1gary

The problem I have is you build a relative high compression and give up most of it in ignition timing.Then destroy the good quench number in a effort to fix it.Please,please,don't be offended by this direct post.That is the core definition of a miss matched build.

skinny z

No offense taken. That's the point of the thread in the first place. Although it's turned into a tuning thread what I was after was whether or not the combination I ended up with is workable. By the efforts of everyone involved, I can see that it MIGHT be through tuning and but I don't want the kind of tune where I'm leaving anything on the table. It's looking like a stretch but that remains to be seen.
Please keep in mind that I've gone to great efforts NOT to build a mismatch. There's a lot of research into what was supposed a smallish cubic inch torque generator. You've seen it and commented on it so I think I was on the right track. Through a twist I inherited a short block that's possibly thrown it out the window. That said, it's nothing that cam change wouldn't fix. Just enough to have a managable DCR, keep the timing and the quench, go fast and not rattle the thing the pieces.
Thanks for your input. If we all walked around with kid gloves, then there wouldn't be much progress forward. We'd all just stand around looking at our failures and saying, "good job".

Orr89RocZ

iTrader: (20)

Quick cheap cam to try as a fix is a used cc306 grind. Nasty grind for a 350 lol it will definately bleed off the compression. If that fixes it, you can sell all of them and get a slightly better lobe near similar specs but abit more lift and aggression, to bring back the torque. It would work well with a 4000 flashing converter. Thats why i hinted comp magnum lobes with high lift. Abit more gentle than xfi and tad slower off seat so bleed abit more compression .

FRMULA88

[QUOTE=Fact is I just want to be able to drive to the track, bolt on the slicks, rip off a few respectable ets and go home. You know, like the LS guys do everyday.

As for engine math, a swap in head gaskets from .026 to .040 drops me 10.37 to 10.03. (Don't know where the full point came from?) There's my old CR from the driveable Vortec engine from a few seasons ago.


Performance on the street does have it's advantages. I'd like my build to be driven anywhere. Hence this thread.
QUOTE]


Driving to the track is fun up to point where the car is fast enough that it is just not safe to drive it on the street anymore, also if you do break while racing, it does happen, you are not stranded.

A few 1 1/2 hour tows back home and you could have put a down payment on a car hauler or rented one for the whole season.


Broke my 10 bolt ring and pinion at Cordova at a NMCA event many years ago, this was 4 hours from home, glad I had my trailer and truck. that would have been an expensive tow home !

FRMULA88

to me it seems the easiest solution is a higher octane fuel & the problem is solved.

your car sounds like a strong candidate for EFI system; long distance, daily driver

Orr89RocZ

iTrader: (20)

Thats what good friends are for lol you should always have the number to a friend with a trailer or a shop with a flatbed haha

skinny z

Or a membership in CAA or AAA which I have. I just have to push the car of the track property and call for a tow.

skinny z

For what it's worth, today compression test showed 192 -200 psi (dry). Higher than I remembered but it IS one of the targets I was shooting for. My understanding has always been that a solid street engine should have that kind of cranking pressure and can live happily on pump gas. It just takes a little finesse.
We'll see.

cuisinartvette

Colder plugs for sure drop it down a notch or two
Keep it running nice and cool if you can back your curve off a touch-

Wonder if your idle circuit could use a little more fuel


Most octane boosters at the store are a scam
When the bottle says it raises it say 3 points it means .3

