Ok this is by problem, I have a friend who built an engine.
350
#292 ported heads
Comp 268 he
Victor jr
750 holly vac sec
headers
165psi cranking pressure
He had a performer intake he thought that was holding back. I said it's a couple of things. Like those heads, and the carb is to big and the cam is to small. he thinks that bigger is better and he thinks he has 350+ hp. I laughed cuz in a 3200lbs car he could only run 15.1 @92mph. his uncle had the heads before him and he was running 13's at 8000 rpm and my friend only turns about 5000 rpm. he dosn't beleve me so if you can tell me what else to say that would help thanks

 

Sounds like he has dished pistons or the cam is in retarded. If the heads aren't butchered they're probably worth money on eBay. He could get a set of modern heads for what he should receive from the 292's. Overall I would look into the lack of cranking compression and swap cams if he wants to make the parts work together. FWIW I got $850 for a pair of virgin bare 292's 4 years ago.

 

He has flat tops, now when be broke the engine in he was running 2 coil valve springs, the same spring his uncle used at 8000 rpm. would that flatten some cam lobes? the engine has little bottem end power. he runs 2.3 60' with no tire spin. and less top end! how would sportsman 2 heads do on that set up? cuz thats what he's thinking about doing.

 

With a dual plane intake such as a Stealth or Contender (300-38) that cam runs pretty good in a 350 assuming its installed correctly. If the heads were running 8000 before you have to assume it was with a solid cam and the springs must be pretty healthy so they could be hard on the 268H, especially during breakin. If he has had to go over and relash the valves then I would be suspect. For that matter the valves could be too tight and causing him problems as well. For now though I'll blame the VicJr and small cam mismatch.

SportsmanII's with a suitable camshaft would be fine assuming he can make 10:1 compression. What gear, transmission setup does he have? What the heck is it in?

 

the gears are 3.73, the trans is a 700r4, and it's in a 1984 s10 blazer. when he bought the engine build kit it said that the pistons will give him 10.5-1 compression. but the cranking pressure is a little low for that. and he had a performer intake and he ran the same time.the blazer weight is about 3000-3200 lbs with driver. he has a stock converter.

 

what do you mean that the valves might be to tight?

 

Its common for people to set hydraulic lifters too tight. A wrong adjustment can murder low end torque.

 

thanks i'll have him take a look at that.

 

He should be in the high 13s minimum, mid 13s if he knows what he is doing with the tuning/driving. Carb is not too big, the vac sec Holleys only feed as much air as needed. Same basic carb was used on everything from 302 Z motors to LS6 454s. Heads are ok, not great but they aren't causing the honda like ETs.

Things to check in addition to above suggestions: is the fuel level good on both bowls? is the linkage opening the carb primaries fully? are the secondaries opening fully, or at all?

What is the initial and total timing? some guys think that the best way to set timing is to keep cranking in more till it pings, then back off. That can kill power by giving it excess timing, at low rpm and up top.

Was the TV linkage on the 700 set properly? There are specific brackets for carb applications that will allow TV cable to be properly adjusted. Improper adjustment can cause early shifting, or worse case, low apply pressures that can burn up the clutches. Stock converter is ok with that cam, low 3.08 1st gear of the 700 will get the car moving anyway. Or should if everything is correctly set.

On the secondaries of the carb: first verify linkage is opening primaries fully. If so - I like to verify secondary operation on vac sec Holleys by making a small disc from thin carboard, like the kind used in parts tags or shoe boxes. Cut it about the size of a dime, then cut in from the outside with scissors to the center and cut out a small hole. The hole should fit on the shaft of the secondary cannister, but not so loose that it slides easily down.

Pop the test disk on, slide it all the way to the top against the bottom of the secondary cannister. Take it out for a full throttle blast. Check the disk. If the secondaries are opening, the vacuum in the cannister will pull the shaft up, opening the secondary butterflies. This will push the disk down on the shaft. Farther down means more opening.

