Need some advice asap, I had 350 engine with 327 cylinder head. I guess the last owner rebuilt for short length racing only. Anyway, I test drive yesterday, less than 1 hour, result gasket broken.
Water mixed with engine oil as I opened the beather and oil cap, found creamy stuff. I used normal thickness gasket from Fed-Pro. I think the gasket broke because of too much pressure. My machanic suggest to change cylinder head to 350 for better match then use normal thickness gasket, while the other friend who also a machanic suggested that a thicker copper gasket can be use to reduce the pressure. After discussed with my machanic on the possibility of using thicker copper gasket as it seem to be cheaper solution. His only concern was what is the right thickness of gasket. He said too thick gasket, will take away all the pressure, too thin gasket will break again soon.
Have anyone being in the same situation, what is the right solution. Any advise are welcome. Thank in advance.

Not a big fan of copper gaskets, they all seem to leak sooner or later. Try a standard Fel Pro composition gasket.

Need some advice asap, I had 350 engine with 327 cylinder head. I guess the last owner rebuilt for short length racing only. Anyway, I test drive yesterday, less than 1 hour, result gasket broken.
Water mixed with engine oil as I opened the beather and oil cap, found creamy stuff. I used normal thickness gasket from Fed-Pro. I think the gasket broke because of too much pressure. My machanic suggest to change cylinder head to 350 for better match then use normal thickness gasket, while the other friend who also a machanic suggested that a thicker copper gasket can be use to reduce the pressure. After discussed with my machanic on the possibility of using thicker copper gasket as it seem to be cheaper solution. His only concern was what is the right thickness of gasket. He said too thick gasket, will take away all the pressure, too thin gasket will break again soon.
Have anyone being in the same situation, what is the right solution. Any advise are welcome. Thank in advance.
FEL PRO and read directions..

Who ever told you to replace with 350 heads is giving you wrong information. 327 heads are no different then 350 heads. The differance is outside mounting boss. It only depend on the chamber and valve size. Other then that it's the same bolt pattern. I used Fel pro head gasket and worked fine. Used a 327/300hp 1.94"/ 1.50" double hump heads on a 350 chevy motor and it ran like a charm.

And as an additional comment, I ROUTINELY use 327 and 350 heads on SB400s! :thumbsup:

There's nothing wrong with using that head on that engine. Never put two different heads on the same engine. There was probably an issue with how the gasket was installed and torqued. Maybe the deck of the block wasn't clean or has an imperfection. Something else made that gasket blow out or not seal. Maybe the head is warped. If that is the case, replace the head with an identical head, or replace both with heads that are the same as each other. You don't need to use copper gaskets, and stock thickness felpros are just fine.

If using 327 head on 350 engine is possible then what cause the gasket to break? Please advise. What is the benefit of using 327 head on 350 engine? Higher torque or increase horse power or etc????

Additional info: head i used was the same size, 327 both. Thank you.

If using 327 head on 350 engine is possible then what cause the gasket to break? Please advise. What is the benefit of using 327 head on 350 engine? Higher torque or increase horse power or etc????


There's nothing wrong with using that head on that engine. Never put two different heads on the same engine. There was probably an issue with how the gasket was installed and torqued. Maybe the deck of the block wasn't clean or has an imperfection. Something else made that gasket blow out or not seal. Maybe the head is warped. If that is the case, replace the head with an identical head, or replace both with heads that are the same as each other. You don't need to use copper gaskets, and stock thickness felpros are just fine.

There is a chance that the 327 heads make flow a little better or make a little more compression that what was originally on the engine. Either or both of those things will make more power. You are nowhere near making enough power to blow out a gasket just by running the engine.

If using 327 head on 350 engine is possible then what cause the gasket to break? Please advise. What is the benefit of using 327 head on 350 engine? Higher torque or increase horse power or etc????

It depends on WHICH 327 head is being used, as well as what the shape is of the 350 piston top. MOST 327 heads had a combustion chamber with approximately a 64cc combustion chember volume. SOME of the late 60s 350 heads also had combustion chambers around 64cc, but after 1970, ALLLLLLLLLLLL 350 heads had larger chambers usually around 76cc. The 305 engines had heads with smaller chambers, but they also had smaller valves which would be less than ideal to use with a 350. Thus with an earlier 327 head with the smaller chamber bolted to a later 350 engine with dished, low compression pistons, the compression ratio would be increased which generally would increase power. Also, ALLLLLLLLLLL 327 heads up through 1968 DID NOT have holes on the ends of the heads for attachment of accessory brackets such as for the alternator, air cond compressor, etc.
But other than those things, the 262-265-267-283-327-302-305-307-350-SB400 heads are completely interchangeable. Of course, the later heads for the larger engines (302-327-350-400) are going to have the larger valves and ports which would make a better head to be used with the 350 engine.

Here few more info on part that I used for rebuilt;
- MainBrgs: .020
- Pistons: .020
- Rings: .020
- RodBrgs: .020
- MolyRings: Sealed Power/Federal-Mogul Moly Coated Rings
- CleviteBrgs: Clevite Brgs
- Camshaft: Crane Energizer Cam & Lifter Kit 2000-5000 RPM #100052 272/272 adv duration .454/.454
- FrostPlugs: Brass
- OilPumpShaft: Oil pump shaft for High Volume, High Pressure oil pumps Must use w/high volume pump
- OilPump: High Volume
- Timing: cloyes true roller # 9-1100SP
- CastPiston: Dish
- HypereutecticPistons: Sealed Power/Federal-Mogul Hypereutectic Pistons Dish # H423NP
Do you think it's too much torque? If yes, will thicker gasket help? How thick is suitable?
Thank you everyone.

As stated before make sure your block surface is clean. You might even want to put a straight edge across the bores to see how true the deck is.Take your heads to a machine shop and have them surface the heads, maybe even .010 shaved of will help with power. Use FelPro perma torque head gasket, should be good to go..

Check all the surfaces and put it back together. For what its worth, I am using a thinner gasket than stock on a 350 that is making more compression than yours, and don't have any problems. Mine are GM .028 comperssed thickness composition gaskets...

http://www.summitracing.com/parts/NAL-10105117?part=NAL-10105117&autoview=sku

Thank you every one, i'll check the surface.

so i finally found the cause of my engine problem. after i removed my intake manifold, i found a crack. i think water leak from that crack and mixed with engine oil. is it possible to weld or do something about it? as i live in thailand, finding a new engine is quite hard. if i fix that crack, is it possible that it will crack again at the same spot?
Please advise. Thank you