As I understand, hydraulic lifters require a lot less tinkering and are preferable for common street use. I've read that all they did in 81 when they switched all 225's to hydraulic lifters was to groove the rear cam bearing to feed the oil up to the rocker shaft and down through hollow push rods to top feed lifters, so the block didn't have to be reworked... so if I have a 77 Slant with a mechanical cam and lifters, I should be able to fit the cam, rods, and lifters from a hydraulic cam 81 in it's place, assuming I use the rear cam bearing from the 81 to pull the oil up, right? I'm already looking at a cam swap for the slant, and I found a great price on 12 new hydraulic flat lifters ($40), would love to have a quieter top end and turn the wrench a little less once the project is done.

If I do end up stuck with mechanical, I'm thinking the Comp Cams 252S, anyone have experience with those? I'm trying to get away from my slant's truck-like behavior -- it can haul pretty much anything around without blinking, but it's never been what you would call peppy. Definitely up for consideration: http://www.jegs.com/i/Comp+Cams/249/K64-240-4/10002/-1

You can install the hydro items, the camshaft will have to have it's rear journal grooved to make it work, you will also need the rockershaft and arms from the hydro slant as well to match the setup. You will also have to determine preload on the lifters to setup correctly compared to the 'lash and go' method of the mechanical unit.

So far comp has been "iffy", some sticks work fine, others have grenaded the oil pump gear. The 252 would be OK for daily driving and has grunt in the low end, but will work better if you can get the engines compression ratio to 9:1 or so then it wakes up in conjunction with the cam. You might consider a regrind on your stock cam, or another brand.


-D.idiot

If you are considering switching from a mechanical lifter cam to a hydraulic lifter cam, you should read THIS article first.

I prefer a regrind on a stock factory cam rather than buying a new cam, especially if you are trying to save money. I can buy reground lifters for $2 each at the local cam shop.

_________________
Casually looking for a Clifford hyperpak intake for cheap.

GREAT link... I dunno if I'm up for tracking down all that for a hydraulic upgrade... so maybe I'll start looking at mechanical anyway. If comps are iffy, is there another good brand of am cam to be looking at? I really don't like what the stock one does, and I do plan to try to get my compression ratio up as high as possible.

Get a stock cam and get it reground by Oregon Cam grinders. There has been much discussion on the board about regrinding stock cams and what profiles to have done to the cam. Search the board for "Oregon Cam".

_________________
Casually looking for a Clifford hyperpak intake for cheap.

If going for an OCG Mechanical regrind I can say that:

819 would be great for about a 9-9.5:1 scr build, similar to comp 252

791 is good for the high 9/low 10:1 SCR build similar to Erson 280

346 would be a good slant six candidate for the 10:1 build
with 4 barrel and headers. Is an RDP cam.

549 if going for 11:1+ SCR-lumpy and not for daily driver (although I did get about a 15-16" bouncy idle in my build...LOL)


-D.Idiot

Only changes I plan to make to the engine are boring up to 3.445" and using the 7.005" piston rods from the 198. I doubt this is going to make a lot of change to the stock compression ratio, so I'm thinking that 819 might be a good place to start, eh? I'm not good at doing compression ratio math up front, but stock should be 8.4 to 1, so getting up to 9 shouldn't take more than a little head milling, right? Where's a good place to pick up a cam for the regrind? Would like to keep my stock one to fall back on, but for instance, the only cam O'Reilly and Autozone have listed for my car has 198 intake and 203 exhaust durations, which I don't think is stock. -- http://shop.advanceautoparts.com/webapp ... fragment-2

*edit* Just used a compression calculator to put in the numbers, it gave me 8.3 on the compression with stock 0.140" negative deck height from the stock 225 piston arms, and going to the 198 rods bringing the negative deck up to about .026" shot the compression ratio up to 10.1 to 1... does this sound right? I don't want to push too high, and end up having to drive across town for race fuel.

