Tuning headache

[brotherGood]

Well, I'm at my wits end with my '69 442 so I figured I'd hop over here to see if I can pick anyone else's brains on this.

I have the original 400, bored .040 over. Engine was "zero decked", however no clue how much material was removed, or what current height is as piston/rod combo was incorrect during initial machining.
Cam is 228/235, with .501 lift.
I am running original points distributor, which has been recurved based on combo.
I have a numbers correct Quadrajet on it now, which has had a couple modifications done to try to keep up with the combo.

Previous/Lingering Issues:

• From initial start-up, I have had extremely low vacuum (best consistent has been 9", but since swapping carbs I'm back down to fluctuating between 6-8").
• Initial timing is now 16 degrees, but had been running 18 degrees based on what the "total timing" method produced. Car still kicks back as if timing is too far advanced
• Engine sputters during idle. Not sure if its due to size of cam, but it has always done this.
• Engine seems to run warm and worse when ambient temp goes up.

Current issues:

• Idles much more inconsistent since swapping to numbers correct Qjet
• Detonation at higher RPM under WOT

The intake has been off and resealed multiple times in attempts to combat vacuum leaks. I have searched multiple times and cannot find any. The cam was degreed last winter, still no real change in vacuum, but the brakes did feel much better. Previously this had a Jet 32002 Qjet, which had the idle mix screws completely closed and was still running rich.

The variable in all of this is the potential for an internal vacuum leak. I have done a compression test, but have not done so since the cam was degreed (I'm planning on doing so soon, both cold to compare, and hot). I am also planning on installing a wide band setup, so I can gather more data as to why its now suddenly detonating.

Short of yanking the engine out and having it rebuilt (again), I'm out of ideas..so I'm open to any suggestions.

Thanks in advance.

[brotherGood]

Forgot to add these (as well as video of it running a couple days ago)..

https://youtu.be/oNLcuvbkvg4?si=Eu7kW8EXqEvKVnx3

[DanStokes]

You mentioned the Q-jet. Have the throttle shafts been rebushed? These were notorious for the throttle shafts getting loose and therefore inducing an unpredictable vacuum leak. There is a system out there to rebush them with brass bushings which hold up better. Just a thought.

[SuperBuickGuy]

Have you done a smoke test to see if you can find the vacuum leak? When you milled the block, it pushed the heads closer to each other - usually it doesn't matter but compound the issue with thicker-then-stock gaskets and you have a recipe for vacuum leaks.

And the other vacuum leak culprit.....

Also, that compression seems low given you've milled the block (I'd expect 180-200) - I'd also verify the cam was properly ground... and in that vein, when you degreed the cam, where did you set it?

[brotherGood]

You mentioned the Q-jet. Have the throttle shafts been rebutted? These were notorious for the throttle shafts getting loose and therefore inducing an unpredictable vacuum leak. There is a system out there to rebus them with brass bushings which hold up better. Just a thought.

Qjet was rebuilt from Olds-Motion. First as a stock restore/rebuild, then we discussed the combo after we realized it was pretty far off. This is the second crack at it and he's not saying he's got it right..but he did say he thought he was close and that he thought it was worth addressing everything else before sending the carb back to him. I totally understand that aspect, though the variance going from one carb to another is still there.

[brotherGood]

Have you done a smoke test to see if you can find the vacuum leak? When you milled the block, it pushed the heads closer to each other - usually it doesn't matter but compound the issue with thicker-then-stock gaskets and you have a recipe for vacuum leaks.

And the other vacuum leak culprit.....

Also, that compression seems low given you've milled the block (I'd expect 180-200) - I'd also verify the cam was properly ground... and in that vein, when you degreed the cam, where did you set it?

I have not done a smoke test. I was advised to take the turkey tray out and instead put thinker gaskets in, but in hopes the thicker gasket would alleviate the gap rather than accentuate the problem.

The compression test was done after the car sat for a few days. Not saying that has something to do with the low numbers, but just for information sake. As mentioned, the block was milled when the original rods/cast pistons were to be used. The assembly shop (different shops-longer story) noticed that not only were some of the rods bent, but also the skirts on the cast pistons were hitting the counter weights. I then (with help from one of the top Olds builders-same guy who recommended this cam) found a set of forged pistons with longer rods. The math worked out, but I don't know if that in-turn put the top of the piston lower than where it was when the milling was done for the cast/factory rod combo.

