Higher comp pistons,new timing chain

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Dec 30, 1999 | 07:57 PM

Fordman

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Higher comp pistons,new timing chain

I have been looking at some performance magazines and have seen some higher compression pistons for a 351C. I have heard that these pistons will work in a 400M if you bore the hole in the piston out. Is this true? If so, how is it done?? Secondly I was looking at a roller timing chain and it has 3 keyways that allow 4deg advance, standard,and 4deg retard. What does this do???

Fordman

Dec 30, 1999 | 08:56 PM

whd507

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From: SW Missouri

Higher comp pistons,new timing chain

no you cannot modify 351c pistons. you need to get them before they are machined as the deck heighths are different.
the easiest setup for a 400 is to get a kit for a 1971 LTD or marquis 400 they had 260hp/400ft.lbs with a 2v carb. put a perfomer intake, and a manual secondary 4v carb on it and convert to electronic ignition and you got a setup worthy of consideration. in a car this will push a full-size LTD past 150 mph, and in a truck will pull stumps with ease untill the tranny blows!
the crank gear is indexed like that to retard or advance the camshaft in relation to the crank. read the index instructions with your cam for recommendations. I personally like the stock cam when timed right.

Dec 30, 1999 | 10:46 PM

Mulletwagon

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Higher comp pistons,new timing chain

Actually, this is true. The difference is the wrist pin diameter for the 400 is .975 and the 351C is .912. Compression heights are the same. To use 351C pistons in a 400 block requires fabrication of bushings that must be pressed into the 400 conrods. The pins must also be shortened so there is a recess in the pistons to cut grooves for Spirolocs which will be necessary since the pin will now be floating. Everything considered, probably not worth it. The extra slots on the timing gear allows the valve timing to be set at 4, 0, and -4 degrees. The 4 setting is supposed to improve low end performance. I use the 4 degree setting just to compensate for eventual stretch and wear on the chain. I don't notice any significant performance improvement however.
HTH
Fl Panhandle

Dec 31, 1999 | 10:43 AM

Fordman

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Higher comp pistons,new timing chain

Since people have said it is more of a pain in the butt to swap pistons, would shaving the heads 0.025 like in the HOT ROD build help compression much? IF it does, how much???

Thanks

Fordman

Dec 31, 1999 | 11:30 AM

Mulletwagon

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Higher comp pistons,new timing chain

>Since people have said it is more
>of a pain in the butt
>to swap pistons, would shaving the
>heads 0.025 like in the HOT
>ROD build help compression much?
>IF it does, how much???
>Thanks
>Fordman

In general, shaving .060 off any head will raise the compression approximately one point, i.e., 8.0 to 9.0. There are, however, other perils that must be considered. The other things affected are valve clearance and lash, pushrod length (for nonadjustable rockers), intake manifold fit, and available meat on the heads to begin with since some are limited in how much can be milled. A mill cut of .025 will raise compression about .2 and may not effect the other factors. Everything must be checked in advance and accounted for, but , it can be done.