pushrod legnth for iron gt-40's?

carbed87 · Aug 26, 2005

i put my cast iron gt-40's on, and im not feeling ANY power, all the low end tourque is gone. so in my quest to get to the bottom of this, the local engine shop told me to put an adjustable pushrod in there to find out what legnth i need. and since i dont have an adjustable push rod, i figured i'd ask you guys before i made one. right now, the stock sized pushrods are in there, and i don't have any power. any help would be great. thanks

txstang84 · Aug 26, 2005

i think they should be the same length as your stockers...6.272" for roller engines.

does it constantly run like poo? or is it only under certain conditions? does it miss, or fall on it's face, or just feel weak? i think i've seen someone post a thread like this recently and i wish i could remember what the fix was...

might wanna kick your fp up a little, and make sure all your electronics are connected correctly

carbed87 · Aug 26, 2005

no its the entire time, i've got NO power. and im pretty sure it has to do with the valve train, it even SOUNDS sloppy.

maverick0716 · Aug 26, 2005

The 6.25" stockers should work, and if they were slightly off, it wouldn't cause a huge power loss anyway.

carbed87 · Aug 26, 2005

do you think my valves aren't adjusted right?would that be the source of my power loss?if thats the case, then how do you adjust them... well looks like i'm callin it a night, any replies would be greatly appriciated

txstang84 · Aug 26, 2005

when you stabbed your dizzy back in, did you put the timing back where it was, or did you retard or advance it? if the timing isn't right, then it will always feel like crap, low idle, poor response, poor acceleration, poor top end...it will also cause a "laboring" idle...sounds like its gonna die constantly...

if there's no valvetrain slop, ya know, nasty ticking sounds, then your vavletrain should be fine

legalize420 · Aug 26, 2005

carbed87 said:
i put my cast iron gt-40's on, and im not feeling ANY power, all the low end tourque is gone. so in my quest to get to the bottom of this, the local engine shop told me to put an adjustable pushrod in there to find out what legnth i need. and since i dont have an adjustable push rod, i figured i'd ask you guys before i made one. right now, the stock sized pushrods are in there, and i don't have any power. any help would be great. thanks

start with checking the firing order and timing. after i installed my intake i reversed plug wires 2 and 3 and car was not happy.

ram360 · Aug 26, 2005

stock length pushrods rods work. I use them in my car with the gt 40 irons.

carbed87 · Aug 27, 2005

alright so i checked the timing, now bear with me, i've never really done timing before but here goes...

with that little block plugged in, the white mark was just about even with the "time" mark.

and with the little block UNplugged, the white hash was about 1/2" to 1" away (to the right) from the "time" mark.
i'm sure that was pretty good, if one of you guy's could let me know, that would be great, oh!, and i do have a reasonable amount of top end, but still, like i said, no low end. thanks :- )

stang0f87 · Aug 27, 2005

it ought to be set at 10 degrees with it unplugged. it'll jump up a little after its plugged back in. i also used stock rods on my cast iron gt40s.

legalize420 · Aug 27, 2005

carbed87 said:
alright so i checked the timing, now bear with me, i've never really done timing before but here goes...

with that little block plugged in, the white mark was just about even with the "time" mark.

and with the little block UNplugged, the white hash was about 1/2" to 1" away (to the right) from the "time" mark.
i'm sure that was pretty good, if one of you guy's could let me know, that would be great, oh!, and i do have a reasonable amount of top end, but still, like i said, no low end. thanks :- )

do you have a timing light? where did you mark the balancer?

dstanggt50 · Aug 27, 2005

I would chk the timing w/a timing light, the white mark being about even with the "time mark" is ok if you marked the balancer to the timing you are looking for. I mark mine @ 10 to reference stock and just try to advance 2-4 degrees. Might want to chk for exhaust leaks, I had some leaks from the head to the header's and my car felt really sluggish, after I fixed it the car picked up nicely. Other than that, maybe chk for codes or re-adjust the valvetrain to double chk.

Grn92LX · Aug 27, 2005

You have to measure, stock pushrods were NOT the right size on my friends combo. We used them anyway because he didn't care about doing it right.

txstang84 · Aug 27, 2005

did you friend have the block decked or maybe a 73-76 block, or perhaps different valve length than stock? ('73-'76 blocks are 0.020" taller)

the GT-40's are designed to fit the 5.0 with no modifications, pushrod length included...now if you're assembling a custom engine with parts that are known to need custom applications, then yes measure everything, but I've never seen a stock deck roller 302 with GT-40 heads whether they be iron or alum, need anything but stock length pushrods. the only exception I can think of would be if the heads had been modified with different length valves, in which case, you would definitely need different pushrods.

but again, if they were stock GT-40's, then they should bolt on with no mods...

Grn92LX · Aug 27, 2005

Stock 302 late model roller block. I believe they were milled (dunno how much) and had a crane stud mount conversion. I knew we needed new pushrods from the get go, but he didn't care. His new motor is being done right and it should be a fast little 306 since i'm picking the parts.

rd · Aug 27, 2005

I have 2 sets of iron Gt40's, one on a 68 block and one on a 79 block. Both are running with stock length 78 and 79 type, non-hardened oem replacement pushrods. The 79 has studs, Comp Cams roller tip adjustable rockers and the 68 has late style bolt down rockers scrounged from who knows where. Both work fine. The 68 will run to 6000 or more, with power and runs high 12s. Obviously, you need to check it, but I would bet the problem is elsewhere. I did not even need shims with the 68 block and the bolt down rockers.

All that said, you need to make sure you have the same length valves as stock. I have stock Ford valves in both sets of heads the SVO on the 79 and production 94 Lightning on the 68. I would check this also.

txstang84 · Aug 27, 2005

Grn92LX said:
... it should be a fast little 306 since i'm picking the parts...

...little full of yourself there aren't you? jk didn't you have Rick build your engine?

but on another note, i ran into that problem once before on my own engine-totally forgot about that crane conversion-probably because it was a bad idea and experience...I swapped those out at my first oppurtunity

they "effectively" reduce the length of the valve which req'd an increased length pushrod...about 6.7" IIRC...

Grn92LX · Aug 27, 2005

Full of my self, nah. Confident Rick built my shortblock and installed/degreed my FTI cam.

The crane conversion did look like a piece of junk.

txstang84 · Aug 27, 2005

it's not so much that it was a piece of junk, but more that, they should sell the kit with pushrods included based on application-5.0's being one of the more popular...but after i installed it and realized that my stock pushrods wouldn't work, i called up Crane and got with their tech guy, and he apologized profusely about the problem that i'd run into...they did however recommend a correct length pushrod, and it did work after i installed them, but i still had to drop $85 on a set of custom length pushrods...ballbags

pushrod legnth for iron gt-40's?

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