Maximum bore size for f-head

The turbo, TBI, computer controlled f-head build is back underway. I need to clean the bores out because of some rust pitting, and to prevent ring flutter. Its bored .030 over now, and I could just go another ten thousandth to make it clean again, but thats not my style.

I can get .060 pistons for about $130 a set. Looking in the books, I can get .080 rings...but not pistons? Brand is Sealed Power. Is their anywhere I can get .080 pistons or larger. What is the safe stopping point for this engine anyway? I get all machining done for free BTW.

also, is their rods from a different engine that are long enough to use in the f-head? I want to try to go to forged rods if I can. Custom ones are way to $$$ for me.

I am only going to be running ~5 pounds of boost when all is said and done, am I still in safe standing for the stock rods?

 

dont think the rods will have any problem with 5 pounds of boost, dont know if my 1955 chiltons will have the max bore in it or not but i will look

 

sorry, my chiltons does not list it

 

I want to say I have heard of .1 over pistons mentioned here before.

And 5lbs of boost is not a ton so I would say the rods should be ok.

 

cool, one less expense their. I have read about someone boring one .120 over, but man the space between the cylinder walls has to be thin. I would worry about the block cracking then.

 

The rods on the F head are forged steel from the factory.

 

ok took some pics just for show and tell, and yup, didn't notice it before, assumed, the rods are forged after all, but do they loose strength the way they are designed, come'on, really, a bolt?

and their is more than 1/4 inch between the cylinders right now and thats with it bored .030 over.

 

I have no experience with boost on any engine but I did have to go .080 over to clean mine up ( the local machine shop was comfortable with that ). I did have to order custom pistons to get the .080 over.

There have been no overheating or other related issues and I have worked it hard on a mountain road just to see.

 

Yep bolts like that were common until the mid 60's, even the dauntless has bolts instead of cap screws. They are quite satisfactory.

 

The distance between the cylinder walls doesn't really tell how much you can bore the cylinders. Keep in mind the small block Chev was manufactured from 265 to 400 ci displacement. the blocks are similar from external appearance but you can't bore a 265 to a 350. The castings are different and because you have a 1/4 inch between 2 adjacent cylinders that doesn"t tell how much material you can remove without getting into the water jacket. I worked in a machine shop many years ago and we commonly bored blocks 30 and sometimes 40 over, we would only bore 60 at customers request. When I needed to bore my F4-134 I checked with Walcks and asked Carl what was the max he would bore an F-4 he would personally use and he told me 60 max. With that said I am sure there are many who have good results at 80 over.

 

OK I found that I can get .080 pistons from sealed power. $35 ea. .080 over ring set is $60.

If you can get .080 over pistons, I would think that their wouldn't be concerns about getting into the water jacket. We shall see.

I think I will go to .060 oversize bore, leave another .020 encase I screw something up. I have 4 of these engines anyway not too concerned about screwing up.

thanks for the info.

 

I had this same problem and after talking to some machine shops this is what I found out.

To insall a sleeve--you have to bore out the cylinder .188 which is quite a bit so according to the machine shop--.080 is good. The problem I ran into is finding a head gasket that didn't over hang into the cylinder. The ring that should compress when the head is bolted down was hanging over into the cylinder space. Not good!! I found that Fel-Pro gasket would seal the head as it has a full medal shim on the bottom of the gasket.

I have also followed along with some disscussion on how at higer RPM the .080 bore will allow for oil to come by the rings---not so sure I follow along with that--However, at the speed we will be driving, it shouldn't be a problem--if it even is a problem.

 

Alright, I dropped the block off at the machine shop this afternoon. I am punching it out another .030 to .060. However, the mechanist said that the rust is .015 deep, I may have to go all the way to .080, but thats a last resort. Cost for me is $87 for all 4 holes.

The guy I took it to has had lots of experience building these f-heads. Mostly for tractor puling, and has also gave me a # for a guy who makes custom grind cams. He said around $250 to do it.

I also need to replace the cam bearings, I got a little carrited away with the wire wheel.

This enigne also has hardned valve seats. Susprise susprise. it has been gone through at least once already.

 

alright, alright, I will sleeve # 2 holes and then be boring the sleeve out to .060. The rust was deep.

At least I got a $500 limit on the machining, so far only at $260.

ordered pistons from sealed power today, I also got the "Premium Rings" set.

 

ahh, you see, that was a different place, and the backed out of that deal at the last minute. They also had a "3 week long vacation" that apparently begin the next day when I called. Gotta love it.

I went to the place I had some other machining done. They are cutting their labor rate in half to $35/hr, the owner was actually upset that the other machine shop backed out of their "deal" with me, and cut me a break. Still expensive though.

Yeah, nothing is free, RTFP (Read The Fine Print) before making free deals with anyone.

 

ok, ok, pistons are special ordered from the Sealed Power plant in California. 7-10 days. California is pretty much a another country. Hope they will be in by the weekend. The shop is done with my block, but need the pistons to do the finial hone for the right clearnces.

 

YAY, Well, called some friends at UPS, they got it overnight from Philly (where it was when I called them, took 6 days for it to get their from CA)

Came in today on the lunch truck. Will drop them off monday, when the shop is open.

 

:?
southerners