he did it and he said there were pits around the main water jacket port on both heads and he wanted to remove all those pits. I can understand pits around the combustion chamber but pits around the water jacket port? There's only 15psi or so running through there. Whatever I guess. I just hope he didn't set me up for a cracked head.

 

[6 Nebraska IDIs]

With the head shaved now that makes your compression ratio higher right?

Yea, kinda negated the whole purpose for me to use the early model A 6.9 heads. Between the model A heads and pistons used in the motor it was a lower compression engine. Now it's probably higher than a 7.3 motor.

 

[dyoung14]

Yea, kinda negated the whole purpose for me to use the early model A 6.9 heads. Between the model A heads and pistons used in the motor it was a lower compression engine. Now it's probably higher than a 7.3 motor.

shave the piston tops down a few thousands then you will be back to low compression again

 

[sle2115]

Are the A heads different too? A flat head being shaved won't up compression, if it has combustion chambers that's different, but these heads are generally flat.

 

[6 Nebraska IDIs]

The A heads are flat. But I thought milling down the precups would raise compression since you're moving that chamber closer to the piston. You guys are smarter than I am. You tell me. Because I honestly don't have a clue.

 

[icanfixall]

Cutting .009 off the heads makes the valves that much closer to the pistons now. That also increases the comp ratio some. The valves need to be sunk into the heads by a certain amount. It .042 to .054 for the intakes and .051 to .063 for the exhaust... The precups can be + or - .0025... The heads are junk when they are less than 4.795 thick measured from the valve cover gasket rail to the bottom of the head. They have a stock mearsurement from 4.795 to 4.805... If you had heads that were 4.805 to begin with then you now have heads that are 4.796... So you can loose 1 thousands and still be just fine.... Now just maybe this guy sunk the valves deeper in the heads the same 9 thousands. Thats fine if he shimed up the springs because if not they wont have the pressure to stay closed. The rocker geometry stays the same but the lifter is now using a 9 thousands differance postition and that just fine too. I find it great that this shop has so much backlog work... It means he is in demand for doing the correct work... Would you use a shop where they sat around waiting for work to walk in the door... Kinda like seeing a dr with no waiting because your the only sucker....

 

[sle2115]

yeah, a lot is dependant on how the precups were handled, were they cut and set properly? I can just about tell you if he used a cutter, not stones on the valves, they are .009 deeper or more than they were. .009 won't make much of a difference on the spring tension as most have a workable range and there are always shims.

In contrast, our shop worked 8:00 to 5:00 PM every weekday, 8:00 till Noon on Saturday. I was always there at 7:00 AM and took a lot of work in before the doors officially opened and I worked past my 4:00 PM quitting time most days, then dropped parts off (free no less) on the way home...I drove 45 minutes each way so there were quite a bit of stops some days.

I agree though, if they didn't have any work, I wouldn't want them doing my work. I'm certain we could have worked 24/7 and kept busy. The other thing we did and this person needs to do as well is be realistic in completion projection times.

I'm guessing you'll be fine on the heads and while we can sit and guess what was and wasn't done all day, without being there with a set of mics we really have no clue. I don't think cutting past the minimum thickness is good, but it doesn't mean the head will crack either. .009 is not that much in regards to valve lift, etc. and hydraulic lifters as well as correct stem height will have no problems dealing with this.

The last small block chevy I built had 5 times that shaved and had no valve train issues with higher ratio rockers (1.7 to 1's), plus the block was decked .030.

 

[dyoung14]

the a model engines have a 20.7:1 compression ratio lower than all the rest, so it must be in the heads? Cause the pistons are the same right?

 

[sle2115]

the a model engines have a 20.7:1 compression ratio lower than all the rest, so it must be in the heads? Cause the pistons are the same right?

No, I believe the pistons have a deeper valve relief.

 

[david85]

These engines have to valve reliefs in the pistons. They only profile you see on the crown is the bottom of the swirl chamber.

 

[The Warden]

the a model engines have a 20.7:1 compression ratio lower than all the rest, so it must be in the heads? Cause the pistons are the same right?

No, I believe the pistons have a deeper valve relief.

Actually, it's the other way around. The B pistons have a deeper valve relief (well, as David pointed out, it's actually the bottom of the swirl chamber)...according to the same document I referenced earlier, the A piston's volume is 4.5 cm^3, and the B piston's volume is 6.6 cm^3. FWIW the B piston's also SLIGHTLY taller, at 1.9465 from the center of the piston pin to the top of the crown compared to 1.9435 for the A piston.

The difference in compression ratio's in the precups. The A precup's volume is 21.89 cm^3, while the B precup's volume is 17.43cm^3. It gives the internal dimensions of the A precup as 1.240" inside diameter at the top (where the precup meets the head), with the throat being 0.270", compared to 1.144 top ID and 0.245 throat size for the B precup.

The documentation also says that the A and B heads are different, but I haven't yet found exactly how they're different (I THINK the A precup might go slightly deeper in to the head than the B precup, but I'm not certain). It DOES mention that the B exhaust valve's head thickness is 0.003" thinner (0.017 compared to 0.020 on the A exhaust valve) to accommodate the taller B piston.

I tried to attach the file to this message, but our software won't accept a PDF larger than 244KB (and this file's 1.1MB). Maybe I'll try to upload it to my webspace tomorrow...but I need to get to bed; just got back from L.A. ...

 

[6 Nebraska IDIs]

Here's a few pics from last night.

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I screwed one rod bearing installing the rod/piston into the block. Nailed the oiler tube with it and put a gouge in it all the way to the copper. Picked up another one today so that part will be finished today. Only got one head on, God I hope those heads aren't too thin.

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Dad always has something funny to say. Can't remember what it was but he thought it was HILARIOUS!

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