Even with the upgraded springs, Jeremie (@ AFR) would recommend changing springs after every season using a cam with slopes like the XFI stuff. That's what he said to me 3yrs ago.

That's why I started looking for a compromise ending up with my own .510" (@ 1.5) lift setup.

Is that an XE series cam? Or high lift HR?

Of course you posted you were concerned about valve float quite awhile back. What symptoms were you getting back then? Fluttering/loss of power at higher rpms?

 

Comp dispenses misinformation, never will a rep admit; I don't care how many I have spoken to on whatever day, they will say their XFI ramps will ever fatigue the springs, EVER. I think they are instructed to say how good the stuff is, hallmark of a well oiled machine,pun.

Who would know more about cams and springs? Comp or AFR?

I don't know what flutter is but when a girl bats her eyelashes on yours is that what that means? joking aside, yes I had trouble, or rather the engine had trouble, going over 5500. so I left that territory alone, for the longest.

you did good, you did your research, I went with third gen's vote on the 280xfi.

now I think even the 220/230 is too big, i am gun shy now....

 

"The gear on a Chevrolet distributor is held in place with a small drift pin. A wear plate and thin shims are used to adjust end clearance. Normally the factory setting is loose and you'll want to close it up to about .015 inch with shim kits available from Mr. Gasket."; Small Block Chevy High Performance, Volume 1 (1994), SA Designs, at page 103.

"Many times, distributor gears fail because of inadequate lubrication. To minimize this possibility, file a .030" by .030" slot on the base of the distributor housing with ths slot oriented towards the camshaft. Some high performance distributors are supplied with a slot already in place.....Increasing oil flow to the disributor gear significantly improves gear life...This can be most easily accomplished by using a 3 cornerned file to cut a notch in the lower sealing flange on the distributor housing. For maximum effectiveness, the notch should be oriented so that it is aimed towards the camshaft when the distributor is installed in its normal position. DISTRIBUTOR HOUSINGS SHOULD BE NOTCHED - irrespective of the type of didtributor gear used - in all engines operating at high loads and / or at a relatively low rpm, ESPECIALLY IF A HIGH VOLUME OIL PUMP IS IN PLACE (emphasis added) "; Small Block Chevy High Performance (1996), HP Books, at pages 120 - 121.

 

Looking at summit, unfortunately I just placed and order today for lifters, and the shim kit's are 5 bucks, any how, should I measure first, then buy, or subscribe to the fact that factory = loose.

they sell nylon for the for the housing and steels for the gears, does than mean they want me to move the gear mesh up or down, how do you know it is in it's sweet spot?

thanks for this exacting information, but from the text, I get the theory but without pitchers, I ain't bringing a file nowhere close to the shaft.

 

 

I don't think it's possible to move the gear too far in either direction; just remember that the natural thrust of the gears is going to move the distributor upwards, and you dont want the cam gear engaging on the lower end of its teeth. Any added shim will reduce this upward movement helping to ensure proper gear mess; plus as the engine speed and load changes, any shifting of the distributor gear upwards or down retards or advances the engine timing. Maybe not a lot, but some.

Installing a shim kit is easy... any local parts store should have one in stock. Just for reference, install the gear, wear plate and original shim on the distributor shaft, the end play is measured by inserting a feeler gage blade between the top of the gear and shim; ...you'll be surprised at how much play the factory leaves down there..

In light of the very impressive buildup you're doing, may I suggest upgrading the distributor? The stock distributor is good as far as it goes, however, most aftermarket distributors seal the oil groove on bottom of the distributor housing to the oil passge in the block with "O" rings. The factory just sticks that ole distributor in that hole down there and calls it good. Plus the oil groove on the factory distributor housing is left "as cast" with casting flash still there; an aftermarket distributor will have a smooth, and probably larger, less restrictive, machined groove.

Although I would verify each distributor, most aftermarket distributors already have a provision for cam / distributor gear oiling. Good luck.

 

I would have to say with all the debris that has been going through your engine I am sure the pressure is droping because of bearing issues.

That cam that cmae out is a cast cam core and that can be a problem sometimes, Billet cam cores are hard to get with such small lobes.

 

Thanks I check pricing, but at the moment I have to consider budget limitations, I think with your help so far, I can "modify" the stocker to minimize it's shortcomings.

so for sure I will shim, I am very interested in this increased oiling mod, but for the life of me don't understand, where to place this "groove". If possible can you drop a picture?

Thanks mtwoolford

 

On the base of your distributor you will see two "cylinders". You could call them bulges. Those bulges sit above and below the oiling "channel" that runs horizontally down the middle of the engine block.

If you cut a groove (vertically) in the bottom ring (ONLY), more oil will pass by this "bulge" down onto the oil gear/ cam gear/distributor gear.

Be smart where you cut the groove or it won't help. Visualize where the gears intersect when the distributor is installed. Any groove should be on that side of the housing.

Do NOT cut the groove very deep. .030" is not very big. Make it more like a scratch. If overdone, you won't have enough oil pressure. I've heard about people trying this and ending up with 10PSI (or less) at idle. (That's because a deep groove will release pressure from the middle oiling channel of the block.)

Don't cut a groove in the top bulge either. That'll lower pressure further and shoot oil up into the valley.

 

did you do yours? how much room to I have for error as far as getting it pointed it the right direction? 45 degrees? can i us a .500 in shim kit my shaft is .491? thanks

 

Spring life is dependant on cam slope (not duration). Actually, longer duration cams can have less severe slope than shorter ones.

How high and fast the cam lobes pick up the valves is the issue. How often you run a higher-sloped cam up to high rpms is something else to look at. Both of these can accelerate the lifter off the nose of the cam lobes.

 

I tried it. After cutting the groove, I showed my machine shop guy (to see what he thought). He laughed because I goofed. I cut a groove in both bulges! Plus, he said my groove would have been too big. That's where I heard about other stories.

I had to buy a new distributor. I didn't redo it. Didn't want to "F" it up twice. (Wasn't sure how to guage the proper depth.) More importantly, my builder wasn't convinced this modification was necessary with a good hi-pressure oil pump. Especally since my car isn't primarily raced.

Theoretically, a groove cut anywhere (on that circle) will provide extra oil DOWN onto the gears. If you're withing 45 either way (90-deg total), I'd think you be fine. You should be able to get it much closer than that.

 

I noticed my pressures degrading, quite a bit lately, so maybe I will forego this mod. and just shim the endplay, but I just found out from summit no one sells a kit for the .491 shaft, go figure...

 

this explains it all:

Cam Modification - Technical Inspection Save That Cam; February 2009 issue of Hot Rod by Jeff Smith:

http://www.hotrod.com/techarticles/e...ech/index.html


and yes, a picture is worth a thousand words

 

let me try this again


http://www.hotrod.com/techarticles/e...ech/index.html

 

one more time; the last part of the address only:

techarticles/engine/cam_modification_tech/index.html

 

thanks just got done measuring the endplay, the stock shim is .035 and the gap is .028.

can i have 2 shims in there to bring the gap to .015? otherwise I would need a single .048 to .050 shim, since the shimless measurement is .063

 

stack away

 

no one sell a shim for the .491 shaft, can I put any old washer in there?

 

yes you can; had to make my own for the stub shaft on my LT engine; I used a stainless washer (they tend to be thinner); had to remove some material by rubbing it across a flat fine toothed file to get it thin enough for the desired clearance...steel or even brass would have worked just as well