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350 sbc power (lack of)


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I recently replaced a 350 sbc in my 1971 Z. The engine lacked power, stock low compression two bolt. I put a 350 sbc 30 over 010 four bolt in it. It has a cast crank, eagle rods, 10.4 to one kb hypert. pistons, comp cams xr288 roller cam cam. numbers are 236/243..520/540 with one ten lobe sep. It has aluminum 1.5 roller and edlebrock 64cc rpm heads(1.6/ 2.02 heads. Air gap dual plane manifold with 750 edelbrock carb and msd 6a box, pro billet distrubutor and blaster two coil. Exhaust is Sanderson ultra shorty headers to 2 1/4 dual exhaust. Tranny is a vette 700r4 1989 model with rear diff at 3.54 with 235/60/15's. The car is not slow but is definetly not quick.

 

My buddy has a Jenson Healy with abuilt 350 sbc, 700r4, 3.89 nine inch. Engine build is simular he is running a roller cam that is tamer than mine, I believe 218/224-480/488 with 9.9 to one compression and single plain instead of dual. He's running 25 inch tires and that car can smoke mine like nobodies business.

 

My question is what gives am I missing something? Do I have to much cam? Im out of Ideas and money as well! Any guesses would be apreciated.

 

zfan..Mike

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Guest Anonymous

Sounds like a good combination, but a cam that size will need a stall converter of around 2800 - 3200, just to get the rpm into the powerband. Also I have had experience with the RPM EDE. heads and while good heads, they have a small 170cc intake runner size. This gives great throttle response, but your cam probably has more flow potential better served by a larger 200cc runner head (ie: Dart, World Products, Trick Flow 23 degr....). Don't get me wrong, I would not attribute the sluggishness of the car strictly to the heads, just that the cams full potential may not be realized with these heads.

 

I also agree that the Edelbrock Carb will not be as strong a performer as the Holley.

 

Does it feel sluggish at lower(what) RPM's or throughout the rpm range? This may help to determine if the problem may be something else.

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As far as a stall goes I've got a B&M hole shot 2300/2500. The car has no real pull like my buddies. He also has 1.60 roller rockers on the milder cam. That car flat out pulls like nobodies business, all the way to 6 grand.

 

I have a set of Hooker super comp headers Im putting on the car next week, no more little shorties. Should help as the sandersons are either 1 1/2 or 1 5/8" and very small/tight.

model number cc2 or cc3's.

 

Also my friend is also pushing me to go Victor jr. and Holley 750 double pumper.

 

zfan...Mike

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zfan

 

ok the most likely problem (looking at your list of parts)is that the cam you picked is for use with a high compression ratio and a single plane intake like a vic JR and full flowing headers now you can do one of two things, you can get higher compression pistons (about 11 to one) and a single plane intake and full length headers or you can pull that cam and install a crane# 114142 216/228 durration .454/.480 lift on a 112 LSA that is much closer to the specs that will run in your car.

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Guest Anonymous

I agree that the Vic. Jr. will probably help along with the 750 Holley(either vac sec. or DP) will work with this cam. My experience with the Ede. RPM's is that they are a little small but do have awesome response as stated earlier by Charlie. The stall converter will need to be in the 2800 min to a 3400 max to be optimal. I doubt that is the problem though. That combo should rip in a Z! I would reflect a little and make sure that the camshaft was degreed in properly and that you aren't a couple degrees advanced or retarded, sometimes it can happen and everything works fine, sometimes it won't work worth a crap. Make sure your timing curve is proper for your cam and head combo also. I would put about 16-22 degrees of initial in her and put the correct advance stop bushing to only add about 14 to 16 degrees through the centrifigal(?)advance to get to the total of 36 to 38 degrees. I would also remove the vac. advance hose and run on pure rpm advance in the dist. That distributor has some cool features for curving it to your liking. Explore your options in the distributor. Your problem could be hiding under your dist. cap! Your motor without dyno tuning should be solidly in the flywheel range of about 400-450hp, and as we all know that should be a very healthy motor for a Z! Keep digging and if you come up empty call me on the phone at work: Performance Plus, Dublin Ca. 925 833 9871 Ask for Jason, I'm the manager of the Hot Rod shop here. It's a little easier for my slow typing fingers to use the phone for brainstorming!! Call me if I can help!!!! icon_biggrin.gifflamedevil.gifbonk.gif

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Definitely mismatched heads/cam/Manifold/carb.

 

If you're going for all out performance...

 

Single plane and Holley - yeah! Not necessarily the DP but the tried and true 3310 (non-emissions 780) since you have the lower stall torque converter (unless you have the money to change that too). Remember that this is the vac secondary carb that came on Z-28s/vettes and fast Fords (square bore pattern unlike the emissions 780), much more forgiving with an auto with low stall.

 

The big factor here is the heads (mucho dinero to get different ones).

 

I believe if I had to do one inexpensive thing, I would change the cam to what would work with the rest of your engine combo.

 

Currently it is the one thing really out of line with the rest of the package, and the PACKAGE is what counts. Yo are experiencing the effects of parts that don't work together.

 

Try it - you might like it - it is the least expensive route. Then you can determine realistically how much faster you want to go at what cost.

 

Just my .02

 

icon_smile.gif

Brad

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Guest Anonymous

D: All of the above. (makes sense) The engine is crying for a single plane manifold, and probably a bit of a jetting. The cam sounds a bit agressive for a street cam, but not that bad for an occasional driver.