Been using this for a yr it works great. Toxic as hell but what isnt these days

Cheaper than race fuel

http://www.wildbillscorvette.com/OctaneSupreme01.htm

skinny z

If figured I'll keep this thread alive rather than trying to start interest in a new one. Same thing over at SpeedTalk.
Here's the latest from a brief test run this evening.
Base timing: 8
Mechanical advance: 20 (all in by 2900)
Vacuum advance: disconnected.
Example 1: 2nd gear, 3000 rpm, steady speed. Pin it. Rpms jump to 4000, very brief but massive knock, then car flies through the rpm range until I lift at 6000. No knock audible beyond the initial hit. AFR gauge shows a lean spike (15:1) at the knock, then settles into the low 12s right through the rev range.
Example 2: cruise in 2nd or 3rd with rpms around 2000. Small bursts on the throttle, hit/release, hit/release, maybe 1/2 applied, will yield a knock as the rpms jump. The lean spike doesn't show as pronounced in the previous example and of course the detonation isn't as intense but it's still there.
Example 3: Steady speed in any gear, any rpm, apply enough throttle to gently bring the manifold vacuum down to 10" or less and the car accelerates smoothly and briskly. No spike in the AFR, no rattle. AFR will move towards 12:1.
My conclusion so far. I need to work the accelerator pump circuit to cover that lean spike. Once that's solved, if it can be, then I work on bringing the timing back. I'll have to decide whether to keep the full manifold vacuum or switch back to ported.
The rest of the fuel curve is easy for me. I've done it countless times with excellent results.
I'm not convinced that I can rescue this combination as the compression ratio just isn't going to be workable.
I'll move up to a bigger cam if I can't sort it out. Keep my quench. Keep my timing. Eat some of fuel economy. Less of a cross country cruiser. Go faster at the track.

1gary

A continuous eye on the compression and oil pressure and any changes while you end up knocking on this engine while trying things out.It is certainly one of the high risks that doesn't have a endless time limit.

skinny z

All of that I'm frightfully aware off.
Yesterday's compression test was just for that reason and happily, nothing appears to have changed. This isn't to say I haven't done something undetectable. Could be a broken ring in there already.
Oil pressure is still good.
Interestingly, the plugs showed no evidence of detonation. At least not that I could see. I've installed a fresh set and will be keeping an eye on them.
The racing season in these parts has only a few months left. Some brave souls get out to race in November if the weather stays nice but for me, I'm almost looking forward to putting this car away for a while.
I see a new cam in my future.

FRMULA88

I carefully read your 2nd to last post.

Before you go off the deep end:

You should have the vacuum advance connected to the TIMED vacuum port.
The vacuum port which has NO VACUUM at idle is the correct port to use.

Connecting to a full vacuum port is going to create a big problem: Your timing will always be too advanced way too soon and not based on actual engine load (vacuum) / throttle position / RPM.

at idle you want base mechanical timing only (initial timing)
at WOT you want max. mechanical timing only (total timing)

I think this is your real problem. in your quest for max. fuel economy & lean burn at low loads part throttle
You have too much timing with the vacuum advance & it is connected to full vacuum port. (wrong port)

You only want max. vacuum advance to occur at high engine vacuum under light to partial load conditions only.
The Idle circuit does not need vacuum advance.

This is why you need to be connected to the timed vacuum port and this is why the OEMs designed this port on the carb, it creates the correct transition for the vacuum advance to operate only when it's needed, which is not all the time.

Try running the car without vacuum advance.. and see what happens.. then connect vacuum advance to timed vacuum port and see what happens.

also you should never need more than 40 degrees timing with vacuum advance on a carb... you will never be able to have perfect mixture / timing control unless you go efi.. which is why the OEMS stopped using carbs.

You will have to compromise a bit with a carb.

FRMULA88

rule of thumb:

If knock occurs under load @WOT you retard mechanical timing until the knock is gone.

If knock occurs at part throttle you retard vacuum advance. You have an allen head screw for adjustment, clockwise retards... counter clockwise advances. BUT you have to be connected to the TIMED vacuum port for the adjustments to work correctly..

FRMULA88

http://static.summitracing.com/globa....jpg?rep=False

skinny z

I followed up on some of your suggestions prior to testing and I posted that the vacuum advance not was active during my latest test (you must have missed that). The knock is every bit as pronounced as it was before disconnecting.
I don't wish to get into a discussion (here) about ported vs full manifold vacuum. I've read too amny technical publications, reports and forums to get into it now other than to say up until recently, I was ONLY ported vacuum. I argued staunchly against full manifold vacuum with the same logic and reasoning as you are. Then I tried full vacuum with any array of adjustability and test tools. I found it to be a real benefit in certain aspects of the engine's operation. Not all, but some.
At this point in time, I'm undecided which direction I'll go. My interest now is solving the issue at hand.
It's not vacuum advance related as my test demonstrates.

