Which Cylinder Heads?

LeeRoy · Guru

Which Cylinder Heads?

4SPEED427 · A Poncho Legend!

Likely 64cc heads, 1.94" intake valves, commonly called F.I. heads by the old guys because they originally were used on the Corvettes with fuel injection. Great heads if you want to do an old school type build keeping an engine looking original. However, if you put those on a 327 with an original piston the compression is a bit on the high side, I believe 10:1.

LeeRoy · Guru

Carl Stevenson wrote:
Likely 64cc heads, 1.94" intake valves, commonly called F.I. heads by the old guys because they originally were used on the Corvettes with fuel injection. Great heads if you want to do an old school type build keeping an engine looking original. However, if you put those on a 327 with an original piston the compression is a bit on the high side, I believe 10:1.

Thanks Carl. These heads are on the 327 that's in my 67 Malibu. Internet says 62cc chamber volume. The specs from Oshawa refer to a comp ratio of 10:25 to 1 for the 275 horse version. Block is # 3858180 so maybe 300 horse with these heads? Maybe my L 79 clone is just a camshaft and a carb away!

-- Edited by LeeRoy on Thursday 22nd of May 2014 12:27:51 AM

4SPEED427 · A Poncho Legend!

In 67 it would have been rated at 275 I think.

Nice engine you have, I'd leave it pretty much as is, but that's just me. Most guys like to "upgrade" them.

LeeRoy · Guru

Carl Stevenson wrote:
In 67 it would have been rated at 275 I think.

Nice engine you have, I'd leave it pretty much as is, but that's just me. Most guys like to "upgrade" them.

You're up late! LOL. I just edited my last post. Time for bed.

66 Beau · Poncho Master!

Double bump heads are good, but Vortec heads flow a lot better and are the same 64cc. If the double bumps need rebuilding, you might find a new set if vortecs will be pretty comparable cost wise. You'll need a new intake manifild & valve covers and it won't look stick, but vortecs flow better than most after market performance heads...

4SPEED427 · A Poncho Legend!

If you want to bump it up to an L79, you need pistons, cam, intake and carb. Quite a change from a 275 horse. Lots of fun though, and even just putting that cam in your engine is a nice upgrade. I've had a few 327's with that cam over the years, still my favourite.

And yes, I'm a night owl and an early riser as well...

65 SD L79 · Canadian Poncho Superstar!

461 heads are good but if you have to rebuild I would upgrade to 202 valves with harden seats, 490 intake with holley and the L79 cam. You may want to stick with flat top pistons for a few reasons

GLHS60 · Poncho Master!

1968 L-79 with a Q-jet and cast intake actually make 10 more H.P than a 1966 L-79 with Holley and factory alloy intake.
Source: NHRA engine H.P. factoring guide. Q-jet engines always make more power than the small Holleys, and are equal to the larger Holleys.

Thanks
Randy

65 SD L79 · Canadian Poncho Superstar!

GLHS60 wrote:
1968 L-79 with a Q-jet and cast intake actually make 10 more H.P than a 1966 L-79 with Holley and factory alloy intake.
Source: NHRA engine H.P. factoring guide. Q-jet engines always make more power than the small Holleys, and are equal to the larger Holleys.

Thanks
Randy

was this real test hp? 1966 L79 350hp 1968 L79 325hp

65 SD L79 · Canadian Poncho Superstar!

GLHS60 wrote:
1968 L-79 with a Q-jet and cast intake actually make 10 more H.P than a 1966 L-79 with Holley and factory alloy intake.
Source: NHRA engine H.P. factoring guide. Q-jet engines always make more power than the small Holleys, and are equal to the larger Holleys.

Thanks
Randy

for the record a well built Q jet is way better then a holley but if you are going with the the factory look

Beau 69 · Addicted!

Carl;

For the record do you have the GM PN specs handy for L-79 upgrade RD: cam, intake, pistons ,etc with 461 heads.

Is there an aftermarket spreadbore alum intake that would work well with existing Qjet 750 carb? Might
wake up our 327. Is that a solid lifter cam?

