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Old 07-31-2013, 11:32 AM
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cam help

hello i hate asking a question that has been put to death already but here it goes. i have a 94 suburban tbi putting in a 99 vortec block hydraulic roller heads and need a mild cam it pulls boats and goes on camping trips it has a edelbrock rpm manifold on it and it will remain tbi.I figure while the motor is out and heads are off of i might as well drop a cam in it still looking for good idle quility and help is welcome. thank you

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Old 07-31-2013, 09:35 PM
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go about 8º more duration and .040 more lift.keep the lda close to original and maybe advance the cam 2º
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Old 08-01-2013, 10:41 AM
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Quote:
Originally Posted by mbwhat View Post
hello i hate asking a question that has been put to death already but here it goes. i have a 94 suburban tbi putting in a 99 vortec block hydraulic roller heads and need a mild cam it pulls boats and goes on camping trips it has a edelbrock rpm manifold on it and it will remain tbi.I figure while the motor is out and heads are off of i might as well drop a cam in it still looking for good idle quility and help is welcome. thank you
Here is a list of the best factory roller cams that work with all forms of the OEM EFI systems without having to install chips on OBD I systems or programmers on OBD II.

The durations measured at .050 lift. Total lift at valve measured with 1.5 rockers, add 7% for 1.6 ratio rockers.

- 10241264, 1996 Vortec 190/.414 intake; 195/.412 exhaust; LSA 116. (The Vortec cam will run with 1.6 rockers without problems)

- 14093643, 350 TPI 87-94 roller 202/.403 intake; 206/.415 exhaust; LSA 115

- 12551705, 350 LT1 93-95 roller 201/.447 intake; 208/.459 exhaust; LSA 117 (TBI loves this cam because of the 117 LSA it will also accept 1.6 rockers without issue)

- 12551142 350 LT4 95-97 LT4 203/.446 intake, 210/.450 exhaust; LSA 115 (with more duration and lift with less LSA this cam is a bit edgy with the stock programming, especially if mixed with a 1.6 rocker)

Stay away from the temptation to use the Ramjet cam, although the timing and lift is in the ball park for TBI at 196/.431 and 206/.451, the 109 degree LSA makes it unsuitable for TBI without a new program in the chip.


These cams are right around the upper limit of timing and lift that allows the best fuel mileage and power combination whether injected or carbed. Shorter cams may improve mileage but cost power, larger cams improve power but cost more fuel.

These cams are also a guide for duration, lift and LSA when looking at aftermarket cams for similar performance. Lobe Seperation Angle (LSA) is very important with EFI cams, this controls or expresses what will be the effect of overlap for a given lobe duration. Short LSAs bring the lobe centers closer together which increases the overlap while reducing manifold vacuum. Wide LSAs stretch the distance between lobe centers which reduces overlap, increasing idle vacuum. Factory EFI likes a lot of idle vacuum so you want a cam with LSAs of about 112 to nearly 120 degrees with total durations not exceeding 210 degrees on the intake and 115 on the exhaust. Keep the lifts under .5 inch at the valve.

As a data guide, these cams tend to bracket the timing of the old 300 horse, 327 cam. However, getting 300 horses from a TBI requires larger injectors which will also drive a custom chip as larger injectors increase fuel flow everywhere while the added fuel flow is only needed at WOT in the higher RPM bands, so a new on-off schedule needs to be programmed.

Bogie
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Old 08-01-2013, 01:57 PM
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ABout Bogies cams.

The 203º/210º 0446"/0.450" witth 1.5 rockers 0.476"/0.480" with stock 1.6 roller rockers on an 115ºLSA. was used in the 1996 Corvette with manual transmissions and around 105 1997 LT4 SS Camaros and 33 1997 LT4 Firehawks.

The GM MArine cam is also used on the Ramjet 350 crate engine which uses speed density injection which is the same speed desnity as the TBI system uses. This same cam is also used in teh HT383 crate engine and the HT383 E crate engine kit ofr use in 1996-99 Vortec 350 equipped trucks and SUV's.
It does jhave a 109ºLSA but I ocntend that it does pull lots of vacuum for speed density use.
Its my opinion that any cam change should have a chip change for maximum performance benefit.

There were stock GM trucks that used an L31 Vortec longblock with TBI injection on top. Thats where the GMPP TBI/Vortec conversion intake came from.
Supposedly it used Broad Cast Code or BCC BRDW. It was use3d in 1996 G35 1 ton Vans and some Mexican Export 1996-1997 trucks.
Intake part number 12496821 $369 at Jegs.

I can attest that the 1996 LT4 roller Production Corvete camshaft works well in a TBI truck, esp with the Vortec heads.

peace
Hog
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Old 08-01-2013, 02:23 PM
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I have the 96-00 vortec 350 cam,springs new crate take out if interested.
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