Projectz28

whats acceptable and whats not?

I was out in the garage tonight putting my new Manton #5 3/8" pushrod in. I was checking things over for clearance and found a few that are just way too close to the head for comfort.

TFS heads, manton 3/8 pr's, Jesel SS shaft rockers.

I started working on the first one which was cyl 7 intake pushrod was actually just touching the head when it was under load. Basically just taped the motor off and stuck my shop vac right into the pushrod hole. I started opening it up with a small 80grit roll on my dremmel. Seem to work very well actually. The tape under the head sticky side up caught and filings that didnt get imediately sucked up into the vac. I'm gonna use alot of tape here but its much easier than pulling the heads off just to be messy.

Anyway, I have about .025" on that pushrod now and I figure its good but I dont know. There shouldnt be any flex with these pushrods... and if they do flex its because they are being bent by something

Is there an actual minimum clearance I should shoot for here or is a .025"-.030" clearance ok? I read somewhere on line that .010" is acceptable but I am not comfortable that close.

Josh'95Z28conv

I was told .060" by an engine builder. Thats way more than it needs to be imo. Mine all touched even with .015" offset intake rocker arms. I pulled the heads to touch them up. It got very messy. You may want to rethink doing that with them bolted down.

Anyway, after touching each one up, I have close to .25" on each one. I think .030" is enough, but I rest easy knowing I have much more

89TramsAmGTA

If your intake ports have been opened up you need to be carefull how far you go and what area. The pushrod pinch area could be relatively thin.

Projectz28

yeah thats exactly where its tight on cyl 7. The heads are opened up alot but they are Trick Flow heads and they seem to have alot more meat in that area even though they are big 220cc runners.

I still have room to go a little more so I'll try to go a little more this weekend. Not worried about doing it on the motor. I'm very clean about it... not the first time I've done something like this either.

rskrause

I am sure there is some kind of minimum. But to be honest, if they don't touch I don't worry about it. The aluminum of the head is a lot softer than the PR, so I don't see a little light contact as a problem. I suggest calling Manton. They are great PR's and the company is fantastic to deal with,.

Rich

Projectz28

I agree, Manton so far has been a pleasure to buy from and has been very helpfull. I'll call them when I get home, but the pushrods are great. The head is the problem. Looks like Trick Flow basically has the pushrod holes cast into the head and somewhere during the machining process they send a drill down each to take out the metal in the way. Only a few spots where this is even a problem. Most of the openings are huge and way out of the way. I'm going to clearance the rest this weekend and see how it looks.

I never thought of it that way but yeah I guess the aluminum is a ton softer than the PR so a little contact probably wouldnt hurt it. I'll still clearance it a bit though cause I am ****...

89TramsAmGTA

I did what Rich suggested. Just enough clearance. So far so good.

Projectz28

great, sounds like the 25-30 thou clearance I cut in there is probably enough then. I'll do the rest just like that also. I'll let you know what manton says...

rskrause

Yeah, Kasse or Reher Morrison would probably have a seizure about it doing it that way. OTOH, Smokey Yunick might like it! Seriously though, I am far from a shade tree guy when it comes to motors but this is one area that I have taekn the "easy way out" for years without an issue. OTOH, if Manton says different I'd have to respect that. So, please let us know what they say. I am always willing to learn.

Rich

SStrokerAce

Rich and Manton have you on the right track.... I know they don't need a lot of clearance. I think it's as small as .010"

The TFS PR holes are a certain size, 7/16-1/2" maybe. The best way to do this is put the head on the mill and enlarge the holes with a endmill or drill but that is slightly larger. If I remember right there is a step to those holes, you probably don't want to go that big, and want to watch out for where it meets the port wall thru the pushrod restriction (pinch).

BTW found this on Mantons site:

"Do not allow over clearancing for the pushrod. This may cause the pushrod to move around or deflect more than needed. Clearance of .010 at the closest point, wherever that may be during its complete cycle is sufficient. The cylinder head and engine block can often be utilized like a big guide plate and dampening device, which stabilizes the pushrod. Just make sure that there is no interference problems when turning the engine over on the engine stand."

Thanks,

Bret

Projectz28

Bret saves the day again! I was looking around on their site and didn't see anything so I just shot an e-mail to their tech line. That was around lunch time here on the east coast. Haven't heard back yet but I am sure they will tell me that the .025" I got there is fine.

The TFS heads I have are the "new desgin" so they have the cast openings and then the drilled holes. Not like the old desgin of just a totally covered pushrod area and then just drilled. I'm sure Bret you are familliar with these but here are some pics I have of both styles for everyone else.

Old TFS LT1 head: (this is actually a LE head a local guy bought a ways back but didnt install yet, we did some side by side comparasions a few months ago)


New TFS LT1 head:


Honestly if I had the old style head I probably would take them back off and have them drilled. But the new style head has a ton more room and they are only closein a few select spots which I am comfortable doing on the motor. Trust me not a spec of metal will make it into the motor. And even if a spec or 2 did, its only aluminum...

The first spot I started work on is #7 right in the pinch area. Like I say it was just barely touching and I only removed a small amount of material to get the clearance. I'll take pics this weekend of that if you guys are intrested.

Projectz28

Before clearancing:



After clearancing:

89TramsAmGTA

Looks good. Have you rotated the motor over and watched the pushrod in action?

Projectz28

Absolutely. Those pics are actually at full lift. I watched every one for a complete rotation.