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Custom grind
https://slantsix.org/forum/viewtopic.php?t=59091		 Page 1 of 3
Author:  225kid [ Mon Feb 08, 2016 2:01 pm ]
Post subject:  Custom grind
Hi, ive been looking for a good cam and havent been able to find any that i like and fit my build so ive decided to get a cutom grind, however i know nothing about that.
I have a 225 offy intake, 500 cfm edelbrock avs, long tube header, no stall yet, i will get one after i get the cam, 8 3/4 with 3.23 gears, i want to change the gear to a 3.91 or something of that nature, im going to put the engbuilder valves in the head and port and polish the head. Id like to be able to wing it to about 6,500 rpm. Suggestions would be appreciate.
Author:  CNC-Dude [ Mon Feb 08, 2016 2:55 pm ]
Post subject: 
Since you said you know nothing about this, why do you think that none of the many dozens of off the shelf grinds wont fit your build and you need to go with a custom grind? I'm just curious.
Author:  225kid [ Tue Feb 09, 2016 6:33 pm ]
Post subject: 
I dont think i need one i just cant find one the fits my desires 8)
Author:  Dart270 [ Wed Feb 10, 2016 5:58 am ]
Post subject: 
Hi 225 68 Valiant,

It would help us trying to answer your question if you gave us more info about your build.

Most importantly:

1) What compression ratio will you run and what fuel type?
2) What usage (street only, street-strip with pump gas, street-strip with race gas, track only...?).
3) How fast do you want the car to run?

Thanks,

Lou
Author:  225kid [ Wed Feb 10, 2016 8:13 am ]
Post subject: 
Hi, so far my heads been milled .60, its a stock bottom end
Its gonna be street/strip, id like it to be pump gas or maybe e85
And i wanna go as fast as i possibly can :lol:
Author:  Joshie225 [ Wed Feb 10, 2016 9:19 am ]
Post subject: 
Then you're probably budget constrained. So, how much do you want to spend?

If you increase the valve open duration without increasing the compression ratio the bottom end torque will suffer and with a stock torque converter the performance will be lazy. At some point you can't increase the compression ratio enough to compensate for the reduced low-speed cylinder filling from a late closing intake valve and low speed torque drops off regardless.

The static compression ratio and the intake valve closing point determine the dynamic compression ratio. Try out these calculators to determine your static and effective compression ratio. https://www.uempistons.com/index.php?ma ... alculators

You'll need to match the cam (intake closing point), compression ratio, torque converter stall speed, and gear ratio to have a well matched package. And that package should fit the way you want to use the car. So your usage needs to be stated.
Author:  Badvert65 [ Wed Feb 10, 2016 9:34 am ]
Post subject: 
Without measurements (such as deck height and cylinder volume) the best I can do is a guestimate. A 0.060 shave will give you around 9:1 compression give or take.
Author:  Joshie225 [ Wed Feb 10, 2016 9:39 am ]
Post subject: 
Quote:
Without measurements (such as deck height and cylinder volume) the best I can do is a guestimate. A 0.060 shave will give you around 9:1 compression give or take.
I took .080" off a head to get 8.5:1. You have to measure!
Author:  225kid [ Wed Feb 10, 2016 10:01 am ]
Post subject: 
I am budget constrated seeing that im 17 and still in school, i appreatie all the insite, i was looking around and i did see howards makes a cam the .473 lift cam, would that be an okay cam with a slight stall? My relastic goal is to run a 14.
Author:  Rick Covalt [ Wed Feb 10, 2016 1:34 pm ]
Post subject: 
Quote:
And i wanna go as fast as i possibly can
That leaves open a pretty big window. Here is what I have.

I am running the Howard's cam in my car right now (and for the last 2 seasons) My car has a 3000 stall convertor, 3.91 gears, engine builder valves, home ported, and about .070 off the head. Car weighs @ 2850# with me in it. I have gone 15.11 with it and only turned 5200 RPM doing it. I feel quite certain it would run a 14 sec ET if I turned it a little more rpm. This will be my back up motor and I wanted it to be in one piece when I swap in my new "race" motor.