FWIW, here's an interesting article and one that got me to rethinking my approach. Like I said, I'm not convinced either way.
http://classicinlines.com/spark.asp

skinny z

[quote=FRMULA88;5636545]rule of thumb:

If knock occurs under load @WOT...
quote]

Please note there is no knock at wide open throttle. It's only occuring at the examples listed in my previously noted tests.
I may have to back the timing out in the 3000-4000 rpm range (from the 28 it is now) to eliminate any knock caused by timing. That seems absurd and this is what is leading me in the accelerator pump direction.
If Ican't solve it with fuel and I have to keep the timing unreasonably dialed, then I'll call my engine combination a failure and cut my losses.
I'll have some more testing to report in a day or so.

FRMULA88

if fine tuning the carb and timing does nothing, then run higher octane fuel

if that is not prudent then any other approach means giving up some power, how much I don't know.

But if we are only talking 10-15 hp then who cares.

You will not feel that in the "seat of you pants" and at the track we are talking "thousands" of a second in ET.



Various approaches you can take now, unless you want to "upgrade" to alum. heads:

Colder heat range spark plugs, and a bit richer mix. help pull heat out of chamber.

Cometic .040 thick gaskets to drop compression a bit.

or / and

Keep pulling out timing until the knock is gone.

FRMULA88

when I built my 383 many years ago I had similar issue. matter of fact desktop dyno even showed a mid-rpm knock count. on simulation but also offerered timing scale to eliminate the mid-curve knock.

THIS is a function of the fuel & timing curve (cam pattern, CR, etc etc) your build is not a failure however what you are failing to grasp is this occurs every time you floor the throttle (which is WOT). The knock is occuring at same RPM / load point each and every time.

with EFI it's easy you fine tune the timing scale. pull out some timing at that point, or you tweak the fuel map to dump a little more fuel (injector volume) at that specific point.

My 383 had holley projection 4Di so I based on my timing scale on desktop dyno build, and my fuel map was straight from the engine dyno after we ran the engine.

Installed in the car with a narrow band 02 sensor 12 years ago:
I idled in the 12s, part throttle in closed loop was 13s to low 14s WOT 12.8

You can adjust your mech advance to come in @ slower rate (change the springs) this will pull some advance out at the point you are having the knock occur..

jet up a bit and or more accelerator pump shot. (primary and secondaries) 15s AFR at 3000 RPM WOT is a problem.

Also If you have vacuum secondaries they may be "slow" to react, I would adjust them to open sooner.

when you "floor it" you need enough fuel to compensate your afrs AT WOT should be in the 12s... this will keep you safe. low 12s are a bit rich.. but mid to high 12s should be good.. You will never hurt the motor if the fuel curve is a bit rich... it also helps compensate for the crappy fuel..

Lean is mean, but lean breaks parts !

skinny z

I've been thinking about all of the above.
The loss in power is a tough one to pin down and dialing the timing back looks like it would have to be ridiculous amount. The result of just working the timing would probably mean a substantial loss in power not to mention fuel efficiency. Of course that's just timing and not dealing with the lean condition I'm seeing at the hit.
So a combination of timing and fuel might do it. I'll have a better idea tomorrow. I'm adding a considerable step into the squirter size, along the lines of 28% so I'll see were that gets me.
Regarding my other options:
I'm going to resist the move to aluminum heads unless a sweet deal comes along and I can move these very nice RHS heads along to someone that can use them. Expense mostly. Principle some. But mostly expense.
As for the colder plugs. I'm not sold on that. I have installed a fresh set of what I've been using as the old ones didn't show any signs of distress from heat. Or detonation for that matter although I haven't put them under a microscope. I'll be checking on these new ones as I move along.
I've thought about the thicker head gasket with mixed feelings. The tight quench is a hedge against detonation although it's obviously not the only spec in a engine such as mine. Moving up in thickness might just move me sideways.
As for the timing, well, I'm working on that.
One thing not mentioned here is the cam. While the same principles apply to my wanting to keep what I've just purchased and specified it's clearly not the right choice now the short block has changed and my desktop dyno calculations have gone out the window. Still the expense is less than getting new heads so I can swllow the principle should this thing not be manageable.

