Possible to bore 351E to use 401 Pistons?

[lizziemeister'sV6]

Hello-
I'm a new member to the forum but have owned my 1965 suburban since 1991. Want to replace the 305E because of wrist pin noise - have a 1968 351E engine to replace the 305 with - magnum heads are redone and block tested good next step to to bore to clean up cylinders - first I need to find pistons. Need to have oversize pistons on hand to bore for fit - is it possible to bore block for 401 pistons since 351E/M pistons are impossible to find. Any suggestions or know of pistons for sale? Thanks

[bigblockv6]

The 401 block was cast with a larger bore than the 351, just compared a 351 piston vs a 401 piston and the 401 piston is over 1/8 larger in diameter over the 351 piston. there's not enough beef in the 351 cylinder wall to accept that kind of overbore. Try ThunderV12.com for 351 pistons, they rebuild the 702 V12 and claim to have good used pistons. Other alternatives are custom pistons, someone on the website was selling some NOS 351 pistons about a month ago, it's possible that member still has them.

[lizziemeister'sV6]

Thanks for not thinking I'm an idiot for asking if 401 pistons can be fitted into a bored 351. I'm on a quest of rebuilding my 351E - just got the heads/valves all redone at the engine shop - took block in and it checked out OK - now I need pistons of some sort to be fitted to the block - machine shop mentioned custom made. So I have 3 questions - anyone have a set of pistons for sale? - if I went with custom pistons, can I go FLAT top to raise the compression ratio? and I had the cam reground for a little lope, will the extra valve lift canuse problems with different pistons? Thanks for responses!!!

[bigblockv6]

There can be issues with more cam lift causing the valves to hit the pistons but that is usually the case with aftermarket cams with a different centerline which requires to degree the cam. You will basically be using an OEM cam that has been reground, you should be fine as long as you go with some stiffer valves springs to match up with the lift of your cam. I'm using Ford 390 V8 valve springs in my 478M to match the higher lift of the cam.

[lizziemeister'sV6]

Thanks, the cam I had reground was a NOS 305 that I have had since the 1990's - so it would be OK if I had to go with custom made pistons to have them as Flat Tops? The heads are milled .030 - shop would not over that without milling the intake as well for proper fit. What are your suggestions?

[bigblockv6]

The cam grind specs I sent you are basically a mild performance cam but if you are concerned about the valves hitting the pistons then you should take some precautionary steps before having the custom pistons made up. Take one of the original stock pistons and fill in the dished in are with plastic autobody filler(Bondo) and set it up in the bore hooked up to the crank & rod, cylinder head on, cam & timing chain with sprockets, pushrods all hooked up. Rotate the assembly to see if it hits. Also something like "Silly Putty" or similar placed on top of the piston where the valve may hit would be a good idea as well. From that point on you may be able to determine how much relief may need to be machined into the piston where the valves may come in contact, if you ever notice some pistons have indentations for valve clearance. If you think this idea is far fetched I will tell you it's not at all. Years back I installed a Clifford cam in my 4.0 liter Jeep and the idea of the "Silly Putty" was recommended by Clifford, that was the procedure I followed.

[lizziemeister'sV6]

Well finally going forward with my 351E (needed .060 over bore) - ended up buying another complete 351M - turned out 2 pistons was bad - looked for 2 more - found 6 new .030 pistons but had to buy the complete set. Ended up installing sleeves and taking the bore to .030 over on the 351E original engine. The Engine is now being assembled at engine shop. Have a question on the tack cable. The 351M had the drive assembly on the cam and I have an 3000 RPM Stewart Warner Tach that I want to use (install right side of speedometer in dash). I never plan on exceeding 3000 rpm so this tach will work fine - if I had a cable. Does anyone have any extras or know what ends I would need to have one made? The tach I believe has a .105 square female input and the screw cap connector is 5/8" x 18 thread. Any help would be appreciated! THANKS! MERRY CHRISTMAS and HAPPY NEW YEAR!

[tommyduncan]

I can't help you with your problem but I was curious where you sent your cam to be reground?
Did you use the Magnum heads/exhaust manifolds? If not they aren't hard to sell.

I used to work at a very high end engine shop and the silly putty/playdough method was used there as well...

[lizziemeister'sV6]

Thanks for the reply - my cam was reground at the machine shop that my Carquest I use recommended. I used an NOS 305 cam as a core. The grind was one that a member of the 6066 Club sent me - he stated it was a mild performance grind. You now I'm going to keep my extra Magnum parts. Have a Merry Christmas and a Great New Year!