Small Block blowing head gaskets

[MoparMuscl]

I have been having a problem with head gaskets blowing out on my small block. It has about 400-430 hp with 10:1 compression. I have a Performer RPM cam and manifold with KB 107 pistons. The heads are 360 castings that have been backcut for 2.02 valves and ported and polished as well as milled. They have 3500 miles on the heads. I ran this combination for about 3000 miles and then had a spiral lock snap ring broke and a piston pin ate up my block. I got new rings, block, ARP head bolts, gaskets, and bearnings. The new engine ran for 125 miles before I blew both Fel-Pro stock replacement head gaskets. It blew the metal ring out around 1 cylinder and was leaking around 4 other holes. All of them were blown along the top of the cylinder hole (closest to the intalke manifold). I pulled the engine and put some Fel-Pro 1008 gaskets and put it together and had a problem with leaking water. I re-torqued the head bolts and put some copper seal in the water. It seamed to fix the problem for about 300 miles and then started leaking again. I also believe that the cylinders are starting to leak again due to the crankcase preasure that is starting to blow out my PVC valve. I never had any problems with my other block so I was wondering what could be wrong with the block if anything? I don't think that the heads are warped b/c the engine never got hot and ran fine on my last engine. I am planning on pulling the engine and rebuilding it again and was wondering what could be wrong. Any help would be appreciated.

'79 Dodge Li'l Red Express

[Billydelrio]

Sounds like:
1. Bolt holes in the block are not deep enough.
2. Bolt holes in the block are full of foreign material.
3. Bolt holes in the block were not counter sunk after the deck was milled.
4. Head alignment pin is too long.
5. Something is keeping the head and deck apart.

When the deck and block are milled, it is likely that hardened washers need to be used under the head bolt heads, or the bolts will bottom out. This true on my 273. I don't know if your block has open or closed head bolt holes in the block.
Good luck
Billy

[Comp Chassis]

I would also check the head and deck for straightness. You could have warped heads or block.

[340king]

Good answers guys, you covered everything I was wanting to mention. What are you torquing to? If memory serves me correctly, you should torque the heads on a performance app to 105 ftlbs. Have you compared your torque wrench to another lately?

[jn]

I would like to recommend that 1. Go to the MOPAR manual for the proper torque and 2. Have your torque wrench calibrated. Now you won’t have induced any errors from someone else.

John

[340king]

I have the Mopar Performance Circle Track Engine Book open to page 61, Cylinder Heads. It recommends torquing the heads to 100-105 ftlbs of torque and explains a method to get there. The process is torque to 50 ftlbs, then 85 ftlbs, then 100-105 ftlbs. There is a prefered sequence that uses the center top bolt as a starting point, then go to the bottom center bolt and clockwise from there to the next bolts.

[gthomas]

I've put quite a few high performance heads on and IF your machine work is good, and buy the best gasket you can find, I use a method that hasn't failed me yet, but is time consuming. I first torque to about 30 lbs and then 10lbs increments until I get to 60lbs. I then go 5lbs at a time until I'm about 20lbs from final torque. I go the next 10 to 12lbs at 2lbs and finish the rest @ 1lb. I'll do this over a couple of days letting the torque set in. You'll notice that it'll change over night. When you finish the final torque I'd let it set a day or two, find something else to do to your car. When you go back to verify torque you'll find that you will be able to add to a few of them. After running the engine for a while I usually re-torque the heads again. Never blown a gasket after this procedure. This worked great with my 11.1 340 that I shifted at 7500rpm.

------------------
1972 340 Duster
-Dyno @ 420hp/440ftlbstq
-Built 727 w/3000 stall
-3000lbs
1999 2500 4x4
-V10 w/5sp
-Manual xfer case
-Rhino Lining
-Roll Top Bed Cover

[MoparMuscl]

I used the ARP head bolts with hardened washers. They recomended torquing them to 90 lb/ft with 30 wt motor oil. I also looked in the book "How TO Hot Rod Your Small Block Mopar" and they recomended 85 to 90 lb/ft. And if I torqued them to 100 or 105 lb/ft would I have any problem with the head bolts not being able to handle it? When I originally torqued then I went in 3 steps of 30 lb/ft. Thanks for the help.

[340king]

As you probably could tell from my reference material, I race circle track. I have never had a head gasket failure. I have followed the procedure outlined in the book or one very similar thoughout my engine building days.

I have the "Purple Headed Monster" currently setup with stock bolts, hardened washers and torqued to 105 ftlbs. Prior to installing the new heads it was run for about 10 nights of racing. It is an 11:1 340 that turns 7,400 rpm banging the rev limiter in hot laps and heats. The dry slick slows the car to only 6,700 rpm in the feature.

Incidently, I have a 12:1 360 also with ARP studs. I use Felpro race 1008 gaskets. Good luck.

[GTXMONTE]

It is not stated in your post whether or not the block has been square decked. If you don't have a clamping problem it is most likely the deck.

Monte Smith

[MoparMuscl]

The block was obtained from a junkyard out of a '77 Dodge 1/2 ton van. It wasn't ever rebuilt. I didn't have it deck squared.

[Dragracerr]

It may be deck thickness, It seems Chrysler had some serious issues at the foundry in the mid to late 70's, I have seen some very poor castings in this era.
If you have followed the guidelines posted by the responding members and still encounter this problem it would merrit verifying deck thickness when you have the heads off. (assuming both head and block decks are flat)
This may be performed by ultrasonic testing the deck(s) by a reptuable machine shop. This will vary from builder to builder however on 4 bolt per cylinder blocks, I would look for .280+ on minimum thickness.

This process can also cure the problem, Locate the combustion ring of the head gasket on the block and peen just behind this area all around the top between the bolt holes. I have used this procedure on less than desireable blocks with good success.
The Felpro 1008 gasket is a good product, has the pre-flattend combustion ring and should work well, you may also choose to torque set the heads using the three step sequence allow to sit for ~1 day, back off all head bolts in reverse sequence and re-tourque using the same parameters.

Good luck!

[PRO]

Hey MM I cant tell you how many cracked 360 heads Ive seen,if you ever overheat them its just a matter of time before they crack,go to a boneyard and look at any used 360 if it has a greenish growth at the front or rear of the head its cracked.Dont waste anymore time go have them magnafluxed with the valves removed.....PRO....