Fitting new LA X/Indy heads to my 340

Dave-R · Post by **Dave-R** » Mon Feb 23, 15 9:54 pm

They do look sexy.

Les Szabo · Post by **Les Szabo** » Tue Feb 24, 15 6:56 pm

Wish these heads were around when I ran the 340....would've gone in the 11's N/A and well in the 10's with as a bolt on

Les

MilesnMiles · Post by **MilesnMiles** » Sun Mar 01, 15 3:10 pm

ok, few days of with gluey cold and back into the garage.
Got number one piston up to TDC and really pleased. The pics may not show it best, but those heads are near as dammit flush with the block which should give some good compression with the 63cc heads.
Going to check valve to piston clearance next.

Les Szabo · Post by **Les Szabo** » Sun Mar 01, 15 4:09 pm

Near as dammit???......they look like they are about -20 down the bore if thats true tdc? measure it properly....might not be mega important but you might as well know, this is where block decking would come into its own, anyway, you should still see an increase in CR, why don't you CC the J heads Miles, then you'll have a much better idea, J's can be anything from 65>72cc, tend to be more towards the 70cc size unmilled, if they are -20 use a thin steel gasket thats not too much bigger than the bore, some gaskets are around a 4.100 bore which will lower CR some. Its not much, but you might as well get as much as you can.

Les

Mick · Post by **Mick** » Sun Mar 01, 15 5:15 pm

Check it while the heads are off Miles and make a note, straight edge across the block slide the feeler gauges underneath and check them all to see what discrepancy there is.

mad machs · Post by **mad machs** » Sun Mar 01, 15 7:00 pm

Les Szabo wrote:Near as dammit???......they look like they are about -20 down the bore if thats true tdc? measure it properly

I concure, giving the piston crown a bit of a once over first.

MilesnMiles · Post by **MilesnMiles** » Sun Mar 01, 15 8:40 pm

I'll check with feelers. The pics are misleading. There is almost no drop from deck to piston crown, you can barely catch a nail on the difference. The new heads measured at 63cc.
When I ordered the heads we worked on the presumption that the pistons were probably -20thou which with a compressed gasket of .39 gives 9.7.1 compression.
The pistons have a rated compression of 10.5.1 with 62cc heads. Given the nature of slack Mopar tolerances the suggestion of 9.7.1 makes sense. I'll measure tomorrow.

Les Szabo · Post by **Les Szabo** » Sun Mar 01, 15 9:13 pm

Yeah its the deck heights/rod length that can vary, not life changing but hopefully it won't be as much as -.020, but even with a .039 fel-pro, or perhaps you can get something thinner?, you'll still have reasonable quench, doesn't have to be .040 as the majic figure, something close and your still on a goodun, jeeze that head deserves at least a nice .500+ cam, but 1 step at a time eh.

Les

Dave-R · Post by **Dave-R** » Mon Mar 02, 15 9:39 am

That is really good news. Composite gasket, quick clean of the deck, stick the heads on, start saving for a solid cam and adjustable rockers.

MilesnMiles · Post by **MilesnMiles** » Mon Mar 02, 15 12:45 pm

Cheers Dave. Courtesy of one of our long standing stalwarts it appears that I will be likely getting a set of adjustable rockers that will measure at a proper 1.5 too.

Cant go solid cam yet as all the ones I looked at require a lot more convertor and gear. Baby steps, one at a time

Mick · Post by **Mick** » Mon Mar 02, 15 3:32 pm

You need to check your clearances fully and make a log, then you can refer back to it when choosing a cam. You could also pour one of the combustion chambers to check the cc.

Dave-R · Post by **Dave-R** » Mon Mar 02, 15 3:32 pm

MilesnMiles wrote:Cheers Dave. Courtesy of one of our long standing stalwarts it appears that I will be likely getting a set of adjustable rockers that will measure at a proper 1.5 too.

Cant go solid cam yet as all the ones I looked at require a lot more convertor and gear. Baby steps, one at a time

And Gear Vendors to get some MPG back.

MilesnMiles · Post by **MilesnMiles** » Mon Mar 02, 15 4:15 pm

I'll have to re-mortgage for Gear Vendors!
Mick, the heads are supplied and verified by the builder as 63cc.
The valves are now much closer to the piston compared to the J heads.

Dave999 · Post by **Dave999** » Mon Mar 02, 15 4:32 pm

and then work out your dynamic CR

that will indicate if its likley to ping with your current cam and highr static CR

this blokes tool

http://cochise.uia.net/pkelley2/DynamicCR.html

and what he has written are quite intersting and can help you work out likely ping ish ness

i used what i thought was your cam from here

and could well have made mistakes cos i did it in a rush

http://victorylibrary.com/mopar/mpcam-tech-c.htm

and made up the rest based on what i could find about 360s

no idea of your valve relief size

DCR 8.6 (yours will be lower due to me not knowing anything about your pistons gasket or bore)

dynamic stroke 2.6 inches

Dave

MilesnMiles · Post by **MilesnMiles** » Mon Mar 02, 15 5:36 pm

Hi Dave! thanks for caring

I need to go right through that.
Just got in from work and quickly run a steel edge over the block amd piston at TDC.
I can't get a feeler guage under there. It certainly is pretty close to being decked. As for .20 thou, no way.
If I cleaned what little coke there is on the piston top I may just be able to get a sliver under but not as it stands.