If the disk didn't move or moved a little: check for a torn diaphram in the secondary cannister. There are 3 screws that hold it on, remove clip that holds shaft to butterfly linkage. Pop it off and apply suction and see if it holds vacuum. If so, verify that the 2 passages that feed vacuum to the cannister are clear. Shoot carb cleaner into the hole in the carb body vacuum passage. You should see it shoot out into the passenger side primary bore and a second geyser into the passenger side secondary bore. The primary side passage feeds vacuum to the cannister to start opening the secondary butterflies, the the secondary side passage feeds more vacuum to fully open it. If either passage is plugged, it won't open at all or only a little. The little cork gasket between the secondary cannister and the carb body can flake. Those little flakes plug a vacuum feed passage, you lose 20-40 hp.

Might also want to verify for adequate fuel pressure.

.

 

and beyond that make sure that that little cork gasket that connects the diaphragm to the main body is sealing, mine didnt seal, and i thought it quite curious when i pulled a 16... tuning to run off both primaries and secondaries and not realizing that the secondaries never opened... yea that was a little difficult to explain to the guys.... so i didnt , but it can happen, and running off primaries alone just doesnt cut it.

um 10.5 -1 on the kit means precisely %#$@ what matters is actual, they guesstimate those numbers using different head gaskets and different cc heads, use a good compression calculator http://www.rbracing-rsr.com/compstaticcalc.html and find out what diameter and thickness head gasket is being used, the precise cc of the heads, and the precise dish/dome of the piston. then run off of that, to make sure it aint the rings not seating, use a ratio to cranking pressure converter http://www.rbracing-rsr.com/comprAdvHD.htm (not 100% accurate but if the numbers are way out in left field, something is wrong) *SIDENOTE - in order for those values to mean anything you need to know the deck height, the piston dish, the head cc, the head gasket diameter and compressed thickness, and the cam IVCP (Intake valve closing point) ABDC (After bottom dead center)

also check the advance curve, bigger cam can tolerate more initial timing, and total shouldnt be more than 36* (or so many people seem to think, but for me it works), for that cam say 12-14* initial might be fine, but over advancing the initial timing is gonna kill the bottom end, and then also the top end. and even if initial timing is correct and total timing is too high, you're still gonna kill the top end where it counts, so adjust your advance curve accordingly

 

I told him when he was building the engine that what he was told about the compression means nothing if they don't know what heads, gasket,deck height, you are running. what kind of cranking pressure should he have? I have a stock 350 in my car and it's 175psi. I know what you are talking about when it comes to the timming! with my stock motor I was running 15.3@87mph. then took a look at my total timming, and the distributor had broken and the timming was at like 60*. I pulled it back to 36* and ran 14.2@99mph. I will mack sure that the cam is working like it should. I don't trust him. He thinks that he is 99% perfect on the tunning. But I've raced him and I have never seen him do anything with the carb or timming. I was the one who did the compression test. He thought I did it wrong. He just didn't want to listen to me. oh well. I just want to help get somthing back from his engine. He put alot of money and time in it. thanks for all of your help

 

I ment i'll help him with the carb. not cam typo

 

hrmm... well he should have 170 psi cranking pressure... I checked that cam, and my sources tell me that the IVC ABDC is 60*!!!!.... my lunati BM-II is only 44*....that's insane but yea enough of that compression is gonna bleed to put him at lower cranking pressure than your stock 350 and just 5 psi lower is not the end of the world, i'd look at the parts mismatch, intake kills low torque, and for that big of a bleedoff, he's gonna need a stall converter, rpms are gonna be gold.

another note, you said he had a 700r4? I had a buddy with an 80s pickup, put a 355 with a roots blower on it (smoked the tires all the time) but even when he was running good he thought it shifted too quickly into 2nd and held it for far too long, so maybe a ratchet shifter would help, have him shift manually through the gears and see what happens, just make sure he's careful column shifting is not to be taken lightly, slip and you may find yourself in reverse..... not good

 

ya He shifts manually. I don't understand the 60* you said. I'm new to this. like I said I have a stock 350.

