Engine Build

ChunderDownUnder · Apr 12, 2012

Ok my engine build has been a learning curve. Unfortunately for me it aint a machine everything up get new parts and put em all together.

My deck and heads had .003 taken of to clean it up. My crank is .020 undersize on the main journal and .010 under on the big end journal. I have swapped out my PMR's for reman forged. Pistons are .010 oversize OEM. Stock valves. Comp910's install height 1.75 shimmed 134lbs pressure. 3 angle valve job and slight port work which has left me with valve recession of .068 on the intake and .072 on the exhaust. Pistons needed .020 of the top to get me a height above deck of .025. Im running with Matts stage 1 cam and have smith bro pushrods that have .083 wall and +.030 length. Now unfortunately those pushrods are to long due to the amount of meat that has been taken of the engine over its life. So to get the right preload on the rockers (.185 collapsed tappet gap) we have to shim the pedestal .060 to make em work. With all that Im going to end up with a valve to piston clearance of around .110 on the intake and .100 on the exhaust. I cant seem to get a definitive spec on the last bit. I have read .030, .060 and .100. The last number I got from a Swamps post here.
http://swampsdiesel.com/content/projects/Camshaft_Design/

anyone out there who can share their wisdom . And on a serious note if you dont know what ya talking about leave it out. I have been lead up the golden path on these numbers so many times over this build Im really getting over it :fustrate:

TARM · Apr 12, 2012

I am sure someone will have answers for ya. You got all the info I had in the PM.

ChunderDownUnder · Apr 12, 2012

yeh Tim thanks for that.

Hotrodtractor · Apr 13, 2012

How are you measuring your valve to piston clearance? You already have a clearance that is greater than the largest minimum clearance that you were able to find - so as long as you are correctly measuring that clearance - then what is the issue?

golfer · Apr 13, 2012

I would also be more concerned with the loss of flow by having the valves recessed that deep...

the pistons had to be machined anyway...why not have the heads machined to have less (valve) shrouding?

That would have minimized & most likely eliminated the shims at the rocker pedestals...allowed OEM length PRs...and you'd pick up some flow at the valve...

a valve spends more than 50% of it's time at less than half lift...so increasing flow at low lift is where you're going to see the most gain.

but based on your PTV clearance...I don't see an issue...as far as physical contact goes.

PowerstrokeJunkie · Apr 13, 2012

They do everything backwards below the equator LOL

TARM · Apr 13, 2012

Brian,

Correct me if I am wrong here. But based on the what was said on PSN and your PM, I think were most of the idea there was an issue and being unsure of specs came from when you test fitted the heads but the valves without springs which caused valve to piston contact.

What Dave posted makes sense to me. I know its beneficial for flow to reduce the shroud. Why not do the machining necessary to make those recommendations happen then shoot for a .100 final clearance based on HRT comments.

Anyways post up what you finally decide to do.

ChunderDownUnder · Apr 13, 2012

I hear you all. but being my first build and being un prepared for these way out numbers I got a bit behind the eight ball. I could only go by what my machinist was telling me. Was hoping to get this info earlier but thats the way the cookie crumbles. Anyway I have the engine back now. pedestals are shimmed .060 to achieve the right preload. I dont know why the machinist didnt mention machining the head, that makes sense to me now. I will do a final check (plasticine on top of piston) but we are looking at a valve to piston clearance as mentioned earlier. Thanks guys.

Just thinking again - U guys cant see anything there that will effect my HP #'s or back pressure on the 38R ? (other than the valve recession being a little high)

TARM · Apr 13, 2012

Sorry I do not recall did you get any porting or polishing on the head ?

ChunderDownUnder · Apr 14, 2012

cleaned up the pocket and runners thats all.
And the valve to piston contact was due to preload being to high. The pushrods I have are Smith bro .83 wall and +.030 length. I have a set of EOM as well which had to much preload as well. If anything my pushrods should be -.030 or there abouts. Just measured the valve recess myself. I was going of what the machinist said and couldnt remember the exact numbers so I checked again and m8 they are ugly. Im a bit embarrassed posting them up.

ChunderDownUnder · Apr 14, 2012

I dont think taking more meat of the head is an option. Just measured my deck to deck. 5.046. 5.095 is the minimum. what about hardened seat inserts ??

ChunderDownUnder · Apr 14, 2012

Here go's
Valve Head recession relative to deck #'s

Intake
# 1 .065 # 3 .088 # 5 .095 # 7 .083
# 2 .070 # 4 .079 # 6 .065 # 8 .077

Exhaust
# 1 .105 # 3 .113 # 5 .116 # 7 .121
# 2 .098 # 4 .093 # 6 .100 # 8 .102

ChunderDownUnder · Apr 14, 2012

heres some pics

valve seat

deck to deck 5.055

exhaust valve recess .119

ChunderDownUnder · Apr 17, 2012

update.- Heads are going back to get valve seat inserts installed. I have made a deal for supply and fit which Im happy with. This will get the valve recess back to spec across all valves and also bring the preload down so I wont have to shim the rocker pedestal. If I paid more attention to spec'n the heads when I took them off I wouldnt have been in this situation. A lesson learnt.

TARM · Apr 17, 2012

Hey its a learning experience. The ones that hurt and the lessons that are learned the best.

PowerstrokeJunkie · Apr 18, 2012

TARM said:
Hey its a learning experience. The ones that hurt and the lessons that are learned the best.

:whs: that's for damn sure!

ChunderDownUnder · May 26, 2012

Ok starting to put her back together again
I have a collapsed tappet gap of I .106 and E .067
With Matts stage I cam and .060 over length pushrods. Do these numbers work?

Hotrodtractor · May 26, 2012

ChunderDownUnder said:
Ok starting to put her back together again
I have a collapsed tappet gap of I .106 and E .067
With Matts stage I cam and .060 over length pushrods. Do these numbers work?

Take a look at this PDF: HERE

ChunderDownUnder · May 26, 2012

I have that thanks. Thats where I got the .185 (max) measurement. Oh btw my pushrods are .030 over not .060.
Now that .185 Max so what Im getting is OK . Im assuming that if you were up near the max your valve train would be getting noisy..
Also I have noticed that there is some preload on the lifter when I tighten down the rocker pedestal.

ChunderDownUnder · May 26, 2012

Im at loss atm or either Im confusing myself .

Im nipping up the pedestal as evenly as possible until zero back lash then Im measuring the travel with a dial gauge to get the lifter preload

with the .030 under size pushrod Im getting lifter preload of .075 on the Intake BUT I have a collapsed tappet gap (dry lash) of .195 which is .010 over max