budget builder

iTrader: (3)

I have an 010 - 2bolt main Fresh 40 over 350 block 2 bolt main with arp main studs
Bored and honed with torque plate, decked
Brass freeze plugs with clevite cam bearings
Cast crank turned 10/10 with clevite main bearings
Rebuilt rods with arp wavelock bolts and clevite bearings
Speed Pro Hyperutectic flat top pistons with speed pro moly rings
Assembled with all clearances checked. Crank gear timing set on trapezoid position. I think that is 4degrees ret. ( I ran it for 3.5yrs in the "0" position but machine shop "said" that was wrong. Cloyes double roller timing chain.

vortec Heads upgraded for
.525 from scoggin dickey. 64cc 194int./160exh. ( I believe I got the numbers correct). 1 5/8in shorties to y pipe and 2.5 in dual outlet muffler. 700r4 w/3k stall. Cam is 292 comp cam w/501 lift I forget the duration lobe separation is 110 I believe. Upgraded from xe268h. ( Only thing changed after rebuild was cam, timing gear position, carb, and stall. Before rebuild I used a 600cfm holley ran pretty good. After rebuild and cam upgrade, so far we have tried: 600 vac sec, 750 double pump, and a monster 750 vac sec. All holley!

Now we can't get it to idle. Timing is 36 degrees all in before 4k rpm it runs beautiful at 1300 once below 1250rpm it's just like u turn the key off. All 3 carbs. No matter the adjustment. We thought 1/2" spacer we used b/c of 50cc pump on performer rpm intake, intake leak, vacuum leak somewhere, too much fuel, too little fuel, got rid of 50cc pump went to 30 cc and mated directly to the intake, we even cracked back barrels. Got idle down to 500-700 but only running off back barrels ( no adjustment) will not idle. Runs beautiful 1250rpm and up. Cam is broke in. 160-180 temp. 6.5psi fuel press. I know it's long but don't know what else to do. Unless it's a very small vac leak we haven't found. I hope it's not bent valves from crank gear. Before rebuild compression was 200-210 on all cylinders. Only checked 3 cylinders so far just for reference got 165psi on #1, 210 on #3, and 170 on #4, rechecked #3 got 170. Whew! That's alot pleez help. Thx!!!!!! Oh rebuilt because of wiped lobe.

Biledriver

Vader

First, a Performer RPM and idle quality are not always compatible. It's not as bad as a single plane, but does sacrifice idle compared to a stock or Performer intake.

Second, call me lazy, but I've never been satisfied with a Holley being consistent. It's much easier (lazier) to install a Quadrajet and have it just run correctly. Holley seems to be the WalMart of carbs. Everyone shops at WalMart because it is cheap, not because it is better. Second choice would be a Carter ThermoQuad, and third choice would be a Carter AFB. Holley (and all the clones) is somewhere after that, perhaps just after sticking a wick in a can of gas and bolting it to the intake.

We'll need more info on the Holley - What model? What type? Converted to a 4150? The 600 and 750 have several variants.

Finally, vacuum with a XE292 may not be optimal for street use. I'm guessing you might measure 10-13" Hg at a 1,000 RPM idle. Thus, a vacuum secondary carb is going to take some diaphragm spring work to get it even close, and possibly modifying the secondary metering plate, power valve, and air bleed orifices and jets to get it acceptable.

sofakingdom

iTrader: (1)

That cam spec looks like the old Magnum 292 from days long gone by, not a XE series.

Probably not P/V contact... the cam timing would have to be off by like 45° to create that.

Sounds almost like the valves are set too tight. First thing I'd try is zero-lashing them.

Retarding the cam will make this problem worse, regardless. That does 2 things: keep the exh valve open longer as the piston goes through TDC during the instance opposite of firing, when the exh stroke is finishing and the int stroke is starting; and, keep the int open as the piston passes through BDC at the end of the int stroke and beginning of compression. The latter effect causes reversion into the intake tract, which annihilates idle vacuum. These effects together enhance high-RPM pumping efficiency (horsepower) at the expense of every aspect of low-RPM operation (torque, idle quality, vacuum, etc.).

Try setting the cam timing back to 0 if valve adjustment doesn't straighten it out. You may even find it runs better with the cam advanced instead of at 0 or retarded.

I don't think the carb has anything to do with it. You can probably change it every single day, and twice on Sundays just for good measure, and never improve it.

Let's hope your block doesn't have The Lifter Bore Problem, as so many of those do, and just proceeds to wipe the same cam lobe(s) it wiped last time, again. If so, you'll NEVER get a cam to live. See my comment about changing the carb and apply it to the cam.

budget builder

iTrader: (3)

Thank you for all of your responses I will talk to my Builder and definitely let him know some things to check honestly I would have left the gear timing on the crank at zero like it was before but the Machine Shop changed it and he said that he trusted them I found out about it after we started having trouble but it seems like now we're starting to have a problem and we might need to go back and set it back to zero maybe even Advanced it but I will definitely check some of the things that you all have told me about and if anyone has any other suggestions that I may need to check please don't hesitate. thank you.

