Waking up my 350 SBC

[ChevyDude]

My Red 71' called Lil' Red was a big score when I found her 5 or 6 years ago. She was in primer and I was told that the 350 SBC had just been rebuilt. Well, I have had her on the road for about 3 months now and I am just not happy with the HP. The engine doesn't smoke and has very good compression. So.....my Plans: Engine will be pulled from Lil' Red this Saturday. New aggressive Crane 488-515 lift cam, new lifters, new hi Rise square bore aluminum Intake, new double roller timing chain, new mechanical 750 DP Holley or Barry Grant, new aluminum 64cc 202/160 heads.

Should wake up Lil' Red.

[LONGHAIR]

new mechanical 750 DP Holley or Barry Grant

For street driving, you would be ahead to use a vacuum secondary carburetor. Double pumpers are a full accelleration (drag racing only) thing.

[ChevyDude]

I hate the 600 Edelbrock E choke carb I have now and the amount of driving I do.....she is gonna run like a hot rod. A friend just built his 64' Chevelle engine as I discribed above and it runs awesome. That's what I am looking for.....and heck...I only live 15 miles from Bandimere Speedway, LOL.

[cdowns]

you might want to ID what heads you have before changing to an aggressive cam poor heads are poor heads doesnt matter how far you open the valves or how long they stay open/ rhen theres the question do you have pressin or screwin rocker studs not to mention the valve spring height how about piston clearance?

all in all your plan is a poorly thought out one

[whatnow123]

This is close to what I'm running depending on the type of heads you have, but all I can say is it should wake it right up... my truck hauls ass once it hooks up at 40mph or so....

[LONGHAIR]

all in all your plan is a poorly thought out one

That's a little harsh....but the point of the rest of the post is at least somewhat accurate. There needs to be a plan, with matched parts.

Does anyone really make a "bad" aluminum head for a SBC though?
I'm still focusing on the carburetor. I'm not a big Edelbrock fan either, but a double pumper is not going to be optimum for the street. Just because someone else "did it" and it worked for them, doesn't mean that they were getting the most from it either.

[ChevLoRay]

Far be it from me to try and second-guess anyone on their plans.

You mentioned that you were unhappy with your Edelbrock 600cfm (model 1405?) with electric choke. I have the same one, but w/o the electric choke. In the configuration I have, it's classified by Edelbrock as a "performance" carb, with the main jets being .100's. It ran rich and would gas-foul the plugs in a couple or three months.

I changed intakes to a Perfomer and the carb to an Edelbrock 1901 Q-Jet, with electric choke. It's rated at 750CFM and I couldn't be happier. Check out www.edelbrock.com for tuning tips for all their carbs, as well as technical info.

As an aside, and not to hijack the thread, but has anyone ever used a Thumpr cam in an engine? I'm considering the L79 version (350HP/327) for my '69. It's an automatic and the literature shows it to be workable. Just curious. Good luck on your engine work.

[steelhorse]

I would go with the edelbrock performer rpm air gap for intake.Every buildup I have seen with it they are very hard to beat.I too would go with a 750 vac secondary holley.Check out websites like car craft/popular hot rodding for engine builds you should see some good info in them.Remember to check the rpm range for the hp/torque if this is going to be mainly for the street.

[johnnywagon]

The Edelbrock RPM Air-Gap is a great intake. It even helps with slightly lower engine coolant temps. I had one on my 10 second pro-street 406 Chevy Luv w/a Demon 750 DP. Got one on my 65 Chevelle w/Edelbrock 600 carb and my Blazer has one w/a Q-Jet and carb adaptor.

[70c10]

Alex, do you have an auto trans?. That cam is going to want some stall and gears especially in a truck! If your dead set on a DP I'd go for a 650. When I switched from the Edelbrock to the Demon it was a huge improvement! I will be running the RPM Air Gap soon with with my new Brodix IK180 heads!

[straitnate14]

Originally Posted by LONGHAIR

For street driving, you would be ahead to use a vacuum secondary carburetor. Double pumpers are a full accelleration (drag racing only) thing.

??? I dont have any problems on the street with my 700 dp? It gets terible gas milage but thats pretty much to be excepted.