Forget about 6500 RPM's. It sounds good on paper. It sounds a lot worse laying all over the track. 6500 is into full race motor territory. Also don't worry too much about polishing. From what I read it is waste of time on our heads.

A 14sec. ET feels pretty fast especially if the car originally struggled to get in to 18's

Also in the Engine FAQ at the top of the page, you can go in and find all the cams that Oregon cam can grind for you.They are great to work with and will be considerally less than Howard's or anyone else's new cams. I think it is still $75 for a re-grind.
Author:  Joshie225 [ Wed Feb 10, 2016 1:38 pm ]
Post subject: 
You need to be able to check your compression ratio and then adjust it to suit the cam. You will need to be able to degree the cam upon installation to get the expected performance. To run 14s will require high compression, a long duration cam, high stall torque converter, a well prepared cylinder head, high rear end ratio and good traction.

About 7 years ago I put together a performance cylinder head. Even though I did the porting myself it still cost me $500 in parts and machine shop bills. Good machine shop work has not gotten any less expensive. With the good head, a 390 Holley, Offy intake and oversized exhaust off the stock replacement exhaust manifol I got my '67 Valiant to run about 17 flat with a 3-speed manual and 3.21 gears. Stock cam, stock bottom end, 8.5:1 compression ratio.
Author:  slantzilla [ Wed Feb 10, 2016 6:58 pm ]
Post subject: 
Do yourself a favor and start building from the rear forward if you're on a budget. Get a good gear, trans, and converter in, then build a motor. You will be much happier in the long run. Also, do any brake upgrades, and remove as much weight as possible from the car. Your wallet will thank you. :D
Author:  225kid [ Sun Feb 14, 2016 1:32 pm ]
Post subject: 
Okay so im trying to figure out the compression. I had the head shaved .60 so how many cc's does that take away?
Author:  Rick Covalt [ Sun Feb 14, 2016 2:16 pm ]
Post subject: 
You need to measure. :lol: :lol:

You really do.
Author:  ceej [ Sun Feb 14, 2016 3:40 pm ]
Post subject: 
There is a tremendous amount of variability in the castings and factory machine work with the slant six. Sometimes you get lucky, and the combustion chambers of a given assembly actually are centered over the bores.

We don't say you have to measure to be difficult, There are simply too many variations in the manufacturing of these engines to be able to say what your compression would be based on a given cut. If any work has been done to the engine already, that needs to be discovered. I've seen stock chambers from 54cc to 62cc. I've seen variation of 6cc on the same head, and it wasn't warped.

That said, 0.0066" of cut is approximately 1 CC. That changes as you cut further.
Once past a 0.100" cut, the length of the push-rods will need to be addressed, whether you take the cut on the deck or the head. The stock length push-rods may, or may not allow enough adjustment. As the cut progresses, the geometry of the valve train changes as well.

Generally, anything that is stock will need a minimum cut of 0.090" to get into the 9:1 arena, but once again, you have to know where you are starting from. CC'ing a chamber is relatively simple, and is worth it's weight in gold when building the slant six.

A slant six is much more sensitive than a large displacement engine like a V8. You can make a lot of errors with a large displacement engine build, and still make good power. With a small displacement engine, everything has to be built, tuned, fueled, and operated within a specific targeted engine speed envelope to make good power. A slight variation, and the engine may not make as much power as it did stock, or at least within the range of RPM the engine actually lives.
We can set an engine up perfectly to run at 6000 rpm, but if we operate it at 3500 rpm all the time, it's not going to deliver acceptable performance. Bigger is not necessarily better. Big valves can be over-done when bore shrouding comes into play. With a given engine, more lift won't increase flow. Bigger carburetors may result in less torque across the entire operating range.

Building power with a slant is possible, and very satisfying. Watching a Big Block car leave the line a second or two in front of your slant car, then reeling his heavy butt in is a real hoot! It's also going to require a lot of work. Everything has to be just right to do it. The tune gets off even a little bit, and it's back to the pitts.
Last year we found an error in my ignition timing, corrected it, and took 1/2 second off my E.T.

Hope this helps you to understand the reasoning behind the insistence that you measure before proceeding. It could save you a big wad of cash, and perhaps help you to reach your performance goals.

CJ
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