The CS-380 is a stocker replacement, and the advertised duration is a mistake that's the duration at .050 which is about right.

Yes, that sounds right for SCR, milling the valve reliefs in the piston tops wil change that along with the true volume of your head (typical slant six stock deck heights can be .145-.175), 10:1 might be a little high for the 819...

-D.Idiot

The KB239 stats say they have a 5cc valve groove in them... so here's what I think I'm looking at. Am I missing anything?

Bore 3.445"
Stroke 4.125"
Head Gasket .045"
Deck Height .026"
Piston top 5cc
Combustion Chamber 58cc

Static Compression: 9.53

here's what I get with a slightly smaller head cc:
https://docs.google.com/spreadsheet/pub ... 2QzTUREQ3c&

Look in the cells marked "Current CR min/max" that will tell you the CR range for a 57-58cc head. It also says you have to mill off .023 for a 10.0:1 CR.

Here's my 10:1 engine using the Wisecos.
https://docs.google.com/spreadsheet/pub ... utput=html


I think you have to buy those KB pistons in sets of 4, which might kill most of the $$ savings versus the wisecos.

Head gasket value will be different depending on your manufacturer choice (can be .039-.045, closer to .039-041 if a Felpro, a little more .042 for the Victor Reinz, etc..)

Combustion chamber of 58cc would assume an uncut mid-60's head...thsi will also change greatly with new seats and OS valves...robertob makes a good guess at being conservative but you may be closer to 54 cc after the mods.

Piston top will also change if you are closer to 10:1 SCR and if you centerline the cam at 102, this will require some measuring and fitting
to see if the valves have enough clearance for early opening of the intake valve, or to be safe you can mill the pistons like Doc does and adjust the cut on the head for the added volume.

-D.Idiot

The problem I hit with those KB's is I found one site selling those KB's in a set of four for $179 http://www.cnc-motorsports.com/pistons- ... -bore.html and another site selling them individually for $60 each http://rndperformance.com/i-128803-kb23 ... -each.html so it ends up being cheaper to just buy two packs of four than to buy them individually... but the sets of 4 seem to be more expensive other places, so maybe it's just a really good deal. I was thinking about buying all 8 and then passing the spares off to the next guy so he only has to buy a 4 pack.
I can only find people talking about the mid to late 60's... I have no idea what the chamber volume is on my 77.

Robertob, what are you using to get your deck height to 0? I think the KB's plus a 7.005" arm get usually between .010 and .026, right? Are the Wiseco's a little thicker on top?

Peanut plug heads are 53-54cc stock...so after valve mods you are going to be closer to 50...

Typical late slant deck height is -0.145.

-D.Idiot

Wiseco piston compression distance is 1.625 - giving 0 deck (theoretical). KB compression distance is 1.594.

My block is at the machinist and he will be cutting down the block to give a measured 0 deck if they are a little low. If the pistons are high I will have him cut them down.

This is pretty standard for machining a custom engine combination - you are in charge of all the dimensions, so figure out up front what you want and choose parts and machine work to get you there.

For example, decide what compression ratio you want, and what pistons you want to use. Then have your headwork done, and measure the head CCs. Use that information to calculate the deck height you need. Then have your machinist cut the block (or pistons) to give you that deck. It may change later if you have to cut special valve reliefs in the pistons (which you might need to do).


You can't just throw parts together and hope for the best.

Yep, you will need to line your machinist out on what is being done to what.
I actually differ in robertob's path in that I get the block calculated and machined , then while the machinist is working on the valves and guides, I do a mockup to make sure we hit the target, then adjust the cut on the head to fit the target since it's less work for the machinist to make those adjustments than remount the block for another few passes on the deck and saves money on the labor side of things for a build. You may be going back and forth to the machinist if you are setting up a long rod to fit correctly and trying to utilize the proper quench numbers and doing mockups/clearance trials.

-D.Idiot