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Topic: 87 5.0 tbird Flat top pistons? (Read 225 times) previous topic - next topic

87 5.0 tbird Flat top pistons?

does the original 5.0 in the tbird for 1987 come with flat top or is there valve reliefs?  I've been getting mixed info on this.

Re: 87 5.0 tbird Flat top pistons?

Reply #1
When my 88 had the original motor it had no valve reliefs. A borescope would tell you for certain on your motor though.

Re: 87 5.0 tbird Flat top pistons?

Reply #2
if they have flat top pistons, what cam/head options do i have so i don't have to change the lower end, im trying for 300hp/300torque.  i'm going to do some research myself, but if anybody has a flat top piston motor getting 300 please let me know your setup.  I don't want to knock the valves if they end up floating at high rpm.

Re: 87 5.0 tbird Flat top pistons?

Reply #3
What must have been years ago, I had a 86 Tbird with the original 5.0 engine using stock but mildly ported 3 bar Gt40 heads and a small Lunati roller cam. That engine also had the flat top pistons with zero dish and no valve reliefs.

Everyone told me it would have valve interference on the intake valves. I got everything mocked up using the old headgaskets and clayed one piston on each bank of the motor. Plenty of clearance, Im not even sure I bothered to mic it, there was that much.

Just FYI, on more serious engine combo's where the clearance may be close, even the stock HO pistons sometimes do not have wide enough valve notches to help provide the radial int valve clearance needed on 2.02 int valve heads as is commonly used on AFR, some of the Edelbrock Performer RPM heads, etc.  This usually happens only when a fairly serious cam and/or milled heads or deck surface of the block are brought together. I've seen it.

The HO pistons have a small dish, and the valve reliefs may be wide enough for 1.94 int valves, but it can get tight near the edge of the piston which the dish doesnt extend to, when using 2.02s.

Always clay your own combo to be sure, but generally speaking I'd imagine that any of the common inline valve aluminum heads using the 1.94" valve should clear fine using a mild street cam or the stock HO cam with a 1.7 roller rocker.

Re: 87 5.0 tbird Flat top pistons?

Reply #4
Are you staying injected?  Speed Density is a little finicky with cams and increasing the airflow through the motor but it can be done.  I will say the easiest route is switching the car over to mass air but that's just my preference.  From what I remember on the '86 GT Mustangs (SD & flat tops with no reliefs) most guys ran a B cam with 1.72 roller rockers and they did not have PTVF issues but the best way to check is clay the motor.

83 351W TKO'd T-Bird on the bottle


93 331 Mustang coupe that beat your mom's LTD

Re: 87 5.0 tbird Flat top pistons?

Reply #5
Im converting it to maf.  For B cam,  were you talkin about the ford motorsports 303B?  I found a company that has new 1.94 intake cast iron heads for a decent price.

Re: 87 5.0 tbird Flat top pistons?

Reply #6
Im converting it to maf.  For B cam,  were you talkin about the ford motorsports 303B?  I found a company that has new 1.94 intake cast iron heads for a decent price.

Are they Dart Windsor Jrs?  I didnt know any ther aftermarket company was still casting iron SBF heads. Or is it a factory casting head with the 1.94 valves installed ?  And what is a decent price ?  Just so you know, a factory head casting like E5 or E7's have a very modest intake port cross section and a combustion chamber designed with smaller 1.78" intake valves in mind. Not to mention the bowls under the valves are inadequate to take advantage of the larger replacement valves.

 In other words, unless some considerable labor is spent on opening the bowls and intake ports in addition to chamber work to unshroud the larger valves, no power gains should be expected.

I've ported E5, E7, the old C9 and D00E castings, plenty of them. After substantial time and effort, and good money if stainless valves/performance springs/seals/locks plus the maching work are used, they can be improved on, but its a losing proposition if results/$value are of ANY importance to you.

Better to get quality aluminum performance heads, this is coming from someone who has ported plenty of iron heads, including darts.

Re: 87 5.0 tbird Flat top pistons?

Reply #7
Carolina machine engines is who i deal with, ive bought several engines from them, i will ask if it is a in house head when im ready, most likely im going to replace the short block with one of there's.

Re: 87 5.0 tbird Flat top pistons?

Reply #8
10-4. Good luck with it.

Re: 87 5.0 tbird Flat top pistons?

Reply #9
I've been down the cast iron GT40 head route. I recommend you save up some more money and get a good set of aftermarket aluminum heads. Just going from iron GT40s to Edelbrock Performer heads with no other changes my car picked up half a second an 4.5 mph in the quarter.

