rebuilding a rebuilt slant

-
7

72_dart

Well-Known Member
Joined
Jul 27, 2013
Messages
91
Reaction score
0
Location
Chicago burbs
I recently purchased a rebuilt slant with the intention of just dropping it in my 72 swinger. After thinking it over I have no idea what it was built for. *I purchased it from a parts re builder in Michigan and they don't rebuild engines. They acquired several of them in a surplus deal. The motor is setting in a crate with plastic and some old detroit gaskets. The guy said that that should date it as detroit gasket hasn't been around for quite awhile. All I really know about the motor is that it's a peanut head 225 long block. *It's been bored 60 over and the rod and mains are 30 under. *So what I would like to do is have the block decked and get a new cam have that installed and degreed. *my machinist said that I could get the compression up to 10 to 1 and run on pump gas if I back off the timing a bit. I plan on reusing all the international components. I have a offy 4 barrel intake and no carb yet.
Does anyone have any suggestions as to which cam will work best with this compression? *Has anyone built a high compression slant that runs on pump gas? *How high can I get the compression and have everything work nice? I don't mind it if I have to use premium, or if it is a premium only engine. I should also note that this car is a driver however I would prefer it to be more wild than mild. One other thing I should mention is that I have no intention of ever turbocharging this motor.
All your help will be greatly appreciated.
Thanks, John
 
If you want 10:1 CR, make sure you use new head bolts or head studs, then you'll need the dizzy to be regraphed, use a billet cam gear set, and around the 35-75 (3/4 Race as they were known in the day) mark for a cam with about 0.500" lift.....and balanced.
A 600 square bore, vac 2nd Holley will do the trick.
A good electronic ignition system too, MSD or IC&E....need a good strong spark to light the fire.
 
If you do get pinging problems, one solution is to install a GM 8-pin HEI module, GM knock sensor & module, and an engine controller that can manage the spark. The Holley Commander 950 is one. That is my plan. There was a simpler ignition-only controller called Rabid Gator, but apparently never went live.

I wonder if your engine was one of the lot I saw on ebay a few years ago. They were rebuilt slants in crates, U.S. military surplus, later vintage. I recall they were buy-it-now fairly affordable ($600 or so). If so, probably has a mild, driveable cam.
 
chj, I'm guessing that you mean billet timing chain gear set? Also I didn't catch the 35 -75 (3/4 Race as they were known in the day) reference. Could you please elaborate a little?

BillGrissom, when I bought the engine I just assumed that it was either a car or truck motor from a smaller company. It was listed on ebay. When I bought it the buy it now was 350, when I returned home I looked and the buy it now was 600 I actually only paid 300 for it just because I thought it would be a good base to start from. After doing some thinking that motor could have been for a forklift, an airport tug, or even an aircraft generator. That's why I want to choose a different cam and bump up the compression. I don't want to go all out on this one but I want to have some fun while I plan and work on the other parts of the car. I do have an hei setup but nothing with a controller. I just have to find time to wire it up... One of my problems is I find good deals on parts so I buy the stuff that I'm going to need and that sets me back on other things that I have already started. Right now I'm just trying to focus on the motor.
 
Yeah....a roller chain style cam timing set, that has billet steel sprockets, and you can alter your cam timing with.....see pic.

35 - 75 refers to the Inlet timing of the cam...opens 35* before TDC and closes 75* after BDC....meaning it has 290* duration at about 0.001" lobe lift, or close to it.....they were called a 3/4 ( Read :- three quarter ) Race cams.....full race cams were 40 - 80 and bigger.
A good set of headers helps heaps....as well as big valves and a port 'n' polish.

I am in the process of doing a 225 slant ( N/A ) for drag racing.....I will be using 3 x 45mm DHLA Delortos......makes it a 6 Pack of sorts.
 

Attachments

  • IMGP2986.jpg
    64.6 KB · Views: 386
  • IMGP2987.jpg
    45.4 KB · Views: 390
Cool, thanks. One other thing that I was wondering is am I going to have to get the pushrods cut down or should they be alright?
 
72_dart,
Read up a bit on cams. If a later motor, yours probably has hydraulic lifters. If you pull the valve cover and the rockers have no adjuster bolts, it is hydraulic (view photos first). If so, I don't know if you can change it to mechanical lifters and cam. They changed the oiling system I recall. You can probably go that way (not the other), but would need rockers from an earlier motor. Not sure you can get performance hydraulic cams for a slant, so maybe no choice but to swap.
 
Ok so I did some looking Clifford has a few cams 2 of which they say are for manual trans. only... I spoke with a guy from Clifford and he said that with the bigger cams the motor wouldn't create enough vacuum to shift the trans....Is this right? I don’t remember any vacuum lines going to the trans. Any thoughts?
 
