Mystery Motor Cam/Smog question

[Oakland_Jack]

Good morning all,

I purchased a used '73 (marked 'w' for year) 345 to swap into my '79 Scout II. My running motor has issues and long story short, I chose to rework the purchased motor at my leisure and keep the truck running. The new motor I refer to as the mystery motor as it came in a state of partial rebuild without info/history. I bought it from a guy who had traded it for a boat and the original guy's contact info is gone.

Anyway, all is going well with my first engine build as far as I know. That said, I'm worried about the cam in the motor as it needs to pass smog. The mystery motor came with a comp cams 260h cam.

Does anyone have info on the smogability of this cam?

This is the comp cam 260h card from their website:

Your expertise on passing smog with a bigger cam is most appreciated!

Thank you very much, jack

ps. Full disclosure, I have been writing my engine build over on bp but was advised by a trusted soul to try the experts here for the best info. This is by no means an advertisement for the other site, I just thought it was only fair to mention the other thread. Thank you for the understanding.

 

[Dealbreaker74]

Here's the specs on the cam I run in my '79 345. The great thing about comp cams is they'll grind any profile on an IH blank. So I picked one of the Chevy extreme 4x4 grinds and had them put it on an IH stick. It passes no problem using a q-jet, air pump, egr and a 2-into-1 exhaust thru a single cat. Your cam doesn't look too much different, and I'd say you'd be ok.

I also run an isky grind in my other 345 Scout. Its a '74, so smog checks don't matter anymore. But there was a time when it was tested biannually, and it too never had a problem with the same q-jet setup.

You can compare yours to see its pretty close. I seriously doubt it will have a problem.

 

[Robert Kenney]

Ohhhh, that cam is big indeed. You might be able to get her to pass with some tricky fuel calibration but I'd say step it down a notch or two. Intake duration should be close to 206@.050 or less with 112 lobe centers or larger.

If you were to chose a good smog cam the split duration isky is nice. 202/204@.050. 112 lc stick her is straight up to 4* advanced. Lemme look up the number. Isky-190125-26
should be fine with a good tune. Check out the store or give the shop a call.

 

[Oakland_Jack]

Gentlemen, thank you for the advice, I really appreciate it. I'm hearing it might work but there's a chance it won't, and safer bet is tone it down a bit. I did not choose that cam, it was a discovery that came with the mystery motor.

...so, anyone out there with a milder, new cam want to trade for a brand new (unused) comp cam 260h? I'm in the bay area...

I'm sure the extra new cam inventories in the 'I need to trade this box' are real high this time of year, it being cam season and all.

I welcome any other advice folks have, specifically folks that pass smog with a similar cam.

I have only run my stock 345 to date. Robert, how does the cam your recommend compare to stock in overall driving feel (on pavement most of the time with ambition to get off)? How does the 260h compare if I want to roll the smog dice? Any fuel economy differences going from stock to isky recommendation to 260h? Dealbreaker, how would you describe fuel consumption and power changing when you went to the cam you mentioned?

Thanks all, jack

 

[Dealbreaker74]

Well first off, Robert is right about that cam you have. I missed the intake duration. 212 is probably fine on the exhaust side, but its pretty meaty for an intake number. I'd still put it right on the line as far as passing. The numbers below sort of bear this out. There's quite a bit of leeway between the cam I have in the '79 and how much farther I could go. I would think you could land near the top of the values and depending on your carb, dial it back enough to pass.
The upside is, it'll be a real hotrod of a motor the other 729 days between smog checks!

As far as my experience goes, both trucks were rebuilt from bone stock specs. Each had about 220-250k miles. The '74 had a couple cam lobes going flat as well. Its also a t-18 equipped rig, which I think makes it a lot more spunky and snappy compared to a tf727 version. Manual trans just feels quicker and more nimble. Stock or otherwise.
Switching to the isky grind gave a real boost in low-end grunt according to the butt-dyno. I can literally dump the clutch at idle in 2nd, the rpms dip to 400, and it still pulls away. This is with 33s and 3.73s. Really feels like a diesel. It runs out of breath around 4k, but I'm fine with that. I really like this cam in this truck, but I wonder how much better things would be with the split pattern one Robert recommends....

