Tail_Gunner

have gotten the bug. There is no better way to describe it. Here is what i am working on, a 2001 volvo brand a 4.3 gm pushrod. It is all factory and my goal is of course higher speeds without to much sacrafice. After a lot of research and I-net gabbing i do believe i have some sort of plan, one that will give me higher speeds and not much of a down side. This is what i have to work with and again its all stock. TBI with 2" bore's...mated to a stock 4 barrel manifold...there is some kind of spacer that bridges the gap. The heads are 113 or L-98's in a cast material...counter balanced motor and i cannot find anywhere the stock cam profile for this motor.. http://www.volvo.com/volvopenta/na/...ion_engines.htm Engine 4.3GIPEFS Production period 1999-2000 Operation 4-stroke Cylinder configuration V-6 Bore (in.) 4 Stroke (in.) 3.48 Compression ratio 9.41:1 Displacement (cu. in.) 262 Power (hp) 205 Max engine speed (rpm) 4400-4800 What i intend to do is as follow's CS XM 270 HR-12 Basic Operating RPM Range: 1,200-5,200 Intake Duration at 050 inch Lift: 218 Exhaust Duration at 050 inch Lift: 224 Duration at 050 inch Lift: 218 int./224 exh. Advertised Intake Duration: 270 Advertised Exhaust Duration: 276 Advertised Duration: 270 int./276 exh. Intake Valve Lift with Factory Rocker Arm Ratio: 0.495 in. Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.503 in. Valve Lift with Factory Rocker Arm Ratio: 0.495 int./0.503 exh. lift Lobe Separation (degrees): 112 Springs: COMP Cams 26918-12 Retainers: COMP Cams 787-12 Locks: COMP Cams 611-12 As per this article: http://www.carcraft.com/techarticles...ade/index.html Keeping the stock TBI and manifold And having OBD flash a new maps for the changes....MEFI-3 prom Opininos and suggestion are welcome... Opps that is what i have to work with

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dimented24x7

Sounds like it should be a fun setup. Do you have any plans to port the heads? If there like the L-98's, they could benefit from some porting and polishing. Also probably wouldn't hurt to check to make sure they really can accomodate teh lift of the cam and replace the pressed in studs if they use them on those heads.

The delphi MEFI-3, how are those set up? Is it like the later OBD PCMs where it has to be reflashed? I assume it is. Be a neat setup to use in a car. Late model flashable PCM that can still drive TBI injectors and use the older distributers.

Tail_Gunner

Opps i will need to a bit more careful here. The heads appear to true vortec heads cast 12557113 and with fulcrum rocker's... Never seen them before..but it has been more than a few years since i opened up a engine. That might change things a bit..i will have to call Comp Cams to find out

Ive done a lot of research on this and i will tell you it can be a bit confsueing. When i saw the 113 i just assumed they were L98 heads...I was also under the impression you cant mate a tbi intake to vortec heads?

As to the MEfI-3 yes it has to be flashed, for now i will have OBD 11 flash a new map, Way to much to learn in the time span i am using for this mod. Distraction's poping up all over such as this thread...http://www.chevytalk.org/fusionbb/sh...hp?tid/205486/ I must be missing something here doesnt the ecu control the timing curves..

Damon

Yes, they are "Vortec" heads but are the V6 variety, which means there are differences. Right off the bat, they use a different style of rocker arm/stud than any of the V8 Vortec heads. They have screw-in 10mm studs and matching rockers. The valvetrain is non-adjustable (V8 Vortecs are adjustable). Won't work with anything from a V8. You can buy 10mm-to-3/8" conversion studs and then you can use V8-style self-aligning rocker arms. Those studs ain't cheap, though- on the order of $100-120 for a set.

That's just about even money vs. having the heads machined to take standard V8 studs + guideplates which then allow you to use plain old V8-style non-self aligning rocker arms of your choice. It's really a toss-up cost wise. I went this route- having the heads machined for standard V8 studs and guideplates and then used a cheap set of stock non-self aligning rockers. Because I had guideplates I also had to spring for a cheap set of hardened pushrods to work with them (stock sticks wear out quickly against guideplates).

