350cid heads on a 267cid?

1368 Views 15 Replies 8 Participants Last post by maliboo, Jul 16, 2009

maliboo

Discussion Starter · Jun 11, 2009

Hi!

Racing class rules dont allow me to change bigger engine, so I'm stuck with this original 267cid small block. However, I can kick out more power from it, and thats why I'm considering this head swap. I have pair of ported heads with bigger valves (1.94" & 1.6") from a 350cid, will they fit on a 267cid?
I know they have slightly larger chamber, but that wont be a problem for me. I just need to know if they fit and work, or not, before I take those stock heads off.

1 - 16 of 16 Posts

BogiesAnnex1

· #2 · Jun 11, 2009

maliboo said:
Hi!

Racing class rules dont allow me to change bigger engine, so I'm stuck with this original 267cid small block. However, I can kick out more power from it, and thats why I'm considering this head swap. I have pair of ported heads with bigger valves (1.94" & 1.6") from a 350cid, will they fit on a 267cid?
I know they have slightly larger chamber, but that wont be a problem for me. I just need to know if they fit and work, or not, before I take those stock heads off.

Nope, you only have a 3.5 inch bore, the 350 chambers and vaves will be outside the bore diameter. The 305's quarter inch larger bore is a just at sometimes with a 350 head.

Bogie

SSedan64

· #3 · Jun 11, 2009

A ported set of these which came on the HO 305 Eng may work without valve to cylinder interferance. > http://www.chevytech.com/3c14014416.html

DoubleVision

· #4 · Jun 11, 2009

Providing you could get 350 heads to work, the larger combustion chamber would lower the compression ratio down to around the 5:1 range, it wouldn`t make enough power to spin on mud.

maliboo

Discussion Starter · #5 · Jun 11, 2009

The 350 heads I'm thinking of buying have 64cc chamber vs. stock heads 58cc. CR will drop from 9.0:1 to 8.2:1 with flat top pistons and that would be enough since I am running a blower on top of it. But if the chamber diameter is too large, it makes that idea just about as good as crap..

my87Z

· #6 · Jun 11, 2009

maliboo said:
The 350 heads I'm thinking of buying have 64cc chamber vs. stock heads 58cc. CR will drop from 9.0:1 to 8.2:1 with flat top pistons and that would be enough since I am running a blower on top of it. But if the chamber diameter is too large, it makes that idea just about as good as crap..

the problem is not the combustion chamber but the valves, you said that they are 1.94/1.60 valves, if you add that up it = 3.54" your bore is only 3.5" standard, the valve are already .040 to large you would have to go .085" -.100 over bore for them not to hit the cylinder block or cylinder walls, i believe the stock 305ho 416 heads were priduced with 1.84/ 1.50 valves = 3.34"and a 58cc chamber unless you have bored you motor over they may still be tight, as they have a small gap between them maybe .010-.020" which would be more like 3.44-3.54" but if you've had the cyl's over by 030 you should be fine, they are probably the best production head that you would be able to have put on this motor, if i were you i would look for a set, have them cleaned up, mild port polsih, swirl polish valves, replace guides and even milled a bit to give you even better comression ratio, if you did all of this i would certainly think it would be worth 30hp over what you have now

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matt167

· #7 · Jun 11, 2009

the 267 has like 55cc chambers.. smallest 350 cylinder head has 64cc chambers.. so you'd kill the performance even if they did fit

cobalt327

· #8 · Jun 11, 2009

maliboo said:
that would be enough since I am running a blower on top of it.

You gotta like the rules that come from some of the further-flung racing venues!

Gotta use the stock displacement, but you can use a blower! Brilliant!

But the racer in me has to ask- why not a 305, at least? IIRC, there were optional 305's in all applications that got a 267. Some apps could have a 267, 305 or 350 for that matter (as well as the 90 degree V6, but we won't go there...).

maliboo

Discussion Starter · #9 · Jun 12, 2009

cobalt327 said:
You gotta like the rules that come from some of the further-flung racing venues!

Gotta use the stock displacement, but you can use a blower! Brilliant!

But the racer in me has to ask- why not a 305, at least? IIRC, there were optional 305's in all applications that got a 267. Some apps could have a 267, 305 or 350 for that matter (as well as the 90 degree V6, but we won't go there...).

