I know nothing about cam's. I like the sound a Thumpr cam can give, but people are always talking about springs, lifts and such. I've read that website on cams but didn't really understand it. Can someone tell me what cam could directly swap into a 1978 5.7L V8 engine? It's all stock.
Cam Fitment
- Thread starter 87GrandPrix
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A stock 1978 350 has very low compression, and therefore can't take a very large cam and remain drivable. Cams in older engines without some sort of variable valve timing and lift system (like Honda's VTEC, Toyota's VVTiL, etc.) need to be compromised. The reason is that the more time the valves remain open, the less time there is for pressure to build on the compression stroke. So, to run a bigger cam, you need more static compression. Is there more to it? Yes, but I do not have the time or space to get in to all that theory on an internet forum. My recommendation is the cam I use, the Comp XE262. It will require better valve springs than 32 year old stockers, but it should be able to run with shitty compression. I'd also say that the heads on that engine are not very good either. They will be an impediment to making all the power that cam can provide. Also, that cam does not have a choppy idle, but you get tired of that very quick in a car that can't deliver the performance you usually get when giving up that much driveability. However, while it is smooth in my engine, it may be less so in your 78 350 due to mine having more compression.
What things would you recommend doing to a stock 78 350, small things that make the engine up to snuff. I don't want to dump all my money into it.
Well, it all depends on your budget. I would go with a set of Vortec heads, a Performer intake and the XE262 cam as a basic bolt on package for an otherwise sound engine, but that may be above your budget. The heads not only flow much better, but also have smaller chambers by around 10cc, which will give it a much needed boost in compression. It could potentially take you from about 160hp to around 300-320. However, it is pretty much a package deal sort of thing. I will probably write more later, but I gotta go to work.
The bad thing about your engine is that while it is a good core to mess with, it has a terrible choice of internal components. The compression is way too low, it uses dished pistons with lousy quench, the heads are the "lightweight" castings with a bad reputation for poor flow and cracks, the cam is tiny, the intake is restrictive and heavy, etc. Plus, any cam you choose will require new springs. If you just want to drop it in as is, I would suggest new gaskets, a new timing set, a used aftermarket dual plane intake, and small tube headers. Anything more than that like a new cam, is a waste of money. The cam you would have to use would be too compromised for the heads and compression to be worth the money. My advice is to save up some more money and seal and store the 350 properly until you are ready. There is no good that will come of buying parts twice because they are incompatible with your future plans. All that does is waste money that you really don't have. It's frustrating, but it is how it goes sometimes. My car is built on a micro budget and I need to stop and save up more cash all the time too, so you aren't alone. Also, my engine is a 1977 350 (the same engine as yours) that has been gone through on a tight budget with an eye towards a good torque curve and fuel economy more than all out performance. It was, after all, originally planned out by me as an engine that could be used for pizza delivery since that is what the car was used for at the time. Mine makes around 350hp and 400-420 ft/lbs of torque. If I was building it today, I could probably build a better engine for around $1500-2,000, without giving up any of the driveability and fuel economy I have right now.
If you want the most bang for your buck, think about adding some decent rear gears like a 3.23 or 3.42. Compared to the 2.29-2.56 gears you probably have now it will really help acceleration. I would also consider an exhaust system upgrade. What kind exactly depends on your local laws, but I tend to play it safe and use a catalytic converter. If you want a single, use a 3 inch model as it will really improve flow over the 2 1/4 in singe cat that the LG4 305 cars came with. Also consider installing a new governor in the transmission if it is a TH 200 4R. The upshift governor in yours shifts at 3k, while the performance models got one that upshifts at 4500-5000 rpm. The extra RPM will wake the car up a bit.
If you want the most bang for your buck, think about adding some decent rear gears like a 3.23 or 3.42. Compared to the 2.29-2.56 gears you probably have now it will really help acceleration. I would also consider an exhaust system upgrade. What kind exactly depends on your local laws, but I tend to play it safe and use a catalytic converter. If you want a single, use a 3 inch model as it will really improve flow over the 2 1/4 in singe cat that the LG4 305 cars came with. Also consider installing a new governor in the transmission if it is a TH 200 4R. The upshift governor in yours shifts at 3k, while the performance models got one that upshifts at 4500-5000 rpm. The extra RPM will wake the car up a bit.
I agree 100% with what has been said so far. In fact I just want to comment on the Comp Cams Xtreme line. These cams are great! I, personally, think you should either save up and do a complete package or keep an eye out for another engine that is already built the way you want. That being said, I've been in your shoes and just HAD to put a cam in a low compression engine. In my case it was a 307 Chevy. XE256 IIRC. It changed the whole personality and really woke it up.
85 Cutlass Brougham said:
Haha oh no sir, this engine is currently sitting in a 1978 Chevy Scottsdale K20 with a 14 bolt full floating rearend and a Dana 60 front end.
You guys here at GBodyForum know more about engine and equipment then the guys at the truck forum I believe.
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How much would direct fit new pistons cost for this engine? I know vortec heads are bigger, I have never had an engine bored out and im sure it costs a lot.
there are a few ways to do this. one takes patience and a few bucks, and you'll walk away a little smarter, with something that you helped pick out yourself. the other is fast and easy, and can be done cheaply or otherwise.
either take your motor, and buy yourself a rebuild kit from northern auto parts, then have your motor bored to fit the pistons you picked out in your kit and build the motor yourself. this will take patience, and you might need to ask a lot of questions, but you'll be smarter when you're done. you can pick out your own cam , heads, intake and carb to fit your package, and northern will even let you substitute flat-top pistons in your kit.
given that recipe, and a few careful decisions, you will make out well.
the other is a crate motor, new or used. there are new ones available for most price ranges, and again, you can even buy a short block that will allow you to pick your own heads cam carb and intake. or you can go all out and buy a turnkey package.
if you browse craigslist for "chevy engine" "SBC" or "chevy motor" you're bound to find some schmoe who yanked a crate motor out of a rustbucket who's selling it for a few beans and a goat. is this way easier? most of the time. is this the preferred method for many people? also yes.
if you don't have a good shed or garage in which to build a motor, you might just be better off either buying a crate, or dropping your core engine at the engine builder's and say "i want X-hundred and twelve horsepower please" or "i only want to spend X-thousand dollars please" and come back in a few weeks.
either way, you'll be alright.
either take your motor, and buy yourself a rebuild kit from northern auto parts, then have your motor bored to fit the pistons you picked out in your kit and build the motor yourself. this will take patience, and you might need to ask a lot of questions, but you'll be smarter when you're done. you can pick out your own cam , heads, intake and carb to fit your package, and northern will even let you substitute flat-top pistons in your kit.
given that recipe, and a few careful decisions, you will make out well.
the other is a crate motor, new or used. there are new ones available for most price ranges, and again, you can even buy a short block that will allow you to pick your own heads cam carb and intake. or you can go all out and buy a turnkey package.
if you browse craigslist for "chevy engine" "SBC" or "chevy motor" you're bound to find some schmoe who yanked a crate motor out of a rustbucket who's selling it for a few beans and a goat. is this way easier? most of the time. is this the preferred method for many people? also yes.
if you don't have a good shed or garage in which to build a motor, you might just be better off either buying a crate, or dropping your core engine at the engine builder's and say "i want X-hundred and twelve horsepower please" or "i only want to spend X-thousand dollars please" and come back in a few weeks.
either way, you'll be alright.
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