I had a thread on here about a slightly odd 511” stack injected bbc Dragster we put together a few years ago. It was working great, printing slips, best of 5.02, then failed a lifter and destroyed the short block.

So we went even weirder.

500” (4.56x3.83), 11:1, .850” lift 286/308 @ .050 115.5 lsa.

I put in as loose of an 8” as I could find and it only goes 5800. Whatever, it’s a bracket car. Runs 5.20s. Shifts at like 7400 @ 3.8 (moved it back to 3.5 seconds because I normally start cracking the throttle around 4.0 if I’m holding a bunch).

Here’s the problem. The idle and throttle whack are all screwed up. The old combo was perfect with typical ~.003 blade gap. Now I’m up to ~.010 to get the idle over 600 rpm, guzzling fuel to keep from melting the heads off, and still won’t throttle whack for nothing and using over 2 gallons per pass (had it down to almost 1.5 with the now deceased short block)

It dawns on me today, I bet the well meaning engine guy who begrudgingly got involved in this deal put the cam in straight up.

Dial indicator shows the cam is in about 115 (came up with 114.5 - 115.5 depending on who was working the cheater bar)

I’m debating between moving it to 108-109 in the car vs pulling the motor and putting a different cam in.

Again. It’s JUsT a BrACKet Car. Don’t care what it runs. Just can’t for the life of me get the thing to throttle whack worth a crap the way it is and not willing to make it work because that would burn 3 gallons per pass. I can drive it the way it is just fine, but the car owner has declared it UnACCEPTABLe.

So, long story short, will 108 ICL make it happy or do I have to change cams??

Assuming the cam was ground @ 108-112, in my opinion it would really respond to advancing the cam....not seeing the cam card, I can only guess, but I would move it to 110*....
Not sure if it would help with the 2gallons a run, but it sure couldn't hurt it....isn't it milking the oil at that rate??

Have you leaked the barrel valve and verified idle check pressure? Those are both key components of idle and "whack". Also make sure any of your poppets aren't installed backwards (won't flow).

quote:

Originally posted by BJs Wild Ride:
I had a thread on here about a slightly odd 511” stack injected bbc Dragster we put together a few years ago. It was working great, printing slips, best of 5.02, then failed a lifter and destroyed the short block.

So we went even weirder.

500” (4.56x3.83), 11:1, .850” lift 286/308 @ .050 115.5 lsa.

I put in as loose of an 8” as I could find and it only goes 5800. Whatever, it’s a bracket car. Runs 5.20s. Shifts at like 7400 @ 3.8 (moved it back to 3.5 seconds because I normally start cracking the throttle around 4.0 if I’m holding a bunch).

Here’s the problem. The idle and throttle whack are all screwed up. The old combo was perfect with typical ~.003 blade gap. Now I’m up to ~.010 to get the idle over 600 rpm, guzzling fuel to keep from melting the heads off, and still won’t throttle whack for nothing and using over 2 gallons per pass (had it down to almost 1.5 with the now deceased short block)

It dawns on me today, I bet the well meaning engine guy who begrudgingly got involved in this deal put the cam in straight up.

Dial indicator shows the cam is in about 115 (came up with 114.5 - 115.5 depending on who was working the cheater bar)

I’m debating between moving it to 108-109 in the car vs pulling the motor and putting a different cam in.

Again. It’s JUsT a BrACKet Car. Don’t care what it runs. Just can’t for the life of me get the thing to throttle whack worth a crap the way it is and not willing to make it work because that would burn 3 gallons per pass. I can drive it the way it is just fine, but the car owner has declared it UnACCEPTABLe.

So, long story short, will 108 ICL make it happy or do I have to change cams??

Up the compression a bunch or put in a good bit smaller in duration @.050 cam. 11:1 compression with too big of cam, IMO that's the issue here.

quote:

Originally posted by bry-war:
Have you leaked the barrel valve and verified idle check pressure? Those are both key components of idle and "whack". Also make sure any of your poppets aren't installed backwards (won't flow).

Yep. Slid in the new short block and all of a sudden wouldn’t idle even though everything worked fine the week before with the old one.

So we checked the bv leak, poppets, and even bolted on a new fuel pump when we couldn’t find anything else wrong.

Then it dawned on me, oh ya, I bet it’s the cam.

quote:

Originally posted by imakehp:
Assuming the cam was ground @ 108-112, in my opinion it would really respond to advancing the cam....not seeing the cam card, I can only guess, but I would move it to 110*....
Not sure if it would help with the 2gallons a run, but it sure couldn't hurt it....isn't it milking the oil at that rate??

Ya, it’s a little milky. It’s still running slightly hotter than id like which keeps it from getting too milky. Into the puddle at 160, staged at 170, back to the trailer at 190 with the fan on after turnoff. Would hit 200 with no fan. That’s not terrible, but it’s hard to keep it under 160 before getting in the puddle.

When it was set up “right” from the old short block it wouldn’t idle at all. It might sit there at 600 for a few seconds. So naturally I leaned it out as a first response. I could get it to idle at 1200 but it was dead lean. Gained a bunch of temp at idle and no throttle whack. No response from pulling the fuel handle because it was already leaned out. So that’s when I started cranking the blades open and changing parts before my realization that it’s probably the cam.

