I have a 350 engine with crappy 76cc low cr, smogged up junk heads, now that i have something to put it in i figured it would be better with the heads off of a 62 327 engine, since they didn't have smog laws and the v-8 was made to perform not look cool(well maybe that too). Anyways i was also thinking about putting a larger cam which i believe has about.455 int and 465 exhaust with a moderate duration at .050. would i HAVE to put new valve springs on to prevent float or could i get away with the stockers. would shimming them help. If it is neccesarry what kind of price are we talking hear, also is a higher stall convertor needed or could i get by with the stock one too. I'm only being cheap because i have VERY limited funds.

 

you've been grossly misinformed about 327s, there were some that made great boat anchors and soem the preformed. don't you think after 43 years the springs might need replaced even if they would of originally worked for your cam? do you have the acessory thing worked out yet or were you going to wait untill you were trying to get it all back together. i wouldn't bother with a cam swap for a .445/.465 lift cam.

 

Thanks for reminding me about the accesory hole thing. The cam is actually .460 .480, anyways yea they probably could have used new valve springs, not quite sure what I was thinking. However those 350 heads are just too much of a flow stopper to even make sense in modding the rest of the engine. What about the 305 heads i'll be getting from the engine that is currently in it. The engine overheated which leads me to believe their was some warping or cracking in order for it not to run.

 

'62 327?

You can probably find much better heads in a salvage yard. For a smog-dog pre-roller engine, look for 14014416 castings and plan on a little home machining and porting. As for the springs, if you're on a tight budget and plan to stay under 0.525 lifts, the GM LT4 "Hot Cam" spring kit, screwed studs, and titanium retainer/lock sets can be had for under $80. That's dirt cheap for 100# springs and the necessary hardware:

Valve springs - GMPP 12495494 - Oval wire LT4 springs $35.95
Valve spring retainers - GMPP 12495492 - LT4 lightweight $15.54
Valve retainer key set - GMPP 12495503 10° locks $ 6.83
Rocker Studs - GMPP 12371058 LT4 Stud Kit$18.60


For another $60, you can get a set of 1.94" intakes, then pay the machine shop the $75 to cut the seats for them.
If you get the heads for what they are probably worth, get them hot tanked and crack checked, and do most of the stud/spring pocket/porting machining yourself, you should have less than $350 in heads that can flow far better than the 76cc "smogger" examples. I've ported '416 castings to 178cc with 1.94 valves for a 350, and the results are noticable. What head castings do you have currently?

 

I have 462624 castings, the engine came out of a military van and also had A.I.R injection which i got rid of. About those 416's i see that they are 80-86 305 heads did those come stock on our model third gens or not. Wow taking it to 178 cc must be some feat. Sounds like a great deal for decent flowing heads and having the option of camming. The engine in the 84' camaro is a stock 305 and i'm kinda hoping it already has 416's on it. What kind of compression ratios am i looking at with 58cc heads, it has stock flat top piston w/o valve reliefs. One more thing where can i find the zz4 springs and such at. Thanks much, now i actually have some hope of it performing.

 

Your going to have a crazy high CR with 58cc heads and flat pistons.

With my setup, 58cc heads and -10cc dished pistons w/ valve releifs came out to 10.5:1 wich is going to be touch and go on pump gas depending on what cam i go with.

 

Could you post a picture of these?

 

What year engine is this? Flat tops and no valve relief? This wasn't a propane/CNG engine, was it?

 

I could be wrong about the valve reliefs but i swear there wasn't any. The heads that were on it which i'm highly assuming are original only came on 350's and 400's between 1975 and 1986. Do you suppose it is a 400, did the 400 ever have 4-bolt mains. I guess tomorrow i'll get those pics and try to post them, i'll also find the casting numbers on the block to know for sure.Is it odd to not have valve reliefs.

 

I ain't propane, I've seen lots of those, same as gas. I think it must be like those early 10:1 forged pistons that have a slot. (picture the 11:1 with the dome sliced off) I think he means it doesn't have "eyebrows".

 

Alright it doesn't have "eyebrows" which i've been informed were the valve reliefs, i have no idea otherwise what valve reliefs are. What about compression ratios, i'm assuming it was about 8.5-1 factory,maybe lower. With the 58 cc heads which will be probably brought up to about 62cc after the intake valves are refitted to fit 1.94s. I would imagine it would be a hair under 10-1 which is where i want it since i don't care about buying premium gas anyway. I've got another car i'll drive for gas mileage. Question is are my theory's right or am i wrong, please help me i need to get this straight. Thank you.

 

Your theories are right. It will raise the compression ratio. How much you end up with depends on a few other factors. Piston deck height (how close to the top of the block the piston comes at TDC), the thickness of the headgasket, and the amount of area on the top of the piston that is below the top surface of the piston. There is a web based calculator that you can plug your numbers into that will tell you what it will be. If the block is stock and you can get some numbers off of it, we can tell you about the pistons.

 

Yes, the "eyebrows" are valve reliefs, and apparently, you have none. Even the dished pistons typically had valve reliefs, but I haven't seen every engine configuration of the SBC.

Presuming that you had 76cc heads, and presuming that the deck height and casket volumes were typical, C/R with flat top pistons in a 350 would be about 8.97:1. Changing to 58cc heads would bump that to 10.96:1 with no other changes.

FWIW, when installing larger vales in the past, I've experienced smaller chambers as a result, since I generally prefer the to have the valve seats cut as little as possible to retain their hardness. Usually, longer valves (Buick or SBF) can be used to regain spring installed height without having to cut the spring seats dangerously deep and retain nearly original valve train geometry. Then again, there are probably about a hundred "right" methods to change valves.

If you install 1.94" intakes in the '416 heads, you may end up with 57cc chambers by the time the valve preimeter is unshrouded. That's what happened on the last set I did.

That would be a lot of compresion on pump gas for something that doesn't have SFI and individual cylinder ignition timing control (like an older ECM). With that type head, an 0.051" head gasket, and typical flat top pistons with 6cc worth of "eyebrow" valve reliefs, you'd still be at a static C/R of 9.99:1. You may want to consider 64cc heads as a possibility without having to change pistons. Then again, if you're planning to change pistons, the gloves are off and everything is fair game.

 

If the pistons are full dished, they won't need the eyebrows because the floor of the dish is at or below the depth of the eyebrows. Starting in '87, the factory used partial dished pistons that had both a dish and eyebrows. The pic is of the pistons I put in my 350 this spring, between the dish & eyebrows they're 10cc. Flattops with eyebrows are typically 4-5cc.

 

This is a full dish piston.

 

Pulled the head off today to show you guys what i was thinking, turns out they are dished and have valve reliefes i know i was totally wrong thanks. Heres the bad news, my dad had this engine in a project and as we were adjusting the rocker arms a knock developed, i think ok oil pump cut and turned a bearing no biggie i was getting all new bearings and an oil pump anyway which is inexpensive, however when i pulled the head off today i managed to luck out and find the knocking problem (sigh)somehow a bolt got into the cylinder and punched a hole in the head and then mashed the piston out wide enough to crack the cylinder wall. So the head is junk and i would imangine the block is junk too. seems like thats just my luck. Life gives you a junk engine you make a boat anchor.

 

I have calculated the compression ratio of that engine.
It is 1/4"bolt to 1 ;piston that is.
Should run fine on "grade 8" gasoline.
Anchors away!!
(sorry, couldn't resist)