so im about to pull the trigger on a 351 donor setup, was just wonderin who's runnin gt40's on their SD 351? ive read some guys say dont do it, others say its a good mod. i will scavenge a MAF setup as i find it, but i hate doin work without handlin all the "misewells" like cam/head swap (while retaining the SD for now)

with that bein said, can i run ported gt40's and a SD friendly cam? how bout a mild compression bump also (via milling)? i know im askin a lot of the SD, but i would love to just do the head work now while the motors out, swap a mild cam, and be able to use the truck while as i piece the MAF setup together as i get the time/parts. that way i wont have to tear the heads off in the truck later on, rather just do a cam swap once i get the MAF setup.

is it possible: ported/milled gt40's and one of the SD friendly cams?

also, the 5.0 and 5.8 intake manifolds are not interchangeable? at what point does the 5.8 manifold become a restriction?

 

The Gt 40s will work good , just don't get the gt 40p heads , different plug angle , something like the ford HO cam will work with SD , im not 100% sure but i think 9.5 -1 comp ratio should be ok.....but to run the HO cam the block needs to be roller ready....

 

Head porting is fine so go to it. The Crane cam I always suggest for this motor (444232) is in use by several guys here on SD trucks and it cooperates just fine. The 5.8 intake would be the limiting factor on a stock motor if it wasn't for the 302 heads Ford installed on them, but you can squeeze a little more life out of it by porting the lower and in particular opening up the port exits where they meet the heads.. for some reason there is a serious narrowing there on all stock intakes.

 

dont all the ole ford efi blocks come roller ready (i.e. lifter galley is tapped for the "galley tree"). i noticed the funky manifolds they put on the gt40p's. i was gonna go that route and just do some cut-n-weldin (thinkin "how bad could it be") but after i saw what ford did to clear the plugs, the gains arent worth the means.

the better 5.0 intake wont fit the 5.8, correct? i was plannin on portin the **** outta either one, but if the 5.0 bolts up ill start with that one.

ill definately go with that crane cam 444232 until i go maf, for simplicity and $ sake.

thanks for the info. i feel pretty comfortable goin the 351 route now. it will save me a lotta money/headache in the long run goin 351 and keepin it blue oval. and i love the 351's stroker potential

 

Most of the 5.0 blocks from around 88 were roller ready , the 5.8 didn't get the roller cam till 94 , the 5.0 intake will not fit the 5.8....

 

What's wrong with GT40Ps??? Mine clear fine with normal ol' Ford Racing shorties.. Ok, I admit, they are mustang FRPP shorties.. Custom Y pipe needed. As Lew said, the 5.0 intake won't fit.. It's too small for the 5.8 block.

 

ya know this is what i thought until i saw the crazy shaped manifolds ford put on the explorers. . .ill have to study your pic you posted. . .

how close are your plug boots to the pipes? what plugs are you runnin?

 

You just have to get the right headers to fit it. It has Motorcraft coppers in it. The spark plug boots have plenty of clearance, but I put THESE on there just in case they are a bit close. I can get a closer pic if you want.. Ported GT40 heads should run just about as good as these ported "P" heads will though.

 

searchin around, it looks like people are havin the most trouble with shorties, since the collector natrually forces the tubes to stay higher, longer. i think most long tube designs wouldnt even be a problem. . .

i was thinkin bout ported gt40's vs ported 40p's also. . .there isnt much gain with ported p's over reg ported 40's? the way i saw it, the smaller exhaust valve of the P's would allow the reg 40's to "catch up" a bit to the flow of the p's (after porting). of course, the "better" plug angle is what it is, but i would avoid problems altogether if the ported 40's flowed as good as ported p's.

its the same with ls1 vs ls6 heads. . .everyone thinks ls6 heads are superior (which they are in stock trim), but after porting both the ls1's actually outflow the ls6 to mid-lift. porting exposes strange differences sometimes.

 

I'm not sure on the flow difference between the ported GT40 and the "P" heads, but I know mine flow pretty well.

 

ok i decided to go with the p's so i can start with the samller combustion chambers. gonna squeeze as much compression out of them as i can. can you show me some more pics of your headers/plugs? if you can get the camera directly above to get an "aerial" view that'd be nice. a good pic of both sides would help me out a lot. thanks.

 

Got some pictures uploaded for you. They are cell phone pics and I just took them, so it's dark outside, but they are good enough to get the idea. The spark plugs are standard length spark plugs.. Nothing special there. The wires are Taylor spiro-pro 8mm with 45* boots on the plugs. 90* boots would be better for clearance, but it'll work this way. Headers are FRPP shorties, but BBK shorties should work and mostly all LT headers will work no problem. Also, all the spark plugs are easy to change with a standard spark plug socket. The cylinder 7 plug by the dipstick is pretty tight, but not too bad. The pictures are in order from cylinder #1-8.

Passenger side


Cylinder #1 (plenty of clearance)


Cylinder #2 (good clearance)


Cylinder #3(middle wire) Good clearance, but the cover does touch the header. The wire does not touch. Should be fine, if not a shorter wire will fix it


Cylinder #4 (again, cover touching header, wire not touching)


Cylinder #5 ( Lots of clearance)


Cylinder #6(It is not touching the header. About 1/4" clearance)


Cylinders 7 and 8 (#7 touches the dipstick, but neither 7 or 8 touch the header tube)

 

those pics are awesome. thanks a lot, i know its a pain in the johnson to take and post all the pics and i appreciate it.

 

The 93-95 Lightnings came with GT-40 heads from the factory and they utilized speed density, not mass-air.

You won't have a problem with the heads. NOW,....the camshaft is a little different story. If it has a lot of duration, you won't be able to get it to idle properly, no matter how much tuning you do (with speed denisty)

With a BIG cam, you'll really need to switch to Mass-Air.

 

Good to see you over here Keith. I hope you can spread some of your knowledge of performance tips on this board as much as you have on NLOC.

Randy Alexander aka rla2005