4.0 OHV Persistent Hard Start. Looking for ideas

[Kirby N.]

@gaz thank you for the reply.

I run 87 octane all the time. Sometimes I run 91. This summer I noticed a little pinging going up hills so I would run 91 more often. That may have been due to the higher compression?

I only ran the 93 computer for a few days. It ran fine but with the cel I took it out pretty soon. Maybe started and ran it 5- 8 times. I returned the ecu to the junk yard. It was off a 93 exploder without a cam sync sensor. My truck has no egr. I didn’t see her on the exploder either, but it may have had it.

the rebuild has 38k on it. 2 years since completion approximately.

 

[Kirby N.]

well based off the last thing I googled up, I would try the quickest/easiest/least destructive tests and work up to the more invasive (i.e. take the oil cap off and look for smoke/steam/pressurization etc - blown headgasket, before pulling a valve cover- costs a new gasket, before pulling a head - lots of lots of work)...

double check your coolant for signs of contamination from a headgasket issue.
maybe do an oil change and check the oil for contamination.

run over the complete vacuum system for a leak is on the list for all your issues except low compression... low compression tosses that out as a primary issue, might have it, but it would be secondary.

I will check the coolant again. I am heading out of town, but I can check it. I just changed the oil and didn’t notice any gas smell or anything odd with the oil- and I did check.

I did the smoke test on the intake system and smoke did get all through the vac lines. I even had it in the air box from the lines there, but got no smoke leaks from anywhere else that I noticed.

Now on the idle- it does sputter pretty hard. Almost like a babbling brook. My dad put his glove over it last night and said it feels like it is sucking his glove back (no hand) every few sputters- so he is convinced it is a valve issue. I may just pull the heads when I get a chance in a couple weeks and have them tested. It’s not a giant job, and though it is invasive I kind of want to see what is going on with them.

 

[Kirby N.]

I changed the radiator in October of 23 and drained the coolant and put it back in, then I changed the thermostat in September of 24 and drained the coolant and put it back in. Didn't see anything weird either time, but I will check it again.

 

[gaz]

@Kirby N.
If any part of your issue is the result of the increased C/R, run your fuel low and replace it with the highest octane your area sells; 92, 93 or 94...see if it makes any difference.

The compression results are the most troubling. Unless your battery is dying while performing the test, that alone rates getting to the bottom of. My mechanical mentor always looks to the valve train 1st for failed cylinder compression and your compliment of parts should read on the high side, not near none existent.

I would persecute the valve guides seals, valve guides and valve seats. The valve seats are often let go or overlooked by assemblers depending on their wheelhouse; if this is the case your fuel economy should also be suffering.

35k on the rebuild, that is enough for the non-adjustable valve train to have worn itself past optimal (if it was replaced to new when rebuilt). You could pop the valve cover with the weakest overall compression results and check the condition of your rockers/pushrods and the preload

I would slap on a fresh gas cap and fill it up with the highest octane premium in town first, before I disassembled anything else. You are going to need fuel anyway and if you've never replaced the gas cap, could, could...nail right there.

 

[Brain75]

Before you pull the head (more work and needs new head gaskets once you do that) pull just a valve cover off (cheapest gasket and least work on the invasive list), and check your valve events.

Basically at this point of lightly disassembled you might find something like lifters sticking/failed, valves sticking, and of course the possible damaged stuff - broken springs, missing keepers.

by watching the angle of rotation of the crank (harmonic balancer) versus what valves are currently doing what you might also figure out if the timing chain is slipped or installed wrong (don't think it is possible to be anything but off by 1 tooth/180 degrees/etc - not like there is a fancy route with an idle gear you could have mis-routed).

I was looking for a valve events chart for this motor but haven't found one... it's should be fairly easy to deduce from the firing order.
6 cylinders, 2 engine rotations per cam rotation = 30 degrees between valve events
1-4-2-5-3-6

Ford 4.0L (244.6 cu in) firing order — diagram & guide | REREV

Demystify the Ford 4.0L firing order for superior engine output. Dive in to enhance your vehicle's operation with trusted expertise.

rerev.com

the one pretty authoritative thread I found on this confirms that at 0 on the harmonic balancer cylinder 1 should be TDC and also says 30 degrees between events.

How to check camshaft/crank timing on 4.0 OHV?