When the cam was degreed, IIRC it worked out to putting on the "A2" notch on the gear, and it was still 1 degree off, but much closer than the 20 degrees off or whatever it was.

[fatguyzinc]

ok, ive only done 2 olds motors a 330 and a 455. but i have done tons of pontiacs, a cadillac 500, a zillion small and big block chevys, and both
small and big block fords mopars. although every engine is different, they are also operating on the same principles. so, going by your previos posts
here is my best educated guesstimate....i appologize in advance if it sounds 'preachy', im not trying to dumb anything down, its actually easier for
me to think in laymans terms, and im just trying to help a fellow gearhead out if i can.
hey, be flattered i usually charge for this kind of custom hillbilly engineering, hah hah...

im thinking you may be a victim of the classic and oh so common mistake of "mores law"- if some is good, more must be bettter. aint always so..

a 296-306/.504-,504/108+2 is a *HUGE* cam, and the "+2" moves the LC to 106... you need more compression, a better flowing intake,
and that Q-jet should go in the trash, its probably got the enrichment rods WFO due to the low vacuum. my choice would be an 800 edelbrock
if you can find one. or an 850 holley but i dont like them too finicky. personally i would chuck that cam in the round file as well, the 228/[email protected]
shows that its a "pointy" (for lack of better word) cam with not much area under the curve-- in comparrison the 292/.591/110 in my 454 chevy has
[email protected], a 'fatter' not so pointy lobe. the cam you currently have would seem to be a good boat cam with a peaky higher rpm powerband.

its a 455 olds. like a pontiac they like to tug not scream. i would run something like this isky cam

https://iskycams.com/shop/index.php?main_page=product_info&products_id=928

you can see it has more lift but over 20 degrees less duration, while still having the 108 LC so it will still have plenty of rumpity rump and
a very explosive powerband from 2500-5500+, and it has [email protected] despite having over 20 degrees less. this is a 'fatter' less pointy lobe.
it will make more torque and drive better as well.even with the 108, it will still make better vacuum than your current cam due to the much
much shorter duration.

the initial timing needing to be at 18 degrees is pointing again to a WAY too big cam and not enough compression to support it--and the overlap
actually bleeds off some of the static compression thereby compounding the issue even more. but again, over 20 degrees less duration would
make a monster difference.

i realize thats a big job, but if youre ready to pull the motor out at this point id risk it. i am 100% certain this would help a ton, though you may have
other underlying issues as well but (to beat a dead horse) over 20 degreed less duration would make a HUGE difference. and dont forget new lifters,
matching valve springs (your current "might" be ok, but check first) etc etc etc....

[SuperBuickGuy]

I have not done a smoke test. I was advised to take the turkey tray out and instead put thinker gaskets in, but in hopes the thicker gasket would alleviate the gap rather than accentuate the problem.

The compression test was done after the car sat for a few days. Not saying that has something to do with the low numbers, but just for information sake. As mentioned, the block was milled when the original rods/cast pistons were to be used. The assembly shop (different shops-longer story) noticed that not only were some of the rods bent, but also the skirts on the cast pistons were hitting the counter weights. I then (with help from one of the top Olds builders-same guy who recommended this cam) found a set of forged pistons with longer rods. The math worked out, but I don't know if that in-turn put the top of the piston lower than where it was when the milling was done for the cast/factory rod combo.

When the cam was degreed, IIRC it worked out to putting on the "A2" notch on the gear, and it was still 1 degree off, but much closer than the 20 degrees off or whatever it was.

I hate to say pull it but pull it. So many questions that need answers. At this point, you have no idea what your compression ratio is (guessing 8:1) - with that big, thumpy (technical term) cam, it would be an utter pig - pull the motor, as FGZ says, bin the cam, check the compression height and calculate your CR then order something appropriate for it. I'm not sure what the A2 mark is on the timing set; however, it was already bleeding off compression at +2 degree lob centerline.... which makes your effective compression ratio somewhere around 4 cylinder flathead .... (6:1)

[brotherGood]

The only other engine I've built thus far was an LA 318 with magnum heads and a Summit 6900 cam. While it was much more wild than the factory smog 318 it replaced, it wasn't that overly complicated. This has been much more difficult, and I'm sure part of it due to trying to make sure I preserve the factory numbers matching aspect.
When selecting the cam, I was advised this is "two steps above a W-30" and would necessitate a larger converter. Since install and the first sign of an issue, I had been reassured by multiple people who have used this cam in their Olds engines that it doesn't create any vacuum issues. The odd thing though, anyone who looks at the cam sheet says there may be issues with vacuum for this cam.