skinny z

I use Desktop Dyno quite a bit (exhaustively for this build in particular) and I've never come across a knock-count function. I'll have to look deeper.



Lets hope lean can wait until I sort this out!

Jonesyfxr

iTrader: (2)

Here's something that just popped into my head. My engine builder said that when you get over 11.1 CR you get spark scatter. He said that I had to run a special NGK plug (4554 IIRC). He said the plug will prevent scatter.

Just thought I'd put it out there.

skinny z

I've heard the term spark scatter used to describe several different things.
Do you know what he meant specifically?
I understand that high compression can snuff out a spark. When higher compression pressures are realized along with higher rpms, it's essential to improve on the ignition system.

1gary

Gezz Skinny.I read where you snuffed out the possibility of aluminum heads.You do have the perfect build plan if you where to buy a set.Hell,you then wouldn't have to give up anything and damm near a matched build.
I when I read that thought oh well I tried.But given the clearly amount of research you have done,short of the iron heads,got to like you some.Really don't want to see you hurt anything and don't want you to miss out a the matched build opportunity.

OK-this could seem like I am bugging you.If that is the case,tell me so and I'll stop.Just sad to you not have long term "that smile" everything you turn the key.Ya know??.

Orr89RocZ

iTrader: (20)

I have made a few mistakes on my build. Only way to fix them is to cut your losses and buy the right parts lol if the tuning doesnt work you need a cam or aluminum heads

skinny z

Bugging me? Hardly. I'm taking a shitekicking over at SpeedTalk though. It's kind of funny too because like the title of the thread said, I was looking for real world results on whether anyone has built a engine such as the one I "inadvertently" ended up with. It's turned into a tune-fest and I've always been a little leery about soliciting advice about that subject. I've seen too many people get their noses out of joint on both the giving and receiving end. Now I'm seeing it first hand.
Lets say that I haven't entirely given up on aluminum heads.
I'm more inclined to move up in cam duration or even the same cam with a tighter LSA. Lower my running compression ratio to something more streetable. A DCR of 8:1 is very workable. Hell, I could probably even run it on mid-grade premium.

skinny z

Exactly my thinking.
These heads sure are nice though. With the exception that they're iron, and I understand the benefit of an iron head from a power production standpoint, I don't think I'm going to be able to make them truly "streetable". At least not my definition of streetable, which I've said before is everything from the drag strip, to daily driver, to cross country cruiser and anything in between.
A cam on the other hand would also fit the bill here. Properly spec'd I wouldn't have to give up too much on the driveability or fuel economy and would probably happily trade that off for an 11 second time slip. Not sure if a change in cam is going to net a half second in ET though.

cuisinartvette

Good move.

Still thing yes on the colder plug.

Then some good gas/additive in it and drive er til you can upgrade parts.

skinny z

With only a few months left in the driving season here, and less 2 months for the drag strip, a barrel of 110 unleaded might be the ticket.
Hell, with enough octane, I could drive this thing like it was intended.
It'll be interesting to see how these new plugs look. I've never been much into reading spark plugs for the carb tuning I do. The heat range has never been in question until this engine iteration. The AFR gauge tells me everything I need to know about fuel mixture when I'm tuning. Easier for sure.

Orr89RocZ

iTrader: (20)

Yeah colder plugs do work. I have seen that first hand. I dont think i could run 18 plus psi on straight 93 oct if plug and tune wasnt dead nuts

Jonesyfxr

iTrader: (2)

I'd have to ask him. I gotta get over to see him anyway, gotta see when my mill is gonna be built......then dynoed by Mike Janis.