It is my understanding that the 4.0 OHV rarely has timing chain issues however I have a 4.0 with no start, an unknown history, and all kinds of parts thrown at it by previous owner. I'll certainly verify fuel, spark, compression, etc but is there a way to verify cam/crank timing without taking...

www.explorerforum.com

If you figure out the timing is off then don't pull a head and pull the timing chain cover, etc... limit your invasion to what makes the most sense step by step instead of jumping to a complete tear down.

My hunch, I would start with the timing cover even if it is twice as much work (1hr) as a valve cover (30 min)... But you are the one who put this together right - how confident are you that you got the things lined up correct? (rhetorical - keep that answer to yourself, not trying to embarrass you )

If you have a fiber optic cam you could check pistons heads and cylinder walls without having to buy gaskets. I wouldn't spend time on that though if it never ran right after rebuild.

my suggestion to double check coolant and oil can be called off, if it was not right before you did those back in sept/oct and it still isn't right there's no need to go down that path...

 

[Kirby N.]

Thank you for the suggestions! No offense taken at all.

I didn’t have much to do with the timing chain. That was all assembled and shiny new with the short block- so I didnt mess with it. I think I looked at the marks and made sure they aligned on the tdc stroke- beyond that I didn’t mess with it.

I am confident in taking the head off. I have done that a lot. Of course I have to take off valve covers before taking off the heads, so I could do some poking around there and see what I find. I guess it could have a flattened cam- the heads would have to come off for me to check that or swap one anyway though. I would have to pull the lifters and they don’t come out without the head coming off.

It did run pretty decent up until about 6 months ago. It always idled odd, but that could have been other things. Iac, the had cleaned the throttle body with carb cleaner and removed all the film off of it- so I learned a lot. Replaced that. Then messed with the new throttle body, iac and the tps. I am wondering if between the 3 I could have gotten it fixed if the rest of the engine was good.

 

[Kirby N.]

Thank you for the suggestions! No offense taken at all.

I didn’t have much to do with the timing chain. That was all assembled and shiny new with the short block- so I didnt mess with it. I think I looked at the marks and made sure they aligned on the tdc stroke- beyond that I didn’t mess with it.

I am confident in taking the head off. I have done that a lot. Of course I have to take off valve covers before taking off the heads, so I could do some poking around there and see what I find. I guess it could have a flattened cam- the heads would have to come off for me to check that or swap one anyway though. I would have to pull the lifters and they don’t come out without the head coming off.

It did run pretty decent up until about 6 months ago. It always idled odd, but that could have been other things. Iac, the had cleaned the throttle body with carb cleaner and removed all the film off of it- so I learned a lot.

@Kirby N.
If any part of your issue is the result of the increased C/R, run your fuel low and replace it with the highest octane your area sells; 92, 93 or 94...see if it makes any difference.

The compression results are the most troubling. Unless your battery is dying while performing the test, that alone rates getting to the bottom of. My mechanical mentor always looks to the valve train 1st for failed cylinder compression and your compliment of parts should read on the high side, not near none existent.

I would persecute the valve guides seals, valve guides and valve seats. The valve seats are often let go or overlooked by assemblers depending on their wheelhouse; if this is the case your fuel economy should also be suffering.

35k on the rebuild, that is enough for the non-adjustable valve train to have worn itself past optimal (if it was replaced to new when rebuilt). You could pop the valve cover with the weakest overall compression results and check the condition of your rockers/pushrods and the preload

I would slap on a fresh gas cap and fill it up with the highest octane premium in town first, before I disassembled anything else. You are going to need fuel anyway and if you've never replaced the gas cap, could, could...nail right there.

I literally lost the cap about 2 months ago and replaced it. When I did the compression test both times I had a charger on the battery and the battery is a hi performance odyssey that has plenty of juice. So I don’t think that’s the deal.

 

[Uncle Gump]

Probably the last thing I would do is add higher octane fuel and a gas cap.

I'm kinda surprised it runs at all...

For the sake of root causing this issue... I think i would also start with the valve covers. Ensure the rocker shafts didn't loosen up... watch valve events and inspect rockers pushrods and valve stems.

from there... pull the heads.

Also of note...

