A 262 comp cam has been recomended for use in my 350 p.u., it's 218* /224* @ .050 with a 114* LCA. Is that a good cam for use with my TBI? should I expect to have to upgrade the chip? If so, what's a good route to go on that?

Any and all help appreciated.

 

You'll definitely need a custom chip. Burning your own is the only way you will get it right.

It's my opinion that the 262 cam is too much for a heavy truck. Especially if you are keeping the stock heads (they are junk).

I'd stay around 204-208 intake duration.

[This message has been edited by Brent (edited October 04, 2001).]

 

Actually, I'm not planning on using the stock heads, I've got some better flowing small chamber heads, a performer intake (carb design), headers, flowmaster.

Thanks for your reply.

... Still think a 204* cam is the ticket?

 

Yeah I'd still stay in the 204 to 208 @ .050 range for the intake duration. Stock intake duration is somewhere between 180 and 190 degrees so anything over 200 is a sizeable jump. If you go too big, it will be a big dog off the line and it won't run up hills with out downshifting.

You haven't mentioned the trucks gearing, tire size or converter stall speed so I'm assuming everything is stock. Look at the rpms your engine spends most of its time. Thats where you need the power.

I'd get a Compcams Extreme Energry series roller cam (112 LSA). I think the 88 trucks have the roller block (better check). It will cost more but the additional lift and area under the curve is worth it IMHO.

 

Actually, that came will work better than you think with its 114 lobe sep. Should make nice vac signals at all rpms/loads. May only need some timing and fuel pressure changes, which you can try in the garage for free before buying the PROM. Just my opinion. Plus, COMP cams have pretty low adv durations which, too, will help the vac signal.

BUT, a roller cam (LT1 or LT4?) in the GMPP catalog has 114 Lobe sep, which would be nice, as suggested.

 

Just realized that is for a pickup. If you are using the truck as a pickup (ie, plonking around at low rpms) and not a sport truck (ie, racing/burning-out, high rpms all the time), I would just go with a cheapo Summit/SIS cam/lifter kit ($79?) of the 204/214 or 214/224 variety, all having 112 lobe sep. You won't need any chip work with the 204/214 cam, which has a recommended highway cruise rpm of 2200-2600rpm for best efficiency. The 214/224 cam like 2600-3000 highway cruise speed. The Comp cam you suggested will probably like 2500-2900 cruise.

 

Thanks again,
There seem to be varying schools of thought on this. Some guys are running cams of 220 in. duration (approx) with their TBI motors and seem to be quite happy with them, yet the cam manufacturers (edelbrock,comp,crane) all promise "drivability problems" with any cam over 206*.
"drivability problems" can be a matter of personal opinion, I realize. And in my opinion this truck has inherent drivability problems, it has a hard time staying in high gear on the grades. That is one of the bugs I'd like to work out of it.
With the gearing it's got, it cruises at about 1900, locked up, in overdrive.
It does ok on MPG, but it hates hills, and it's worse when I tow or carry a load.
it seems like the problem it's got is related to part-throttle response, because when the cruise control is on, the pedal goes waaay down when we hit a grade, then it shifts into third.
Doing the ultimate TBI mods. helped some, but it also confirmed my suspicion that the problem is in the engine.

So, originally my question was regarding cam and chip selection and it still is, but perhaps it should be reworded as;
Can the drivability problems mentioned above be corrected with the proper selection of a cam/ chip?
As I've mentioned, ultimate TBI has been done to it, I took it in for a diagnostic and it's working the way it's supposed to be. Full throttle, it's fine.

It's a truck, I use it for work, mainly.
350 w/ TBI, TH 700 auto, right now, it's stock but I've got some heads for it and it's getting a cam and headers also, a chip if I need it.
But right now , I'm wondering about this "drivability problem" and whether or not that is something that is still going to be there after my mods are completed.

Hope this isn't too lengthy or vague.
Thanks for helping.

 

Some more on that;
I'd really like to get into a discussion on this and I'd be happy to provide more info if nessecary.
I've got some background with carbs, but not with EFI and the associated problems.
I'd like to do as much as possible to get the project to work out right the first time.
I'd like to hear some more on burning chips too (Brent ..if you're still there)

thanks

 

Anything you do that lowers torque at 2000 rpms and under is gonna make the hill climbing problem worse unless you change your final drive ratios. Increasing intake duration will lower your torque at those engine speeds.

I garantee the guys with 220 cams aren't towing at 1900rpms. I'm now thinking you should stay under 200 degrees on the intake.

Its either that or run more cam and down shift or step up to a 383.

Really the problem is overdrive is such a tall gear it really isn't intended for towing up hills. In fact, my C2500 owners manual says to select drive when towing in hilly areas...

I'd suggest talking with speed shop that builds engines for towing and get their input.

 

It's the tranny that does not like 4th gear towing.

As others and I stated, you will HAVE more problems with even a moderate cam change in OD while towing with your existing gear ratio. That is why I stated the appropriate RPM cruise rpm's for your highway driving and to pick the cam accordingly. In theory, if you came to me, I wouldn't change your cam because of what you told me about how you use your truck. I WOULD, however, suggest a gear ratio change OR smaller tires if they are huge (to get your highway OD rpm's between 2200-2600) and the 204/214 camshaft, along with some minor Prom changes, perhaps, that would mainly deal with spark parameters.

Trust me, if you change your cam/intake, you will not be happy with your existing setup. Things WILL get worse. Trucks are a whole 'nuther animal from a car. I have a Wrangler with a 350 so I know where you are coming from.

 

No doubt ... could be the gears.
I've got 3.73s w/31" tires, that puts me at 2500 or so @ 60 in drive.
The answer: downshift!
That's what the trans keeps wanting to do anyhow.
Thanks

 

.... back, I was pressed for time on that other computer and had to close.

I've had great success using cams in the
204-210 (int.@.050) range in chev pickups that I've built in the past, and I'm thinkin that's what I'll stick with.
I'm used to carbs and smog exempt engines, so some of the new rules had me thrown off a bit.
The XE-262-H comp cam was suggested by one of the other guys, based on a higher CR and may have been a good choice.
Robert, if you're reading this, it isn't that I doubt you, I've opted to use my stock short block with dished pistons, which ought to lower the CR to 8.5 or 9:1, depending upon the deck height and such. That should put me in the ballpark for that smaller cam. Considering my lack of experience in burning proms, I have more confidence in my ability to handle whatever problems might come up.

This is an experiment for me.
Thanks to everyone for the feedback.



[This message has been edited by 88tbi4x4 (edited October 08, 2001).]

[This message has been edited by 88tbi4x4 (edited October 08, 2001).]