1gary

Mikey huh.I haven't talked to him in a while.Been around since Jim Sr first started.Is the old man still around??.

1gary

Don't know if you guys in the great white north have taxes returned.That would be a prime time to be torn down ready for replacement heads.Even through it is prime selling season during the winter months,some companies like RHS and Competition Products run specials and show specials at winter swap meets.Now I have never suggested you spend AFR kind of money nor the cheapest junk you can find where you move from the pan into the fire so to speak.But a decent set like the RHS or Brodix sells nice heads with a very good 180cc intake runner.

skinny z

My testing procedure and earlier test results are listed below:

Base timing: 8
Mechanical advance: 20 (all in by 2900)
Vacuum advance: disconnected.
Example 1: 2nd gear, 3000 rpm, steady speed. Pin it. Rpms jump to 4000, very brief but massive knock, then car flies through the rpm range until I lift at 6000. No knock audible beyond the initial hit. AFR gauge shows a lean spike (15:1) at the knock, then settles into the low 12s right through the rev range.
Example 2: cruise in 2nd or 3rd with rpms around 2000. Small bursts on the throttle, hit/release, hit/release, maybe 1/2 applied, will yield a knock as the rpms jump. The lean spike doesn't show as pronounced in the previous example and of course the detonation isn't as intense but it's still there.
Example 3: Steady speed in any gear, any rpm, apply enough throttle to gently bring the manifold vacuum down to 10" or less and the car accelerates smoothly and briskly. No spike in the AFR, no rattle. AFR will move towards 12:1.



Now having said all that the following is what I've found with the #35 pump nozzle and a pink cam in the number 1 hole.
I'll reply to the other posts a little later.
Same testing procedure as before (although I've limited it to that of example 1). Timing as noted above. The only change is an increase in pump nozzle from #31 to #35 (28%).

The knock is still present at the initial hit. It seems to me it's reduced somewhat. Not in intensity but in duration.

As an additional observation, AFR while cruising at 3000 in 2nd or 3rd are in the high 14s to low 15s. Not excessvely lean I wouldn't think. At the hit, the rpms jump instantly to 4000 rpm accompanied by the intense spark knock but only briefly. From there, despite the tire spin, the car accelerates as I would expect until I lift. At the hit, there is a lean spike still but it's diffficult to pin down. I can see 15s, maybe leaner but that's only an instant. Then past that point the afrs drop to the 12:1 range and the car goes like a "bat outta hell".
Keep in mind that the total timing for the duration of the test is 28 degrees.
I'm going to move up to a #37 shooter (which I think is getting ridiculous) but will test again and report back. Mind you, it IS only one accelerator pump I'm talking about. Maybe it'll take a really big shot.
If the 37s don't make a significant difference then I'll be switching carbs.

skinny z

So the latest testing yields results really no different than the previous test.
Detonation is significant anytime the throttle is opened abruptly. It basically occurs at any engine speed (when cracking the throttle opened quickly) but the testing procedure outlined earlier is where the most significant knocking is heard.
I don't believe it's a fuel issue.
I've moved up to a #37 pump nozzle and can see that the afrs aren't too far off of what I would think is acceptable.
As has been suggested, I'm going to have to get into the ignition and check to make sure everything is 100% there.
I'm not entirely sure where I might be going with that as at higher rpms, once the engine is past the initial opening of the throttle, it's smooth as glass without a hint of misfire or spark knock.

skinny z

Went up to a #37 pump nozzle. While I can see the AFRs have improved on the hit, it still knocks considerably. I'm thinking now that it's not fuel related.
It was suggested that I verify the rotor phasing and while the symptoms don't fit a misaligned rotor exactly, it's something to investigate.
This engine, once past the initial knock from whatever rpms, pulls strong to the upper end of the rev range. No hint of misfire, knock or backfire. In fact, despite the dialed back timing (28 degrees at WOT ) it's running the strongest I can ever recall.
Perhaps it's just something fundamental, something that's slipped or broken that I haven't been able to find.
One thing I will do is follow up the Pro Racing Fuels suggestion. There are several distributors in and around here and I can pick up a few gallons of 101, 110, or 114 unleaded. Once I build an edge against the knocking I'll be less concerned about breaking something while I'm tuning.

cuisinartvette

You probably already know this but when you open that can of gas have a GOOD respirator on and do it outside

I opened/poured a jug of VP 100 the other day and didnt wear one. held the breath turned the head etc.

