Fox T-Bird/Cougar Forums

I'm sitting in my barn drinking a beer and looking at the 5.8L motor from my truck sitting on the stand. I pulled it to remove the pan and other sheet metal and clean out 145k of sludge. (The motor runs strong but has lost oil pressure lately in a way that tells me the pan is full of ). And I start thinking, why not just drop the truck motor into the T-Bird? It might be a good match for the 2.73 gears... more torque than the 5.0L. Eventually I might steal the 3.55 gears from the truck, too. It is the same locking 8.8in. diff in both. What I will actually do for now is just weigh the 5.8L while it is out so that when I do have occasion to pull the T-Bird motor (soon, because the rear seal leaks like the Exxon Valdez) I can compare the weight and get an idea of how my front springs will take the new motor. Here in the hills I really need a 4wd truck anyway, and my old F-150 would not be worth much as a used truck. Maybe it will end up sitting on cinder blocks behind the barn. The T-Bird radiator has been leaking lately, and I happen to have a 4-row NIB, so a bigger motor is no problem. That may be an omen!

Is the Bird a 5.0 car? If so, the springs will be fine. Start gathering the parts you need and drop that 5.8 in there. I wanted to do that as well, but ended up finding the GT40-P score of a lifetime, so, I took it.

5L springs will be fine.  I did this swap years ago.
This would be a good time to build that 351

OK, an update is in order. The 5.8L is almost built. It is going back into the truck because it is a flat tappet block. Not suitable for high revs or radical cam. Is there a 5.8L block with rollers for the police pursuit cars? That would be cool for the T-Bird. If I had the 5.0L apart at the same time I would see how the long stroke crank fits in the 5 liter...must be clearance issues. Anyway, I went      .040" over for 355.4cid (an honest 5.8L now), with a CompCams RV grind. It has about .020" more lobe lift than stock, with what appears to my eye to be less duration than stock (anybody know specs for a stock 5.8L truck motor cam?). They say it provides "noticeably improved performance" while being compatible with EFI. Chamber volume is now 94-96cc for a mathematical compression ratio of about 8.5:1. It should run on regular with no ping, but I expect to see a drop in fuel economy because the only tuning option I currently have is turning up the FPressure and throwing more gas down the hole. A heavy Duty upgraded torque converter from torqueconverter1.com is on the way. It is supposed to have stock stall speed with beefed up internals. I hope I am not building a herky jerky hotrod that squeals the tires every time. D**n it's hot in the barn. I should be out there turning wrenches instead of sitting here staring at the glowing screen of this time-wasting machine.

Can you explain why a flat tappet block isn't good for high rpm?????? I'm baffled! When I was 20something, I had a 69 stang fastback with a 351w that would turn 8500 rpm at the strip. And it did it without a complaint what-so-ever. Oh ya, it also idled at 1200 rpm. Yes I drove it on the street, but back then I was never concerned about fuel mileage. Back to the original point, I'm still very baffled as to why you would say that.

Yeah, flat tappets can work, but the reason for rollers is to reduce friction and allow for greater valvelift and faster opening. With moderate cam profiles it is not really an issue, but I notice Ford's engineers selected rollers for the 5.0 Mustang block. Reckon they are onto something? My stock 5.8L cam had several lobes rubbing away at only 106k miles.

I know why they went to rollers, the reduced friction helped with mileage. But for greater lift?? I had a .788 lift, solid lifters, roller rockers, gear drive timing set. Stock cams do tend to go flat when not properly maintained or many other causes, but we're not talking stock items here are we. I had a stock 2.3 lobes go flat too, but that was caused by a plugged oil passage.
Point of what I'm saying is this, You shouldn't go around saying "It's not a Roller block so it's junk or not worth building".
Yes we are in agreement that reduced friction is always better because you do get less parasitic loss which helps with the HP or mileage.

Do it..............

I did.

I fired up the new motor Sunday. Ran it at 2000rpm per the cam mfr. instructions but I did stop after a minute or so and look for leaks. All was well and soon I felt confident enough to put the pedal depressor on it and get out. I kept it at 1800-2000 for about twenty minutes, then set the timing and drove the wife around the neighborhood. Today I put about 30 miles on it. The TC feels just like the OEM as far as normal driving. Have not given it much throttle, but the motor seems to "come onto the cam" at just about 2800rpm. The guy at the machine shop told me the cam they sold me is a "flat tappet version of the 303 mustang cam". Well, it is .303 lift on the ex lobes. That is .020 more than stock, similar increase on the in lobes. But the lobes are much "pointier" than the OEM cam. I see that the idea is to have more lift for less duration to give it some more top end without screwing up the low and mid range calibration of the EFI. Very limited range to play with there. If I wasn't such a tightwad I might buy a programmable ECM. I had the SnapOn Scanner hooked up today as I drove, and the STFT varied from 0 to 16 or so. It never went negative, even though the O2 sensor was switching just fine. It is running lean. I think I will need to increase the fuel pressure just enough until I see the STFT drift into negative numbers occasionally. Hopefully the system will be able to keep the idle mixture in range.
Now, if I had a wet manifold and a carburetor, I could open the valves a lot earlier and hold them open longer. This would require a more abrupt cam profile, and the forces applied to the surface of the cam lobe would be too great at high rpm if it was in contact with a flat tappet. blah, blah, long section edited out here.
So anyway, yes, one can do great things without roller lifters. For a while. Roller tappets are all about durability, but they only become necessary when you try to do more than flat lifters can handle. Car motor= high rpm oversquare design; Truck motor = low rpm high torque undersquare design. I think I am going to like my new truck motor and I have lots of data for the next one I build (??? to relieve the long suffering original motor in the T-Bird Sport?)