[lowriden58]

Originally Posted by straitnate14

??? I dont have any problems on the street with my 700 dp? It gets terible gas milage but thats pretty much to be excepted.

same here with my 750DP i drive it on the street with no problems at all even witha 3k stall. only problem i have is "she will pass everything but a gas station"

[67_C-30]

For a daily driver I would not go with a DP, but there again I would not go with Holley at all. However, If you looking for HP, I'd go with the DP. In my experience, the double pumper can make for significantly more low speed torque, at the expense of fuel economy. As long as you don't actuate the secondaries, it uses no more fuel than a vacuum carb with the same size primary throttle bores, booster type, jetting and idle mixture. On a vacuum secondary carb, the vacuum is only actuated after a certain point of throttle opening. Then the airflow through the primary venturi (not engine vac) actuates the vac diaphragm which opens the secondaries. Because this is slow and linear, it is not neccessary to have the second accelerator pump which hides the "hole" created by the near instantaneous opening of the secondaries when you "punch it". The bog from most carbs when flooring it is by too little gas being applied from the accelerator pump and not by too much gas as most people believe. I have never had a DP bog on any engine, even if it was too big for the engine. The vacuum secondary carbs can be troublesome to keep adjusted as well in regards to the vacuum diaphram. If I were buying a carb for power (which what you seem to be doing) I would personally would not waste my money on a vacuum carb even though the so-called experts say you should use them on the street. JHMO

[ChevyDude]

Originally Posted by cdowns

all in all your plan is a poorly thought out one

Hey Dude you have absolutely no idea what you are taking about, period. This package is has been matched and put together by Smith Racing of Denver, whom has done numerous winning engines. Seems a bit out of line for you to tell me my plan has been poorly thought out after many hours of disussing what we should do with the owner Tom Smith, when you know NOTHING of what has been dicussed.... but whatever Cdowns. and cdowns...heads were ID'd long before you spoke up and they are lousy heads for making power...that's why I said new aluminum heads were being purchased. Your negitive comment is out of line, and adds nothing positive to this board!

I did not post what I was doing to get a cheap shot from someone, seems kinda F'd up....don't ya think??? I will probably delete this whole post if it goes on a negitive pissing match route, as I cannot stand some idiot spouting off like this when he knows nothing of what has been discussed...it pisses me off and truly I do not come to this board to share info only to get slammed by someone like cdowns.

Trans is a 500 hp rated 700R4 built by Monster Motor Sports...It has a 2500 Stall convertor, because when I bought the truck the PO told me the engine had been rebuilt and was near 400 hp....he lied!!!! So to leave it as it is, nothing is matched up as I had the trans built thinking the engine was 400 hp.

This truck is not a daily driver, nowhere near. This truck is a HOT ROD, and when I want the secondaries open ...I step on the pedal...and do not have to wait for vaccuum.

[straitnate14]

Originally Posted by ChevyDude

This truck is a HOT ROD, and when I want the secondaries open ...I step on the pedal...and do not have to wait for vaccuum.

[milled]

Ok, if it wher me I wouldn't exceed .500 lift on the cam. I perfer a carter 4bbl jetted and metered, it'll feed anything. Other than that small blocks rule

[ChevyDude]

Cam spec: 488-510 LIFT, 234-244 DURATION, 114 LOBE SEP.

[milled]

Originally Posted by ChevyDude

the lift is 488-510 w/ hydralic lifters...that's nothing...not even a roller.

That's the limit, it'll run but run it leaner.

[LONGHAIR]

Far be it from me to "tell" anyone how they have to do anything.
My point was exactly as covered by several others, there is a big fuel mileage hit with a double pumper, for no real performance gain to go with it.
It's not like there is some huge horsepower advantage. You could measure it on a dyno...and maybe see it in quarter mile times, probably as dependant upon traction as much as anything.
Properly tuned, I doubt that anyone could tell from the driver's seat, so why take the mileage hit? or the price of the carb itself?

As a side note:
ChevyDude, go easy....the point was already made.
You could have explained a little further, but certainly didn't have to....no one should have commented in that way.
You really should not have retaliated though....I realize that is far easier to say than to do though.

III. No pissing matches. Its fine to disagree, but once a thread has run its course, and degenerated into little more than an insult fest, it will be locked. While this will require a judgment call by the Administrators & Moderators. The members of this site can keep our moderating to a minimum by exercising a little discretion and self- control.