If I can get the balancer off in the car I’ll try ~ 109. Do you have a rule of thumb for how many rpm peak hp/tq might move per degree of intake centerline?

quote:

Originally posted by B KING:


Up the compression a bunch or put in a good bit smaller in duration @.050 cam. 11:1 compression with too big of cam, IMO that's the issue here.

I sure hope that’s the problem, can’t think of anything else. Just trying to decide if moving the cam would make it work for now.

Just trying to minimize down time. The way this year has been I figure we should take advantage of every outing we can get.

What is the LSA measured?

quote:

Originally posted by adv ET 266:
What is the LSA measured?

I didn’t measure lobe sep, but I can check. It’s 115.5 on the card.’

This cam was great at 40 psi boost and 8500 rpms.

I had your old cam in the old shortblock. It worked great, would love to have it in this motor.

The lobe with the lifter failure survived but one of the other lobes had started delaminating so they tossed it in the junk pile.

You said bolted on new pump. Did you have old one checked? Do you know flow of new pump? Rare for two pumps to have exactly same curve even if total flow is the same.

Opening the fly's that much tells me too much fuel,compared to old. What was cranking compression on old vs new engine? Are heads the same(may have missed)?

You stated totally different combo and stands to reason totally different fuel demand for idle and mid range rpm.

Every change effect another part of tune up.

Check Cranking compression. Move cam and recheck. if drops go other way same amount be it 4 or 6 degree which ever. 2* rarely has big effect but it has happened. Be sure when checking CC that everything is assembled the same with full battery or its useless. I would say 180 psi is minimum and would like 210 or more for NA motor.

Wide,

Yes pumps are different. Had a 110 on there, went to a 990. I know the flow of each pump and adjusted accordingly. I have flow tags, but I don’t really use those. I have different methods , LOl. Car ran the same with both pumps. I had already done a fuel sweep until it slowed down with the first pump. Started on a timing sweep but didn’t see much change there.

Same heads.


My calibrated finger tells me cranking compression is about 100 if the battery is fully charged. About what I’d expect given the components. No way it will ever make 180.

I have street cars with 9.5 that make 140 to 150 psi cc. Might want to re-calibrate that finger.LOL

E#ven then I would move cam around some and see what you can get.With in reason of coarse. I fcan not get anywhere near 180 I would consider a smaller cam,but that is just my opinion.

This message has been edited. Last edited by: wideopen231,

Both are big pumps for injected motor 13 to 16 gpm. Just curious do you know pressures on system?

If you where running Nostalgia A/Fuel I would understand its the big thing ,large pump restricted to allowed flow and getting to that flow sooner. Then thats nitro not alky.

Not say it will not work because obviously it will,just seems as you said odd combo.

I would call Bullet cams and ask them what they think on the cam.

As for the fuel system I was fighting with one Enderle hat I had. It idled good and worked good wide open but I was trying to footbrake it and nothing worked. I talked to several people about the check valve settings "Oh, you do not have to worry about those they are set from factory."

Well I did some digging and found out where they were supposed to be set and then checked them. The check valves were wrong. The idle was supposed to be 2-5 PSI and the secondary 12-20 PSI or something like that. Swapped them and was able to tune it much better.

Wide,

Pumps are just what I had laying around. Probably more like 10.5 and 12 gpm.

I had the 110 on a stock pump gas 454 at first with no pump loop. I just kept drilling out the main until it would come up on the converter. I think I was over 1/4” before it would come up ok. Ended up running 5.62@121 (I did eventually put the pump loop on so I could move the jet around easily). Not bad for a dump truck motor with an rv cam.

If I hadn’t had this whole system on 2 motors in the past (454 and 511) I would be convinced the fuel system was jacked up. But like I said it was perfect on the 511 right before it expired and then 2 weeks later with the new short block it’s acting up and has continued to do so.

Curly,

I’ll have to check my notes but I’m pretty sure the idle check is 5 psi (my enderle on my car is at 10, but this one has food adjustment so never tried higher)

The pump loop I set by rpm. It cracks around 2600 and is wide open by about 3000 in neutral. I assume these rpms would be a little higher on the converter (metering valve open more so less system pressure) but I’ve never checked it that way back to back. I had the pump loop opening sooner on the other motors, but raised it while messing around with this motor. No affect on whack but I like it better here because it’s easier to lean out on warmup. Before it was touchy because it was starting to open the pump loop just as you would get it where you wanted it. Minor detail but, again, didn’t change the throttle whack at all.

I thought about opening the pump loop at idle (i.e. lighter spring than the idle check) but the system worked so good in the past I just didn’t think it would improve anything. I think most people leave the pump loop closed at idle right?

Just verified the cam is straight up. Only option on this crank gear (unknown brand) is “A” or “R”. Trying the A to see if that’s enough, will probably get an offset bushing if not.

Measured intake to valve real quick too. Something like .160. Any rule of thumb on clearance reduction per degrees of cam advance?

A VERY general rule of thumb is .010" per degree. Obviously each cam profile will have it's own exact ratio.

Id try increasing the idle check pressure to closer to 10, see if you can get it to act right. Could try to add some ignition timing, say 2 to 4 degrees additional. 2 gallons trailer to trailer is a bit much, should be about 1.25 or so, that's what aggravates me the most about those combos. Last option is to advance cam till it does something different assuming you have plenty P/V clearance....