Tunnel rams for ported heads

[DRHEMI]

Hello everyone,
I have returned my attention back to my ongoing building of an unblown 354 racing engine for my FE dragster. As has been discussed in an earlier thread about PAW's tunnel ram, all of the available manifolds for the 354-392 hemis seem to be small port designs, meaning that a serious manifold for good ported heads just isn't available. I had planned to simply go with a sheet metal tunnel ram, but I thought of exploring another way.

Nascar engines seem to be in the 800+ HP range, and both GM and Mopar have left bank leading, even intake port spaced manifolds. I have heard that M&M Competion Engines in Indiana has, or soon will have, a cast tunnel ram manifold for the R7 Mopar Nascar engine.

My question was how practical would it be to machine a pair of adapters to use this manifold on an early Hemi? To answer this question, I purchased a cheap used Nascar restrictor plate single 4-bbl single plane manifold. I have mocked up my 1st pair of adapters from wood, and I am so far very encouraged.

The Nascar Manifold ports are spaced slightly closer together than the 331 heads, but this is mitigated somewhat by the nascar ports being curved slighly outwards, so a very gentle transition radius in the adapter has the ports lining up nicely. The Mopar Nascar manifold's ports are very similar in size and shape to the heads I am using. The largest difference is that the corners are much more broadly radiused then my own ports.

My plan is that I will try this single 4-bbl with my adapters, and if encouraging, I will purchase the M&M tunnel ram. I will take my prototype wood adapters to a CNC machine shop and have a pair cnc'd in aluminum.

I would like to post pictures of the Nascar manifold, and my mock-up adapters. I have never posted pictures to a forum before, so it someone could educated me on how to post them, I would appreciate that.
Thanks,
-Andy Carlson

[NE57]

OOO I'd like to see that! I'm toying with the idea of fabbing a crossram manifold using the intake adapters for 354 heads on a 392 block, as the flange.

on the reply page click on the Upload Attachment tab. click Browse to locate the file on your PC and click on the filename, then click Add The File

[DRHEMI]

This is the Nascar Mopar P7 single 4 bbl manifold. Note that it is the restrictor type (look inside the carb base).
-Andy

[DRHEMI]

The manifold alongside the ported 331 head.
-Andy

[DRHEMI]

The mocked up wood adapter will give me the critical measurements to be used on CNCing the aluminum pieces.
-Andy

[NE57]

This might be a dumb question and a bit off the subject but how come that manifold has slots instead of round bolt holes?

The project looks very feasable though. Will you have recessed bolts to join the adapter to the head and then similar for the manifold to adapter? Or do you think you can drill the manifold for direct bolting? If you have to mill the block and/or heads much, will that alter the fitment of the adapter?

Thanks for posting these pics, it helps me visualize my own idea, especially since my block is the shop and I can't do any sort of mockup yet.

[DRHEMI]

The adapter will have countersunk holes for machine capscrews to bolt the adapter to the heads. The manifold will bolt down to the heads to the already mounted adapter using the manifolds existing mounting holes for the manifold bolts. My intention is to use the Nascar manifolds without any machining or modifications.
-Andy

[NE57]

I was thinking more about this. Since you will have recessed bolts from spacer to head and then bolts from manifold to spacer, wouldn't it be in essence having two forces pulling the spacer apart?, since there will be no thru bolts to clamp the three pieces together as a unit? If the aluminum spacer is not rigid enough maybe it might be prone to leak, as the spacer might warp from its own opposing bolting pressure. It might depend alot on how far apart the two sets of bolts are from each other and how thick the spacer remains under the recessed bolts. Maybe steel spacers might be something to think about, as a backup?

Or maybe its not an issue and I'm overthinking again ? Which I tend to do.

[DRHEMI]

I have included pictures of the cast tunnel ram offered by M&M competition engines for both the GM and Mopar (P7) nascar heads.

I don't believe that the clamping forces required to attach the manifold to our hemis is so strong as to warp the adapter. Of course, real world tests would be necessary to verify that. I don't think that there would be very many folks who would hoist a Hemi engine with the 4 bbl mounting plate used for hooking a chain fall to an intake manifold. The shortest thread engagement would be the screws clamping the manifold to the adapter (about 1/2 inch). Care would be needed to avoid over tightening these screws.

There would not be any material in the heads to drill and tap mounting threads using the manifold's factory attachment slots--the water ports and the exhaust cross-over ports are directly below this area.

I will mention this: an adapter to fit these Nascar manifolds to a 392 Hemi with 331/354 heads would be much thicker, and would provide much more thread engagement and more rigidity. Plus the adapter would be a great place to have nozzle ports for EFI or for N02, without the need for any modifications to the manifolds.

I will post later a close-up of the finished mockup adapters.

-Andy Carlson

[NE57]

>I will mention this: an adapter to fit these Nascar manifolds to a 392 Hemi with 331/354 heads would be much thicker, and would provide much more thread engagement and more rigidity.

great idea, plus you'd have more room to blend the differently shaped ports. I looked more closely at the side by side pic...would you say the bolts to the head would be like within 3/4 inch of the manifold bolts? If so that does sound reassuring, warpage wise. No I couldn't see catastrophic failure but if there's even a small chance of a vaccum leak its better to design in the fix from the get go. How much meat would there be under the recessed bolt heads? Wouldn't want that area to dish out. I wonder if there's enough room in the manifold to cut a recess on the manifold flange to clear the bolt heads, allowing you to basically have more meat under that spacer to head bolt.

Or am I overthinking again?

[mart]

I have included pictures of the cast tunnel ram
offered by M&M competition engines for both
the GM and Mopar (P7) nascar heads. -Andy
Carlson

----------------------------
Very, very slick! I wonder if once you get everything worked out with the adapter plates, it'd be worthwhile contacting M &M and seeing if they'd be interested in casting some dedicated early hemi manifolds based on your work? Since they already have their basic manifold designed for GM and Mopar NASCAR heads, it might be fairly simple and profitable for them to do a run of castings based
on your 'adapter plate' manifold flange, but making the
'adaptor' integral with the casting.

mart
======================================

[DRHEMI]

I have the 1st mock up photos to share. I have found some areas which will need to be addressed. The fastener holes for our early hemis are located close to the edge of the ports, so close that a ported head's ports come close to these holes. Because these Nascar manifolds have outward splayed ports, the transistion in the adapters shows as an angled path. The inside intake fastners for the hemis are aligned with the sweeping port in the adapter (They compete for "air space" within the port). Gene Adams told me that the hemis just need one fastener per port, so perhaps not all is lost.

My next photos will show the adapter plate with the counter sunk fastener holes. My goal of using a Nascar manifold with no modifications might be compromised....I may have to drill 2 holes per side for mounting the manifold to the adapter.
Later,
-Andy Carlson
Ojai CA

[NE57]

Its nice to see the work in progress!

I don't know if this is even possible or practical but, if the bolts are "competing for "air space" within the port"...could you minimize the bolt intrusion by using a smaller sized bolt with a thread adapter? I mean a tube that is threaded on the outside with what's necassary to engage the head holes, and threaded on the inside of the tube with a size that both fits the tube (obviously) yet is strong enough for the job. It might be possible to gain a small amount of offset?