72_dart said:
Ok so I did some looking Clifford has a few cams 2 of which they say are for manual trans. only... I spoke with a guy from Clifford and he said that with the bigger cams the motor wouldn't create enough vacuum to shift the trans....Is this right? I don’t remember any vacuum lines going to the trans. Any thoughts?
Click to expand...

Bigger cams need a high stall convertor.....makes a pig motor nice.
Probably 2,800 to 3,500 rpm stallie depending on diff gears and vehicle weight.
 
You could go with a floor leve, manual shift auto at that point too. Just based on the descriptive info you relate, the lack of idle vacuum means it will not idle worth a hoot on the street.

As an FYI, for a vaccum controlled trans, the trans will shift without high vacuum but at a higher RPM shift point. For trannies of this era, you should find either a vacuum line going to the trans, or a shift linkage from the carb to the trans; either is used as a signal to the trans indicating how much load the engine is pulling and cause the shifts to go a higher RPM when the carb is open (linkgage is moved or the vacuum gets lower).

If you have the linkage from the carb to the trans then you have that settled. Then the issue may be that for mild starts; the carb may not be open much and the trans will want to shift at lower rpm's, where the enigne will not run well due to the wild cam. In short, it may drive like crap unless you are near wide open all the time as you acdelerate.

Is that what you will settle for? What kind of driving will you be doing with this car? Commuting every day or ??
 
72_dart said:
Ok so I did some looking Clifford has a few cams 2 of which they say are for manual trans. only... I spoke with a guy from Clifford and he said that with the bigger cams the motor wouldn't create enough vacuum to shift the trans....Is this right? I don’t remember any vacuum lines going to the trans. Any thoughts?
Click to expand...

Danger, Will Robinson, Danger.
Stay away from Clifford for cams. Larry doesn't know what he is talking about. There is no vacuum on a Mopar auto trans. Clifford has sold Hydroulic lifter cams and lifters, for solid lifter motors, and there is no way to get oil to the lifters, with adj rockers and pushrods. There are much better places to get slant six cams.

PS: You can swap from hydro to solid, or solid to hydro, IF you use the complete valve train assy as a set. Cam lifters, pushrods, rockers, and shaft.
 
I plan on driving the car ad much ad possible. Right now it's a daily driver, when I was younger the motors I built with my dad were real conservative. He was all about building something practical, smoothly idle, good cold starts, nothing with headers. Now it's my turn to build a lumpy rough idling car to have fun with. If I wanted to be practical I would buy a Japanese import. I'm not building a race car but I definitely want something more wild than mild.
 
Thanks Charlie_S, that's what I thought about the trans the motor I am working on is a rebuilt that was never run. It is a hydraulic cam motor but like I mentioned above I could've been built for a forklift for all I know. I bought it because most of the machine work has already been done and it's clean. All I want to do is bump up the compression (a lot) and slap in a lumpy cam for a little fun. I don't want to go all out with this motor, but I think with a big cam and a 4 barrel with a bump in compression it could be done on a budget.
 
I have done some reading on cams lately since I found my timing chain has slack. Comp Cams has a performance solid lifter cam they say works on slants from 1960-1987. You can find on ebay or Summit for ~$130. What they don't tell you is that for your hydraulic engine, you would need to get adjustable rocker arms and pushrods from an earlier (solid) slant. I haven't heard of any performance hydraulic cams for a slant. Check with Oregon Cam since they could grind one if anyone could, though switching to solid lifters might be better, if you don't mind adjusting valves every few years.
 
BillGrissom said:
I have done some reading on cams lately since I found my timing chain has slack. Comp Cams has a performance solid lifter cam they say works on slants from 1960-1987. You can find on ebay or Summit for ~$130. What they don't tell you is that for your hydraulic engine, you would need to get adjustable rocker arms and pushrods from an earlier (solid) slant. I haven't heard of any performance hydraulic cams for a slant. Check with Oregon Cam since they could grind one if anyone could, though switching to solid lifters might be better, if you don't mind adjusting valves every few years.
Click to expand...

You can get performance hydraulic cams for a slant. The major issue with them is getting the correct pushrod length. A performance hydro cam will have a smaller base circle, then stock. Then when you mill the deck and/or head, the stock pushrods may or maynot have the correct lifter preload. Everything should be mocked up, and the pushrod length checked by using an adjustable "checking" pushrod. Then he correct length can be ordered.
 
Maybe Ed/805 Moparkid,will chime in. His /6 was healthy, & and a daily driver......
 
Abodybomber said:
Maybe Ed/805 Moparkid,will chime in. His /6 was healthy, & and a daily driver......
Click to expand...