 

oh, cam card...
uh when you buy an aftermarket cam, it comes standard with a cam card (if it dont...oh god.... lol), but this 'cam card' has your lift, advertised duration, valve overlap, lobe center, and so on.... but most importantly it has the valve opening and closing points....new paragraph.

Ok so here's the scoop, the cam card tells you when your valves open and close, to allow air to flow in and out, the important event as far as compression goes, is when the intake valve actually closes....next

This is where we go into static compression ratio, the amount of compression from as far down as the piston goes, to as far up as it goes. And more importantly dynamic compression ratio, which is important for knowing when you're going to detonate on 87, 89 and 93 octane.

dynamic compression ratio (technically geometric, but everyone calls it dynamic) gets calculated based on when your intake valve closes, which happens to occur after the piston has made it all the way down the intake stroke, and is beginning to rise on the compression stroke. When the piston goes back up on the compression stroke with the intake valve open yet, you bleed your compression back into the intake manifold, instead of compressing it for power.

What happens when you measure your cranking pressure is you're measuring the pressure that builds after the intake valve completely closes, or the dynamic compression. Now back to the cam card.

The cam card tells you when the intake valve actually closes after bottom dead center of the intake stroke. My cam card tells me that my intake valve closes 44* after bottom dead center on the intake stroke, (lunati BM-II cam). Now I looked into your buddy's cam, his intake valve closes 60* after bottom dead center, effectively bleeding off a nice chunk of compression,

Which is why he can have 10.5-1 static compression and not have as much cranking pressure as your stock 350 with probably something like 8.7-1 or 9.0-1 static.

Now the reason that cam manufacturers do this (make the intake valve close later), and consequently make you bump compression.... is so that you can rev faster, and a lot higher, and make a lot more power at the high rpms. which makes sense, because you only have to suck a fraction of the air into the cylinder in order to make the same power.

Think of it like a syringe, pull it out really far and you get more suction, at high rpms, the engine is spinning very fast so the piston goes out really far, really fast, creating a massive suction force, thus allowing more air to get sucked in a lot faster.

But, the engine spins so fast that the entire cylinder doesnt get filled with gas/air mixture, instead the piston returns back up (on the compression stroke) before the mixture has been completely sucked into the cylinder to fill it. However, enough mixture has been sucked in to fill the cylinder at the point where the intake valve closes.

conversely these motors have a very low efficency on the bottom end, because it sucks all that air into the cylinder and spits a lot of it backwards.

So, after all that, the point is his compression is where it should be, kinda, he could actually use a bit more. But his problem is going to be getting out of the hole, (let me guess, he bogs like a manual honda civic, with too high of gears.... and a driver who snaps the clutch in and out like it's a top fuel car), ok enough bashing the imports, TO THE POINT AGAIN !!!!

he's going to need a big stall converter umm 3000 area looks good in desktop dyno, dont quote me on that though it is only a cheap computer program, I'd also recommend 4.10s in the rear, but what is weird is the bhp band is dropping off at 5500-6000 so close ratio tranny would be nice too. uhh

if he doesnt wanna change the rear end or at the very least the torque converter, next best bet is a big bad mean dual plane intake as a last ditch effort to grasp a couple extra foot pounds on the low end but if he does that, he better be shifting at or around 5000 in the quarter

once he gets it wide open and on the run, he should have pretty nice torque (and decent hp towards the end) in the 2700-6000 area and outside of that... yea i dont have a good idea. if he cant shut most crap down on the run there's something else wrong, cuz compression is fine, intake isnt actually that bad, carb isn't gonna hurt (vacuum secondary only uses what's needed) , rings have seated fine, the heads should be fine, but they could be warped if he really screwed something up,

intake could be leaking, could be rich, or lean, could be timing... What does the exhaust smell like? has it backfired a lot (if backfired good and exhaust smells like rich gas, check the power valve in the carb, if you dont know what the power valve is, i can scan you the pages out of my holley carb manual).... otherwise yea i'll think about it some more,