So here's my situation. I'm getting an all original 350 for free from a friend's dad that came out of a '69 Caprice wagon to put in my '79 LeMans. It is a stock original L-48 300hp 350, and it was torn down into pieces for storage. Obviously I will have it in to a machine shop for cleaning, checking, and any machine work (I don't think it needs much, there's barely a ridge on the top of the cylinder walls). I'd like to get around 325-350hp out of it when it's done, but I'm not exactly sure the best way to get there. I'd like to do it as economically as possible but still do it right. I'm debating on using the stock heads or going with an Edelbrock top end power package (Performer RPM air gap intake, carb, and cam kit, and heads). My dilemma is that I'm not sure what size carb to go with (600 or 750cfm), the cam specs (want to have a nice rough idle but still be streetable and good for vacuum accessories), and like I said before the debate about the stock or aftermarket aluminum heads. I don't think that getting 325-350hp would be too difficult from an engine that was 300hp from the factory. I'm also looking at cost effectiveness because I'm not sure if it would be cheaper to get the stock heads rebuilt or just go with the aluminum ones. Any advice would be greatly appreciated. Thanks in advance 🙂
Need some engine advice
- Thread starter Wildmani
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if you want to do it economically why not get a set of vortec heads and with a nice cam you'll get more hp than your looking for and better fuel economy than with the original heads....I'd stick with the 600 carb or a 650 cfm
well im not sure about the heads dilemia ive never had a set rebuilt so i wouldnt know about a price tag but a mild cam if u want the idle would be good. im not sure but i think the comp cams magnum is good for that and still be able to have ur power brakes at idle. 600 carb is good to run a mild cam like that and u get better fuel economy with the 600 compared to a 750. i have a 750 and my gas milage is in the tiolet if i feather it i get about 12 miles a gallon if im lucky so a 600 is good with a mild cam. get urself a good ignition set up to go with the carb i run a Hei accell distibutor and coil. all that stuff there with a good 350 is good for about 320 to 360 horse maybe
What is the casting number on the stock heads? In that late 60's, Chevy had some killer heads. My car has 1964 model double humps on it with a .503/.518 crower comucam cam shaft and a 650 holley double pumper. If i had to guess, i'd say it"ll make 375-400hp. As for your carb issue, i'd go with a good holley 650 vacum secondaries. For a a cam, to have a rough idle i'd look into a .447/.447 hyd. It'll give you good power and the idle you are looking for. I'm no expert but i have been around this stuff all my life and have built and helped build many vehicles over the years.
If I remember correctly the heads are "041"'s. The one issue I might have is the fact that they were designed for the leaded gas era so I'll likely have to get some mods done. Although my friend's dad drives a '65 Impala SS with an original 396 and he says all he does is add a bottle of lead additive every other tank of fuel. I'm really leaning towards the aftermarket heads I think, but I'd like to stay with an Edelbrock carb (Had both a Holley and an Edelbrock on an '81 Z28 I used to have and much preferred the Edelbrock). And I'm definetely upgrading the ignition 🙂
Just an FYI; that 300 hp factory rating is in gross hp. If it was rated in net hp like all of the cars from 71 onwards are, it would be about 220 hp or so. So you need over 100 hp to reach your goal.
Having such cheap aftermarket heads available is a no brainer. Us Olds guys would KILL for just ONE aluminum aftermarket head for a small block, and you have like 15 to choose from. Plus you have Vortechs too. A quality head rebuild with new valves and a good valve job will run about $800.
You should not pic a cam untill all the other aspects of your entire build ( engine, transmission, rear ) is known. Do NOT choose a cam based on sound. Choose a cam based on what is best for your application and a nice sound will come along with it. You should consult one of the 800 billion Chevy builders/cam grinders and get their expert opinions on selecting the best cam.
The best street carb ever is the Qjet. IMO, there's no other choice. The others don't even compare ( especially the Edelbroke ). What's not to like about a carb that gives you killer throttle response, the best MPG, a cool sound when the secondaries kick in, perfect factory fitment, and all the CFM your engine needs ( and only what it NEEDS ) up to 750-800 CFM?
Having such cheap aftermarket heads available is a no brainer. Us Olds guys would KILL for just ONE aluminum aftermarket head for a small block, and you have like 15 to choose from. Plus you have Vortechs too. A quality head rebuild with new valves and a good valve job will run about $800.
You should not pic a cam untill all the other aspects of your entire build ( engine, transmission, rear ) is known. Do NOT choose a cam based on sound. Choose a cam based on what is best for your application and a nice sound will come along with it. You should consult one of the 800 billion Chevy builders/cam grinders and get their expert opinions on selecting the best cam.
The best street carb ever is the Qjet. IMO, there's no other choice. The others don't even compare ( especially the Edelbroke ). What's not to like about a carb that gives you killer throttle response, the best MPG, a cool sound when the secondaries kick in, perfect factory fitment, and all the CFM your engine needs ( and only what it NEEDS ) up to 750-800 CFM?
Interesting note about the hp ratings, thanks. Maybe I should consider a crate motor instead for the cost? As far as the transmission goes, it will be a TH350. I'll be putting a shift kit in it and a stall converter (stall TBD). Rear end is a 3.73 posi out of an '87 Monte SS.
DoubleV said:
yes a q jet is the best carb money can buy. small primarys for gas milage huge secondarys for power and the secondarys are mechanical not vaccum. dont ever get a carb with vaccum secondaries or holley for that matter they are slow opening where as mechanical open right away as soon as u smash the pedal. and with a q jet u dont have to constantly tune them once ur timing is set and u wanna adjust air fuel ratio i can almost promise u that once its right u never have to touch it again which is another plus over the holley sorry holley guys but q jets got u beat
While it's at the machine shop get that b*tch punched .030 over and make a 355 out of it....The Eddy total power system will give you over 400 HP no problem........I would say go with a 650 carb......Then again, all depends on your "Plans" for that ride 8) of yours.......
Hmm, I'm supposed to be getting everything that came with the engine. I wonder if it came factory with a qjet or a holley. If it's a qjet I might just get that rebuilt... One of these weekends it's supposed to be getting dropped off at my place so I'll see then I guess. Not sure about boring it out. I'm not planning on racing or anything, just something fun to boot around with on the weekends 🙂
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