You can say that again

dum rules, but what can you do.. with the weight of my car, this class allows up to ~275cid with forced induction, after that only n/a up to ~375cid. I could get enough power out of 350cid n/a, but I think I'll get better power and torque curve from a blown engine, even when it is 100cid smaller than the maximum allowed displacement. That makes it easier and more fun to drive

DoubleVision

· #10 · Jun 12, 2009

Sheesh, I`ve only seen one 267 in my life, and one 262 for that matter.

cobalt327

· #11 · Jun 12, 2009

maliboo said:
with the weight of my car, this class allows up to ~275cid with forced induction, after that only n/a up to ~375cid.

Ahhh, make sense now.

Cool as can be, though. I wish our stateside tracks would get resourceful like that and maybe breath some extra life into the Saturday night tracks. Like as a exhibition class or something. And I bet that car is a ball to drive!

Whatcha using for a carb?

maliboo

Discussion Starter · #12 · Jun 12, 2009

cobalt327 said:
Ahhh, make sense now.

Cool as can be, though. I wish our stateside tracks would get resourceful like that and maybe breath some extra life into the Saturday night tracks. Like as a exhibition class or something. And I bet that car is a ball to drive!

Whatcha using for a carb?

Yeah, sometimes these rules are a ***** to follow, but after all they are just what makes things interesting

I have a Holley 9776 four barrel. Its 450cfm single pumper with mechanical secondaries. It could use a bigger carb or at least a double pumper now that its been blown, but I'll be going with this for now since it has served me better than well so far and I have a ****load of different size jets and pv's. I originally bought this carb just to get rid of the original 2bbl rochester and crappy iron intake. So i bought that holley and Edelbrock perf. airgap rpm intake. It really gave this engine a taste of life, at least compared to stock carb&intake.
Now it has Procharger blower and custom intercooler, mocked it up and made brackets and such and took it apart again for finishing work and paint. Then decided to go for better-flowing heads. or as it seems to be, just do some porting with the stock ones and toss some bigger valves in them :mwink:

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cobalt327

· #13 · Jun 12, 2009

Well, keep us posted- and send a couple pictures if you get a chance. Good luck and give em hell!

maliboo

Discussion Starter · #14 · Jul 16, 2009

Been busy for a couple of weeks, and finally got some results after long day running the motor at dyno.

Basic parts list on the engine:

-Bottom end, other than a hi-vol oil pump and balancing, completely stock with new bearings & rings

-Crane Z-274 cam, hi-intensity lifters, comp cc3100 gears&chain

-Stock 305 heads, slightly ported, 1.84" & 1.5" valves, K-motion K-700 springs, otherwise all stock, measured 8.2:1 CR

-edelbrock rpm air gap intake

-procharger blower, 10psi boost limit, limited with a by-pass valve

-holley 450cfm carb, list 9776-1

-msd boost-retard box

Thats about it, nothing fancy, hope it holds together

After one day at engine dyno, we got 372hp @ 6000rpm and torque peaked 350 lb-ft at around 4500rpm. Seems kinda lowish, but when i look at the torque curve i see torque climb over 300lb-ft at just over 2000rpm and there it stays right to 6000 so it'll make the car very driveable. We didnt rev it over 6000 altough the power curve indicated that there'd be some horses to get with 500 or 1000 more rpm, but we got what we wanted with 6000rpm and were happy with it.
Now just the final squeeze to complete the car and we are off to the track for testing hopefully at the beginning of august!

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ericnova72

· #15 · Jul 16, 2009

You might be surprised the amount of power that you could get by going to a bigger carb like a 600 DP or even bigger. wouldn't surprise me to see 40+ hp come from it. Just a thought.

maliboo

Discussion Starter · #16 · Jul 16, 2009

ericnova72 said:
You might be surprised the amount of power that you could get by going to a bigger carb like a 600 DP or even bigger. wouldn't surprise me to see 40+ hp come from it. Just a thought.

Yeah, it sure could use a douple pumper, that we noticed already on the dyno. As for the size, with this rpm & boost, i get exactly same pressure before and after carb on WOT. So its not THAT big of a restriction. Later on I might go forged pistons, more rpm and more boost, and thats when i surely need more carb cfm. Right now i just miss the secondary pump, when i hit the throttle hard at the sec. opening, it drops a little lean. not much, but lean is lean and it is not good.

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