Or you could just keep using the stock V6 rockers/studs as-is and cross your fingers that the (non-adjustable) stock rocker geometry is close enough to work with your different cam. In my case I didn't want to risk it nor did I want to live with a non-adjustable valvetrain in the long run anyway.

None of that addresses the other issue you will have, though- those heads won't take the lift of that cam. The retainers will hit the stock guide seals around .470" lift. You'll want to have some machine work done to open up the clearance. I had it done at the same time I did the stud + guideplate conversion.

Once you've gone through all this, you're golden. But getting there will cost a few bucks. Still, probably a cheaper/better alternative than going backwards to non-Vortec stuff (which means the cost of different heads AND intake, plus still throwing some money into the machine work).

Tail_Gunner

You mean these i presume...




Part Number:ARP-100-7201Base Thread Size:M10 x 1.50mmRocker Arm Nut Thread Size:3/8-24 in.Guideplate Locator Shank:YesRocker Arm Nut Thread Length (in):0.580 in.Effective Stud Length (in):1.595 in.Base Thread Length (in):0.580 in.Quantity:Sold as a set of 12.

There $50.00 scoots.

Using the new Comp cam behive spring along with those stud's should allow lift up to .550??

http://www.carcraft.com/techarticles...ade/index.html

Here are some actaul photo's of the bracing






I have never seen those alum rods or bracing..It's been that long..Updated again. It seems that is a design from a LS head design..Mybe they are a L-98 head. If anyone knows what i have here your input would be greatly appreciated...from what i understand now is i either have a L-98 head with there some kind of rail system or a vortec head with a L series valve train mod..

Damon

That's stock 4.3L V6 Vortec valvetrain gear. It's just totally different than V8 Vortec stuff.

Yes, those are the studs I was talking about. When I looked at them they were $50 for only 6.

A Beehive spring/retainer upgrade should work on a V6 Vortec head exactly like it does on a V8 Vortec head. Not sure I'd push them as far as .550, but certainly .500 is very safe. Just watch the cost on that upgrade.

There's nothing necessarily wrong with the stock valvetrain in a modest performance application except it is non-adjustable. If you find the rocker geometry/lifter preload is not close to exact when you drop in the new cam you have no option but different length pushrods (possibly custom length pushrods) to fix the situation.

dimented24x7

I think they use those on a lot of (or maybe all) the pushrod V6's. Im pretty sure my 3.5L uses those same rockers/studs.

Tail_Gunner

There gone just as 2000 has come and past....But i have a very serious question for the TBI guy's have guys ever looked at your timing curves,,aka this thread... http://www.chevytalk.org/fusionbb/sh...hp?tid/205486/

I am tired of hearing people say this. ITS NOT THE HEADS PEOPLE. The TBI engine actually peaks at a slightly higher RPM than the 70s smog heads used before them. Guess what they have the same cam and same exhaust setup. The weakness in the TBI engine is the cam, exhaust, and factory prom tuning. Even the factory intake and TBI are not much of a restriction until you have passed 280 flywheel HP.

For those of you noticing a fall off of power after 3,500 rpm on even a stock TBI engine in good shape, pop off the distributer cap and look at the ignition control module. If its a stock GM module, look at the numbers inscribed in it. You will either have 048 or 369. The 048 is a TERRIBLE module to have as it will pull a ton of timing over 3,500 rpm. The 369 will actually add a 2* of timing advance over 4,000. The 048 was like a built in rev-limiter, the 369 was used in performance applications and applications that needed upper rpm performance. TPI Camaros/Firebirds and TBI Fullsize Vans and 9C1 cop cars came with the 369 module. TBI Trucks and Civilian B-cars as well as TBI F-cars came with the 048 modules.


Is that old news...I am dealing with so many little trivia bs items on marine stupidity i have not had the time to check into that issue.