Pontiac GTO Forum banner

1 - 20 of 95 Posts

·
Super Moderator
Joined
·
5,741 Posts
Discussion Starter #1
FINALLY - in the process of rebuilding my engine. This time, I'll be using Crower stainless rockers and Crower mechanical roller lifters (with their High Pressure Pin Oiling Option). I'm also stepping it up a little :grin2:
This cam delivers 15 degrees more duration and 0.020 more lift than the previous one, and does that with 1.5:1 rockers instead of the previous 1.65's.
I'm also using file fit gapless (top) rings.

The new cam needed new springs with more pressure to control it, and those springs needed a taller installed height so instead of taking them out, I bought a cutter and machined them myself. Fun stuff!! And I can be positive they're right. The intakes on the drivers side head were already just a touch deeper than my objective of 1.910, so I had to cut them to 1.925 and will use 0.015 shims on those to bring them back to spec.

I'm doing more test fitting and measuring today.

Bear
 

Attachments

·
Registered
Joined
·
3,759 Posts
Sounds like fun. :thumbsup: I have done the "web research" and book reading and it seems the steel roller rockers are the way to go versus the aluminum. More money, but you won't have any problems.

1.5 ratio, in my opinion, can be a better choice with the roller cam. The 1.65's with a flat tappet cam opens the valves quicker and the "under the curve" slight gains tooted by some of the engine builders are fine for a race engine, but the required heavier valve spring pressures and repositioned pushrod cup on the rocker arm put additional side loading on the rocker arm stud and even the valve guide. I don't think you really need the 1.65's in your application because the roller cams typically have a fast ramp to open the valves sooner and keep them open longer. Isn't that really what the 1.65's are doing in a flat tappet cam in theory anyway? So you compensated for the change to the 1.5's with the slightly higher lift and longer duration - am I right?

I can't tell from your pics, but do you have the lifter bore braces? I read they are highly recommended when using the roller cams as they can add higher side loading to the lifter bores and that's when they can break. Just added insurance in my book and something I would install if going with the roller set-up. :yesnod:

Did you ever decide on double roller timing chain or gear drive?
 

·
Super Moderator
Joined
·
5,741 Posts
Discussion Starter #3
I'm in agreement about the 1.65's, especially since that's what sidelined me last summer - a rocker failure :)

That cam was 236/242 @ 0.050 and made .600 lift (110 LSA installed at 106) - all with 1.65 rockers. It too was a solid roller. This one is 251/257 @ 0.050 and makes .615 lift with 1.5 rockers, also with a 110 LSA and will likewise be installed at 106. It's from Bullet Cams and I like their approach quite a lot. The opening ramps are more aggressive than what I had, even after taking the difference in rocker ratio into consideration. However it has closing ramps that are much gentler and don't slam the valves shut like the Comp profile tended to.

Yes, I will be installing a bore brace this time. I'm running a double roller timing set this time, just like last time, but I'm changing brands.

Bear
 

·
Super Moderator
Joined
·
5,741 Posts
Discussion Starter #6 (Edited)
Degreeing the cam. I'm using a Romac/Rollermaster timing set, double roller, 9-way adjustable. It's also 0.005 shorter to make up for the block having been align honed. The fit is very good - VERY little slack.

In order to get the cam intake centerline installed according to Bullet's specs (106 degrees) I wound up needing to use the timing set's 4-degrees advanced setting which, interestingly enough, also caused the 0.050 intake and exhaust opening/closing events to shift about 2-3 degrees from what's printed on the cam card.

I've also included a photo that shows a tip I learned/copied/stole from Paul Spotts. If you file a slight bevel onto the nose of the crank and cam keys, it makes it a TON easier to install the parts that have to engage with the key. Maybe everyone else already knew this, but it was new to me.

Just for grins, I also measured cam lobe lift for both intake and exhaust lobes at every 10-degrees of crank rotation.

Bear
 

Attachments

·
Registered
Joined
·
34 Posts
Since I do not have the knowledge to talk tech , I would like to note that in the above picture you did a nice job with the oak chair placement. The back drop of the chair and angle of the timing chain really draws attention to the iron that seems to float in space. All those horses waiting to stampede with fury and fire.. and then the chair beckons comfort and a naturalism to your endeavor. Nicely done. Its that attention to detail that is impressive to me. Keep up the good work. Cant wait to see it all done. Seriously , I envy your ability.
 

·
Registered
Joined
·
118 Posts
bear very cool...what is the cc dish of the pistons and what is the cc of the heads? what will be your static compression ratio? thanks john
 

·
Super Moderator
Joined
·
5,741 Posts
Discussion Starter #12
Heads are 72cc's, piston dishes are 17.19 cc's, pistons are 0.013 "down", the head gaskets I'm using compress to 0.045 static compression ratio is going to be 10.2:1 (Aluminum heads can run higher than cast iron).

Today I checked and verified all the rod bearing clearances and fit the balancer. The hub was super super tight, so I worked it some with a ball hone. It's still a nice tight press fit (I have to use a balancer installer to get it on), it's just not crazy. This is a different balancer, a Romac SFI rated one, and I had to grind some on the bottom edges of the timing cover to open up some clearance so it won't rub. It's a Kauffman repop timing cover.

I also verified that the TDC marks on the balancer are accurate.

