I've got big block experience, but this will be my first slant 6 build. It's a 225 and I can't find much info out there (slant 6 sites) on building for quench. Anyone here done it? I think the 198 rods would help, but what about pistons? Any advice will be appreciated!

maybe 2.2 turbo pistons. Go here, www.slantsix.org EDIT missed that you have been there, I'm surprised that they dont have a ton of knowledge on this. I dont even know if those heads are open or closed ch's

http://www.slantsix.org/articles/combustion-chamber/sl6-combustion-chamber.htm

Might help.

It's my understanding that the heads have a very thick base, and can be milled as much as .100", which will bring them very close to closed chamber. I guess what I'm thinking is to find pistons with a somewhat positive deck height to make up the difference. I realize that much measurement and mock up would be required. Maybe the 2.2 pistons would be a start.

Just throwing this out, but if you mill the head .100" and run a positive deck height piston your compression will be well over 12-1.

With a 198 rod and 2.2 turbo pistons you will have a deck heght of -.025/.030, depending on whether your stock deck is unmolested or not. This will give you roughly 9.5-1 with a stock CC head and a Fel-Pro gasket. Stock is usually around 58cc.

The turbo pistons have a dish in them and do create somewhat of a quench effect.

On the sl6 combustion chamber link, arent they showing a comparison of the older vs newer sl6 head with the newer being more like a closed chamber. 68 and later.

There is not very much difference at all in Slant chambers from beginning to end. I always use the later model heads to get away from those oil leaking spark plug tubes.

One other small point, the Slant head was designed to work with 170 cubic inches. It was never improved when they went to the 225.

slantzilla, you said that the 198 rods and 2.2 pistons would give about 9.5:1 comp with the Fel Pros and a piswton deck of about -.025"/-.030". If the later head was milled to closed chamber, and a steel gasket (.020") was used, would this not render .045 to .050" quench, or am I missing something?

Also, excuse my ignorance, but what 2.2 pistons are we talking about here? Who sells them?

What are you actually trying to accomplish? A good MPG street motor or a performance build?

You have to remember that you are dealing with a very small bore here. A lot of milling on the head increases compression like crazy. Cam choice will become pretty critical so you don't build too much cylider pressure.

My motor has the head milled .065" and has the 198 rods, 2.2 turbo pistons about -.020" in the hole, and a Fel-Pro gasket. I am right under 11.5-1, and it is NOT pump gas friendly. I also run a cam with 300* advertised duration and .558" gross lift.

My pistons are KB Silvolites. They have a narrow ring on them too.

There is a deal on Wiseco pistons and K-1 rods on www.slantsix.org . When the deal started they were about the same as rebuilding a set of 198 rods and using KB pistons. Not sure how much they are now.

You'd want tighter than 45-50. I think w the long rods/2.2 turbo pistons you could mill the head/block enough to get .035-.040" but you'd have to do some valve relief milling on the pistons as said to get the CR pump gas friendly. Polkat I think your plan is solid, to get an efficient /6 (which means quench) for an economy build. Holler what you end up w

Thanks Robert. I plan to research the **** out of it and I'll get back with what I find.

His first mistake was buying the whole Clifford catalog. With a few exceptions, most of Clifford's stuff is useless. Building a small CI motor is not just a throw money at it and it will be fast.

Why do I do it? Because I have had tons of big and small block cars and wanted something different. I used to park my 15 second Duster next to my buddy's 10 second 383 Demon at the track, and for every person who came and looked at his car, 10 looked at mine.

I have also run 12.0@110 in a Slant street car on nitrous.

FWIW, a former co worker was an engineer on that 300 CID I-6 ford had in their trucks. when they developed the EFI for it, they had to detune it, because it made more power than the optional 302 V-8.....

If you plan to do more research,
you might consider writing a letter to
Willem Weertman
who is now retired
and seems to want to
pass on knowledge to a new generation

http://www.allpar.com/corporate/bios/weertman.html

notice the bit about the Slant 6 diesel engine project

sample quote

Q: The various programs to modify the Slant Six that I have read include things such as a turbo charged version and another aluminum version and a fuel-injected version, is there anything that you can tell me about those and what instigated them and why they were not pursued?

I think I mention both the diesel and turbo versions in the book. The diesel version was a pretty neat program when we were working on that one. It was quite well developed; we had a 4-cylinder version of the Slant Six engine for use, it was a turbo-charged 4-cylinder diesel version of the Slant Six engine. It was no longer slanted though. I’m sure it was upright. But the diesel version of the Slant Six was slanted.

That program died when the interest in diesel engines in the U.S. died following the unsuccessful launching of General Motors diesel version of an automotive engine. That gave the diesels a bad reputation in the field and the market dried up and with that we quit our diesel program. That cessation of our own diesel Slant Six program was a decision by Lee Iaccoca. He figured the market wasn’t there and we shouldn’t be spending any money in that direction and he was right and we just stopped working.

300 is doable, but I'm not sure I would call it a "budget" build. 300 N/A is also getting right on the ragged edge of a streetable Slant.

More is not always better when porting a Slant head. Be careful when choosing valve sizes too. What makes for great flow on a flow bench does not necessarily work on an engine because of the small bore.

Dig around on www.slantsix.org and you will find an engine build matrix that details many of the motors we have done.