sentein1

Okay i have a 357 chevy sitting in me 1989 camaro it had a 305 TBI i converted this 357 to TBI right now it has an RV cam and Flow tech headers with a 2.5" Exhaust all the way back(not real sure if its stock or not!).Also FYI i have 454 80Lb injectors in my TBI (I can crank them up if need be).I also have a multi port fuel injection pump hooked up.The Fuel Pressure Regulator held up to 40lbs of pressure without problem.Please don't say i need a turbo cause i tried that and a Megasquirt, neither worked so hot.

Okay my question go as follows.
1.)I have a set of 202 heads sitting around if installed what would my resulting Compression Ratio?I have 8:1 right now.i have heard that bumps it up to 11:1.True or not?

2.)Also on the 202's how much if any can i shave them without a valve hitting or something of that nature.(Just curious)or what would get me to about 12 13 or 14:1 compression Ratio?(Again just curious)

3.)I also have a Comp Cam that will have a good lope to it bought used with 1000 miles on it $50.Anyhow do you guys think it'll work okay with TBI?You probably need more info(i'll see what i can do)!

4.)Another thing that i was wondering was where can i get a performance intake manifold with a way to fit a TBI on it or maybe even 2?would i have to make a plate of some sort to convert it to a performance intake?

5.)I can get a single plane intake for about $150 can i use it with my TBI or would it not be worth it?

6.)If i do all of this or even some of it will it work togeather well?or can my TBI even take it?

Sorry for all the questions.If i do it i would like to do it right.


P.S. I do realize a 2 barrel TBI will only allow enough Air Flow for ab 500 HP max.I can fuel it to that point with my two injectors pumped up to 40PSI.

sofakingdom

iTrader: (1)

Not familiar with that casting # .... ?? New one on me. Can't help you there.They only make about 10,000 different ones; what's the specs? Some will work and some won't. You'll need a part # or grind # or something. TBI does not care how many miles it has on it or how much you paid for it, it mostly cares about duration and lobe separation angle.

Yes you can use most any 4-barrel intake, with a TBI adapter. That's really the way to go in fact, a much better deal than a "TBI" intake. Watch out for the adapter though: some of them put the TBI in a bad spot, I think it's the Holley one; maybe do a search for "adapter" onthe TBI board or something, and see which one(s) work and which don't.

dimented24x7

iTrader: (2)

The holley projection one is the plate to look out for. Moves the TBI forward (or back). Back makes hood clearance much easier with a hi-rise intake, but requires fabbing a bracket and/or throttle cable/tv cables.

As far as the cam goes, the BBC TBI is limited to around 650 CFM of flow in carb terms, so you dont want it to rev too high or the TBI will become a restriction at some point. Also, the LSA is important with SD systems as if its real tight, itll lower the vacuum it pulls, which will cause you to become confined to the high MAP areas on the fuel tables at lower RPMs, which can hinder the resolution of the fueling as well as require careful tuning to make the computer idle well and not surge or anything like that. Id say something like 210-220 degrees of duration with a 112-114 LSA with a good intake, 2" TBI, higher stall, gears, and free flowing exhaust should make for a good street setup. I wouldnt use anything with much less then 210 degrees as itll basically make for a torque happy tire peeler like it is now with the RV cam.

sentein1

well thanks for the input.I will get the specs on the cam by the latest thursday.Also a 202 head is no cast # it is actually a valve size alot of stock car drivers like getting there hands on these.As i have herd the 202 heads were manufactured in the 60's or early 70's and used on stock cars and trucks to get a few more ponies.Back in those years gas didn't cost much so not many people worried ab filling up every other day.This made the high compression heads a good stock power adder.I was just wondering if anyone knew the final comp ratio is all!

oh i guess i better add this question while i am thinking about it.Did the 350's have 2.5" exhaust stock?I am not sure how stock all of the stuff on this is honestly.

sofakingdom

iTrader: (1)

OOOooooohhhh, THAT!!!!

No, 202 isn't a valve size. 202 is a 3-digit number with no decimal point and no units; in the format commonly used as shorthand for casting numbers.

2.02" is a valve size. There's a difference.