[special-K]

Sounds like it`ll be another honkin`little 350 to me.I never knew it had to be as complicated as some make it appear.There are proper combinations.But,in the end they`ll all run and most of the time we don`t see the difference.

[ChevyDude]

Engine was removed from truck today and heads were removed, I discovered the block had low compression dished pistons. -18cc dished pistons = Low Compression. Decisions Decisions. So I decided to buy a Smith Racing 3970010 SBC w/ SRP flat top pistons w/ forged crank he had just finished building. We installed the Crane 488/510 lift cam and Sealed Power hydralic lifters and the Cloyes 1100-SP double roller timing chain. Installed Cam @ 4 degree advance at the crank. Build specs have already been on the Dyno and produce 418hp at 5700rpm. By advancing the cam timing 4 degrees, it achieved hp numbers of 418hp, yet maintained torque number near 400 ft lbs all thru out the power band. Now to bolt on the top end.

[67_C-30]

Originally Posted by LONGHAIR

Far be it from me to "tell" anyone how they have to do anything.
My point was exactly as covered by several others, there is a big fuel mileage hit with a double pumper, for no real performance gain to go with it.
It's not like there is some huge horsepower advantage. You could measure it on a dyno...and maybe see it in quarter mile times, probably as dependant upon traction as much as anything.
Properly tuned, I doubt that anyone could tell from the driver's seat, so why take the mileage hit? or the price of the carb itself?
.

Again, I respectfully disagree. I have compared them at the track and on the street, and there is a very significant difference. I have seen more than 2 tenths difference in the 1/4 and I have seen 30-40 ft lb difference across the torque on dyno tests comparing the same cfm carbs on the same engine. In fact, a 650 DP will wipe the floor with a 750 VC everytime at the track. I have proved that time and time again. A vacuum seconday carb will keep the secondaries from opening fully until fairly/very high RPMs. That hinders the torque curve throughout, as well as hurt peak HP. Vac sec carbs are only better in heavy street driven cars with no stall and high gears turning very modest RPMs putting around town with the occasion burst through the gears.

As far as mileage, its not that much (if any) difference. A double pumper has progressive linkage, and the secondarys are not squirting fuel just driving around. That's a common mistake people make. Some people think that all 4butterflies pen as soon as the throttle is opened, but isn't the case.

The bottom line is a vac sec carb is a compromise, and it comes at cost. They are fine for a stock or nearly engine, but there is absolutely no advantage to having a vac carb on a heathly engine with an aggreesive cam, aluminum heads, low gears a stall. With a difference of 20 peak HP and 30-40 ft lb of TQ on the dyno and 2-3 tenths at the track, I'd go as far to say that I doubt that anyone could not tell the difference from the driver's seat. I have been building race engines for nearly 15 years, and raced street/strip and bracket cars for 10, and this has been my experience.

[special-K]

I think you guys are saying the same thing.Just,one is puttimg emphasis on track/dyno and the other on street use.One`s a comprimise on the track and the other`s a comprimise on the street.They both do the job with minor differences when it comes down to it.The main thing is to have a carb suited for your engine build/use.

[Bob 68327]

I say it's your truck and your engine build it however you want !! I run a DP on mine my cam is a 292/.510 I have an auto trans w/a 3500 stall and I drive it on the street . Build that screamer and Drive the wheels off it !!

[ChevyDude]

I can tell you one thing for sure...I am building this engine the way I want, and it will be a runner for sure. Remember I said Hod Rod...never gonna be an everyday driver, but it sure will get up and go when I mash the pedal. Here she is...don't ya think she deserves some ponies???


Lots of opinions here when it comes to an engine...I can see that clearly. I guess some of you will think I am misguided or nuts on my other project...this is what I built for my 68'. It's a 496 with a 1050 Holley Dominator DP flowed & bowl blended by Chuck Nuytten..and it's got a solid roller cam and lifters, oh the lift is .650 and the Edelbrock heads are rectangular port, K-Motion dual springs, roller rockers, 10.5-1 compression. Gas mileage estimated at around 7mph, LOL. But HP...some where between 700-750 LOL.