[TheSilverBuick]

Stronger outer spring, but then supplemented with an inner spring to bring the net pressures up more than just the single spring. And looking at the specifications, it sure didn't look like, at least in '69, the dual springs net had much more pressure than the single. I'm thinking like 10#'s more. I cannot remember the numbers right now, but something like 90# versus 100#, and that was a maybe.

I want a stiffer spring, though admittedly not sure how much stiffer. I've revved it up, in first gear, to 5,800rpm, a couple times and that's where the engine refuses to go any higher. About 5,300rpm the rate of engine acceleration starts noticeably dropping off, so that is either valve springs, C-cam (1bbl) going past peak HP point, or port choke. I think it's valve springs.

[Jack Gifford]

Just a reminder- that many times, manufacturers went to dual springs mainly to cancel a particular harmonic wave in a single spring.

[TheSilverBuick]

Noted!

Last night I got contact information for one of the Crane Cam engineers that was recommended I get a hold of when I go to source springs as he should have some good insight on things like harmonics and the effect of adding spring pressure effects them.

[TheSilverBuick]

Pulled the car into the shop to start pulling the cam housing. I might take this time to pull the engine wiring harness off to lengthen it a few inches as well as possibly pull the oil pump on the accessory drive apart for inspection.


A new E cam and new followers ready to go. I've numbered stamped them 1 through 12 to keep them matched to the lobes when I go to do the springs. I'll do the same for the 1bbl cam when I pull them.

[TheSilverBuick]

Got it up and running on Friday, then re-engineered the alternator bracket again and I'm much happier with it now.

I've gotten tired of the bog off idle and decided to make a bigger effort to install a throttle position sensor on the Holley carb throttle body. With it done and with minimal tuning of the accelerator pump shot it's running pretty good and 90% of the bog is gone. I still have a bit of work to do, but it's pretty good now. And of course the first time I wired it up it registered backwards so I had to reverse the power and ground wires.

Closed throttle


Wide open throttle.


Since I am not gaining the 1.5 points of compression with the 4bbl cam, I've installed the Sprintbird adjustable cam sprocket I have and set it for a full 8º advance. Should help the low end and bring the power level down the band a bit. Might even pick up a few mpg's.

And being a non-interference engine, there is no risk of valve to piston contact in the event of a goof up The piston reliefs are stupidly large for the lift.

I ran the engine before picture, so the timing mark doesn't line up in the photo.


and just a shot of the whole engine bay with the timing belt cover off. I installed the cover after the picture.


A short video of it running with the timing belt cover off.
http://youtu.be/Kb0T5-OFJnU

Driving it around town some and it's running pretty good. The TPS sensor is working like a champ. 'll get it further dialed in over the next week. I think after I do the weekend R&R on the engine I may actually go to a chassis dyno to satisfy my curiosity of what it's making.

[Jack Gifford]

This project continues to impress me.
So the Sprint didn't use a flanged upper sprocket?

[TheSilverBuick]

Thanks! Flange upper sprocket? No it's a simple threaded hole and hole that a dowel pin on the cast iron OE sprocket aligns itself with. The Sprintbird sprocket is one that Sprintbird Rob machines the inside of an OE sprocket open and inserts and chunk of steel with the adjustments you see there. There is no ability to adjust the cam timing, short of jumping a tooth, with the stock sprocket.

Here is an old picture of what the OE sprocket looks like.


On another forum someone was asking me about what port work I want to do to this engine and the Turbo engine. This is just pasted from that post:

They are opened up a bit and cleaned up a lot. I don't recall the exact measurements off hand but I think they were essentially gasket matched to this gasket.

(this is my cleaned up head in the photo ready to go to the port shop)

This is what the head on the engine currently looks like. No work done to the ports.


I scaled the pictures best I could and cropped them next to each other to show the difference in the chamber shape. The top head is currently the one on my engine. Basically opened up around the intake valve to unshroud it.


Hard to believe this engine looked like this when I picked it up a few years ago.

[TheSilverBuick]

My attempt at chamber re-shaping. Over all I am quite pleased. This was about 30 minutes worth of work. I had to account for a bigger/deeper chamber than in the picture because the one in the picture is a high compression head. I wonder if I should smooth out/open up the other side of the intake valve as well? Who needs compression anyways?

[TheSilverBuick]

I took a dial indicator and some calibrated rocks and set the intake valves at 0.438" lift, which is how much lift my current cam has to show the difference. It was recommended to me, if I can, to get 0.020" shaved off the bottom of the head if I can. Hmm, I may try that after I port and re-shape the chamber on my running head, I'll see if the Machine Shop in Elko (2.5 hours away..) can shave the head in the same day. In the past they have been able to do same day work for me when scheduling it in. I need to run some numbers, but l don't think it's possible to bring the compression up too high from shaving the head while using a head gasket that is around .030" thicker than the stock steel shim gasket that is impossible to get now.

I adjusted the color for more contrast because the sun was white washing it out.


Then I brought it indoors.


You can see where I was working with the dial indicator as it scrapped the carbon off the valve on the right. I just shifted the set up left to do the other valve.

[Jack Gifford]

I was asking about belt-guide flanges on the sprocket. I never worked on the Sprint OHC and don't know what quides the belt.

[TheSilverBuick]

Originally Posted by Jack Gifford

I was asking about belt-guide flanges on the sprocket. I never worked on the Sprint OHC and don't know what quides the belt.

Ah! No. Only the crankshaft has belt guides. The accessory drive is like the cam sprocket. It's in the belt design. the engineering reports say the cords wound into the belt determine which direction the belt will track on the sprocket, so the cords are wound in alternating directions and it seems to keep the belt in place. If you look at modern timing belt application, none I've see have any guides on the upper cam pulleys. It's a proven design that Pontiac was on the fore front of. I don't know what other engines prior to this one used a belt driven cam (any? anyone know?).

[PMD1969]

IIRC each calibrated rock can bring 8-10hp. You definitely need to get it on a dyno

[Jeff Hamlin]

Originally Posted by Jack Gifford

I was asking about belt-guide flanges on the sprocket. I never worked on the Sprint OHC and don't know what quides the belt.

If interested check out the SAE report for full engine details.
Belt details/info; can be seen on pg 4&5.
http://forums.maxperformanceinc.com/...d.php?t=753468

Sorry for the jack.

[TheSilverBuick]

No problem at all. Those were the engineering reports I was referring too.

[Jack Gifford]

Thanks for the link to the SAE paper.
So, apparently all of the Sprint's fore/aft belt positioning is done by the flanged crank sprocket? I was planning to employ all flanged sprockets on my inline-four DOHC hemi- crank, both cams, and both idlers. But judging by the Sprint setup, I guess that might be overkill, since my "un-guided" belt spans aren't much (if any) longer than the Sprint's. Perhaps I should compromise- use flanges on just the crank and one cam?
[Sorry 'bout hijacking this thread]

[TheSilverBuick]

I don't know of any inline 4-cylinder that uses a timing belt that uses guides on their cam's, DOHC or SOHC. Likewise on V8's that have been converted to belt driven cam's. I've never seen guides on their cam sprockets either, though it is a shorter distance.

[Bill Hanlon]

I need to do some work on my Acura. Do you know where I can get metric calibrated rocks?

[TheSilverBuick]

Honda parking lot =D

[Jack Gifford]

Originally Posted by Bill Hanlon

I need to do some work on my Acura. Do you know where I can get metric calibrated rocks?

You been drinkin' Bill?

[Bill Hanlon]

Originally Posted by Jack Gifford

You been drinkin' Bill?

Not any more Jack.










No less either.