Ok, quick back story, bought 79 F250 4x4, had 300 in it, ran on about 3 1/2 cyl. found 300 in 89 F150, heard run, bought for $300. Had rebuild stamp on back of cyl. head,,,
Put on Offy intake, used the FI exh. manifolds, had a 2 into 1 exhaust, 2.5" all the way out.
New water pump, t-stat, hoses, flushed rad. was running good, didn't seem to have the power it should, truck has 4.10's but I also have 255/85/16's. Always ran warm in summer, going up Deadwood out of town to home, would spit up if I put to much a-freeze in. Loaned to buddy over winter, he brought it back, I drove to work, was going to go cut wood after work, on way up hill started getting hot, then pegged, blew head gasket.
Trailered her home, pulled head, broken head bolt where head gasket blew, when removing head bolts, all "felt" like different torque,, some hard as hell, others not so much. Head straight-edges good, doesn't seem to be warped or bowed, found out it is punched .030.
So, question is (finally, I know ) because it was FI, is the cam timing different, what would make her run hot, all the passages look good, I think I put a 180* t-stat in, don't remember. Are there differences in the heads from carbed to FI?
My last 2 300's I had dual outlet headers and ran duals all the way out, is it choking for not enough air flow out?

Any and all thoughts please!

 

The cam timing isn't different but an EFI head might require the ignition timing to be retarded vs. a carbed 300 head.

I put the thermostat in backwards and it ran super hot, like bend the needle on the temp gauge hot. As far as overheating goes that seems to be a common snafu.

 

When you replaced the H2O pump, was it for a 1979 [v-belt] or 1989 [serpentine?]? If the donor engine had a serpentine belt, and you replaced the H2O pump with the newer style, it may be running backwards. This would cause it to run warmer than normal... you might have been okay during the colder winter months, but not when the temperatures are warmer and running uphill???

 

Hmmm... I don't remember,,, I will call NAPA and see if they can find which one I bought, I think I have the recpt. somewhere,,, I think I had to buy the 79 so I could use my pulley on it,,, And I know the t-stat is in right, I too did that once! I am thinking about swapping radiators with my 66 and seeing if that does the trick.

 

also check your fan clutch.

 

I went with old style fan, the serpentine had smog pump and all that crap, I just went with the 79 setup. But since I have it apart, I am going to really look at things,,,

Are there different heads from FI to Carbed? Some of the cooling passageways in the head don't go into the block? Are there different blocks for FI? Older block, newer head?

 

i'm betting the blown head gasket was causing the overheating- not the other way around.

 

Thanks, I was wondering that too,,, and oh yeah, by the way, had one broken head bolt, twisted off when I was removing them,,, AND it was the one in between 3 & 4 where it blew out,,, would that have been causing it to get hot?

 

maybe the broken head bolt was causing a loose spot, and the improper torque around the bolt allowed combustion gas out of the cylinder, and it eventually ate the gasket?

 

YUP, that's my story and I'm stickin to it!
I hope that new head gasket AND new head bolts TORQUED correctly, will take care of it, I am going to check my t-stat, I thought I put a 180 in, but you never know, I will write it down this time!

 

I'm not a big fan of the factory head bolts, had trouble with them years ago and the TTY bolts are even worse.
Last time, I used an ARP stud set I got from eBay for 30 bucks and a severe duty head gasket. No problems since.
I'm convinced the headbolts caused the problems initially.

 

Do you know if I can replace the head bolts with the head still on? My I-6 has 65k miles and Id rather replace head bolts now than head bolts and head gasket later.

 

Ok,, SUCCESS!!! New head gasket, new head bolts, yadda, yadda, and viola! Had to back the timing off also, it was @ about 14* for some reason, new t-stat, checked in bowl of hot water, old one was barely if even opening. So along with broken head bolt, blown head gasket, advanced timing, stuck t-stat,,, no WONDER she was hot!
Thanks for the info guys!!

 

"...is it choking for not enough air flow out?" No way unless there is a serious blockage down stream in the exhaust system...not unusual on these older vehicles when a catalytic convertor gets plugged.

 

NO CAT!! Just a 12" glass pack and 2.25 or 2.5 all the way out, has a nice raspy bbbbrrrrrrappppp up and down! Thought about trying a flowmaster I have in my shed on it, just to see if I like it on the 6.