pre-1994 engine mods - Chevy Impala SS Forum
 
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post #1 of 7 (permalink) Old 02-28-2001, 07:58 AM
kdrolt
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For owners of TBI-equipped LO3 and LO5 engined cars looking for more, check these out:
http://users.ev1.net/~sdbuss/mycar.html http://users.ev1.net/~sdbuss/index.html

Briefly, the owner rebuilt his 350. His first cut used the 65# injector TBI (i.e. the one used in TBI on LO5 9C1s) and an unknown cam, and Vortec heads and he ran 13.6 @ 100 mph on skinny 225 tires with a bad trans. With a hotter cam, better tires, and the 85# (454 truck) injectors, he figures to run deep in the 12s.

Using a Bcar to Fcar rule-of-thumb, the weight difference is some 600 to 800 pounds, so the ET difference will be about 0.6 to 0.8 seconds. That would be high 12s or 13.0, and that's EXACTLY the kind of times 94-96 Caprice/Impala owners are running using the LT4 HOT cam (specs very close to the ones used in the above engine).

The main point of this post is to show that TBI-car owners have used the bigger injectors plus Vortec heads, plus a cam swap, and gotten tremendous results.

I don't advocate the LT4 HOT cam unless you really know how to tune your car, and you are willing to give up some low speed torque. But I do advocate a moderate cam swap, say using the stock Bcar LT1 roller cam at the minimum, and up to the stock F or Y LT1 cam (nearly the same as the stock LT4 cam).
Remember that the LT4 engine was rated at 340 fwhp and 350 ftlbs, and the new Ramjet 350 (w/iron Vortec heads, and using a cam that's in between the Bcar and Fcar LT1 cam specs, i.e. it's a MILD cam) is rated at 350 hp and 400 ftlbs.

You don't have to use a hot cam; you can keep the torque needed for the Bcar and still have better-than-LT1 power. The key is in the heads, and hence the use of the 96-99 Vortecs. HTH, FYI. - Ken '94 9C1

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post #2 of 7 (permalink) Old 02-28-2001, 01:23 PM
sar_moby
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Ken- thanks for the info. My 93 LTZ L05 uses 55lb/hr injectors and responded well to AFR and air box mods. For future ref. is the cam on LTZ vs. 9C1 different and would 1.6 rockers improve the stock cam without needing a cam swap?(I understand that Dave Green recommends a std. LT4 cam, not the hot LT4). Will the ECM handle 65lb./hr injectors if I were to install them? Since I am in Ca. I worry about passing smog w/mods to the engine that are not easily reversible. I have 54K on the car(original). Your thoughts are welcome - Scott
post #3 of 7 (permalink) Old 02-28-2001, 02:28 PM
kdrolt
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<BLOCKQUOTE>quote:</font><HR>Originally posted by sar_moby:
Ken- thanks for the info. My 93 LTZ L05 uses 55lb/hr injectors and responded well to AFR and air box mods. .... Your thoughts are welcome - Scott<HR></BLOCKQUOTE>

a) is the cam on LTZ vs. 9C1 different?

Yes. The cam and the slight exhaust differences are responsible for the 180 vs 205 hp differences from the civvy LO5 and the 9C1 LO5. I think the 9C1 cam is an Fcar TPI cam. Chris McCabe posted on this exact item recently on the 9C1 digest. You can probably search for it using his name. The digest is from [email protected] or something like that.

b)... would 1.6 rockers improve the stock cam without needing a cam swap?(I understand that Dave Green recommends a std. LT4 cam, not the hot LT4)?

1.6 rockers would improve the lift of the stock cam, and hence cylinder filling, but not by that much. I suppose you could justify the $65 cost for 1.6 stamped self-aligned rockers and the small time effort needed to install them -- it probably would be worthwhile. Small money, worthwhile perf gain. BUT to compare, then you would have to look at either a used Fcar roller stock cam, and/or the LT4 cam (nearly the same specs). That's the same cost (used) or double the cost (new), as the 1.6 rockers. You'd have more effort to do the cam swap, but far greater perf results.

I guess the real way to answer this question is how much improvement in perf do you want? Do you want to equal (or better) a 94-96 LT1 car? If yes, then you need to change the cam at the minimum, and the cam+heads at the very best. We're also still talking inexpensive stuff too.

c) Will the ECM handle 65lb./hr injectors if I were to install them?

Probably, but the way to be sure is to see if the ECM pns are the same for the 93 LO5 LTZ and for the 93 LO5 9C1. If the p/n is the same, then the answer is definitely yes. If the p/ns are different, then it would still work but not optimally. It might be easier to get a junkyard 92-93 9c1 chip.

As far as passing smog tests, that's really a matter of having near-optimum combustion and cat(s) that work. Your car is low mileage so the engine is probably tight. Better heads (Vortec e.g.) would help combustion; 1.6 rockers would help cylinder filling but probably wouldn't alter the emissions at all. I suppose the cylinder filling might be a bit better with 1.6s, so you might have to tweak the fuel pressure up a bit to avoid leaning the mixture out.

AT the very least you could take your engine and bring it right up to smog-legal '93 9C1 LO5 spec, with a similar cam, 65 lb injectors, and either the your present ECM or the 9C1 ECM 9depending on the answer to item (c) above. You could also mod the intake and exhaust for better breathing and up the fuel pressure a bit to help.

Any mods beyond that CAN be tuned to easily pass smog (better performing engines are almost always lower emission engines) but TUNING the engine to get it right might become an issue.

