Hello everyone,

Im fairly new to american cars, SBC's and corvettes. Not very common here in england ! I was lucky enough to be able to buy a '79 C3 last year and i love the car. It has an ATK Crate engine in and runs very well and feels strong. The engine was installed 2016 and has had no issues that i know of.

Ive been reading and watching alot about SBC's and have really enjouyed learning about them. I am hoping to get some advice about cam and head combos and genral power mods. if i was to change the heads to some.with 200cc intake runners and a bigger cam will hurt the low end or will everything increase across the board so much that its will feel like a different car. Its definitely a street car so dont to sacrifice all my low end for a high hp number.

Right now the engine is made up of -

357 ( .040 over) with standard stroke
4 bolt main
Quick Fuel 680cmf vacuume secondary
Weiand speed warrior intake
hypereutectic pistons 9.1:1 Compression
OE rods
​​moly rings
OE reground crank
Cast Iron Dart 76cc heads 165cc intake
​​​​​​224/234 @50 .465in/.488ex 112lsa hydraluc flat tappet cam
Melling oil pump
Holley mechanical 110gph fuel pump
MSD distributor
2200--2500 stall
longtube headers
2.5" custom exhaust - she sounds great !

I dont know the brands of everything and imagine things like the cam and pistons are generic. I would love to have this car up at 450+ hp. - dyno states 340hp currently.

go easy on me 😄 Thanks in advace, Chris - from over the pond

 

Use either the Dart 180 Pro 1 Platinum or the Trick Flow DH175 head. Either will pickup nicely over the Dart 165cc.....although you could bowl blend and mildly port the heads you have and they will respond very well......clean up the bowls, all the sharp edges and tool marks from machining should be blended.....then use a 1.6 rocker arm....if you do it right, you will see over 400hp.....the Trick Flow head will definitely put you in the 425hp range.....the 60cc chambers will pick up a point of compression......at 10:1 you will hit your goal....
200cc head is too big for a street 350.....they make more average power and are more responsive with the smaller head.
You will not hit 450hp without more cubes or more cam......the latter will start to kill low end torque over than what you have already.....
What and where did you get a 340hp dyno number? Is that at the rear wheels?

Jebby

 

Hi Jebby,

The 340hp number came with yhe engine so wasnt in a car at the time it was put on a dyno, the engine was advertised as a 325hp ser up in thr spec sheet and inlie. i am planning in getting the car on a dyno soon so i have a starting point to measure from. Jusy eant to do the water pump, thermostat and fan clutch first which i have just got from roc auto.

Should i consider a bigher cam as well as those heads or perhaps a similar cam with a tigter lsa ? That wicked resposive low end is the main goal for this car.

thabk for response

 

1.6 rockers with better heads would work fine. With a tighter lsa you would make better use of the added compression of the new heads smaller chambers.

 

Thank you for that. would it be advisable to keep the duration and other cam specs the same - 224/234 or there abouts ? At what point would the torque and low end start to take a hit

I have also been wondering about a thinner gasket to increase CR when I change the heads, is this worth it or is that really splitting hairs

 

At not much more duration you are going to need a higher stahl speed torque converter. The 1.6 rockers will give you more lift and a tiny bit more duration. Don't get ridiculously thin on your gasket you want to seal everything up.

 

[QUOTE=Jebbysan;1607449553

Jebby[/QUOTE]

Jebby, does using 1.6 rocker arms on a stock L48 head with mild cam make a difference? Or it is not worth it?

 

Does almost nothing. And you can't really because the pushrod will run on the pushrod hole in the head....

Jebby

 

Thank you Jebby, in the context of a better head like the Dart 175 head woth 60cc chambers suggested above would he rocker arm upgrade have a better impact on power output.

I have been reading about 1" carb spacers also and would love to hear opinions on thise.

Rocker arms, spacers and thinner gaskets all seem like simple and cheap upgrades to do if i doing the heads anyway and it must all add up ?

ThankS for the advice Chris

 

The car has a 2200 - 2500 stall in it, would that still be to small with even a small add in duration ?

 

The 175's are Trick Flow not Dart......and yes, with this cam the 1.6 is desired as the heads flow just slightly past .500 before they stall. The 1.6 will take advantage of that flow. 1.6 on a stock head is worthless because the heads do not flow well at the lift you already have.
Read about the meat and potatoes of things....not carb spacers.....carb spacers in the 1" range are a tuning device and barely have an effect on the street.....it is much more important to have proper jetting and timing......you will never notice one spacer to another on the street. I run a 1/2" open spacer on a single plane intake for a little height ( I have an L-88 hood with air chamber) and to thwart heat transfer......open spacers are not happy on dual plane intakes and four hole ones are pointless......
If you buy a small chamber head....you don't need a thinner gasket.......I am using the Mahle 5746 gasket these days......but with 60cc heads and a flat top piston....you have to watch the compression closely.....with that cam you can get away with about 10.5 to 1.....on a 357ci engine with 60cc heads with the piston .010 in the hole you end up with 10.6 to 1 with a .039 Fel pro gasket.......050 quench.....which is fine......I have one out there and it romps on 93 octane fuel no problem......
The SBC has more print on it than any engine in the world....which also means it has more bullshit to sift through. Buy a copy of "How to rebuild a Small Block Chevy" by David Vizard......I got my first copy at age 10 from my Dad.....built my first small block at age 13......point is, figure out how it all works together....save the fluff and buff for the racers.....a LOT of stuff crosses over from racing but just as much doesn't........

In the 12 years I have been here a LOT of people have made their cars run very well using the advice on this forum.....I tend to sound like an Pessimist because I am way past all of the fluff and buff.....I think the modern news media took cues from the Engine "Enthusiast" groups on Misinformation.......your build is a combination of parts.....stay with your build and out of the magazines and videos.

Your engine upgrade should be:
Heads
Head Gaskets
1.6 rockers
Premium pushrods (which the length HAS to be checked)
Head Bolts

The rest of your parts are fine......the carb will need rejetting.....the total timing will be 32-33 degrees instead of 35-37.....don't overthink this.

Jebby

 

Thank you jebby, and my mistake on the heads !

Your absolutly right and im in my infancy with all this and enjoying it very much.I am reading and watching as much as i can and as you say there is no doubt alot of bullshit out there so im navigating it best i can 😅

That little list is perfect and im going to get to work on it this year, i will do dyno runs before and after so will let you know the results ! ,