Slant Six Forum :: Down in a hole

I just measured how far down the pistons are from the deck surface on this 198, and they average a whopping 0.1084 below the deck!

Is there such a thing as a zero deck slant? Is that a good idea?

Quote:

I just measured how far down the pistons are from the deck surface on this 198, and they average a whopping 0.1084 below the deck!

Is there such a thing as a zero deck slant? Is that a good idea?

The 170 engine deck spec is zero, but most actually are around .010-.015
Most 225 engines measure around .170-.180 below.

You could probably make a zero deck 225, but be prepared to use either race fuel or alky.

What would be ideal? I'm going to order some 2.2 pistons and get this block a haircut at the machine shop. Is there such a thing as a zero deck slant? Is that a good idea?

I guess the best thing is to just give it a cleanup pass on the block and head

Quote:

I guess the best thing is to just give it a cleanup pass on the block and head

It's easier if you take the block and parts to the machinist, have him make a pass on the deck... assemble block with crank and one rod/piston take your deck height measurement... run the calc... then you can determine if you need to take block back for another pass or let the machinist know how much to cut off the head... he can work on the head while you do the initial block work and measurement... once he puts your new valves, seats, etc in... you can take a new combustion chamber measurement then determine the final cut to the head...

Now that makes sense!

Author:	coconuteater64 [ Sat May 20, 2017 1:26 pm ]
Post subject:	Down in a hole
I just measured how far down the pistons are from the deck surface on this 198, and they average a whopping 0.1084 below the deck! What would be ideal? I'm going to order some 2.2 pistons and get this block a haircut at the machine shop. Is there such a thing as a zero deck slant? Is that a good idea?

Author:	SlantSixDan [ Sat May 20, 2017 2:50 pm ]
Post subject:
That ain't no whopping. Stock 225s'll run more than a fifth of an inch negative deck height.

Author:	Charrlie_S [ Sat May 20, 2017 3:13 pm ]
Post subject:	Re: Down in a hole
Quote: I just measured how far down the pistons are from the deck surface on this 198, and they average a whopping 0.1084 below the deck! Is there such a thing as a zero deck slant? Is that a good idea? The 170 engine deck spec is zero, but most actually are around .010-.015 Most 225 engines measure around .170-.180 below. You could probably make a zero deck 225, but be prepared to use either race fuel or alky.

Author:	coconuteater64 [ Sat May 20, 2017 4:22 pm ]
Post subject:	Re: Down in a hole
Quote: Quote: I just measured how far down the pistons are from the deck surface on this 198, and they average a whopping 0.1084 below the deck! Is there such a thing as a zero deck slant? Is that a good idea? The 170 engine deck spec is zero, but most actually are around .010-.015 Most 225 engines measure around .170-.180 below. You could probably make a zero deck 225, but be prepared to use either race fuel or alky. Yikes! So I guess the immediate top of the cylinder is, by default, part of the combustion chamber. The local machine shop has never done a slant six, so I will have to tell him exactly what I need step by step. They've done a whack load of inline Fords and Chevrolets, but never one of these critters.

Author:	SpaceFrank [ Sat May 20, 2017 5:31 pm ]
Post subject:
You really need to decide what kind of compression ratio you want first. That'll dictate how much you cut off the block (or head).

Slant Six Forum https://www.slantsix.org/forum/

Down in a hole https://www.slantsix.org/forum/viewtopic.php?t=61158	Page 1 of 2

Author:	GTS225 [ Sat May 20, 2017 6:02 pm ]
Post subject:	Re: Down in a hole
Quote: What would be ideal? I'm going to order some 2.2 pistons and get this block a haircut at the machine shop. Is there such a thing as a zero deck slant? Is that a good idea? ******************************************************* WHOA! Slow up there, Hoss. You want to clarify this statement? It sorta sounds like you believe a set of 2.2 pistons and a deck cut will give you a zero deck motor. Such is not the case. What you would need is a 225 crank, 198 rods, and an overbore to match those 2.2 pistons. Even then, I couldn't say you'd end up with a zero deck engine, but you would surely have a high static compression ratio. Roger

Author:	Charrlie_S [ Sat May 20, 2017 6:14 pm ]
Post subject:
Just for giggles and grins, I ran some numbers. Bore 3.460.... .060 over stock Stroke 4.125 ...stock 225 Combustion chamber CC's 54... close to stock Gasket thickness .038 Gasket bore 3.500 CR=11.6 to 1 You would lose a little for valve reliefs, which would be required if running much more then a stock cam, with the zero deck hight.

