10.5 - 1 compression goal
Postmaster
Joined: Aug 2001
Posts: 4,270
Likes: 5
From: Delaware
Thread Starter
|
Senior User
Joined: Sep 2003
Posts: 298
Likes: 0
From: Central Texas
Yes, thanks Danlee. I am familier with TMI but would like to know what he will suggest. I would also like to know what I might be able to do to increase the CR, like milling the stock heads or different head all together, while the engine is still in the truck in it 351M form. I plan to rebuild the engine and drop in the 400 crank and pistons, knowing I can increase the CR with the right choice of piston.
I am moving really slow on this truck, so I can take a couple of intermediate step on the way to getting the engine I would like.
Thanks for the help.
I am moving really slow on this truck, so I can take a couple of intermediate step on the way to getting the engine I would like.
Thanks for the help.
Senior User
Joined: Mar 2008
Posts: 149
Likes: 0
10.5:1 CR
The compression issue with these engines are 3 fold: open chambered head, dished piston, pistons that are decked 0.067" down from the deck. The most difficult part to attack first, so to speak, is the pistons. Thankfully TMI have these available for the canted head SBF. You'll want to check out what he has available. Ideally you will want a piston that's a flat top design, and taller than stock(1.65") in the neighborhood of 1.70" pin height, and a 0.975 pin diameter, if you plan on reusing the stock rod. A 1.70" pin height flat-top piston @ 4.030 bore and 400 crank will give you 9.86:1 compression given a 76cc (stock 351M/400)combustion chamber. Keep in mind from these numbers, you will have a 0.0155 deck height, which leaves room for milling the block square, and also milling the heads square, which are customary on a rebuild, will only increase your compression. With the 1.70" piston example, zero deck milling the block, and milling the heads 0.010" will yeild a 10.62:1 CR. Hope this helps.
Thread Starter
|
Senior User
Joined: Sep 2003
Posts: 298
Likes: 0
From: Central Texas
That is great information. With the correct piston on the 400 crank, I can use the stock rods and heads and still get the 10.5+ CR that I am looking for. I want to be able to get the higher compression w/o much custom mill work to avoic any problems with valve lift and fitting the intake manifold. The more stock the engine the more work I will be able to do and the less I will have to pay to have someone else do the work.
Will I need to be concerned about the valve lift and the intake manifold?
Will I need to be concerned about the valve lift and the intake manifold?
Senior User
Joined: Mar 2008
Posts: 149
Likes: 0
valve lift will only be a concern when the lift gets into the 0.600" area, and as far as the intake goes, i dunno which one you will use, but fitment after milling should not be an issue until you start milling past 0.025" on the block/heads.
Postmaster
Joined: Aug 2001
Posts: 4,270
Likes: 5
From: Delaware
Why not get yourself a set of Aussie closed chamber heads. They should get you up to about 9.4:1 with a stock 351M. The 351M piston is ony 0.016" below deck, but it has about 12cc dish. The factory heads have about 78.4cc combustion chamber, while the Aussie closed chamber heads have about 62cc chambers.
The next step would be to get a 400 crank and zero deck pistons. These will get you as high as 12.1:1. With a small dish/valve relief of 16cc, you would be at 10:5:1 CR.
BTW, I have a 400 with 351C-4V closed chamber heads and flattop pistons that is about 10.3:1. I am interested in selling that motor, if you are near the East Coast.
The next step would be to get a 400 crank and zero deck pistons. These will get you as high as 12.1:1. With a small dish/valve relief of 16cc, you would be at 10:5:1 CR.
BTW, I have a 400 with 351C-4V closed chamber heads and flattop pistons that is about 10.3:1. I am interested in selling that motor, if you are near the East Coast.
Trending Topics
Posting Guru
Joined: Nov 2008
Posts: 1,937
Likes: 2
From: wyoming
400 ford spec's
73 cc head, 2cc valve relief flat top piston cleveland with a bushed rod to fit to a smaller pin. head gskt .038. 4.060 head gskt bore. 4.030 cylinder bore. deck height .000. 4" stroke crank. 11.069 compression. If head gskt at .060 its 10.533 compression. If .060 head gskt and .005 below deck its 10.421 compression. Just been playing with this very situation and had it handy. I'm wanting to get below 10 to 1 compression and gonna have to leave piston about .030 below deck for my application.