By the time a set of GT40s, the best factory iron head, is ported pretty much to the max it is barely the equivalent of an as cast aftermarket aluminum head.
88 Thunderbird LX: 306, Edelbrock Performer heads, Comp 266HR cam, Edelbrock Performer RPM intake, bunch of other stuff.

Re: 87 5.0 tbird Flat top pistons?

Reply #10
Yes, I was referring to the Motorsports B303 cam of the alphabet soup of cams Ford made.  Being you are moving to mass air then to get the most out of a speed density short block without cutting reliefs in the pistons then I would suggest you settle on which heads you want.  From there leave the cam that is in the motor and install one head with the exact head gasket you are going to use and clay on one of the pistons.  Only install the pushrods and rockers on that cylinder and run the valves on that cylinder (assuming you will go with adjustable rockers).  Pull the head and you should know your intake and exhaust valve clearances.  From there call Comp Cams and get a tech on the phone and tell them you are trying to maximize the performance with what you have i.e. you are not changing pistons or rockers.  They can spec a cam that will work and give you the most for the given constraints.

Most folks have a good basic understanding of cams but that isn't enough to start looking at cam cards and selecting a cam.  You really have to understand the entire motor combination and know that the cam is the brains of the whole thing.  I cannot stress how important the cam is to making a really good combo perform to its full potential or just disappoint the owner with a big steaming turd under the hood.

83 351W TKO'd T-Bird on the bottle


93 331 Mustang coupe that beat your mom's LTD

Re: 87 5.0 tbird Flat top pistons?

Reply #11
I decided to swap out the block. The heads are cast iron 1.94 intake 1.60 exhaust 60cc chamber 180cc intake runner, Comp cam magnum 270hr.  I was thinking going with gt40 intake upper/lower.  What do u think?  Trans will be AOD with 4r70w gearing, chromoly input shaft with tci street valve body rework.  Rear end i have just finished my 8.8 build with ford traclock 3.27 gear.  This is just for street

I had a 65 merc comet with a 347 with alum heads 2.02/1.60 270h flat tappet 5speed, it was awesome.

Re: 87 5.0 tbird Flat top pistons?

Reply #12
So back in the day Comp Cams recommended 3.55's or 3.73's with that cam.  I know this because the first 306 in my Coupe had this cam with ported and polished DOOZ 351W heads with 1.90/1.60 valves, 1.6 RR, 10:1 compression, and a Cobra upper and lower with the lower ported by TMoss.  I was also running a Pro-M MAF with 24 lb injectors and a 70mm TB with a full 2.5" exhaust and an X-pipe.  I had and still have a 5-speed in the car and 3.73's but the AOD cars ran 4.10's.  Not sure what the gearing change is with the 4R70W guts though.

So with this I am saying that a GT40/Cobra upper and lower will be fine with the lower ported and my bet is you need to change gears.

83 351W TKO'd T-Bird on the bottle


93 331 Mustang coupe that beat your mom's LTD

Re: 87 5.0 tbird Flat top pistons?

Reply #13
aod 4r70w conversion brings it from 2.4 to 2.84 on 1st gear, i had a similar cam to this on my 65 comet with a t5 5 speed & 3.00 diff  didnt have an issue, it was awesome.  For the xe270hr (a step above the Magnum 270hr) it recommends 3.20 to 3.73 gear

 

Re: 87 5.0 tbird Flat top pistons?

Reply #14
Your putting a 302 in a fairly heavy car. You really need a good torque converter. It's going to make all the difference. I run a 9.5" billet PI Stallion non-lockup converter with a 2800 rpm stall, stock AOD gearing, and 3.73 gears. The car pulls hard from any rpm and just rips. A lot of it is in the converter. I think if I had gone with the 4R70W gear set when I had the trans built it would be even more fun. I'm really considering swapping out the 3.73s for 4.10s on my car. It'll just make it more fun.

Engine in the car is a 306 with Edelbrock Performer heads (1.90 intake/1.60 exhaust valves), Comp 266HR cam, Edelbrock Performer RPM intake, 30lb injectors, Edelbrock 70mm throttle body, FRPP 1&5/8" headers, 2.5" exhaust. I ran a GT40 intake on the combo for several years. It was ok but the car always felt flat above 5000 rpm with it. I switched it out for the Performer RPM and it was a night and day difference above 5000 rpm after that. The GT40 intake probably makes more torque below 2000 rpm but with a 2800 stall and 3.73 gears the engine spends virtually no time at that low of a rpm.

If you get a good converter in the 2800-3000 rpm stall range and some 3.73 gears I wouldn't even bother with the GT40 intake. Just find an Edelbrock Performer RPM intake or a Trick Flow Track Heat intake.
88 Thunderbird LX: 306, Edelbrock Performer heads, Comp 266HR cam, Edelbrock Performer RPM intake, bunch of other stuff.