100k 4.9 freshen up advice please.

deere114

Well-known member
I've got a strong running 94' 4.9 I want to freshen up to drop into my turbo truck. It's current engine has seen 20 psi of boost more then a few times on e85 and has nothing done to it other then arp head studs with a felpro 1024 head gasket. I'm going to be setting this truck up for my daily commute to work and haul landscaping equipment and materials for my brothers company 6 days a week. I want a trouble free mill that I won't have to pull out of service for repairs. As of now my plan is: switch from 2.73's to 3.55's on stock tires, switch to pump gas and limit boost to 6psi or so, add a water meth kit for safety against detonation (this engine should have the cast pistons. Remote dual oil filters with an oil cooler. The engine itself will receive the studs from the old engine, a felpro 1024, all new engine gaskets, a metal straight up cam gear set, and a fresh coat of paint. Now the questions: is it worthwhile to install a high volume oil pump while the engine is out? If so is the stock oil pump drive shaft up to the task? Debating on switching from the efi head to a carb head thinking it will be less prone to detonation, I'd be tempted to add stiffer valve springs and an aftermarket camshaft at that point though, what're your thoughts? Am I forgetting anything I should be doing to help this engine live a long happy life?
 

bubba22349

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For one thing you should forget using the stock cast pistons. At least use a set of the late 1995 to 97 Hyper. If you are rebuilding the rods use some ARP bolts there too. Good luck (y) :nod:
 

deere114

Well-known member
I was originally looking for a 96 engine for the hyper pistons. This 94' I bought for $300 and the motor ran very strong compared to other 4.9's I've driven. I needed some other stuff off the truck and wound up with the motor almost free after I scrapped out the rest of the truck. I didn't have any plans to rebuild the bottom end, thinking low boost and a very conservative tune should keep the pistons intact. I'm not the kind to lug my engines down hard. Hoping for the best as far as the pistons go I guess.
 

jason832

Well-known member
Stock pistons are not very strong. Its well known around here that when you open up a bottom end it has a decent chance of missing piston chunks.

I have also built a mild engine (stock low milage bottom end, carb, intake and headers). Shortly after it has 40psi of compression on one cylinder. I pulled the head and one area of the cylinder was scratched up and down indicating a broken piston or ring. Still haven't pulled the piston though....

If you are building an engine beyond stock get at least factory hypers or a set of sealed power hyper pistons (h519p I think).

Factory rod bolts are fine unless your building a screaming motor. The French town flyer reassured me before my build, and I haven't had an issue with any of the factory fasteners.
 

THE FRENCHTOWN FLYER

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I have had no problems with the stock drive quill on a hi-volume pump. The EFI head is actually less prone to detonation when used with the correct spark schedule. It burns faster resulting in less end gas tendency to knock. But it requires less spark advance (a GOOD THING) than the carbed head.
 

deere114

Well-known member
It definitely likes less timing. Naturally aspirated on 87 octane it only likes 28 degrees total. I guess I'll polish the chambers up while I have the head off and re install it. My current stock cast piston motor has taken 20 psi fun along with some 8 psi daily driver miles on e85, it also has just shy of 180k miles on it. I think the key to keeping cast pistons in one piece is a really conservative tune, and the right driving style (not holding it at full boost low rpm where the cylinder pressure is highest) worth using a hv pump in this engine FTF?
 

pmuller9

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Please do a leak down test on your present turbocharged engine before you take it apart and post the results.
It will be good reference info.
 

deere114

Well-known member
I like that electric oil pump! I'll look into that thanks. The current engine has a cracked cylinder head I believe at this point. Had the wastegate reference line come off (completely my fault I forgot the hose clamp) on that pass it maxed out the map sensor in the datalog. My fuel map didn't go that high so it went lean, it happened so fast by the time I let off the gas it had already done the damage. Funny thing, it wasn't very violent, it pulled like a train up to 20 psi like it normally does, then just broke up lean. The wastegate line flying off made a pretty loud noise though! I let back off and it drove back to the shop like normal. When I saw what happened in the datalog I checked the oil expecting to find it full of coolant, it wasn't. Put the wastegate line back on (with a hose clamp) and went back out. After 5 psi it would start missing on a cylinder. I figured I blew the head gasket between two cylinders. I pulled the head and slapped in a new one (head gasket was blown out between the middle two cylinders) after that it was consuming coolant and I could actually see it pushing oil vapor out a hairline crack in the cylinder head while its running. I could check the cylinders that still seal well, but keep in mind what this engine went through! Ironically enough it still fires right up and drives fine, and actually makes power. Tough engines these things are for sure.
 

guhfluh

Famous Member
Seen you post on Facebook. ;)

I'd keep it simple. Hyper pistons, metric ring set, new stock bearings, new stock pump, stock cam and metal gear degreed in, swap studs, add a gasket and a freshened stock head. No need for more on a driver.
 
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