Author Topic: cam selection  (Read 1912 times)

Offline Cliff Ruggles

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Re: cam selection
« Reply #30 on: October 07, 2019, 04:20:30 AM »
Tough call there.  Wider LSA will idle better and slightly broader power range and peak cylinder pressure slightly.  I think you'd be OK either way......Cliff

Offline tayto

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Re: cam selection
« Reply #31 on: October 07, 2019, 07:06:27 AM »
I'm running tbi heads, apparently they start to run out of steam around 4500 rpm if that helps?

will the 112* help more with my higher compression?

Offline Cliff Ruggles

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Re: cam selection
« Reply #32 on: October 07, 2019, 09:19:07 AM »
It will add some overlap but also close the intake early if you put it at 108ICL.

Sort of a trade off, but I think I'd go 112LSA with those heads to pull power down slightly and tighten up the power curve for the RPM range.....

Offline lightning boy

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Re: cam selection
« Reply #33 on: October 07, 2019, 10:09:31 AM »
The GM845 cam would be a good choice for you as well if your running a late model block with a step nosed cam. they ran alot of these in 350's making good power. they have a fuel pump lobe.

Offline tayto

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Re: cam selection
« Reply #34 on: October 07, 2019, 11:28:25 AM »
The GM845 cam would be a good choice for you as well if your running a late model block with a step nosed cam. they ran alot of these in 350's making good power. they have a fuel pump lobe.
I believe cam is discontinued but crane still grinds it. Too bad crane thinks their cams are made out of gold, over $600 canadian, howards cam is $380.....I was also told by a fellow that played around alot with TBI heads that they really like straight pattern cams and to not have more than a 5* split in duration. The Howards cam fits this bill and is 10* more than the TPI cam thay Cliff recommended.

Cliff, I assume the 108 is already ground into the cam when installed "dot to dot". I could figure out when the intake closes and check my dynamic compression. I could install it "straight up" on a 112* ICL??

Offline lightning boy

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Re: cam selection
« Reply #35 on: October 07, 2019, 01:26:05 PM »
they are $219.00 at jegs.
I had the 847 cam years ago and it was a steel billet core.

Offline tayto

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Re: cam selection
« Reply #36 on: October 07, 2019, 05:02:35 PM »
not sure what part number you are searching but the crane # is 109821 and it's not cheap.

Offline lightning boy

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Re: cam selection
« Reply #37 on: October 08, 2019, 03:14:15 PM »
Sorry, your're right thats the wrong part #
However, they are still available at GM performance for $300.00
part # 24502586
214/224 488/500 lift on 112 l/s angle
these are nice cams on a hot 350
I believe they are on a billet core.

Offline Cliff Ruggles

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Re: cam selection
« Reply #38 on: October 08, 2019, 04:38:27 PM »
I wasn't even aware that GM made any roller cams on billet cores.  Do they specify this someplace in the specifications?.....

Offline tayto

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Re: cam selection
« Reply #39 on: October 08, 2019, 08:49:31 PM »
that's the LT4 hot cam, duration is 218/228. I actually HAVE one brand new but its SUPPOSE to go into my buddies boat....

Offline Cliff Ruggles

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Re: cam selection
« Reply #40 on: October 10, 2019, 02:16:56 AM »
The LT4 "Hot" cam is excellent.  I've used them here a number of times in the 1987 and later blocks.  It's a drop-in for over 1hp/CID depending on heads used. 

I customer recently used my basic "recipe" to build his 355.  His used Trick Flow heads, 64cc chambers, quench at .035", flat top pistons, GM LT4 cam, high ratio rockers, factory iron intake, Q-jet, HEI and good set of headers. 

He brought the vehicle here for custom tuning as the Q-jet he built for it was down about 15 HP to the shops dyno mule Quick Fuel carb.  I found a few issues with the Q-jet and got it up to par for the combo.  We took the vehicle out and it was an "animal".  Very impressive for a "little" 355 build and had excellent street manners as well.........Cliff

Offline tayto

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Re: cam selection
« Reply #41 on: October 10, 2019, 07:05:12 AM »
I am worried it may be to much cam for the TBI heads? The heads don't need much over .450-.500" lift. I could just run 1.5 roller rockers and I will need to upgrade my valve springs.

Offline Cliff Ruggles

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Re: cam selection
« Reply #42 on: October 11, 2019, 04:09:57 AM »
The early Vortec heads were excellent for low and mid-range power. 

I've used them on 350's for towing applications and they make the grade well there.  Never tried or even considered using them in a "high performance" application where upper mid-range and top end power was part of the equation.......Cliff

Offline tayto

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Re: cam selection
« Reply #43 on: October 11, 2019, 06:16:11 AM »
The motor is for towing /hauling that is why I went with the TBI heads. If you think the LT4 hot cam is a good choice then I will use it especially because I already have it. My compress is 10:1 so I am definetly not "stock" any more. If not I will go with the Howards cam as it seems to match nicely with what we originally talked about. Thanks Cliff.

Offline Cliff Ruggles

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Re: cam selection
« Reply #44 on: October 12, 2019, 04:01:19 AM »
Towing/hauling requires a cam with smooth idle and strong power right off idle and in the lower RPM range.  The LT4 cam even in a 350 build even at 10 to 1 compression will be a little "soft" below 2500rpm's but really come on strong in the 3500-4500rpms range with those heads....IMHO.

I'd rather see you use a smaller cam and pull the power down a bit.  It's not going to need a lot of timing any place but will make great power and be fine with custom tuning on pump gas.

WAY back when my dad's 1991 350 HD truck engine cracked a piston at 240,000 miles we bored in .030" and put flat tops in it, and the stock early style Vortec heads.  I replaced the flat cam with one we had here from a late 1980's 305 IROC Z-28 engine.  Going from memory it was a pretty small cam without much lift.  It ran flawlessly with the higher compression and made butt-tons of low and mid-range power.  It also kicked the fuel economy up to about 16-18 average and it would get over 20 at times on the highway if you drove it like you had some sense.

It was pretty darned impressive to all of us at it's towing capabilities.  He had a huge steel horse trailer and would load it up with 4 mules and all the gear, plus put another trailer behind it with his covered wagon on it.  The truck was a 4 x 4 HD 3/4 ton with a NV-4500 trans and 3.73 gears.  It yanked that deal around with great authority for a "little" 350 engine. 

Prior to the engine upgrades it did OK but you were really having to run the "bag" off of it to get up to speed or in hilly country.  He ran with a bunch of "high rollers" with big diesel rigs and was able to keep up with them without a lot of trouble with the new engine.  Just amazing to all of us how much better one of these engines does with some compression in it and cam/heads targeted for the RPM range it's going to be used in.......Cliff
« Last Edit: October 12, 2019, 04:08:42 AM by Cliff Ruggles »