4.0 OHV Persistent Hard Start. Looking for ideas

[Kirby N.]

Ok. Thank you all. I feel good about going forward with this setup now! With the same setup before I didn’t have any odd noises and like i said a little piston rattle/ predetonation on hills when it was hot with 87 octane and I was going uphill before, but I started running 91 and I will just run 91 that all the time now- as it’s not worth the risk. Other than that no signs of an unhealthy or lean mixture- so I expect it to be fine.

 

[Kirby N.]

sweet. i was missing part numbers.

there is...rather you can end up with a bad combo that will really fawk shit up. fast.

several times i have been bit.

that is an updated article from the data i had.


in any case it is simple.

listen carefully when you mix and match. preferably run it on a dyno or where you can concentrate on it when it is under load with low grade fuel and if its good...it is good. if its knocking bad, figure it out.

in this case it is obviously a mechanical issue with the seats.

i was planning at looking to see what we had when i got back home...but with nos units on the way i suspect you will have it going in short order.

i will print that and put it with my notes....great detail.

this really helps. Thank you.

I agree it was mechanical, and it didn’t go bad fast, it went bad in 38k miles. So I don’t think it was a bad mix of parts issue.

 

[Kirby N.]

I'm a bigger fan of OBD2 than OBD1 only as far as diagnostics, but in addition to the work of changing it, could you even get a pass at a Colorado emissions station?... They would take one look at it and go it has an OBD2 port it has to pass the full monty instead of the lesser "grandfathered".... That said supposedly they only check if A) the CEL is lit or off but stored in computer, B)there are emissions sensors "not ready" (like you just disconnected the battery to clear a CEL), C) what the actual tailpipe emissions are (hence the run running test on the treadmill) D) headlights and horn.

So as long as you can fool a handheld OBD2 reader into believing all sensors are ready (or all but one), you should pass... but again they might just fail you rather than deal with figuring out your "weird" config.

we don’t have emissions here in El Paso county anymore. I am so thankful too!

 

[Kirby N.]

I am reading that as "Don't use 95TM heads (or newer ones) on a 95-96 Aerostar" and that it only applies to those two years of Aerostar vans. And that would make sense given that those two years of Aerostar engines would have had the shallow dish pistons, add the fast burn heads and you've got a fairly high compression engine. I think that's where they made a mistake with one of my 4.0's, it was a 94 short block but someone put 98TM heads on it and it would ping under almost any load, even with a full tank of 91 octane and added octane booster.

I guess I'm just not seeing why 95/97TM heads and deep dish pistons wouldn't work for you after reading all that, compression ratio being close to what it was in 1991 would be the main thing in my mind. Obviously I do not build engines for a living so I would sure like to pick Mr. Anderson's brain on that topic - what causes those engines to melt down, is it simply detonation from high compression & low octane, or is it some little detail programmed into the ECM that messes with the timing or fuel or something, IE, a software problem?

I think that is the motivation of this statement from an engineer too. I think he was talking about the earlier pistons with later heads in the aerostars 100%.

 

[Kirby N.]

I got a couplePackages today!

I

I think these will work fine. I am going to run them. They look to be as advertised. New old stock 95tm factory ford heads. eBay. Sometimes I love it, sometimes it’s hate it.

 

[RobbieD]

OOOHHHH . . . SHINY !!!

Nice score.

 

[Kirby N.]

Going back together. I am going to get a baseline for compression before I fire it. I need to prime I anyway. Probably button it up on Monday.

close up of the old heads compared to the new one:

Way less recessed. I don’t think the new ones don’t have seats, but you can see where the area around the valves is heat treated. The machine shop also guy said they use induction to heat treat them.

The springs and seals look new.

I decided not to use rock auto for the gaskets because I hate when they send the wrong stuff or jacked up stuff. AutoZone was having a Black Friday sale so I got victor reinz or Dana gaskets.

good thing too. They were boxed up but had 2 different gaskets. So annoying.

This was the gasket that was different I didn’t like that it didn’t have steel around the cylinders. It may have had it under the gasket material- but it was frustrating that it was different. So I returned it to the local hub autozone and got a felpro set. It came with cork valve cover gaskets so I bought another set of valve cover gaskets separate.

 

[Kirby N.]

We are at 130 psi in all cylinders cold and dry. It should start better with those numbers. I will have it together this week I think. I had my drag link redone so I can use a different tie rod end- and that is the hold up currently.

 

[Kirby N.]

I got her together tonight.

She runs real nice, Clark.

Smoothest I think she ever has.

It had a little squeak from the alternator. I think maybe it got some dust or something in it while it was sitting on the work bench. We blew it out with the air gun and it quit.

Other than that it sounds like a sewing machine. Starts easy too. Sounds wicked on the rev. I am stoked to drive the darn thing!

 

[bobbywalter]

nice

 

[Kirby N.]

Running great. Put it to work this week pulling a trailer full of wood and 55 t posts in the bed.