Bear
 

Attachments

·
Registered
Joined
·
118 Posts
Heads are 72cc's, piston dishes are 17.19 cc's, pistons are 0.013 "down", the head gaskets I'm using compress to 0.045 static compression ratio is going to be 10.2:1 (Aluminum heads can run higher than cast iron).

thank you
 

·
Super Moderator
Joined
·
5,741 Posts
Discussion Starter #14
Spent a little more time on it tonight. I trial fit the heads last week with #1 valves installed with checking springs so I could measure for pushrod length, and I decided that I didn't like how close the rockers were to the retainers with the valves closed. They were 0.020 or less. So, this past weekend I made a sojourn to the new Summit Racing retail store in Arlington, TX - and bought a set of Isky chromoly valve locks in standard height instead of the +0.050 offset ones I started with. These will give me another 0.050 clearance between rocker and retainer which should be more than enough. They also leave more of the valve tip exposed so there's no chance of the rockers touching the locks --- they were VERY close before.

Of course, this means that I have to re-cut the spring seats in the heads down another 0.050 to get my spring installed heights back to where they need to be (1.910) with these new springs. I got one head done tonight. I'll test fit it tomorrow night and measure again for pushrod length, then cut the spring seats in the other head.

This is fun!

Bear
 

·
Super Moderator
Joined
·
5,741 Posts
Discussion Starter #16
NICE !!! What are you expecting for HP ?
Oh, I'm guessing 550 "or so" at the crank >:)

I got all my spring seats re-cut now and have great clearance for the rockers. I checked for pushrod length and it looks like 9.350" is going to be the number. I'm leaning towards Smith Brothers 1-piece hardened chromoly with .083 wall thickness right now, but I hear good things about Manton also. Pushrods, oil pump, and one intake valve are about all I have left to get at this point. The one intake valve is for the cylinder where the previous rocker failed. It scarred up that valve tip a little so I'm hesitant to try to reuse it. I'll probably go with a Luhn oil pump. They're WAY pricey, but I don't want to ever have problems in that area.
 

Attachments

·
Registered
Joined
·
3,759 Posts
Checked out the Luhn oil pump just to see what it was.

I bought the Butler Pro 60PSI pump which I feel is added insurance over the stock 60PSI pump. I see a few differences between the Luhn & Butler pumps, but not sure enough to warrant the cost difference. The High Performance Mellings pump has a .750" dia pick-up while the Luhn version is opened up to .814". Not sure I like the "cone" pickup screen.

Butler has the Pro series in 80PSI and 60PSI. https://butlerperformance.com/i-24453827-butler-performance-pro-60psi-oil-pump-w-pickup-screen-bpi-m54ds-pro.html?ref=category:1234738 They do give you a flow rate of the pump tested included with the pump. Flow rate is what I would compare versus pressure between the 2 pumps.

I don't like the fine mesh screen as pictured as I feel it is too fine, but I assume you have a different pickup screen to match your deep oil pan?
 

·
Super Moderator
Joined
·
5,741 Posts
Discussion Starter #18
I don't like the fine mesh screen as pictured as I feel it is too fine, but I assume you have a different pickup screen to match your deep oil pan?
I do, the one from Milodon that goes with my Milodon kickout pan:
Milodon 18425: Oil Pump Pickup Tube Pontiac Low Profile | JEGS

I've actually decided that I don't like it though and would prefer a finer screen. Last summer when that rocker came apart, that Milodon pickup did very little to stop the fragments from getting into the bearings and taking them out. My son and I actually briefly considered trying to limp the car home with some big honking magnets on the oil pan to try to corral whatever was in there, after we replaced the one rocker and pushrod in the motel parking lot and got it running again. It's a good thing we didn't. When we did get it home and torn down, there were massive gouges in the cam bearings, and the mains/rods were none too happy either.

Bear
 

Attachments

·
Registered
Joined
·
3,759 Posts
My opinion is that I don't like the Milodon racing pickup either as the screen holes are too big for a street engine. Fine for drag racing where you want the best flow, but want something to keep the big chunks out of your engine. Figure they tear down and rebuild their engines a lot more than a street car so getting metal in the bearings is just part of the business.

On the other hand, too fine a mesh on the pickup is not good either. Keep in mind that it may screen out more particles, but if it gets to the point where flow is compromised, there is the hole in the center of the screen that will open to bypass the plugged up screen and then you are right back to square one as metal particles can scoot right by.

I got a screen that is in between the big holes on the Milodon racing pickup and the real fine mesh often seen on the typical Mellings oil pump pickup. I got one with a Mellings that had the fine mesh (when I rebuilt my earlier 400CI and it was part of a "rebuild kit") and when I ordered a recent 60PSI Mellings pump with pickup from Butler, it had a screen with the larger mesh. Since Butler came out with the Pro 60PSI pump, I ordered it to replace the standard Mellings 60PSI pump I was going to use on my engine. So I do not know why one pump had a fine mesh screen and the other a larger mesh screen.

Again, just my observation and opinion. :thumbsup:
 

·
Super Moderator
Joined
·
5,741 Posts
Discussion Starter #20
Moving forward, slowly. Tonight I intended to tear everything back down from all the measuring/mock up work I've been doing and start cleaning the block, heads, all the parts to get them ready for assembly. I didn't get that far though, I just got it torn down and all the parts packed away. I need to spend some time putting tools and stuff away too, and some general clean up. My tendency is to create huge piles of stuff all around whatever I'm doing that starts to get in my way after awhile.

Slowly but surely...

Bear
 
1 - 20 of 95 Posts
Top