Yes, a few of the factory high-perf heads from days gone by, before aftermarket heads became so cheaply and widely available, came from GM with 2.02" intake valves put in them. Mostly, 186, 487, 461, 461X, 462, 492, 041, 291, & 292 castings. The number of stock heads running around with that size valve in them nowadays though, is probably AT LEAST 50 times greater than the number that the factory did it to; not even counting aftermarket ones. Any jackleg can take any random set of SBC heads, and jam 2.02" intake valves into them. A quick surf through eBay listings will show you that. Since 2.02" intakes cost the same as 1.94" intakes, and require the same machine work during head rebuilding if machine work has to be done (as it about always does), and the uneducated general public has been conditioned to think that the larger valves all by themselves will make more power, people stick them into ANYTHING and EVERYTHING to help them sell. Makes good ink for the auction. 882 or 624 smoggers, 434 castings off of 267s, whatever. People will even stick them in a set of 305 swirlies and call it "good".

How good a set of heads is, IS NOT determined by what size intake valves have been installed in them. It's determined by the CASTING. If you want to know what the heads are capable of, the only really useful piece of info, is the CASTING #; the intake valve size installed in them is totally incidental.

Same for the compression. The intake valve size doesn't determine that. In order to know what CR you have, you need the CASTING # (among other pieces of info). And likewise, the CR doesn't determine how often you have to buy gas; not now, or back when I was buying it in the days when factory heads with 2.02" intake valves installed in them were still brand-new. Get the casting number, and from that you can find the chamber size, and if you know everything else about how the motor was built, you can then calculate the compression ratio. Remember though, no "assumptions"; you have to KNOW, by measuring, what the piston dish volume is, the deck clearance, and the head gasket thickness, in addition to the head CASTING, to make an accurate determination. Anything you don't know and just "guess" or "assume", makes calculation meaningless.

Since there were no 350s with TBI in these cars, there is no stock exhaust size for them. But since your car was a 305 TBI car, that's probably the exhaust it has on it, to whatever extent it's still stock; which IIRC was 2" at the manifolds and 2¼" from the Y-pipe back.

sentein1

Hey next time could u at least let me down a little softer sofakingdom!I honestly don't play with SBC alot at all.Trust me i do realize that valve size has only a small part on how an engine will flow.I picked these up for the simple reason or even the possibility of higher compression ratios.Oh and higher CR does make more power and will have some effect on how often u fill up!When everyone talks ab these heads they say 202 not 2.02 so i just put it in as i heard it.i also kinda figured GM heads would be kinda sandardized so all the CR's would be the same.

I am a diesel tech.I play with 19-36:1 CR's all day no throttle bodys no carbs no spark plugs and I almost never play with gas engines.Let alone SBC so i don't know alot of details about head castings, valve sizes, header flow, intake flow,or even the best intake for the particular job.That is why i asked these questions.

I will get the cam #'s and the Casting # of the heads or do u know a really good site to look up the casting # on!?

sofakingdom

iTrader: (1)

I don't mean to be a jerk; it just comes natural to me I guess.

www.mortec.com has a good listing of casting #s.

Yeah the problem with just listening to what "people say", is that they tend to just throw around alot of buzzwords without any real thought to the reality (if any) that lives behind them. If you're new to the bobby, or to some particular part of it, you kind of get infected with stuff that "everybody" says, until you find out that it's just a bunch of hot air. The whole "202" thing is about like that. Like you said, accurately, a bunch of the hottest cars of the late 60s and early 70s (L79 Novas, Z28s with the 302 and the LT1, the Vettes with the LT1, etc.) had 2.02" intake valves installed in their heads, which were the same casting # as the heads in other cars (186 for example, I usually used to get out of 69 & 70 model Impala station wagons.... I'd see one of those cars, about 40% odds it had 186s). So it kind of became shorthand for "the good heads". But after a while, after you couldn't find the "good" ones or even the "not as good" ones either in unmolested original condition any more, and a couple of new generations of participants came into the hobby, all of that got forgotten. All that's left now, is the buzzword.