My neck swelled up so bad Dr was close to sending me to the ER to get a tracheotomy no chit lasted over a week! I dont know whats in that crap but my god it plays hell with your glands and everything else. Car runs and smells good though

37s an awful big squirter sounds like youll get it sorted though.

skinny z

Yikes! Let's hope it doesn't play hell with your other organs and show up 20 years down the road.
Advice taken. I have a organic compounds/pesticide rated respirator that I use on certain work related projects. I'll be sure to have it on when I'm transferring fuel.
Thanks for the heads up.

Regarding the squirters. It doesn't look like adding a ton a fuel is doing much to alleviate the problem. Despite having changed the AFRs at the hit from high 15s/low 16s to something in the 13s (it's difficult to tell when glancing over and the change is instantaneous), the knock is still there. I can say it's somewhat less (maybe as I'm losing track) but it'll break something if I keep at it.
I should really have my data logger hooked up for this. I had a hardware issue with it a while back and haven't re-installed it after the repair.
Today is ignition day.

FRMULA88

Increase primary and secondary jets. +3 jet sizes min.

when you floor it is the issue,,, not enough fuel.

skinny z

I would think that the jetting is more about WOT and once I'm past the initial "hit", the ARFs are actually rich and in the low 12s.
It's the sudden opening of the throttle, even half way, where the knocking occurs.
Lots of too.

skinny z

Here's the latest:
At the suggestion of several, I swapped out the BG with the QFT carb I have. It's a 680 vacuum secondary with adjustable bleeds ( thought it was a 750 but no matter).
No change. Still knocks as before. Even worse before I installed a #37 pump nozzle. It runs considerably richer than the BG which I expected as it was on a little more radical engine than mine. That richness I had hoped might have taken some of the edge off the knocking but it's not the case. On that engine it performed really well. Not only did it work well at the track, it also did a great job on the street and returned some pretty decent mpg considering what it was.
So here's the scoop. I'm pretty sure I've assembled something along with it's 200 psi cranking pressure, nearly 10.4:1 compression and iron heads that's going to be a handful no matter what I throw at it. As it is, the timing has been dialed back to 8 initial and a whopping 28 at WOT and no vacuum advance. Surpisingly, it still has lots of beans once I get past the inital hit and it can rev. That's encouraging but I can't drive it like it is so something has to be done.
Here's my plan:
Get into the distributor to be sure that something's not out of whack. Rotor phasing has been tossed out as a probably cause and I'll investigate that. The timing is rock solid via my timing light (more than one) so I'm not convinced that there's anything to be seen but I'd hate to leave that stone unturned.
I'm going to take more timing out of it. Another 4 degrees initial will drop the total to 24. I may add a stronger spring to the advance weights and get the advance total to hang on to 3500/4000.
I'm also going to look into some racing fuel. It'll be interesting to see if 110 octane will allow the full timing to be restored. If it does, I'll pack up a jug or two ($$), take my timing light and slicks and head to the track for a little testing. I know this thing has a lot of potential. It may not be a rocket but I've tried to assemble a car (and a heavy one ) that'll do low 12s. I've built this to be as much of a cross country cruiser as I have a weekend racer. Hence my emphasis on a carb tune that's as much about fuel economy as it is going fast. That's always a compromise.
At the end of all that, depending on how it goes, I'll probably make a cam change. Either retard my current cam by 4 degrees or get another altogether. I have options there.

FRMULA88

try the 110 and I am sure it will be fine. There is no replacement for octane.