The '79 was a 727 equipped truck. Also 33s, but 3.54 gears. I drove it like this a few years before I lost a head gasket and parked it for a couple more. When I revived it, I went with the 700r4 conversion, and the comp grind previously listed. I also zero decked the block and shaved the heads to get a true 9.0:1 compression.
This cam is also pretty mild. To really do an apples-apples comparison, I'd have to feel it behind the t-18. But my opinion is its a nice step up from where the truck was. Previously, it was a really sluggish beast. Now it gets up and goes (lower first gear helps) and will chirp the tires on the 1-2 shift. It also runs out of breath by 4k. So its about what I was expecting. Plus, it looks like it will pass smog forever based on these numbers. Except for the nox levels. That I am sure has to do with the higher compression, and the egr valve which is of unknown provenience. I am pretty confident I can tickle that as needed.

Hopefully there is something helpful in all this rambling. Keep us in the loop on your progress! Any clue how all the friggin' sand got in that thing???

 

[Robert Kenney]

Remember duration is only half of the emissions problem. The other is the lobe center line. The split duration is ground at 110 while the single pattern dealbreaker has is @ 112. The dual pattern will have more overlap and make more cylinder pressure then the 112.

If you install the dual pattern straight up it will make more hp and have longer legs. Advanced 4* I would worry about cylinder pressure being high. Run the intake at 108 or 2* advanced and I bet you love it...

 

[Oakland_Jack]

Gents,

I'm planning on going the route of Robert's recommendation, the isky split duration. I called isky (they are in CA, I was hoping they'd know about smog) and the kind fella there did not know specific performance for their cams on an IH. He said the split duration on a Chevy sb does great with smog and he thinks the IH will do the same (not that I condone comparing Chevy with IH, just passing on the good word).

I welcome any personal experiences with smogging on the isky cam with a 345 or similar. I plan to pull the trigger within a day on the purchase. If any of you were wondering what to get me for all those birthday gifts you forgot to send, this sure would be real nice!

Dealbreaker, thanks for the smog info! I see max, ave and measured. What is the allowed (the max)? I have the exact same setup,'79, 33's, 3.54, 727, 345. You know we are in a special little world when you all know exactly what that string of digits mean! Anyone that knows what that string of numbers mean but doesn't know the color of their wife's eyes...rut row.

-jack

 

[Dealbreaker74]

Yeah, kinda tough to read. I'll look for the actual hard copy. Standby...

 

[Dealbreaker74]

Took me a min to find that page. Here's what the little numbers say.

at 15 mph

Hc max allowed: 189
measured: 10

co% max allowed: 1.33
measured: 0.00

nox ppm max allowed: 1448
measured: 901

at 25 mph

Hc max allowed: 113
measured: 7

co% max allowed: 1.13
measured: 0.00

nox ppm max allowed: 1308
measured: 795

I'm looking for smog records for the '74. That one has the smaller isky. But its been well over 10 years since I've had to smog it. It would be fun to compare them, but its not looking good!

Edit- I just got done looking through the dmv website. You can access a given vehicle's smog inspection history, but it only lists pass or fail status of the test. No other details are available. The last test was in 2002, and it passed.

 

[Oakland_Jack]

Dealbreaker, thanks for the heartening numbers. You passed with lots of margin! The nox were the closest to limit but still plenty of margin. Thank you for digging that out.

I'm planning on the isky split duration. I'll stomach the expenditure...I just hope Robert doesn't try to get me to buy new pistons next!

Have a good evening all, jack

 

[Dealbreaker74]

I'm sure that cam is the way to go. Plenty of satisfied builders have used it. I went my way to be different, and its been great. But if I do another one, the isky would be my choice too.

Be careful dipping your toes in the water around here. The last one I did started as a simple head gasket....