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2.02 heads on a 305

Old 03-30-2002, 11:19 PM
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2.02 heads on a 305

hey guys i am wondering if i got the sportsman heads with the 2.02/1.60 valves and the 67cc chamber what problems woudl i run into? i know i would lose compresion but i am savin up for a 350 swap so i don't wunna buy little heads for now.why do they say not to put 2.02 heads on a 305? also what is valve shrouding?thanks
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Old 03-30-2002, 11:22 PM
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You will lose compression for sure. You will also notice a loss of low end torque, but will gain upper rpm power.
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Old 03-30-2002, 11:31 PM
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I don't think you can put 2.02 heads on a 305, the bore is too small. Plus 67cc chambers would seriously kill your compression.
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Old 03-30-2002, 11:39 PM
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With the valve right up against the cylinder wall there is no room for any air flow in that region.
Having too much valve can result in lower air flow thru the engine.

Generally you only want the sum of the valve diameters to equal 85% of the bore. thou due to cam selection, folks have found HP above this. And in all out racing you can go above it, but drivibility can suffer in street use.
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Old 03-31-2002, 12:20 AM
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NJ Speeder, aka Tim, Has Edelbrock performer heads with 2.02" valves and 60ccs.

Important Notes:
When using stock rockers on Performer & Performer RPM heads, .100" longer than stock pushrods are required.
Please use Head Bolt Kit #8550 for an easy installation.
S/B Chevy heads may not be used on engines with less than 4" bore (262, 265, 283, 305, 307 c.i.d.) except with cams having less than .450" valve lift.

Last edited by Tas; 03-31-2002 at 12:23 AM.
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Old 03-31-2002, 12:31 PM
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ok so i can get the sportsman 2.02 heads and i will just have to use the lt1 cam? with them heads and lt1 cam,performer intake,650holley, msd ignition,and a blaster 2 coil i should be well into the 13's right? then i can swap it all over to a 350 except the cam and i will have a low 12 secound car.
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Old 03-31-2002, 12:42 PM
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i have 2.02/1.6 valves and now im running into some problems. some people say i used valves too big for the block and i have valve shrouding or something. engine shakes and sounds like really loud ticking coming from under the valve covers. dont screw up like i did and get those big valves. go smaller
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Old 03-31-2002, 04:05 PM
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2.02 valves fit fien onto teh 305. i have been running mine for 3 years now with out any problem. the cam is what creates shhrounding issues, not the valves. any cam that puts the intake valve past .460 total lift will start to get intopt eh grey area of lift, .470 will cause a noticable vacuum loss, and .480 will require a lot of tuning time and a very custom chip.
with the lower compression on the car you will be able to run a lot more timing too, prolly another 4-6 degrees of base and even more total timign at higher rpms.
big heads are good

later
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Old 03-31-2002, 07:35 PM
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im thinking about going the same route as you...i was wondering the same thing...i still havent decided if i wanna go 350 or not ive been toying with the idea of just supercharging the 305 but i dont know yet
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Old 03-31-2002, 09:26 PM
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2.02/1.6 valves will fit fine on a 305. I have an early 90s issue of Car Craft where they put Trick Flow 23* heads on a 305 with a .480 lift cam and made like 280 hp. They claim that the bore of the 305 can handle any lift. They showed a pic of the trick flow heads on the 305 from a bore perspective and they fit fine.
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Old 03-31-2002, 10:04 PM
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ok so if i run the world s/r torquers with the lt1 cam do u think i would have a pretty good combo? also its either get them heads with the lt1 cam and an edelbrock tbi intake with the stock tbi and stock chip or run a better cam, performer intake,holley 650 carb,msd ignition,accel dist., blaster 2 coil,mallory afpr. so wut do u think is the better setup? i am think if i run the carb setup i will make more power because of the bigger cam and ignition and just cause carb makes more power then tbi. the upside to runnin the tbi is i get the good heads but i am restricted on the cam and i don't have access or the money to get a custom chip burned. so wut do u think is the wiser choice and wut do u think i will run better times with? i'm not goin on the well if u do this and that then u will get that cause i am not goin to spend a million dollors. thanks
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Old 03-31-2002, 10:06 PM
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the carb is a step in teh worng direction. you will need some custom tunign to get the most of out of the cam wiht the tbi.

later
tim
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Old 03-31-2002, 10:11 PM
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ok see but i have no way to do custom tuning to the tbi. and why do u think carb is a step in the srong direction? i don't see many top fuel tbi dragsters outs there. tbi just seems like sumthing to get u from here and there not to go fast. well please try to prove me wrong. also i could give a **** about cold weather start ups and all that crap just as long as it starts up its fine with me. i'd rather wait 15 mins in the morn and go fast then get up and go slow lol
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Old 07-02-2002, 06:28 PM
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i'm putting a set of 2.02 valve heads on my 305


how far down can i have the heads milled so i can retain my 9.3:1 compression?

i'm not sure on what the head cc is currently

i should have the casting numbers on friday when i pickup the heads

then i guess i can give you guys the casting numbers and you can tell me my head cc.........?

can i shave my heads AND use thinner head gaskets?


