BTGSTUDIO

Im installing a TSP 224 cam in my LQ4 along with a set of 243s milled .030 I plan on running a .040 head gasket with new ls7 lifters. My question is what Pushrod Length? I'm sitting on TSP's checkout page right now debating.lol I will be buying a tool to double check the length I just want to get everything ordered now. I called TSP and the guy guessed a 7.350. anyone out there with some input?

87silverbullet

iTrader: (11)

The guy at TSP is close then. A stock pushrod is 7.400 and if you do the math, .030 off the head and .011 off the head gasket compared to a stock gasket of .051. That equals .041 total. Subtract that from the 7.400 and you end up with a pushrod length of 7.359. So the .009 will not be that detrimental.


Now I will say this, all that math I just did means nothing. MEASURE YOUR PUSHROD LENGTH! DON'T GUESS.

BTGSTUDIO

Thanks for the reply, from my understanding the base circle of the new cam also plays a role into this math. Which is the only number I don't have. I do have the new 224 cam sitting next to me with cam card on hand, but I don't see any info about the base circle on it.

For the record I will measure before install. I am only guessing at this point because this car is my DD. I need the parts on hand to get everything done in a timely manner. I will not install the wrong pushrods. I was just hoping someone with a similar setup could tell me what they used.

Maybe if someone could tell me what pushrod they used on a comp cam only swap. That would give me a better idea at this point. I have a feeling its going to be close to stock length though. Keep the advice coming fellas!

trw427ssrs

The stock cam BC is 1.550" so measure the BC of the new cam and take the difference and divide it by 2 and that's how much to add to the pushrod length, Example 1.550 - 1.450 = .100 / 2 = .050

BTGSTUDIO

Thanks for the input. I went ahead and ordered 4.350 length pushrods, I have a feeling I should have gone with 4.375 but we'll know within this week. I start the build the day after tomorrow!

PhoneniX

OP did you get the results?

Whistler

iTrader: (46)

Im curious too. That cam may or may not have had a reduced brace circle depending on if it were a .567 lift or a .581 lift. Also the LS7 lifters don't have the plunger in the same spot as the stock lifters. So that combined with all the other variables makes it hard to get the best result by guessing.

LsF-150

iTrader: (2)

Are you sure about that? I thought that myth had been debunked, the ls7 is the gm replacement for everything now, I can't imagine they would expect everyone to also replace pushrods because they've changed the plunger location. I always measure and don't run ls7's, so I don't really care either way, just trying to stop some misinformation for some future readers. Someone correct me if I'm wrong.

Burken01

iTrader: (88)

Ls7 lifters are a hair different in length which doesn't affect preload too drastically as a replacement lifter..

But when you start stacking tolerances (new lifter, different cam, etc... Then you should measure because you've created a custom setup with new parts!

Tin Indian

From everything I have read and understand, the ideal OEM spec lifter preload on these engines is .060" (60 thousands)

Each 1/4 turn of the rocker arm bolt equals approx .020" movement of the pushrod into the lifter.

So, if you set the set the rocker to zero lash while the piston is at TDC (on compression stroke), it should take approx 3/4 of a turn of the bolt when it reaches it's desired torque of 22 ft lb.

If it does, you should be very very close to .060" lifter preload.
.

masterz28

iTrader: (8)

Its been a year since a changed a cam so i'm rusty, the base circle will seat it deeper thats for sure. Even buying new 7.4s are exactly 7.4

BTGSTUDIO

Sorry for the late reply, been away from the forum's. I built the motor now with 5k miles running strong putting down a respectable 375whp/420ftlbs through the A4. I'll link a thread with the breakdown of the build in time.

As far as pushrod length is concerned, The length I told you guys I purchased worked just fine but my preload is high .80, This is with a 224/224 tsp cam and 243's milled .30, head gasket was the stock width. Now here's the kicker, during installation I went ahead and measured pushrod length, I did lots of research so I was counting on having the correct length, Which I did.. for 6 cylinders... I got 10 turns on my checker for the back 6 cylinders but the front two were at 8 turns.. Wow! I was shocked after remeasuring checking for tdc, over and over I came to the conclusion that my heads were milled unevenly... So moral of the story guys, buy multiple sets of different lengths and return what you don't use or wait, measure and then purchase.

trevmust

so.. moral of the story... buy a pushrod length checker? lol

Briou

iTrader: (1)

I would recommend this over anything...

BTGSTUDIO

Yeah even if it cuts into your build time, hurry up and wait kind of deal.

Herkaleez

A length checker is a must...I was getting diferent measurements also measuring on TDC, the only way i was able to get consistant measurements is to MAKE SURE THE CAM IS ON THE BASE CIRCLE of the lobe u r measuring...i used this method...
measure the Intake valve when the EXHAUST valve begins to open, this will assure that the intake valve is on the heel of the intake lobe.
measure the Exhaust valve when the INTAKE valve has just closed .

Jacktuner

How much preload you guys putting on your lifters?

mcdonald77

iTrader: (21)

I will give my .02, I rebuilt an lq9 and ran an 04 z06 cam. everyone said I needed a 7.425 push rod. After I bought the tool I ended up with 7.35 and it was loud. I ended with 7.3 which seemed to be the sweet spot. I recently did a cam swap and put in 7.35's after measuring which leaves me around .050 on my preload with BTR lifters.

In closing, always measure!

zackpowerls

i have a 2008 LY5 (5.3) topped off with a set of 243's, it was a DOD motor. I had Cunningham Motorsports grind me a comp cam, (stock rocker assemblies, stock valves, stock gm gaskets, i havent bought springs yet... ), he set me up with 7.4" hardened rods. I haven't run the motor as im assembling the long block this weekend. Hope this helps!!!!!!
cam ground at 227*/234*- .613/.576 @ 110*Lsa

pannetron

While I fully understand the desire to order the push rods now, I humbly recommend that you install the heads on the block first and *measure* what push rod length you'll need. With a 0.040" thick head gasket, make sure your pistons protrude no more than 0.005" above the deck. And since you removed 0.030" of valve clearance when you had the head milled, you may want to double check piston to valve clearance if your cam has more lift than stock.