Pushrod Lenght in gt40p heads with a lot of play

[charlymunozg]

Okay here i go, im rebuilding my engine with a lot of changes and it’s the first time i do this kind of job on my own, i have a 302 engine from a 81 mustang, i changed the heads for gt40p and the cam for a 1800 from summit, the point is, i used the same pushrods that the engine had, but the rod have a lot of play even with the rockers full tight, it can even go up and down without leaving the tappet, or the rocker, this were the rods that i had in the engine while it was stock and it worked just fine, so my question is, are the length of the pushrods too short? Is something wrong with the rocker or heads?

forgot to mention the rockers seems to be the stock of the gt40p heads

this are the specs of the cam: Hydraulic Flat Tappet, Advertised Duration 282/282, Lift .498/.498

Thanks for the help with this common issue

[854vragtop]

Before ordering new pushrods, buy this pushrod length checking tool from Summit and determine the exact length that you need for your combination: https://www.summitracing.com/parts/c...EaAgP5EALw_wcB

I ended up using these pushrods with my GT-40P head, Comp Cams XE264HR-14, and stock GT-40P rocker arms, because I had a similar problem with the length like you're having: https://www.summitracing.com/parts/cca-7622-16

Have you changed your valve springs or are you using the stock valve springs? It's been posted numerous times that you can't use the stock GT-40P valve springs, even with a 5.0L HO cam. I used valve springs from Alex's Springs: https://www.alexsparts.com/categorie...GT40P%2C-GT40/ I'd contact them to get the right spring for your application.

You are going to love these heads! I had to add an MSD box with a built in rev limiter because I kept revving past red line. My mild combination pulls hard all the way to red line, where it used to fall off just before it. I also did a mild port job to the heads using info from this site: http://www.diyporting.com/
http://www.diyporting.com/gtpin.html
http://www.diyporting.com/gtpex.html

I ported the heads with a Dewalt corded electric drill and 6" carbide bits and some sanding rolls. After I was finished I took the heads to a local machine shop to have them do a 3 angle valve job.

[gmatt]

I'm curious. Is the pushrod difference because of the heads? Rocker arms different or pedestal height? Or is this cam ground on a smaller base circle? If this is the case, would it affect the oiling of the lifters?

[mcb82gt]

Subscribing. I'm planning my GT40p build also.

[v8only]

guessing the earlier motors have different length pushrods, because with the later roller engines the stock pushrods work perfect

[Walking-Tall]

Roller blocks take a shorter push rod because of the taller roller lifters, and vice versa in a flat tappet block, or when flat tappet lifters are put into a roller block... but none of any of that is the OP's problem...

As chance would have it, I was just reading about that camshaft at Summit the other evening... and somebody asked something down in the reviews/questions section, and Summit themselves answered, and for whatever reason, that camshaft has a smaller than usual diameter base circle... so meaning, you'll need custom-length (longer) push rods to take up the closed-valve clearances you are having...