Also mentioned the stall speed is probably killing you a bit as the motor isn't getting into the torque curve as fast as it could, although with a light car and 3.54's it shouldn't be as big of a factor as a big car with like 3.08 gears or something. *shrug*

I'm not sure how the 2.25" exhaust is, but you may want to think about 2.5" at some point since your performance level probably warrants it. icon_smile.gif

 

Regards,

 

Lone

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A couple of things mentioned earlier, the distributor is non vacuum,mechanical msd. Im currently upgrading exhaust to Hooker super comp full lengthe headers,may look at going 2 1/2" exhaust but just put spintechs 2 1/4' (not cheap) ouch!! Also a good friend offered a victor jr to try, If I like it I can get him a replacement.

I do want a Holley 700-750 double pumper. Can you say EBAY! Also grumpy, you mentioned going with a milder hydraulic roller cam. I have a newly installed roller set up, not to savvy when it comes to roller set ups. I had springs upgraded on heads to accomadate cam. If I swap cam do I need to go comp cams to match other components?

 

I want to street/strip the car. Looking for 11/12 second streetable car what cam would you recommend in the comp cams roller set up?

 

zfan..Mike

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Guest Anonymous

I didn't see any mention of a stall converter. A cam like that would def. need a stall.

 

Also, IMHO, I'd ditch that Edelbrock carb and dual plane intake. Get a 750 Holley with a good single plane like a Vic Jr. You would be amazed. Just my opinions though. icon_smile.gif

 

FWIW, I ran an Edelbrock and RPM manifold for a while on one of my old projects. I hated that carb!! Give me a Holley DP any day. icon_smile.gif

 

Mike

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I agree with Grumpy that that cam needs some good compression (like 10:1 or more). What is your ACTUAL compression? Also, I agree that you might want to check that the cam is degreed in correctly. I screwed up one of those 3 keyway sets before, making the cam timing very retarded - the car was a dog.

 

I also think 2-1/4" could be limiting you, but that should only show up at the top of the rpm range.

 

How large is your primary ignition wiring? Just wondering if the ignition is getting enough current/voltage.

 

If everything is right with your setup, it should be pretty awesome compared to most cars. It should be impressive.

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after reading all the other input here it seems that you should check your cam is deg in correctly first because like pparaska said that will kill your engine power faster than almost anything else! and if your useing one of those 3 positition roller timeing gear sets they are well known for haveing the timeing marks stamped several degs off true anyway, add the possiablity of lineing up two marks that should not be used together and you have an engine that seriously down on power, now since its a roller cam (I think thats what you said) and they are expensive, lets try to get it to run correctly, first deg in the cam,read this,

http://64.90.9.168/cranecams/pdf/803.pdf

http://64.90.9.168/cranecams/pdf/215e.pdf

 

http://victorylibrary.com/mopar/cam-tech-c.htm

 

now that cam requires a good single plane intake like a super victor #2925 (my choice) or the #2975 victor jr (the more common choice)to breath well, basically try to get what you have now running correctly and only swap to a milder cam if you find you have way to little low end torque, Id love to be able to help you personally and find and show you whats wrong but your 800 miles from here!

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Pete the engine was built by Competition Machine in Plano,My home town. The shop said it was 10.4 to 1 compression. The car has a gear drive, no double roller chain set up. Builder liked the gear drive over roller chain due to old style block would have to be shimmed for roller chain as I have roller cam set up. Hope that makes sense. And no the gear drive is not the real noisy type! Thank God!! Will go 2 1/2 exhaust I guess well Im at it.

 

Anyone looking for low clearance 2 1/4 spintechs. They are great for clearance issues, paid 120 each malebitchslap.gif Not cheap. Dont laugh!!

 

zfan..Mike ugg.gif

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if your running 10.4 to one compression and useing a gear drive(good choice) that still leaves the cam could be indexed wrong (unlikely)and the cam you installed is a good one its just that it does not match a dual plane intake and restricted exhaust, and as mentioned check your ignition timeing curve ,if its off much that can hhurt performance also , you should be running someware close to 35-38 degrees total advance and it should all be in by about 3000rpm!

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Thanks to Everyone for the imput. Im going to the Barrett/Jackson car show/auction this weekend but will be back monday and will start some changes asap.

 

I think the Victor jr. and holley double pumper are a good start and will put my full lengthe headers on with 2 1/2" pipes as well.

 

Looks like I'll have stuff for sale in the next two weeks.

 

Thanks again,will post results as well and will look into distributor/timing issues as well..

zfan..Mike icon_biggrin.gif

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  • 4 years later...
Guest smokin350

now that hes had his questions answered allow me to ask one of you guys. I have 1990 350 sbc and I am in the process of tearing it down to rebuild for an 85 camaro. my question is is this What intake carb would you recommend for a stock 350? the motor was orginally throttle bodied

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Wow, how times have changed. That was me a few years ago and that 350 is history except for the block. I stroked that motor out to 385 cubic inches. It runs high 10 second quarters now. Power issues solved..Ha

 

Mike

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Words of wisdom..... Always match parts together, Nice cam, then a victor jr. intake along with good heads, and decent compression 10.1, good dizzy, like a msd and lock out your timming etc.

 

If you go roller cam (big) the super victor intake, at least 220 heads, bigger carb, more compression... etc....

 

If you plan on doing it in stages then, go with good intake for later, good heads for later, then when you are ready, bump up the cam, compression, and bigger carb.

 

You have to ask yoursel what do you want to do? What is your goal? then make a plan. Do not half step if you know what I mean. If we can help let us know... I love my 355 cu Chevy...... Maybe have some parts if you are interested.

 

John

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