The non adjustable valves could pose problems when swapping later heads on earlier blocks... heads being milled for flatness... etc... I've also read that installing fast burn heads on an Aerostar block in some cases would burn up your rebuild in short order. There is a tech article that identifies this. I've also read that there were three different lengths of pushrods offered for the 4.0L. Too short... noisy valves. Too long... it could hold valves open or not allow proper valve to valve seat pressure and burn up perfectly good valves.

 

[Kirby N.]

First up, leak down test. I tested cylinder number 4 because it was easy. I lined up the tdc mark. When I did pressurized the cylinder I could feel air in the exhaust and the intake. So I turned it 1 full turn just in case it was 180 off. Same results. So I turned the crank one more turn. Same results.

So off with the upper intake and valve cover. Then I took off the rockers just in case I didn’t have the valves closed. Pulled all the pushrods. Tested again. Same results. I could feel air coming out of the intake and out of the exhaust.

Off with the heads!

 

[Kirby N.]

I tried calling machine shop that did my valves- they obviously screwed something up big time- and I think they are out of business. That’s handy. They were in the biz since the 60s at least. My dad used them the first time late 60s. I had some issues with them when they first did the head and had to take them back. Perhaps they sucked themselves out of business.

So I don’t have a ton of options:

I might be able to get some 95tm heads from a national place, but it seems like it was 93tm or 98tm. The 95s have the right exhaust ports and right volume.

Anyone have experience with Odessa or King or Clear water heads?

Anyone know a good machine shop in Denver area?

 

[Brain75]

Since I am one of the few other Coloradoans here (active right now), I kinda feel like eyes are on me... unfortunately if you had said muffler or powder coat I could give you names, machines shop .... not so much.

I pulled up google maps just to see if any names rung a bell (I used to hang out with the Bandimeere Club Clash guys - 1/4 mi drag folks and knew of several who really worked over their rides, we'd BS between heats), but none of these would be used myself - just names that ring familiar....

DenverMachine is one of the oldest (and farthest away), but their splash page is all heavy equipment doesn't even say if they do auto.

Industrial Machine Repair & Rebuild Services in Denver CO | Denver Machine Shop

Denver Machine Shop specializes in repair & rebuild services for heavy industrial machines such as mining & power generation equipment. Call today!

www.denvermachine.com

I have at least heard of Gunn, but don't remember what was said, could have been rave blessing could have been cold shudder curses... the name is familiar is all.
Gunn Automotive Machine Shop
145 S Federal Blvd, Denver, CO 80219
3039343134

same thing goes for Mountain Performance and Western Engine... though I thought once upon a time Western Engine only did Semis...

MtnHiPerf, mtnhiperf, Mountain High Performance, Diesel Performance,Cummins big valves, Cummins performance, Duramax big valve,Powerstroke big valve, diesel Oversize valve, Cummins oversize valve, Duramax oversize valve, Powerstroke oversize valve, 5

Full machine shop services offering performance Diesel upgrades including oversize (big) valves for Dodge Cummins 5.9, 6.7, GM Isuzu Duramax 6.6, Ford Navistar Powerstroke 6.0, 6.4 engines. Upgrades for springs, retainers, pushrods, guides, & seats are all available. Also many gas engine head...

www.mtnhiperf.com

Western Engine Supply

westernenginesupply.com

everything else I saw on google maps was names that did not ring familiar.

I got totally different results for "auto machine shop" and "auto valve machine shop"... might try a few combinations and read a lot of reviews..

 

[Brain75]

One thing that stands out in my brain is that some of the deep pocket guys who really threw a lot of money into it (not just the causal turbo/supercharger/shaved heads, but the "replace everything") went to MtnHiPerf.... These were the guys who drove street legal cobra's and such but kept getting suspended from the track cause they were too fast without adding a roll cage or parachute etc etc - the guys who had buckets of money to get 0.1th of a sec.

 

[Kirby N.]

Ah, cool. Thanks. I kind of had the same reaction to Superior https://www.superiorenginescolorado.com

Seems like I have heard of them but I am not sure why. Good or bad.

Mountain high seems like the best move. I don't want to do this again.

 

[Kirby N.]

And thank you!

 

[Brain75]

You didn't show the springs side, and one of the things mentioned was with you might have issues with incompatibility... are all the springs squashed flat, cracked, etc - is it possible you just had a bad combo, no fault of the machine shop? Not trying to defend any particular shop, I just want to see you not have an expensive mistake happen twice.