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help me to choose a cam for my K10

G

GMC500

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hello all

I have a 1986 GMC K10 with stock tired 350 :D
and I am building a carbed LT1 motor for it
it will be mostly stock + 0.03 overbore + home ported heads + cam + valve springs
I will use stock intake / exhaust manifolds temporarly then I will add some long tube headers
the truck has 33" tyres + stock sm465 + stock 10 bolts
and I don't know what is the rear-end ratio ( I will open the cover to inspect it since the RPO codes sticker is missing ) >>> what is a good ratio for 33" tyres ??? :confused:

it is used for sand dunes climbing + some daily driving


so what cam do you recommend ?

http://store.summitracing.com/defau...utoview=sku&part=CRN-113941&Ntk=KeywordSearch

http://store.summitracing.com/defau...4294887485+4294840140+4294887540&autoview=sku

http://store.summitracing.com/defau...4294887485+4294840140+4294887540&autoview=sku

any input appreciated

thanks
 
HMMM... its hard to say. from what I know about Lt1 engines id that the heads dont make as much torque till higher up the band (dont hold me to that) and I dont even know if a regular cam will fit. Lt1 should be roller cam, and in that case I would buy a gmpp roller cam, like I did for my stroker. bought it unused NIB for 50 bucks on ebay. even brand new they dont go much over 100, with out lifters of course. in anything you will want the cam with a lower powerband unless you wheel at 3000 rpm

Ideally if you havent worked on the lt1 any, I would get a vortec motor. got mine with heads and roller equipment and 1 pc rear main, and its nice stuff. I dont know how you would get the reverse cooling to work though. I haven't really thought about it much...
 
you are talkin about the lt1 from 92-97 right?

you cant use the stock lt1 intake as far as i know. the lt1's have reverse flow, where coolant enters the heads first and then through the block. also requires an lt1 specific water pump. since the water pump drives off the front of the cam it requires a roller with a stepped nose (for the retainer) and a lt1 specific dowel in the end of the cam (just longer i think). because of the water pump it will also require a lt1 specific belt drive (serpentine or other aftermarket set up). gm sells an lt1 specific intake that allows a q-jet and regular dist (just make sure the drive gear is compatable with the cam you run.

now for my two cents. the new style lt1's use a hyd. roller. i would use a roller cam with about 210 degrees at .05 and about 265-275 degrees advertised. with about .500 lift intake and a little more on the exhaust. pretty sure that most cam companies have a cam just like that. or like this one:

http://store.summitracing.com/defau...4294887485+4294840140+4294887540&autoview=sku

ryan
 
actually I will use LT1 heads on a SBC block
yes yes :D everybody will say it won't work but it has been done before

http://www.thirdgen.org/techbb2/showthread.php?s=&threadid=178262&perpage=75&highlight=&pagenumber=1

the reason that I used LT1 heads on SBC block is :

* I live in the Middle East and shipping charges are too expensive especialy for heavy parts like heads

* LT1 heads are pretty cheap here :D ( L98 heads are alot more expensive than LT1s and getting rare ) and welding+machining is cheap also

* I don't want to use a complete LT1 engine because I'll have to buy all brackets + accesories +different radiator + starter + EFI pump + EFI fuel tank since LT1 doesn't have a mechanical fuel pump


so what I have now is stock 350 ( non-roller ) waiting to be rebuilt+ modified LT1 heads

so I will buy a cam+springs+headers and I'll use stock 350 intake manifold till I have some money to buy after market one

neverendingproject said:
HMMM... its hard to say. from what I know about Lt1 engines id that the heads dont make as much torque till higher up the band (dont hold me to that) QUOTE]

thans right
but its bacause of the intake manifold design not the heads
Click to expand...
 
aside from the fact that the lt1 heads are alum what performance benefit do they have? iron vortec heads have the same intake ports/combustion chamber and exhaust port. the iron head lt1s had the same compression as the alum head lt1's and made 15 less hp.

5.7l iron head lt1 260 hp caprice motor 10.4:1
5.7l alum head lt1 275 hp f/y body 10.4:1
5.7l iron head vortec 260 hp c/k/g trucks 9.3:1

and they all have similar cam profiles.

why go through that much work unless you had a free set of lt1 heads?

the only drawback of the vortecs is they require machining if lift exceeds about .480 lift

ryan
 
ryan22re said:
aside from the fact that the lt1 heads are alum what performance benefit do they have? iron vortec heads have the same intake ports/combustion chamber and exhaust port. the iron head lt1s had the same compression as the alum head lt1's and made 15 less hp.

5.7l iron head lt1 260 hp caprice motor 10.4:1
5.7l alum head lt1 275 hp f/y body 10.4:1
5.7l iron head vortec 260 hp c/k/g trucks 9.3:1

and they all have similar cam profiles.

why go through that much work unless you had a free set of lt1 heads?

the only drawback of the vortecs is they require machining if lift exceeds about .480 lift

ryan
Click to expand...

vortec heads are rare and expensive here
and I agree with you
they are similar to LT1s in performance
 
i just read most of that thread on thirdgen, and im still very very skeptical. looks like too much work to me. i have to give some credit, looks like it would work ok, but why try to reinvent the wheel?

it seems to me more vortec trucks were built in one month than one year of lt1 production.

ryan
 
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