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What Heads OHV 4.0?


I just saw that this thread is active so I thought it should have an update on my experience.

A little update on my build. I had the new old stock 93tm valves and springs and keepers moved into a set of 1995 heads that I got at the junk yard. The heads were magna fluxed and decked and got new seats. The valves made some noise when I first installed them- so I took them back. The guys at the machine shop said they pressure tested them and they came out fine but they went ahead and reground the seats by hand. They said it was probably the lifters- even though I used new melling lifters. So I put it back together and used a new old stock set of lifters off of eBay. It was quiet, so I ran it. I never got the idle sorted- it always idled fast like it had a vacuum leak but I could never find it.

30k miles later, it lost compression and started running like crap. I took the heads to another machine shop and they said the brand of seats the first shop used had moved production to china and the quality went to crap.

So I found some more NOS 95tm heads (this time they were actual 95TM) and re installed them. The truck runs better than ever and is actually idling well now.

SO I am running a 98 block, 98 pistons and 95 heads with a 91 computer and accessories. Seems to be running awesome, but I will update after some miles get on it. I drive it a ton.
 
SO I am running a 98 block, 98 pistons and 95 heads with a 91 computer and accessories. Seems to be running awesome, but I will update after some miles get on it. I drive it a ton.
Interesting combo which should require less ignition lead than what the '91 is providing, right? But if there's enough safety margin in the timing, perhaps that's not an issue and the little extra ignition advance is actually giving you a performance boost.

FWIW, I bought a 4L engine once which had '98 heads on a '92 block and computer. 24pph injectors were installed, which I suspect was the "redneck tuning" technique from when it started pinging.
 

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