But I'm rambling. Bottom line is, the 2.02" valves were just an add-on; the heads they came in were already good. You don't take a set of inferior heads and stick 2.02" valves in them, and they're suddenly "good" too. eBay notwithstanding. Did you look through there, by the way? Notice how about HALF of all the old stock SBC heads on there, have 2.02" valves in them? Well, here's what happens (taken from an auction there this morning) when you put big valves in smogger heads, and get too aggressive with the seat cutter and the die grinder. Note the thickness (!!) of the metal that's exposed. It's down to business-card level around the seat. No wonder it broke and fell out.

All that glitters is not gold.

sentein1

Very good site for the cast #'s

Mine is 354434.....75-79...262/267/305...60cc chambers

I did notice that the valve sizes were listed on the top two on the list.

330545.....73......350..........76cc chamber, 2.02/1.60
333881.....74-75...350..........76cc chamber, 2.02/1.60

They actaully have 2.02 listed does this mean that mine are really not 2.02 valved heads?But i did notice the chamber size was smaller than the listed 2.02?

Oh and here r the cam specs with the part #113941.
Lift:
Opens Closes ADV Duration
Intake 25 BTDC 67 ABDC 272°
Exhaust 75 BBDC 29 ATDC 284 °

Lift:
Opens Closes Max Lift Duration
Intake 1 BTDC 35 ABDC 107 216 °
Exhaust5 1 BBDC (3) BTDC 117 228 °

Oh and its a Crane Cam not a Comp Cam.so what do u guys think?

discostu

They just don't have all the information on your casting.
Being a 262/267/205 casting, I'd be willing to bet they they have 1.84/1.50 valves, or smaller, even 1.72/1.40 maybe?
Pull out your calipers and measure those valves, and grab your burette and cc the ports!
And if you're feeling really frisky, throw 'em on a flowbench and find out what the CFMs are.

sofakingdom

iTrader: (1)

There were a few castings that were used ONLY in applications that called for the larger intake valves. There are very very few of those castings in existence.

I have a 78 El Camino 305 2-barrel sitting in my driveway. 120 HP from the factory, IIRC. We've had it off and on since about 1984 (sort of been in the family). Has 434 heads. Came with either 172" or 1.84" intakes, if memory serves. I don't know what mine have in them, They've never been off the block, with only 350,000 miles or so there's been no need so far. Just getting broke in good. But at least, that'll give you an idea what that head casting was originally used for.

If the bowls were blended and the guides cut down when the valves were put in, they could be OK; I know they're a "lightweight" casting, kind of thin, so they'd be prone to cracking (like the one in the pic up there) if Cletus or Billy Bob got in there and "hogged em out". But I've never tried to work up that casting for a performance application, so I don't really know how much flow you could get out of them.

One of the things that happens when you put big valves into a small chamber head, is "shrouding". Keep in mind, all that stuff trying to come into or out of the cyl, has to pass through the head port, around the edge of the valve, and in between the edge of the valve and the "side wall" of the chamber. It doesn't do a whole lot of good having a 2.02" valve or a cam with .600" of lift, if the edge of the valve is less than ¼" from the chamber as it often is. In a WELL-DONE set of small-chamber heads, the chamber ALWAYS ends up MUCH larger than it started out. Here's a pic of a 305 head (081 casting) showing what gets done. I was putting 1.94" intakes into these, they originally came with 1.84". The top chamber is with the basic machine work done, and the 1.94" valve just sitting there; imagine how little flow there will be around that valve. The lower pic is after relieving the chamber, kind of laying it back around that side of the valve (which is the high flow side). These chambers started out 58cc, are probably about 62cc now. The valves are sitting on the stem of another valve, a stock SBC one (11/32" dia); note how LITTLE flow there can be over on the side toward the spark plug boss, in the "before" pic.

sentein1

I do see the difference.That bottom valve has 25-30% more area for flow just from the looks of it which is a mojor inprovment.

My cousin had these heads and they were on his custom pulling tractor.He "said"(never saw it) he had a supercharger set up on it and he figured 800-1000 Hp i am thinking he is full of it.These heads look stock to me!I am very thankful for the help.

I am not going to pull the heads and put these on.I am thinking i will just leave the camaro as is for now!Save the cam and heads for another build of some sort.I was actually thinking of sticking another 350 in a saturn see if i can make it fit.(I know way overkill)

Thanks again to everyone who posted especially sofakingdom