I didn't want to take it back out but I'm too far into it now. I should have just went lsx. Ugh!

budget builder

iTrader: (3)

http://www.jegs.com/i/COMP-Cams/249/12-213-3/10002/-1

It's looks like that's what it is the magnum 292. Thx

budget builder

iTrader: (3)

And yes vacuum at 1000rpm is about 10"-12"


"Sounds almost like the valves are set too tight. First thing I'd try is zero-lashing them."

We loosened all the valves by a quarter turn. No Changes

NoEmissions84TA

iTrader: (1)

You chose the wrong camshaft - too big.
Make a better choice.

budget builder

iTrader: (3)

Dang, isn't there a way to make this work? Or at least a choice extremely close? Will not necessarily be a daily driver just a street machine to play with on weekends. Go to beach or ride the wife a little.

Orr89RocZ

iTrader: (20)

Is it running too rich? You almost would be better off locking distributor out at 34 deg or so, it will need alot of timing at idle and correct air fuel to idle well. Thats too big a cam imo for that motor

budget builder

iTrader: (3)

Too big. We will run multiple compression tests. And recheck for intake leak. If push comes to shove we have a set of old skool 72cc ported and polished iron heads and matching intake that came off a monster 400sbc that ran with a similar cam. That I can get pretty cheap. But please keep sending opinions. And thk u all

sofakingdom

iTrader: (1)

Wrong answer.

Larger chamber heads will lower the compression and make it MUCH worse. It's already on the very bottom edge of acceptable, if not below it, for that cam.

Better to sort out the build errors in the combo you have now; especially the mistake of retarding the cam.

NoEmissions84TA

iTrader: (1)

Street/strip special, 3000 stall converter, headers, gears, 9.5:1 compression. Very rough idle.

Operating Range:2500-6500 RPM
Duration Advertised:292° Intake / 292° Exhaust
Duration @ .050'' Lift:244° Intake / 244° Exhaust
Valve Lift w/1.5 Rockers:.501'' Intake / .501'' Exhaust
Lobe Separation Angle:110°


Please don't go down the path of screwing up all of the engines settings and adjustments (carb, timing, valve adjustments, etc.) to try to make that poor choice of a cam work. Your engine is talking to you, trying to give you valuable info. You need to listen to what it is saying.


Sofa can put this a lot more eloquently. He has a way with words.

budget builder

iTrader: (3)

10-4 too much cam. Thx fellas. Back to the drawing board

Orr89RocZ

iTrader: (20)

At the very least, you could try advancing cam 6 deg on a 104 intake centerline. Do not retard it

budget builder

iTrader: (3)

If that doesn't work what is the biggest cam I can cram in and would still be street able and strong below 2000rpm? Xe268, 274, 282, or 284?

sofakingdom

iTrader: (1)

Plenty of people have had that cam over the decades and not had that kind of trouble with it.

For that matter I used to have a 283 with the "30-30" off-road cam in it; 245 degrees of .050" duration on both sides. And it idled just fine below 1000 RPM with several different carbs on it over the years.

We all used to have a saying... "there's no such thing as too much cam, there's only not enough motor". Which in this case, may somewhat apply, with your compression; almost always, people's ACTUAL compression is less than what they think it is. And in your case, even if it WAS what you think, it's really still about a point to a point and a half too low for the cam to really be at its best.

But before making big changes, I'd STRONGLY suggest advancing the cam timing.

If you're just determined to swap the cam though, I'd think the biggest you'd want, i.e. that still would produce detectable power below 2000, would probably be the XE274.

cardo0

First I would measure compression pressure to see if the cam is really to big. For a pump gas performance motor you want cranking pressure between 180 to 210psi. If you keep that 292 cam and since it does idle well at higher RPM it means it's having trouble breathing - do to large amount of overlap - and a common fix for this is small holes in the primary throttle blades. Start with 1/16" and see if it's helping. Much easier than changing the cam.

Hope this helps.

budget builder

iTrader: (3)

Oh​​​​​​
​​​​​​​We have done the holes in the blades. We even opened the back blades that allowed us to drive it. As expected it did decent over 3k rpm. When I had the chance we did the comp test with the last cam it was 210psi we have not decked or shaved anything and now compression is 165-170 and yes that is with timing gear on crank retarded. We were trying not to change cams but my builder does have a mint xe268 on the shelf he said I can have for free. he said we can break it in and be rolling in no time but it will be some work taking motor back out. He said doing oil pan gasket in the car almost always leaks. Thx fellas for all (ALL) of the help. I got two more planned for the summer and now I know to plan the build first esp between the cam, heads, and intake. I'm trying to do a 383 and a 496. Thx fellas. If I find out anything else I'll post.

budget builder

iTrader: (3)

a quick ????
what kind of performance am I looking at with a xe268 and the 3k stall? we decided to go ahead and change cams. thx for all the help fellas.

budget builder

iTrader: (3)

Bump