Thanks Bomber

Well i guess it depends on how "wild" you want it. I would assume you want to be able to run pump junk 91 octane so your limited to about 8-8.2:1 dynamic compression. With that and a 10:1 static your going to be in the mid 230's (~235)* @ .050 on the cam duration. That will give you the most for under 5800rpm. Call Oregon (OCG) and they can get you a regrind for real cheap, but its a good product. You can run the stock pushrods until you mill .150" off the deck surfaces so i would give smithBro's a call and order a correct length set from them, and order 2 or 4 extra! I run the JP/Rollermaster billet timing set as the parts store set lasted 6000 miles lol. What else....

Headwork is 90% of the game with these. since your going low rpm i would stay with the stock exhaust valve but run a 1.7 (enginbildr) on ebay intakes of even bigger, 1.7-1.8. Then have the porting done, "blueprint" the ports for the highest and lowest, then raise the intake ports .100". Have all the port work and bowl work done and you'll be in good shape.

Somethings i picked up
-Mill as much as you need off the block, and only a clean up on the head, helps keep the valves in the head and away from the piston and cylinder walls
-open up the main/rod clearances from stock (.0005-.0015) to .002-.003.
-you can order a second set of half grooved main bearings for a 440 and use the grooved bearing shell on the block side, not cap. I dont know if you can order a half groove or if you have to do a full and then order a no groove set as well. this will get more oil around the crank but you wont have the loss of surface area like a full groove.
-Oil pumps on these are the weak point, "new" oil pumps has gears that are not properly heat treated and will fail quickly. I think frank (66acuda) sells rebuilt pumps with hardened gears.
-DO NOT RUN A COMP's CAM, they nitride their cams and it eats oil pump gears
-if you run main studs becareful as they sometimes block oil passages!
-
 
Wow thanks all. It looks like I have a little more to do than I originally thought. Thanks for all the info huge help.
 
Ok so now does anyone know can I use the pre 80 head with the hydraulic valve train? I know that I can run mechanical cam in a hydraulic head but can I do the opposite. Use the non hydraulic head with hydraulic valve train?
 
its all in the valvetrain... for a solid cam you need solid lifter, non oiling pushrods, and adjustable rockers.

on the hyd cam you HAVE to have the hyd lifter, oil thru pushrods, and non adjustable HYD rocker assembly
 
805moparkid said:
its all in the valvetrain... for a solid cam you need solid lifter, non oiling pushrods, and adjustable rockers.

on the hyd cam you HAVE to have the hyd lifter, oil thru pushrods, and non adjustable HYD rocker assembly
Click to expand...

And the hydo rocker shaft. They are different, also.
 
I understand that all the valve train for hydo. would have do be used. Basically I would like to get all the block work done, then get the motor back in the car the take my time building a head. I plan to use the hydraulic setup. Will the hydro. valve train work on a 75 head? I know that the rocker shaft and one bolt in particular I specific to the hydro setup. What provisions would I have to make to the mechanical head to use the hydro valve train?
 
72_dart said:
Will the hydro. valve train work on a 75 head? I know that the rocker shaft and one bolt in particular I specific to the hydro setup. What provisions would I have to make to the mechanical head to use the hydro valve train?
Click to expand...
There is a great discussion on slantsix.org if you search (ca 2003). I read it just a few weeks ago. Charrlie_S who responded already was one of the posters (he is a slant racing guru). As a quick summary:

The different bolt is unrelated to the hydraulic cam and actually pre-dates it. It was so people install the rocker shaft correctly. However, it seems you may need it for the hydraulic rocker shaft, or maybe drill the rear bolt hole bigger in the shaft.

I recall discussion of drilling an oil passage in the block larger to allow more oil flow to the top. At least hydraulic heads had the larger hole. Nobody ascertained it is required, and seems unlikely to me it would be since rocker arm clearances are probably the main determiner of flow rate needed. Run a wire thru each rocker arm to insure the oil hole is clear.

Much discussion has long been made about the rear cam bearing being different in hydraulic engines, i.e. with a center groove, and that being necessary. A study of PN's suggested there was no changed PN for that bearing, but other ones unrelated to a hydraulic cam did change PN (narrower), probably because their webs in the block got thinner. There never was a grooved cam bearing, it was the rear journal that has a groove in a hydraulic camshaft.

In sum, you probably don't need to touch the block or heads, just install all the hydraulic stuff (camshaft, rockers, pushrods, & lifters).

Let us know what worked.
 
The main difference in the shaft,is the location of the oil holes for the rocker arms. On the hydro shaft installed, they are pointing straight down. With the solid lift shaft, they are down, and slightly toward the valve. AS for the rear bolt, use the bolt that fits the head, and drill the hole in the shaft, if necessary.
 
You must log in or register to reply here.
-

Back
Top