If you are a novice, then you have two choices: learn a lot from a local-to-you CA-based Fcar owner (learn from what s/he did to pass smog, and duplicate their setup), or stick to the minor mod stuff. IMO and HTH. - Ken
 
post #4 of 7 (permalink) Old 03-02-2001, 04:40 PM
sar_moby
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Ken- Many thanks!
Ok the 9C1 has a L98 cam. I believe a LT4 is similar and should work well w/the L05. A few questions in the event that I commit to some changes to the motor.
1.Are new roller lifters req'd? Springs?
2. If I pull just the intake manifold(currently leaking a little coolant) to swap to the LT4 cam, timing set, rockers(?), lifters(?) what other mods? port the manifold? and/or switch to the Holley TBI?
3. what are the exhaust differences LTZ to 9c1?
4. Has anyone done any air flow work on the stock heads( not Vortec) to increase HP?
Once again, many thanks
post #5 of 7 (permalink) Old 03-03-2001, 09:55 AM
kdrolt
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<BLOCKQUOTE>quote:</font><HR>Originally posted by sar_moby:
Ken- Many thanks!
Ok the 9C1 has a L98 cam. I believe a LT4 is similar and should work well w/the L05.


Agreed.

A few questions in the event that I commit to some changes to the motor.
1.Are new roller lifters req'd? Springs?


New roller lifters? Not likely, unless you have a really high mileage engine. It's always been said that the lifters should always be changed when doing a cam swap on a flat-tappet lifter engine --- but that's not the case on a roller lifter engine.

Springs? I'd say yes. They are relatively cheap, and you will be going with more lift so it's better to have springs suited to the job, either using GMPP or aftermarket. IMO.

2. If I pull just the intake manifold (currently leaking a little coolant) to swap to the LT4 cam, timing set, rockers(?), lifters(?) what other mods?

Rockers? My suggestion to others that are budget minded is to wait on changing the rockers because that can be done ON the car later, as money permits. Or opt for the inexpensive self-aligning stamped steel 1.6 rockers (around $65 for a set).

Other mods at the same time? Go to http://www.thirdgen.org and check out the ultimate TBI mods including the adjustable fuel pressure regulator (FPR).

[B] port the manifold? and/or switch to the Holley TBI?

Look for any casting flash in the manifold and clean it up with either a Dremel or with a file. Holley TBI? Nah. If you do anything, use the higher rated injectors. If you need more airflow later, you can always either bore your TBI for the larger throttle discs OR put the Holley on. See the TBI archives on Thirdgen for this type of info.

3. what are the exhaust differences LTZ to 9c1?

AFAIK, the 9C1 gets the bigger Ypipe, and a lower restriction cat. I don't know if the LTZ gets the same. You'd have to check the Bcar Parts Bibles, or call and ask Dal.

Or maybe someone here knows (?)

4. Has anyone done any air flow work on the stock heads( not Vortec) to increase HP? <HR></BLOCKQUOTE>

On a Bcar head, dunno. On an Fcar LO3, yes. The links are at ThirdGen, and well worth seeing how they did. Did it help? Yes. Was it as good as going with either Vortecs or aftermarket? No but a very good learning experience, and for the truly cash-strapped (or married ), possibly the only way to go &lt;g&gt;. IF you wanted to stay cheap, then you could do all the easy cheap stuff suggested by Vizard: back cut all the valves, use anti-flow-reversion rounds on the valve lip, and some basic pocket porting. That's all "free" torque and hp you free-up. You'll feel the difference too, but not by as much as by using stock untouched Vortecs. So it boils down to a cost choice, and a question of how much more performance you want.

If you want nothing more than exceeding the base 9C1 LO5 (205 fwhp, 300 fw ftlbs) up to the 220-230 range, then the cam, TBI, exhaust, cold air intake, and head cleanup will be enough... and maybe even a whisker more.

OTOH, if you want a solid and easy-to-get 260+ hp and 330+ ftlbs, then you want ***at minimum*** a cam equal to, or above, the Bcar LT1, the Vortec heads, and TBI mods enough to provide the fuel needed to match the airflow you'll be getting. HTH. - Ken
post #6 of 7 (permalink) Old 03-04-2001, 07:20 AM
deanstud
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So is all this applicable to an 85 LM1? I was planning on a ZZ4, since I have a carb, but then switched to ramjet because I like the out of the box FI. BUT if I can just put on Vortech heads and an LT4 cam and beat my LT1 in the power dept., I will have a professional 'tune' my carb with the $ I would save...

------------------

-Dean E. Chandler
'91 & '96 9C1's
Cornelius, Oregon
[email protected]
post #7 of 7 (permalink) Old 03-04-2001, 08:29 AM
kdrolt
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<BLOCKQUOTE>quote:</font><HR>Originally posted by deanstud:
So is all this applicable to an 85 LM1? I was planning on a ZZ4, since I have a carb, but then switched to ramjet because I like the out of the box FI. BUT if I can just put on Vortech heads and an LT4 cam and beat my LT1 in the power dept., I will have a professional 'tune' my carb with the $ I would save...
<HR></BLOCKQUOTE>

Carb tuing can be done without a computer so that makes it easier... as long as you (or a professional) are comfortable tuning a carb. You won't be able to use the LT4 cam (or other roller cams) because it is a hydraulic roller cam, and your '85 LM1 is a hydraulic flat tappet cam'd engine.

BUT, that gives you two options: add the roller lifters (either GM or aftermarket) which would cost a few hundred dollars and use the roller cam, OR buy a brand new cam/lifter package with specs close to the LT4 cam. You should be able to buy a cam/lifter package for well under $200.

Vortec heads, cam, tuned carb, cold air intake, exhaust, and yes you will be able to equal or exceed the LT1. The only item I'll add is that the condition of the LM1 you are talking about will have a direct bearing on how well the mods work. If the engine is tired, you would be better off either replacing it with a Goodwrench engine and then do the mods, or rebuild the LM1 with mods.
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