I Was installing my pistons and I broke the top compression ring on one of the pistons. I only broke about 3/4 of an inch off of it but don't want to use it and don't want to buy another set. What do I do? Thanks. Eric

 

DO NOT use the ring. I don't know if you can buy rings separately but if you can't you have no choice but to buy a set. Sorry man.

 

I thought I would have to get another set I am really disappointed in this engine the pistons sit about 1/8-1/4 of an inch below deck. I am jinxed with this truck. I guess the engine will sit there for a while. Thanks. Eric

 

Talk to us and we'll get your back on track as fast and as cheap as it can be done. And vent here, we've all been there (as much as we hate to admit it), done that, and burned the damn t-shirt!

What engine, what rods, what crank, what pistons?

Bob
'66 7 Litre, top loader, 3.25 Traction-lock, Sidewinder Intake, SCJ Exhaust
'88 F150 LWB 4x2, XLT Lariat, 302, 5 speed, 3.08
'99 Ranger, 4x2, 3.0, 5 speed, 3.73 posi

 

That much deck clearance is not normal from what I've seen. My 360 is a very low compression engine and it almost comes all the way up.

 

[font size="1" color="#FF0000"]LAST EDITED ON 27-Aug-01 AT 08:03 PM (EST)[/font][p]It is a 352 crank and rods and pistons I got from the machine shop. The box says 360 but I think they are 390 pistons. The piston to deck clearance is closer to 1/8 than 1/4 but the the old 352 pistonce came all the way up to the top of the deck. Eric

 

You really need to do your homework now. You will loose about one point of compression for each .060 inch more deck clearance. Based on what you described, your compression ratio may be down to 7:1.

 

Take ya "ring" with ya and see if any of the local engine builders have lose rings. If it is 4.050 bore then a 4.060 (chev even) ring could be filed to do the job.

Dont panic

Are you sure you have the early long rods.
Maybe a rod swap will get your pistons up.







In OZ and seeking 427block /428crank

 

I've done about a dozen major engine rebuilds and only 1 went smooth. Every time it's always something. I like to keep in mind that once it's done, it'll be in there for many years of service. That helps 'cool the burn' for me.

Do not run 1/8~1/4 down the hole, if the shop set you up, take it back and if they don't make good find another shop.

I was a bit T'd off at one shop because I spent quite a bit of money there and waited quite a while for the work to get done and then had a rod knock. He didn't seem very helpful at first so I went to a race engine builder and he found the problem was with bad rods from PAW. It cost me another $1,000 to get the engine done right, but at least now it's done right.

The point is, take the time to do it right. And that does sound like 390 pistons or short rods.

 

I am not sure what rods they are they are from the engine which was a 352. The casting # on them are c1ae-a. When I tore it down the 352 pistons came all the way up. Eric

 

My rods are 6.54" Are there any rods that will work that are a little bit longer? The machine shop said he can get me another ring just take him the old one. Eric

 

6.54" rods are standard 352/360 rods. The only other stock choice I know of are the 390/410/428 rods, but they're even shorter at 6.488", so that doesn't help.

Time for a little math. All FE engines have a deck height from the factory of 10.17" (assuming they are to spec, which they usually are). The distance from the top of the piston to the deck, aka the "deck clearance", is 10.17" less the sum of your throw, rod length, and piston height (also known as "compression height"). The 352 and 360 both used a crankshaft with a 1.75" throw, and had 6.540" connecting rods, for a total of 8.29". That leaves 1.880" for the piston. I don't know what height 352 pistons are, but 360 engines came from the factory with 1.776" high pistons. Thus, the 360 came from the factory with a "deck clearance" of 0.104", i.e., the pistons were 0.104" "down the hole."

The 390 FE engines used a number of different pistons, but some were as short as 1.680". If you installed 1.680" pistons, you'd wind up with a deck clearance of 0.20". Even worse, 390 truck pistons are only 1.660" high, which would give a deck clearance of 0.22" in your engine.

It sounds like you got the wrong pistons. You want pistons AT LEAST as tall as standard 360 pistons. Most 390 pistons are shorter than 360 pistons and are the wrong choice.

It may take some searching, but some 390's came with even taller pistons. You could theoretically go to 1.880" pistons for a true "zero deck", but the tallest stock 390 pistons I know of were 1.7919". If you could find those, you'd be at 0.0881" clearance. Then again, you could always shell out $600 for a set of custom pistons. If it comes to that, though, you'd be better off just stroking your motor with a 390 or 428 crank, either of which would both add cid and bring the pistons higher in the bore.

karlsd a/k/a "ksd"
69 F100 Explorer 360/C6

 

well to sound like a broken record

400 clev rods are 0.1 longer and you can pick up 0.125 stroke

so that puts the piston about 0.160 higher and it is a bigger engine


In OZ and seeking 427block /428crank

 

FEina52F1, are you saying that with longer rods the size of the motor will go up? You cannot in any motor change the displacement by changing the length of the rod. The only two factors that determine displacement is bore and stroke (crankshaft throw). Are you talking about offset grinding?

 

I think I followed that. Adding 0.125 of stroke adds 0.0625" of throw, which when added to rods that are 0.10 inch longer would bring the pistons 0.1625" higher in the bore.

Are 400C rods 6.640" and do they interchange easily with FE rods? I've never tried it. Are they as strong or stronger than the 6.488" 390/410/428 rods?

Also, df and oz both mention offset grinding the crank to add throw/stroke, but I don't know much about it. How much throw can you really gain from offset grinding the crank? I would think it would really reduce the size of the rod journals. Are there any strength/breakage issues as a result? Do you need special bearings?

karlsd a/k/a "ksd"
69 F100 Explorer 360/C6