Author:	sandy in BC [ Sat May 20, 2017 6:34 pm ]
Post subject:
stock cam and 11.6:1 ..... Dcr of about 27... .....at least the stock pushrods will work....

Author:	coconuteater64 [ Sat May 20, 2017 6:42 pm ]
Post subject:
I'm not saying I need a zero deck slant, I just wanted to know if there is a happy zone. I'm planning on a 198 block bored to 87.5mm, 198 rods, and a 225 crankshaft. Just trying to get ideas. It's going in a D100 with dual Dutras, 2 barrel carb, and close to stock solid cam.

Author:	sandy in BC [ Sat May 20, 2017 6:50 pm ]
Post subject:
If you raise the compression you need a more aggressive cam. How much more cam can (and should) be calculated. You need a few inputs (like deck/piston clearance and head CCs) ..then you can calculate what cam would go with your vehicle/compression/gears/weight/ build vision. The good news is planning is cheap.

Author:	slantzilla [ Sat May 20, 2017 6:59 pm ]
Post subject:
Which 2.2 piston? A flat top will give you the 11.5+ while the dished turbo slug will come out about 9.5. With an uncut deck the 2.2 piston comes out about .018" down the hole.

Author:	coconuteater64 [ Sat May 20, 2017 7:53 pm ]
Post subject:
I went back and read the non-stroker stroker article. I guess the best thing is to just give it a cleanup pass on the block and head so the gasket can seal, and calculate the static compression once I have all the pieces. Then I can worry about the cam.

Author:	DusterIdiot [ Sat May 20, 2017 8:37 pm ]
Post subject:	Better than that...
Quote: I guess the best thing is to just give it a cleanup pass on the block and head It's easier if you take the block and parts to the machinist, have him make a pass on the deck... assemble block with crank and one rod/piston take your deck height measurement... run the calc... then you can determine if you need to take block back for another pass or let the machinist know how much to cut off the head... he can work on the head while you do the initial block work and measurement... once he puts your new valves, seats, etc in... you can take a new combustion chamber measurement then determine the final cut to the head...

Author:	coconuteater64 [ Sat May 27, 2017 6:21 am ]
Post subject:	Re: Better than that...
Quote: Quote: I guess the best thing is to just give it a cleanup pass on the block and head It's easier if you take the block and parts to the machinist, have him make a pass on the deck... assemble block with crank and one rod/piston take your deck height measurement... run the calc... then you can determine if you need to take block back for another pass or let the machinist know how much to cut off the head... he can work on the head while you do the initial block work and measurement... once he puts your new valves, seats, etc in... you can take a new combustion chamber measurement then determine the final cut to the head... Now that makes sense!

Page 1 of 2	All times are UTC-07:00
Powered by phpBB® Forum Software © phpBB Limited https://www.phpbb.com/

Author:	DusterIdiot [ Sat May 27, 2017 8:36 am ]
Post subject:	Yep...
Quote: Now that makes sense! If you have a good relationship with your machinist, he will know that he will do some work, then you will be back to pick up parts and do some mods, then drop them back by... The best process would be to have everything hot tanked and magnafluxed... then you pick up the head while he works on the block... you do your porting on the head... once done you drop it back to him... that way he can work on your block, rods, etc while you are porting....if he's not too busy he might have your block ready when you drop the head back by, then you can do the initial assembly//measurement then let him know the cut while he does the headwork.... once he's done you can go pick up the head and pay for the services and finish your assembly... makes for a few trips, but you get exactly what you want especially if the long rod combination is in the 11:1 SCR where a couple of cc's can be a real "OOOPS!"....