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
10 Things Every Truck Owner NEEDS (2026 Edition)
Michael S. Palmer
Rezvani's Latest Post-Apocalyptic Monster Is a Ford F-150 Raptor Underneath
Verdad Gallardo
Top 10 Most Expensive Ford Trucks Ever Sold on Bring a Trailer
Joe Kucinski
2027 Ford Super Duty Buyer's Guide (Every Model, Engine, & Package)
Brett Foote
Top 10 Ford Truck Tragedies
Joe Kucinski
AEV FXL Super Duty - the Super Duty Raptor Ford Doesn't Make
Brett Foote
Lobo Vs Lobo: Proof the F-150 Lobo Should Be Even Lower!
Michael S. Palmer
Ford's 2001 Explorer Sportsman Concept Looks For a New Home
Verdad Gallardo
10 Best Ford Truck Engines We Miss the Most!
Joe Kucinski
Thread Starter
|
Senior User
Joined: Sep 2003
Posts: 298
Likes: 0
From: Central Texas
Danlee - thanks for the offer. I am in central TX. PM me with a price and I will check with my father in law about the shipping -he is in the business and shipping is usually not as expensive as I think it is. I am looking to build a torquey motor and run low rpms - will the 4v heads hurt? don't know if I need to run up the air volumn to convert to propane.
I like the suggestions on the dished pistons... but I need to know which pistons meet that spec. I have contacted TMI but not heard back yet.
Wyoming - does the cleveland piston have a larger pin than the Mblock piston? Is that why it needs to be bushed?
I like the suggestions on the dished pistons... but I need to know which pistons meet that spec. I have contacted TMI but not heard back yet.
Wyoming - does the cleveland piston have a larger pin than the Mblock piston? Is that why it needs to be bushed?
Posting Guru
Joined: Nov 2008
Posts: 1,937
Likes: 2
From: wyoming
piston pin?
Danlee - thanks for the offer. I am in central TX. PM me with a price and I will check with my father in law about the shipping -he is in the business and shipping is usually not as expensive as I think it is. I am looking to build a torquey motor and run low rpms - will the 4v heads hurt? don't know if I need to run up the air volumn to convert to propane.
I like the suggestions on the dished pistons... but I need to know which pistons meet that spec. I have contacted TMI but not heard back yet.
Wyoming - does the cleveland piston have a larger pin than the Mblock piston? Is that why it needs to be bushed?
I like the suggestions on the dished pistons... but I need to know which pistons meet that spec. I have contacted TMI but not heard back yet.
Wyoming - does the cleveland piston have a larger pin than the Mblock piston? Is that why it needs to be bushed?
Senior User
Joined: Oct 2010
Posts: 156
Likes: 0
From: Columbia Falls, Montana
Do you have the propane conversion parts yet. You could go up to about 11 to 1 with propane, if you use the aussie heads. I would do the aussie heads and a piston that gets you anywhere inbetween 11 and 10 to 1. Also the stock rod in a 400 is super strong, and I would only get some arp rod bolts. With the cleveland pistons, you can use the stock crank and rod, but you need to have the rod bushed for the smaller diameter piston pin. Then the piston needs to be like WY says and it needs to be a bushed piston, not a pressed piston. These are better anyways, cause most garage mach. can put them together. Not everyone has a rod oven. I have a propane kit on a 360 fe motor that I thought about building a higher compression 390 for.
Thread
Thread Starter
Forum
Replies
Last Post
deckertd
1967 - 1972 F-100 & Larger F-Series Trucks
18
Sep 9, 2015 07:18 PM
Cobra-Kai
Small Block V8 (221, 260, 289, 5.0/302, 5.8/351W)
13
Apr 1, 2014 04:28 PM
HeathJohnson
Excursion - King of SUVs
4
Mar 29, 2012 06:30 PM
