J head mods ?

Ive a stout 318 (326) short block and am starting with a set of J heads that have had zero port work, not even gasket matching yet.

They have been cut for 2.02s from the 1.88s with the nice 3 way bowl cut, nail head ss valves, decks milled and around a 66cc chamber.

Cams a 280adv solid .510 lift, intake is stock 6bbl off my t/a while it sits. Deep gears, mild vert, auto.


SO..... since its no more then a 6500 rpm motor, what porting mods other then a casting cleanup and gasket match would YOU do if it was your build?

Im wondering what would help the lower lift numbers on these heads?

Thanks.

I think Steve Dulcich has some good porting on them. I would Google it. EDIT Google "dulcich porting articles"

A bit of a shameless plug here, take a look at this older post of mine...

If you want to see more of the pics of the finished stuff let me know. I am no pro at this, but these were opened up pretty well while still retaining a smaller port volume.

Thanks, I have seen that before. Porting is not new to me, but trying to squeeze a teener is.

I dont think the level of work for a teener would be the same as a good 360 or long arm build.

Ive managed to keep this a pretty simple build and that goes for the heads, just 13k mile castings, oem guides, I found a good single spring that works, ect...

Ive some new 318 castings but vs putting alot of work in them I figured id use the J heads with a little work.

I live at 4100 ft and with a intake closing point of 68-70 depending where I put it even with the 6cc dome and .028 gaskets im just about middle ground on things looking good on paper, I even took the block back in today to get .015 knocked off it which will get it to true zero, sucks a extra $100 just for 2cc.

I could of went with a bit more modern grind with alot lower intake closing point but ya know how hard headed some of us are.

I would just open up the pocket to the valve job, and match the ports. Try to open up the pushrod pinch but don't go crazy there, it doesn't make a huge difference. Do not touch the port floors or the short side radius.

I wouldn;t even mess with J heads anymore

Thanks Jones, I understand your thoughts SC but the lil project is for me and Ive had the heads on the shelf since 79 and they were free then. I dont even recall where I got the SS valves or how long ago.

Id not use the domed hypers if I were buying them either but I got them in a parts trade by taking 200 off and they are currently 404 from summit.

I just want this to run well for a teener, want folks to think its "ok" for a 318 vs "yep, thats a 318 for ya"

And actually im having fun on the cheap.

Oddly fresh J heads still bring decent money.

Fair enough, sounds more like it's a "I wanna see what I can do" project which is neat

I realize you already have the castings prepped, so those are what you’ll use...... but I would have preferred to use the 1.88 intake valve for that combo.

Actually, I would have probably used 1.94 sbc valves....... along with minimal bowl work and a tweak of the short turn.
I’d have shot for flow in the 220-225 range.

Yea, throw that old stuff away and buy a Demon. Or if poor like me, massage what you have. What's more impressive a 318 with iron heads running 11.50s or aluminum heads running 11.00. Those J heads have worked well for a long time, listen to fast68 he's right on what to do.
Sounds like a fun combo to me.

Fixed that for you.

J heads are so wonderful they quit making them ~45 years ago.

If you are going to mess with iron heads Magnums are a better choice.

Nope, didn't fix it, tell that to the 340 stocker guys. If you want to run fast, spend $20,000 on an engine. If you just want to have fun and run good, spend $0000. Js are perfect for his combo, aluminum is a waste of $2000. Now if he wants to ring it 9-10,000 rpm with no bottom end, go for it.

Can we chill on the pecker thumping?

My street racer is an al headed r block, ive a really nice 360 on the stand ready for something but ive watched over the years so many build motors that are so much overkill its silly.

The 360 mentioned is so basic and im not sure what $$$$ ive in it but a 500hp motor dont care if it cost 3k or 20k its still 500hp.

But back to the posting...

Im wondering if on this application, the high comp 318 if id do ok with a set of ported new smog castings with the 1.88s dumped into them.

Im trying not to make it too hard or think too hard but I need to make the most power from 3-6500 and worry the 318 castings with 1.88s might nose over before the cams done.

These are odd castings, transitional mid 80s as they came in both the small and large holes for the roller cam 318-s.

This set has the smaller and you can see I could take out nearly the whole pinch point and thin the divider and I could cut them for the 1.88 intakes, (second chamber in from the left) I could probably get alot more port volume from them as well but would they bark past 6k?

If you’re trying to “make power”, use 360 heads.

Shoot, 13K mile castings? I'd use them. Stock they're good to 400hp or a little more.

The 2.02 valves won't help but they won't hurt you except below 3000rpm. No use to switch to different heads just to get a little smaller valve, IMHO.

Fast68 outlined it for you. Smooth out the bowls, there are usually discontinuities under the seat. Make sure the short side radius is smooth and I think Fast was saying make it a more gradual transition from horizontal to vertical.

I think the pushrod pinch is large enough to not restrict flow for a 318. I'd leave it. I'd think you don't want to make the port very much bigger.

R.