if my compression does go that low, i am going to think about saving some $$$ for that new vortech supercharger

then when i blow my shortblock, i'll buy a bigger, better motor
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Old 07-02-2002, 07:45 PM
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Originally posted by NJ SPEEDER
the carb is a step in teh worng direction.
only while in the TBI board
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Old 07-02-2002, 08:25 PM
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Originally posted by brodyscamaro
only while in the TBI board

ummmm sorry brody.....i found this thread while using search and didnt realize what forum it was in

i just need to make sure i can run a cam that works with the heads and not plow my valves into my cylinder bore
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Old 07-02-2002, 09:37 PM
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ohhhh no
i was just replying to how nj speeder said carbs are a step backwards.
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Old 07-02-2002, 09:58 PM
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Just get them milled to 58cc. That's the stock cc size.
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Old 03-12-2019, 10:31 PM
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Re: 2.02 heads on a 305

I realize this is an old thread, but I have a set of brand new 2.02s and a car with a stock TBI 305. I was wondering if I could drop them on there and get some more power out of it. If I did, what would be the right size cam to make it all work?
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Old 03-12-2019, 10:46 PM
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Re: 2.02 heads on a 305

No
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Old 03-13-2019, 04:21 AM
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Re: 2.02 heads on a 305

No. Only aftermarket 2.02 heads with non-stock valve spacing can work.
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Old 03-13-2019, 08:13 PM
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Re: 2.02 heads on a 305

Although I've seen this work before, I've also seen it not work. You need to actually build for it, if you do it otherwise (even if the valve clear the bore in a static test) you could have interference problems when the engine is under stress, there would b no room for tolerance.
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Old 03-13-2019, 09:17 PM
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Re: 2.02 heads on a 305

You could notch the bore or maybe offset dowel the head to space the valve over so you dont have the lift limit of roughly .430-.440 or so before valve contacts bore. Else its better to stick with 1.94’s or maybe a 2” at max. A 1.94 on a good head will feed all a 305 will do na for the most part
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Old 03-14-2019, 05:23 PM
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Re: 2.02 heads on a 305

Originally Posted by iroc22 View Post
2.02/1.6 valves will fit fine on a 305. I have an early 90s issue of Car Craft where they put Trick Flow 23* heads on a 305 with a .480 lift cam and made like 280 hp. They claim that the bore of the 305 can handle any lift. They showed a pic of the trick flow heads on the 305 from a bore perspective and they fit fine.
Look at that article again. First Guess: NOT 23^ heads. They were Twisted Wedge heads, first generation, with the intake repositioned at 13 degrees not 23. They also warned about valve-to-bore interference at higher lifts.



GM built millions of SBC-powered vehicles with 1.94" intake valves. When they built "performance" 305s, the biggest valve they offered was 1.85". There's probably a reason they knocked ninety thousandths off the valve diameter.

You'd do better to take .025 off the cylinder decks rather than to mill the heads excessively. Milling the head doesn't improve quench distance--which is almost always too damned big. Thinner head gaskets and/or milling the block removes more CCs per thousanth, AND also tightens the quench distance.
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Old 03-14-2019, 06:39 PM
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Re: 2.02 heads on a 305

Originally Posted by Schurkey View Post
You'd do better to take .025 off the cylinder decks rather than to mill the heads excessively. Milling the head doesn't improve quench distance--which is almost always too damned big. Thinner head gaskets and/or milling the block removes more CCs per thousanth, AND also tightens the quench distance.
Without me having to take my shoes off to count the thousandths of an inch...can you explain this to me?

The distance from the top of the piston at TDC to the roof of the combustion chamber changes (positively for quench) if you mill the heads (bring the roof of the chamber down), run a thinner gasket (bring the roof of the chamber down) or deck the block (sort of bringing the piston closer, so to speak). How does milling not improve quench?

I guess if your piston is down in the hole a lot, you will never get good quench with that arrangement. But it will get better when you mill the heads, no?

Last edited by DynoDave43; 03-14-2019 at 07:02 PM.
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Old 03-14-2019, 07:51 PM
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Re: 2.02 heads on a 305

Not the clearest pictures, but here is my 305 bore notches. And these heads are World Products Dart 305 heads with relocated valve spacing. 2.02/1.60 valves. .030" overbore.









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Old 03-15-2019, 04:36 AM
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Re: 2.02 heads on a 305

Originally Posted by DynoDave43 View Post
The distance from the top of the piston at TDC to the roof of the combustion chamber changes (positively for quench) if you mill the heads (bring the roof of the chamber down), run a thinner gasket (bring the roof of the chamber down) or deck the block (sort of bringing the piston closer, so to speak). How does milling not improve quench?

I guess if your piston is down in the hole a lot, you will never get good quench with that arrangement. But it will get better when you mill the heads, no?
Quench isn't measured to the ROOF of the combustion chamber. It's measured to the machined, flat part of the chamber. Milling the head makes for a smaller chamber, higher compression--but the flat part is still instantly above the gasket. Therefore, quench distance does not change by milling the head.

Cutting the block or a thinner gasket brings the flat part of the head closer to the piston top, reducing quench distance.

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Old 03-15-2019, 08:33 PM
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Re: 2.02 heads on a 305

Thanks Schurkey. I'm sure you're right. I'll pretend that I grasp the difference, and not take the OPs thread any further off topic.
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Old 03-15-2019, 09:07 PM
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Re: 2.02 heads on a 305

Originally Posted by DynoDave43
Thanks Schurkey. I'm sure you're right. I'll pretend that I grasp the difference, and not take the OPs thread any further off topic.
Dave, you're both right. Quench is measured between the top of the piston and the flat portion of the combustion chamber. Milling the head does not affect its' measurement, but milling the head will have an effect in terms of how quench is working during combustion...

- Rob
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