However 110 is typically leaded so your Lambda sensors will have a shorter life span.

You should be OK with 10.4:1 compression using 100 octane unleaded. as I mentioned before you could also blend this with your premium gas 1:1 and achieve about 96 octane fuel. and not affect your lambda sensors.

Most tracks will sell 100 and 110 , 112, & 116 at the facility.

Keep in mind 110 is meant for engines between 12 & 13:1
there is such a thing as over-octaning meaning you are not using the fuel to it's potenial

akin to running premium in a 8.5:1 engine. It will run but will run better on 87...

But try the 110 and wean yourself down to 100, or blended. it is more economical to use blended than straight race gas if you can get by with it

good luck!

FRMULA88

the version of desktop dyno I had you could specify type of fuel..

skinny z

I was re-reading the thread and I saw this. Missed it the first time through. Handy.

skinny z

I was looking for this link to Pro Racing Fuels. Someone had posted but I can't find who.
All unleaded. We've had a ban on leaded fuel at the race tracks for a while. At least it was limited and I think eventually removed entirely. That might explain these guys. There are several distributors within an hour or here. The local circle tracks and dragstrips sell during events too.
http://www.proracingfuels.com/products/pro-racing-fuel/

JesasaurusRex

iTrader: (3)

a couple pails of 110 and you'll be at the cost of a new cam. I still think tightening up the quench and going with a bigger cam is what i'd at least try before going with an aluminum head.

1gary

I think I posted this already,but going to a mismatched cam to SCR's is a band-aid fix at best leaving a ton on the table.That is thread is clearly proof of what not to do in SCR's with iron heads.There is the link"again".

http://www.crankshaftcoalition.com/w..._compatibility

Skinny-sure seems to me now being more direct in this post that your enjoying a quest to try to find a easy fix while punishing this poor engine.That a bigger cam swap leaves you with a longer overlap that is as I said a band-aid fix where some of the A/F mix is forced back into the intake manifold having the SCR's iron heads can't handle and bleeding it off to the exhaust.Also that a bigger cam forces a looser T/C and the combine costs for that either equals or exceeds the cost of the good quality aluminum heads.That I am not insisting only one way,but the way to do a proper fix not leaving anything on the table.This is a mechanical fact.One,before serious damages occur,you need to accept.

Orr89RocZ

iTrader: (20)

Might be a band aid but it will run harder and sound cooler big cams work

skinny z

Probably very true but I really want to know how this things performs. If it takes a few hundred dollars in some decent fuel, then I'm for it. Then I can put the car away and get ready for whatever changes I'll be making.
That said, if it falls on it's face with 110 octance, then I know I've got a real problem.
By the way, I'm already at the limit for quench in this engine which is agruably .040".
The bigger cam, well...stay tuned.

skinny z

You have to remember the title of this thread.
I wasn't soliciting advice on what to do (at first) but was after some real world numbers regarding who has done what and how did they get there. It obvious to me from posters like yourself that I've built a handful and it's entirely likely this combination will never work.
In fairness to me, it wasn't intended to be like this. I spec'd that cam to go with a 10:1 SCR. That would have resulted in a DCR of slightly more than 8:1 which I KNOW from past experience is not only workable, but you end up with an engine that overachieves. That's how my Vortec 350 was. Satisfying performance and great drivability.
Unfortunately those plans went out the window when the shortblock I had intended to use ended up getting shelved. Luckily I had one in reserve that I had been storing for a friend. It, however resulted in a 10.4:1 DCR. We all know how that's ended up.
Now something to consider here. If were to build this engine with a 10.4:1 SCR target, 64 cc heads and a tight quench, I would have definitely selected a cam with either more duration or at least one with a later intake valve. Everything would have been in spec and I'd have a decent performer with none of this trouble I'm having now. Yes, I agree with you that there's more to it than that but that's how I'm working through the thought process. I think I have all of the supporting parts for a step up in cam.
More to come.
Maybe even aluminum heads.