What do you consider "for a while"?? Does 5+ yrs (regrettably sold the car) qualify?? Glad ur happy with it anyway. I'll shut up now.

The last under square engines in any Ford vehicle were flatheads that were discontinued after '53...

Lol, I was wondering how exactly a 4" bore/3.5" stroke was undersquare.  Glad I wasn't the only one.

Well that could be said 2 ways. With over-square being the 4" bore being bigger than the 3.5" stroke or with under-square being the 3.5" stroke smaller than the 4" bore. I would guess it's all in how you look at it.

Not really.  Undersquare isn't a word that's open to interpretation.  The definition of undersquare is simply an engine with a greater stroke length than bore diameter.

Nascar uses flat tappets still, in a block based off the 351 and they turn upwards of 9000+ for hours on end.

Flat tappets are better for the short runs.  If you want a 1/4 car or something you can take around a track a few times a year, go Slider cam all the way.  For a daily driver you can stomp in to when you get that wild hair to do so, go with a roller.  If I recall, you can use roller rockers with slider cam, I could be wrong, but who knows.  I also know they make roller rockers for the 351C and 351W as well as the ever so rare 351 Jasper.  Just sayin, the engine and head doesn't limit you.  Just because it was stock slider doesn't mean you can't make it a roller motor.  On top of that, buy that stock roller motor, keep those xx year old roller rockers in it and see how well that works out for you when you put those 7 - 8k rpms of stress on those 130k mile roller rockers.  That's a conservative 130k mileage.  If you're going to replace the roller rockers in a 351 Roller motor, you're doing the same thing you would have done with your 351C.

What are you talking about?  How do roller rockers have anything to do with the cam?  Also, how did a Cleveland get brought up in this?

I don't understand what's going on in this thread.  What's wrong with hydraulic flat tappet lifters?  This whole "flat tappets suck" thing makes no sense.

Flat tappets are metal on metal grinding.  They sling little shreds of metal in your engine.  If that's your thing, have at it.  For a DD I wouldn't have them.  They don't suck, they just have a use they're better for and they have a use they're not.  That's just my opinion.

Not since last year, they now run the racing specific FR9 that was developed for NASCAR... It's similar to the racing engines developed by Chevy, Chrysler and 'Yota...


Not really, the base of a flat tappet lifter is slightly convex, so spins on the lifter lobe... The 2.3 slider cam is basically a disaster waiting to happen, but in all fairness we ran a '87 4cyl Stang to 192K mi and never had the cam cover off of it...

 
This post is complete BS.  Not a single thing you just said is correct.  No, it's not metal on metal grinding.  Guess you missed out on something they just came out with called oil.  No, they don't sling little shreds of metal into your engine.  TurboCoupe50 is 100% correct.  The lifters spin in their bores because the lifter faces are convex and the cam lobes are slightly angled.  This is done so they wear evenly and INCREASES longevity.  The only disadvantage to flat tappets is increased friction compared to rollers.  As far as reusing roller lifters, tons of us have done it and spun our motors up to 7000 on a regular basis without ever having a failure.  As long as the lifter is in good working order, there's no reason not to use them.  Also, why would you run a flat tappet in a race car but not a daily driver?  This is such backwards thinking.

I understand that you feel this way about flat tappets for whatever reason but there could be people out there reading this that are taking what you're saying for fact and being turned off to flat tappets for no reason.  It's one thing to have an opinion but giving out information that is completely wrong isn't helping anyone.

If I may add to this discussion.

Roller lifters do two things - reduce friction and allow for steeper profile ramping (valves can be open longer).

Regarding the use of flat tappets vs rollers in a 5.8, who cares?  Isn't the point of a "big" displacement engine to avoid the need for high revs?  A 5.8 and numerically low gears sounds like a good compromise for relatively good fuel consumption and drivability.  If you want to really go after it, go with a 5 sp auto or  6 sp manual trans, and don't forget to match the axle ratio to the trans gears and intended use.  Then you might start worrying about roller tappets.

Ford used rollers in the later 5.0s because they were looking for ways to make power while reducing fuel consumption.  In those motors, roller cams reduced internal losses and allowed shorter duration cams with lots of lift.