1986 F-150 with 302 in³/5.0 liter engine. I would like to know if this engine is an interference, or free wheeling type. Today I drove about 150 feet from driveway, and the truck quit @ approx 1500 rpm. For T/S, I pulled the distributor cap, and watched the rotor as the engine turned over. Obviously, it has cam timing issues as the rotor hesitates, & is basically erratic. I assume the camshaft sprocket is one of the "Quiet" types with plastic teeth, of which several are now probably in the oil pan. With 236,000 miles showing on the odometer, I am willing to put a on a new timing chain, but if it's an interference engine, I will look for a new crate engine. In searching the internet, I have found this engine is (BOTH) definitely an interference engine, and definitely a non-interference engine. Hmmmm? I'd just like to narrow it down a little closer! I was hoping for experienced advice before wasting any more time & $$. Thanx for your input.

 

Welcome to the site!

To the best of my knowledge - no, the 302 was never an interference engine.

When I replaced my timing gear set - no plastic to be found, just good ol' steel.

Suggest the timing chain has a lot of slop in it, resulting in the erratic rotation as the cam is pushed off the respective valves? ? ?

236,000? You should be proud - I replaced the chain and sprockets after 170,000 miles and then only because I was chasing a coolant leak. The measured timing chain slack was well beyond tolerance.

On a separate note - the rule of thumb I've gone by is that the 302 is generally good for 250,000 miles if well maintained. Might suggest a compression check and other means to determine the general health of the engine. No need to put a bunch of effort and dollars into something that may already at end-of-life.

 

What is your definition of an interference engine? Yes ALOT of Ford smallblocks had the nylon coated teeth and they can play hell.

 

well i guess the 302 i bought lived a full life. it had 220k before it blew but now im selling parts of which is still good which is quite a bit of them.

 

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An "interference" engine is an engine which the failure of the timing chain would cause damage to either the pistons or the valves, due to interference between the top of the piston at TDC, & any opened valves. So, when the timing sprocket or chain breaks, the cam stops, and the pistons still moving at speed, start hitting opened valves.

A non interference, or free wheeling engine is an engine where the pistons will not contact any open valves at any time.

If you have any engines that use a timing BELT, the Internet is stuffed with info on which are interference or free wheeling. If they are interference type engines, I’d pay close attention to the belt change intervals!

In the past, I’ve heard horror stories of shade tree mechanics installing such high lift cams, with radical timing, that the pistons hit the valves even though everything was timed correctly. They should have cut relief’s in the pistons for valve clearance of course. Next time.

This 302 ran fine until this little boggle. It only uses a qt. of oil about every 3000-3500 miles. Just broken in good. Have used synthetic oil in it a lot, which seems to help.

 

The 302 is freewheeling. I have heard that some 302 high performance engines in the mustangs were interference due to high lift cams but not in the trucks.

 

Check with an engine shop, they should be able to tell you when Ford finally woke up and made the improvement. If it was me, I'd be ready for the worst, pull the engine and have at it. Life is so much nicer with the engine on the stand or as we did it, resting on the floor with a 4X4 under the high point of the pan, then tilt the engine back onto long tranny bolts.

 

Welcome to the forum.the Ford 302 in a truck app. is not a interferance engine .note I have never worked on a 302 square inch engine did they do that for hood clearance or what?.Just kidding. Bubbabud 2011 XLT SCAB Ecoboost

 

Thanks for the welcome. Sheesh, I’m a victim of my own proofreading! Come to think of it, I’ve never seen a 302 in² engine either. Maybe a 302 Chev? 302 in³ it is!

And, thanks for the answers too. In thinking about this situation, the 302 might go either way on the freewheeling issue. I hope this low performance, (185 HP @ 3800 rpm) engine uses dished pistons and low lift figures on the valves, while the Mustang’s 302 HO (?) (200 hp @ 4000 rpm) had flat top pistons, and higher lift cam. Hopefully it’ll have the extra clearance to be freewheeling. Engines from the “Good ole’ days” used crowned, pop-up pistons, and even higher lift cams, and I could believe those would be interference engines.

At this point I am going to pull the front apart, and replace the timing chain. (That is, as soon as the temperature here gets into the 40° zone again.) I will not however, rebuild the engine if there was piston to valve damage. Then it’s crate engine time, and I’ll have a good quality, double roller timing chain to put on it! If I’m going to spend the big bucks, it will go toward an engine that does better than 185 Hp, and 10 mpg for sure.