Thanks

Les

4SPEED427 · A Poncho Legend!

No, L79 is hydraulic. I can find the specs, but don't have them handy. I believe lift is .447 but I forget the rest. You may be able to find it if you google the GM number, 3863151.

It's a nice cam but an automatic with stock converter and gears will have less off the line performance than with a stock cam. However, at about 2500 they wake up real nice.

ARCADIAN · Poncho Master!

Speed Pro makes a nice retro L79 Cam (hydraulic) and Lifter Kit part #CL 179R, INT/EXH 222/222, 2200-5800RPM with a great idle. Edelbrock Performer Intake or Weiand and a good set of Headers, the original L79 pistons were 11:25 to 1 I think too much compression for todays gas. You might like the Speed Pro flat tops with a 64cc head 9:5-10:0 to 1
my nickels worth

4SPEED427 · A Poncho Legend!

I've used the Speed Pro a few times (including the last time in my 327 65 SD) and always been happy with it. Only once have I used it with the actual L79 piston. Like you say, it works fine with 9.5 or so compression too.

Chris, is it just me or do you think it seems a bit lumpier/less bottom end vs. the stock cam? I've used both and thought the GM original seems a touch tamer.

ARCADIAN · Poncho Master!

Yes the Speed Pro is certainly lumpier, my 327 idles at 850 and bottom end response is instant, winds to 5800 in a "hurry". I am very happy with my engine setup, it has awesome power & still braking it in @700 miles.

GLHS60 · Poncho Master!

H70 SS ACADIAN wrote:

GLHS60 wrote:

1968 L-79 with a Q-jet and cast intake actually make 10 more H.P than a 1966 L-79 with Holley and factory alloy intake.
Source: NHRA engine H.P. factoring guide. Q-jet engines always make more power than the small Holleys, and are equal to the larger Holleys.

Thanks
Randy

was this real test hp? 1966 L79 350hp 1968 L79 325hp

NHRA factors engines in stock classes on how fast they run. Stock engines can be rebuilt to stock specs but no porting etc. In the case of the L-79 with it's stock Holley and aluminum intake it is rated at 300 H.P. while the L-79 with stock Q jet and iron intake it is rated at 310 H.P. 300 H.P. 327's are rated at 289 H.P. with a Carter and 275 H.P. 327's with a Q jet are rated at 295 H.P. In every case that I researched, a Q jet is always more powerful than a small Holley. This is general information available to the public, not secret tin foil hat stuff.

Thanks

Randy

65wagon · Poncho Master!

stick with the 461 heads, to pull power they need bowl clean up like most heads , dont go with the massive valves unless you plan to spin her up , 194 with 160 exhust works fine the lift on L 79 cams is more like 450 intake 460 exhust and it works fine run behive springs and have fun. as far as hardened seats i dont use them unless the seat is buggerd, with these oldies we dont put the hard miles on the anymore, i always run a flat top piston and you can get away with up to 10.7 if you tune it on 87 octane the distributers and all factory crappy and need major work

Beaumont4008 · Uber Guru

The L79 cam #3863151 65-68 was .447 int. 447 exh. lift 221-221 duration at .050. The 69 350 l46 350 hp cam 3896962 is .450 int. .460 exh.

Ian

ak 67sd · Poncho Master!

If you're block isn't zero decked the pistons will probably be lower in the cylinder and you'll lose some compression, an engine build really depends on what your goals are... An L79 in a heavy car without steep gears will probably get it's butt handed to it by pretty much any newer car with a six... I'd probably call a couple of cam manufacturers for a more modern cam recommendation, and if you don't have the short block consider a 406 build. Again, really depends on your goals...

ak

sd ragtop · Newbie

you are correct very rarley do the pistons live up to their true compression ratings.adding a cam with more duration or overlap will also reduce true cylinder pressure negating any issues with poor gas

sd ragtop · Newbie

p.s. also flat top 10:1 pistons have a larger quench area on top lessening likelyhood of detonation(less hot spots)