Kennybill

A dead horse is still a dead horse. I've been saying "I've been beating a dead horse since 1975."

ChevyZ06

Just wondering why you would suggest that. Granted the low numbers would have stayed the same. But the gains from my second test were from opening the exhaust bowl. Let me know what you are thinking. Thanks

ChevyZ06

To the death??

VinMichael

ChevyZ06

I see you too have the stingy bench!

VORTECPRO

I probably would just say its calibrated, both my flow benches are very close when it comes to data. Are you going to go any further on the J head development?

VORTECPRO

I would just prefer to be able to cut the bowl to the same dimension as the rest, then go from there. I also like the ductile iron seats because they cut better.

ChevyZ06

Your absolutely correct on the seats. I was going to keep this a secret but I have a new set of 2.07 1.72 SS valves for this project. When I installed the seats I had planned on using the large exhaust valve . To be honest I am not sure if I am going to use them now because I am kinda happy with the numbers. The engine that I am building is for my personal 1970 Cutlass S. 1974 455 long block that I found in the local pick-n-pull. Low compression, I have a tiny cam, and I found an O4B intake. If someone twisted my arm I might be forced to use the big valves.

ChevyZ06

I raised the port roof area around the guide boss about .150 Only a few cfm at usable lifts. I think that my J heads might be maxed out with what I would call moderate porting.

Battenrunner

olds 307 and 403

Most suggest only the larger intake valve, experts say on mild build like yours, that large exhaust valve will do more harm than good. Larger intake valve, yes. I have a 2.05" intake valve on my #6 heads with stock exhaust 1.56" valves and the bowls opened. The other set of #6 heads has 2"/1.625" valves with port and bowl work with the crossovers filled, I may add 2.07" valves.

ChevyZ06

Well the big 2.07 valve does help the J heads BUT there is a catch. From what I can tell so far the J head does have some potential. My goal with this project was to see if the J head could be a good usable casting with minor modifications. Right now I have to say that the answer is no. I have increased the flow numbers substantially, but this is not a DIY port job. The casting is very picky and requires a skilled head porter with the right tools to match the numbers that I have. What I mean to say is that some head casting respond to the basic mods better than other castings. My back ground is with mostly Mopar engines. Mopar has two basic castings for the Big Block engine. One casting responds greatly to nothing more that a big valve and a basic bowl port, The other castings actually loses CFM when a big valve is installed. But with skilled porting the second casting will out flow the first maxed out. With the J head installing a big valve and bowl porting is not going to give the same results as the same modifications on the C heads. I built a set of C heads a few years back that I installed big valves and bowl port with gasket match. I will post the numbers with the "finished product" on my J heads.

J heads 2.07 valve tricky port work
.50 37
.100 69
.150 110
.200 148
.250 179
.300 205
.350 221
.400 227
.450 229
.500 231
.550 232

ChevyZ06

C heads 2.07 valve bowl port gasket match

.50 32
.100 70
.150 106
.200 143
.250 173
.300 195
.350 212
.400 227
.450 236
.500 242
.550 246
.600 251

ChevyZ06

One thing to keep in mind is that the J head has a smaller port volume and will in my opinion out perform the C heads in some applications. If you are building an engine similar to mine, low compression, small cam, dual plane intake. Or if you are building a small displacement engine. I think that the ported J will work great!

ChevyZ06

Some of my other projects. Pontiac 6X heads. Pontiac heads are also very challenging. This set flows just a little more than my J heads. But not much!

ChevyZ06

Both valves are 2.07 dia. Both valves are 45 degree with 30 degree back-cut. Valve on the left reduces the flow 16 CFM. Go figure

Bernhard

ChevyZ06

I have machined one of the valves to regain almost 12 cfm. I will try to post a picture of it tomorrow.

83hurstguy

Looks like the right valve has a thinner margin, wider seat width, slightly undercut stem with polished face... what changes on those parameters made the most difference?

ChevyZ06

The picture doesn't show very well but the factory valve is shaped very much like a nail, the stainless valve has more of a tulip shape. I am grinding as much of that shape away as I can. The more that I change the shape, the better the port flows. But I'm running out of valve material.

Bernhard

Is there any risk that the valve will become weak and fail under load?
What would worry me is that the valve was designed with a lower grade of steel . Is the grade of steel up to supporting your new improved valve design.
Have you tried multiple back cuts on the valve?

ChevyZ06

Probably not with the way I drive I did try multiple angle of back-cut. With the shape of the factory valve I had to machine quite a bit of material away. I will try to post a picture of the finished product soon.

ChevyZ06

Finished product to regain most of the CFM loss

ChevyZ06

I CCed the intake ports. I think that you guys will be shocked when I post the numbers. Spoiler! They are tiny!

Bernhard

Nice work.

ChevyZ06

thank you

Battenrunner

Waiting to see the finished product installed on the freshened up 455!

Also, are you sure that those stock pistons will hold up ok? We did have a badger replacement piston that broke a ring land on us on one of Dad's 455's. You know, those pistons that you going to reuse have never seen the higher side of 3500rpm..... and they are 50 years old and embrittled now.

ChevyZ06

you mean the pistons are BATTLE HARDENED!

Battenrunner

joesw31

This is a great thread! Keep up the great work!

64Rocket

I've said for some time that "J" heads with some work would make great street heads. Nice street cruiser with some pop.

Gene

VORTECPRO

Your thread is making me want to duplicate the 455s builds I built in 1980s, just to see what kind of power they made back in the day, of course you could save me the trouble by just bringing yours up and putting it on the dyno. These are the most fun type of builds-carry on!

ChevyZ06

I totally agree. Some day I would love to build a F.A.S.T. car to compete in that competition. Something unusual maybe. Like my 1976 TA.

coppercutlass

Interesting thread to come across . I just acquired a 455 to make the move away from the small block olds stuff I have been doing. It came with some "ported" J heads and it has big valves. those heads where on a 455 that ran 11.50's in a 3600 lbs car . Once I really have the time to mess with the engine I plan on having the heads flowed. Im curious what they flow as the previous owner has no flow sheets.

ChevyZ06

So am I !

coppercutlass

Mine is a low budget build ..got the heads and a long block with forged slugs. I'm just using whats there. Now correct me if im wrong but doest cam profile play a big roll in helping poor flowing heads.

Firewalker

Any place in the chain, that's weaker or stronger than the rest changes the outcome, but can not change the less than perfect imbalance and make it all ok and equal.

The cam needs to be chosen for the range of power wanted and is practical, and playing to the strength of what the airflow is works out the best. Over caming and running slower and worse than it could be is common. But if you want that lope of a race car then you will join the majority that have over camed, for the airflow and rpms that are actually there or needed.

The air flow stays the same in the heads and intake, or out the exhaust. The cam changes when or the time this is happening.

ChevyZ06

Best advice that I have ever been given on cam selection is "pick out the cam that you want, then order one step smaller".

coppercutlass

I have never over cammed an engine. The only reason i asked is because back in the stocker days head modifications where limited and many ran "cheater cams" i belive they had to measure at OE specs so i assume the ramp profiles where changed to help the heads flow better by . Just from what i know atleast.

Firewalker

Better than what I suspect most do, and that is try and cheat the system with one step bigger.