deck height decision

[swampbuggy]

Slowly getting the parts together to build my max. effort 371 C.I. S.B.C. Block is Dart Cast Iron Eagle. I am trying to decide weather to deck block to 9.00" and use a gasket appx. .035-.040" or leave a little on the deck and use a thinner head gasket ?? would like you PRO's to tell me what you would do. Also----would like to know if a thicker (or) thinner MLS head gasket would be more likely to give trouble ?? Dart T-355 Alum. Heads, 4.185" bore leaves .215" between bores, ARP studs to clamp heads down, static C.R. will be appx. 14 to 1 . Thanks in advance to those who comment, Mark H.

[cgarb]

I always try on a new build to use the thinner gasket and leave some on the deck, if you have a failure and the deck gets torched you can skim off the deck and add a thicker gaskets to keep the clearances the same.

[tresi]

cgarb had a good method. You want to measure all you rods to confirm they are equal center to center length. Just because they are new doesn't mean they are. Do a 4 corner mock up before you have the block shaved. Once you have you corner measurements then decide which gaskets you're going to use and how you're going to cut the block.

[ProPower engines]

I have done many similar builds with both the World and Dart blocks and 2 thing must be considered before machining.

1 is if this is a max effort then keep it close depending on the rod used and piston clearance I have run them as tight as .030 and had no issues but that was a top quality rod and a super lite piston to keep rod stretch to a minimum.

2 is if you want to be able to have a safety margin Then leave .010 down the hole and use a thin gasket to make up the difference. I am just using .010 down as an example not an absolute but depending on piston used you may need more or less depending on dome volume/shape PTV etc. but the larger bore is better for unshrouding the valves if you want to keep the pistons in the hole a bit.

[swampbuggy]

Thanks to you three fellas , a little more information...the con-rods will be most likely Carrillo H-Beams with upgrade options including Carr bolts, pistons will be CP box style pistons w/.827 x .180" (or) .200" wall x 2.00" ( i think ?) no-dome works with 40 cc Dart 9 degree head chamber to get static high enough. I would hope there will be no more than .005" stretch ??? Mark H.

[Frankshaft]

Thanks to you three fellas , a little more information...the con-rods will be most likely Carrillo H-Beams with upgrade options including Carr bolts, pistons will be CP box style pistons w/.827 x .180" (or) .200" wall x 2.00" ( i think ?) no-dome works with 40 cc Dart 9 degree head chamber to get static high enough. I would hope there will be no more than .005" stretch ??? Mark H.

I personally would keep it in that .040 ish range. If this is a true max effort deal, then you should be spinning this thing some serious rpm. I would like more clearance. You will gain nothing and it might actually make more. Small, tight chambered modern heads aren't old school gm 993 open chamber heads that like super tight quench. I have actually made measurable gains by going to .051 thick vs .041 thick gaskets on certain applications. Also, the head gasket sealing will be a non issue. I have ran that same block out to 4.250 bore with a fel pro composition 4.250 bore gasket. Never once in many seasons did it have head gasket issues, in that 14:1 range.

[bigmike]

I'm not a big fan of real thin head gaskets on cast iron block aluminum head combination. But not sure how thin you are talking about here.

You can get custom pistons made with increase piston compression height. Some piston companys such as Ross tend to run increase piston compression height on many of their pistons combo but they might not be enough for what you are after here.

" I would hope there will be no more than .005" stretch ???"

With rods, crank, block flexing at high RPM it may be much higher than that. I know a guy that got .030 clearances on a SBC 383 crank counter weights to the bottom of the pistons. It was not enough!

[swampbuggy]

Thanks Frankshaft, RPM's YEP, planning on 8500 to 9000 Tit. valves, tool steel retainers, Tit. keepers if they are safe, PSI (or) Pac, probably T+D........DEFINITELY Steel rocker arms 1.8 int. min. Thanks F.S. Mark H.

[houser45]

Better off having the squish amount you want set with the gasket and not having the pistons in the hole with a thinner gasket. The decks are very thick on those blocks. Who cares if it takes.010” more off the deck to make it right? Also why are you running that small of a diameter wrist pin?

[swampbuggy]

Smaller diameter wrist pins are used to employ a longer con-rod and not get into the oil ring groove. There may be other reasons i don't know about ? Mark H.

[lefty o]

my thoughts. an iron eagle block is an expensive piece, and once you cut the deck, there is no going back. i would go with a different piston/rod combo vs cutting the block. in the long run, its going to be cheaper.

[MadBill]

Smaller diameter wrist pins are used to employ a longer con-rod and not get into the oil ring groove. There may be other reasons i don't know about ? Mark H.

I have a circa 2000 box-type NASCAR Ford paperweight sized for a < 0.800" x < 2.00" pin...

[geraldtson]

You can take metal off but you can't put it back.The more you take off the deck the more it's inclined to "move a little". The MLS gaskets will probably start leaking a little water- thick or thin- in your application (aluminum heads) in about six months or so regardless. Just freshen up heads and replace gaskets at that time.

[houser45]

Smaller diameter wrist pins are used to employ a longer con-rod and not get into the oil ring groove. There may be other reasons i don't know about ? Mark H.

Ya, i get that, that is a little small of a wrist pin for what you are trying to do. Just because smaller wrist pins are used in Nascar for one race or two and cycled out doesn’t mean they will last very long in your application. The pin bores in the pistons will be iffy

[swampbuggy]

This engine will NEVER see the cycles/stress that a cup engine sees on a 500 mile race weekend....guarnteed. Mark H.