hows it going guys,

I want to build a 400 soon from a '76 351M and I had a question about the speed pro 351c pistons (L2379F30). I noticed that TMI has those forged pistons that need to be bushed just like those 351c speed pros. The TMI's are almost $500 and the speed pro's are like $265 on summit. I checked on a calculater and the 351c pistons can produce roughly about 9.4:1 cr with the 76cc 400 heads. The speed pros have a -1.5cc dome and 2 reliefs. Can these 351c pistons from s-pro with bushed rods fit the '76 2v 400 heads or 351m heads? Are the TMI's pretty much the same thing? OH, and can I use the 351m heads instead of the 400's? Please let me know about any advice or info or just let me know if I got it all wrong, lol.

Thanks, Josh

 

IF you are looking at the kb 2334 , they have 1.720 comp height and that makes it "0" deck height , which with open chamber heads gives you 10.5:1
Check tims comp calculator in the first link.



http://www.tmeyerinc.com/pistoncompare.html

http://www.tmeyerinc.com/cart400pistons.htm




The summit pistons are 1.647 which leaves the piston down in the hole .045 and even with closed chamber heads are useless as they provide no quench but would work ok with 76 cc heads and give you a streetable compression.

Why the need for forged pistons?

Tim has a set of pistons, not sure if they have arrived for him or not but they are in the making for sure and they are hypers i believe that make 9.5 :1 with open chamber heads and are 1.720 compression height. Maybe tim will jump in here and confirm.


Check page one of the is thread, looks like 175 bux gets you a hyper with 9.5:1 and zero deck.


https://www.ford-trucks.com/forums/4...?highlight=tmi

 

I was looking at the forged piston from speed pro because they're aluminum, I just wanted some lighter pistons. I guess I failed to look at the 1.720 compression height for the kb-2334, I did'nt know that they would produce 10.5:1 compression.
I looked at Tim's site and I did'nt see those hypers yet so I was looking at the speed pros. I am only looking to about 9-9.5:1 cr, Do you think those speed pros would put in this much with open chamber heads Socket? $236 bucks are not bad.

 

Man i musta been over caffinated last nite lol. those pistons are 1.647 which is less than stock compression height for a 400. KB149's have been used by some here including myself and they have 1.670 comp height and give 10.6:1 compression. A lot of people have searched for a suitable piston to get the desired 9.5:1 compression . this is why tim meyers has developed a relationship with KB and filled this empty slot for us. Contact tim about his latest pistons , hes a great guy and will give you the straight up skinny and a good price.

 

????..all pistons have been aluminum since about 1947...

 

Damn, that really shows how much I know about pistons!, sorry bmc69, lol

Anyway, KB149's? I didn't see those on tim's site. Are those for stock 400 heads. And will those speed pro's work. I'll have to contact Tim about those new hypers. Should I keep those 351m heads or look for some 400's? I really don'y know different they are from each other. Thanks

 

Our last set of Hypers were shipped Thursday from KB. This should finish the pistons needed for the 400,(I think). The piston comparison chart should help give a good idea of which piston to use. All pistons will be a "zero" deck height. Only the forge piston have smaller pins.

 

Socket, when you summit pistons were you referring to the 351c speed pros? When you said they would work ok, what cr do you think they would make? Thanks

 

So you do already have those 9.4:1 hypers made for the stock 400 heads?
Thanks TMI

 

Yes the hypers that are on the way will yeild about 9.5:1 with the stock 400 heads. They also have the stock 400 pin size.

 

Hey cruz, in my first response i mistakenly said that the summit sourced pistons would work.I corrected this in my second response when i reaslized i had misread the compression height for the summit sourced speed pro pistons.(1.647 vs the kb 149(1.670)


At any rate your best bet if you want compression is to use TIMS pistons
as they do not need any bushing of the rods, they are direct fit and all the other options are pointless.Tim is the man

 

Thanks Socket, and Tim is the man, no a Ford God

 

we better stop before tim's ego gets all out of proportion lol. gl with you build.

 

Its doesn't look like the second part of your question was answered, but basically, 351M and 400 heads are identical. 351M heads have a "M" cast into a corner. I'm not technically sure that all 400s weren't using the same casting, because I have two 400s in my garage that also have the M cast and they are stock.

 

Thanks Matt cool, alot of help Thanks for the replies