When I shared the cold compression test numbers with the builder I'd been using as my go-to for answers (not one of the local shops) he did say that the cam required at least 10:1 compression, and while he didn't want to accuse anyone of anything, he thought the machine shop missed the mark. Being that they machined and balanced a set of pistons and rods that are ultimately not what was installed, I see that as much of a potential variable as I do the chances of an internal vacuum leak.

Then again, I'm a fish out of water when it comes to all of this. My last build, while off the wall, wasn't nearly this complicated.

[brotherGood]

I hate to say pull it but pull it. So many questions that need answers. At this point, you have no idea what your compression ratio is (guessing 8:1) - with that big, thumpy (technical term) cam, it would be an utter pig - pull the motor, as FGZ says, bin the cam, check the compression height and calculate your CR then order something appropriate for it. I'm not sure what the A2 mark is on the timing set; however, it was already bleeding off compression at +2 degree lob centerline.... which makes your effective compression ratio somewhere around 4 cylinder flathead .... (6:1)

I will say, the thought had definitely crossed my mind a few times. I can't tell you the amount of times I've thought with hindsight being what it is..I should have either just had the block fixed and measured everything/assembled everything at home (I'm an over-analyzer, so I would've had countless books and things to make sure I knew what I was doing) or taken the money spent and just sent it out to the guy in FL who is one of the top Olds guys in the country. Let him assemble/dyno/etc..and I'd just pull it out of the crate, slap it in and be done.

[cstmwgn]

What size is the engine?

The biggest thing I noticed on the cam is the difference between advertised and @.050

Advertised is 296/306
@ .050 228/235

The @.050 don't impress me as being large. However the advertised seems too large ~ 70 degrees between advertised and @.050. Other cams are more in the 45 - 50 difference.

[brotherGood]

What size is the engine?

The biggest thing I noticed on the cam is the difference between advertised and @.050

Advertised is 296/306
@ .050 228/235

The @.050 don't impress me as being large. However the advertised seems too large ~ 70 degrees between advertised and @.050. Other cams are more in the 45 - 50 difference.

It is a 400, bore .040 over (406 technically?)

[SuperBuickGuy]

I will say, the thought had definitely crossed my mind a few times. I can't tell you the amount of times I've thought with hindsight being what it is..I should have either just had the block fixed and measured everything/assembled everything at home (I'm an over-analyzer, so I would've had countless books and things to make sure I knew what I was doing) or taken the money spent and just sent it out to the guy in FL who is one of the top Olds guys in the country. Let him assemble/dyno/etc..and I'd just pull it out of the crate, slap it in and be done.

I know the feeling, but the disappointment in myself to even think that someone else can figure it out usually stops me (that said, I spent 5 hours and $1600 to tune my Corvette - so there is a line in my life too).

Just my :2cents: is pull the heads before you pull the motor and send it off.... at least then you can see where the piston is to the deck height.....

[fatguyzinc]

What size is the engine?

The biggest thing I noticed on the cam is the difference between advertised and @.050

Advertised is 296/306
@ .050 228/235

The @.050 don't impress me as being large. However the advertised seems too large ~ 70 degrees between advertised and @.050. Other cams are more in the 45 - 50 difference.

that was exactly what i meant about it being "pointy" lobes, with not much are under the curve.
a 300-ish degree duration cam "normally" runs in the 240-ish to 260-ish @ .050 range.

also, i assumed this was a 455, for a 400 id recommend that smaller isky cam even more!
i dunno if id do the superbuick and pull it, im more inclined to try the cam swap in the car first--
but if you do pull it, use a different machine shop this time and have the block magnafluxed
and pressure tested just to verify its usability. test the heads at same time too.

[brotherGood]

So, when I first got the engine (engine first, then car ironically) it had been sitting uncovered in a barn (section without a roof) for about 15 years. Due to that, the pistons were stuck, one cylinder wall had cracked, you name it. The *first* machine shop it went to, was solely to see if it could be saved. Short answer was, yes. Overbore and 2 sleeves (and about 10 months) later, I picked it up from the first shop. The first shop was also to assemble it, but it was never prioritized.

I took it to a second shop to have them assemble it. At that point, I also dropped the intake off to them to have them check it. They said it was all good and then ran into the rod/piston debacle.

While I don't have a reason to believe the block & heads are suspect, that same reasoning is what has me questioning the block height issue leading to compression & internal vacuum leaks.