Can you mill back the area to 1/8" thickness just in the area where the cam retaining/backlash setting plate bolts down without the cam gear fouling the backplate? If Rich was unaware of the previous modification, he probably wouldn't have offset the cam grind undercuts to reflect the .075" difference in axial position. The undercuts look quite wide; does the motor still have the '28 lifters or has something else been used?
With the fiber gear, no. I'll check with the metal gear. In my old age, I am learning to check more and not just take things for granted. (I just forget sometimes!) When Rich got the engine, it did not have any lifters that would fit in the lifter bores. So, we do not know what the boys ran. Rich put the 28 lifters out of his parts engine into this one. I have a lot of measuring to do to check out stuff. I happen to have a stock 28 cam handy, so will compare everything axial. I think that it will be worthwhile to get the cam in the right place, even if I have to make a new plate. I thank everyone for their comments, they have helped me think in different ways!
I am learning a lot just reading the stuff you all post. Spent a few minutes on the engine today, got the pistons loose, took two out. They are about 3/8 taller compression height than stock pistons, rods are about 1/8 longer. Piston pins are not full floating but are pressed into the rods. Four rings on the pistons, pins are a lot bigger than stock, anyone recognize them? No makers marks I can find. Appear cast, ring groove oil relief are drilled holes. I still think the rods are Model A but I haven't dug one out to compare. Can't find any Ford script, they have a triangle forge mark. Seems like I have seen that on Ford stuff before. All babbit looks fresh. Only pulled the center main so far. All rods are loose from the crank and lifters are off of the cam but it is still stuck. Need to pull the crank pulley and see what's under the timing cover. Little dogs on the clutch just tapped out with a punch. Uploading some pics. Stock 28 piston for compare.
Dan that looks and sounds great! Also, that things are coming apart without a lot of breakage. Those sure do look like modal A rods. Good luck!
Good call, HEATHEN!!! I just picked up a GMC 302 in NC- will try to pull a piston/rod out tonight and compare
That may be why it looks so familiar. I have some 270 pistons around here, I'll take a look. If it is a flat top it would be '55 or later I think. Weren't the earlier ones domed fro the older GMC head?
Yes, the combustion chamber was so large that they had to use domed pistons just to make it to 6.5:1.
Did some investigation of the pistons. They are 3.75 bore and marked std on top. Pins are a little less than an inch. Inside the skirts they are marked "T.R. CO LS563". TRW piston numbers used to begin with L. I had an old TRW catalog, but can't find it. From the dimensions I think they are Chevy/GMC 261 pistons, which I have read is a common hop up for these engines. I haven't got it out yet but I think the cam and lifters will need to be ground. Is there anyone in the US that you all recommend that I could trust to do it right?
The cam in my avatar has an RV grind by Delta Cams of Tacoma, Washington. That was 10 or 12 years ago. I have been planning on sending another one off for one of my roadsters, just haven't got to it yet.
Cam question, are all of the cams with the distributor drive gear ground the same from the factory? For example is there any advantage to using a 27 cam in a 28 with the better rockers. Did they "dumb down" the 28 cam because of the new rocker ratio? And if sending a cam off for regrind what is a good profile? Model B Ford?
No. You cannot use a 27 cam in a 28. Take a look at what 282 door posted on specifications. different bearing sizes. They may have dumbed them down some, I do not know.
Using those 4 cylinder heads to convert the Model A, or T perhaps, to overhead valves was once a popular item. Still being done today.
Definitely not 261 pistons. They were of the three ring design. The stock bore of a GMC 270 is very close to that, at 3.78125.
Here is some stuff from earlier in this thread (page 42) by Rich Fox. I think this is GG2's engine. The piston looks a lot like Dan's except the number of rings. Also info from Herb and the chart I made using numbers from this thread for rod & piston length. Sometimes it helps to see things in one spot. Man there is a lot of information in this thread!! Rich Fox, "I sent my rods to Egge for babbiting. They modified model A rods and sent them back. So now the old cast Jhans pistons are .420 down the hole at TDC. Is this right. Compared to my old GMC with a Howard head that's kind of deep. The GMC was .300 down. But it was about 13 to 1 as I did the math. What is stock for the Chevy?" Check the Hercules OX in the middle with a shortened skirt in this picture from Herb. (Page 43) Here is a chart I made using data from this thread (mostly) about rod and piston choices for early Chevy 4 cylinder engines. It shows how far below the deck the top of the piston. These are basic measurements and should be checked with the actual parts. Remember that early GMC 270s used a dome piston and '55 on had a flat top.
^^^^^^^ Nice accumulation of options Six Ball! I’m not typically a fan of trying to mix and match off the shelf parts… but that may change now that a set of 4 Ross pistons is $800 With the chebby head being flat, it would be real easy to add another column to your table that calculates compression ratios
Doe anyone know the small volume in the head around the spark plug? While the Chevy head is flat, I think this volume would need to be included for accurate compression ratio calculations.
Not a chebby head… but similar recessed spark plug issue. Originally there were various length extension plugs, but not available today. I found these 1-1/8” reach 10mm spark plugs used in motorcycles, then made adapters that present the electrode directly into the combustion chamber
Assuming you used Excel to create your table, here are the formulas. Would be real easy to add in the spark plug volume or remove the valve head volume, but certainly puts the different combinations into perspective
I ran an original style champion plug into my 28 head until it was tight against the washer. Turned valve side up, I leveled the head in two planes, then using a syringe body and cooking oil, I measured the volume to be 12.6 ml. I did this by filling the syringe, removing the air, set the plunger to 5 ml, then ran it down to 1 ml. I did this three times then topped it with .6ml. I used cooking oil so it wouldn't pile up as bad due to surface tension. Dividing by 16.387 I get .769 cu inches. I only did one recess. I imagine they vary a little, and it would also depend on the plug, but I think it's enough to change the calculations a little.
I did a search on the web and came up with a compressed thickness of .050 for a copper type head gasket. The head gasket and the volume around the plug do make a difference in the calculations. With everything included, I get 4.95 to 1. Without including the volume around the plug, I get 5.43 to 1. I did not remove the volumes of the valve heads
I looked them over at fall Carlisle; the problem is that they're for a 4 inch bore. That's a .220 overbore on a 270, nothing I'd care to try. If you had a 302 block that had good, straight standard size bores, you could run them in it in conjunction with a 270H head.
I saw the tape but couldn't really read it. Not the smartest thing but some 270s have been run at 4" but probably not Chevy 4s.
From "The Model T Ford in Speed and Sport" pages 16,17,18 of the May 1929 Catalog for Arthur Chevrolet Aviation Motors Corporation. The Fronty head for the Chevy looks suspiciously like the "23 olds head" with some 1.5 to 1 rockers and a special intake manifold.
Further engine teardown. Got the crank pulley off easily. Upon inspection it has been broken and welded back together. That would probably be fine if I was gonna go around in circles, not sure I trust it 49 miles from home. Interesting that someone added a timing tab, but no file marks on the pulley indicating TDC. Cam gear looks new. I loosened the main caps and can wiggle the crank. Cam is stuck. I really don't want to damage the gear. The holes in the cam are not aligned with the retainer. Any ideas? I could try to pull the fiber cam gear with a puller but I am afraid I will break it. Lifters are all pushed away from the cam. Oil pump and distributor are out, the cam appears to be stuck in it's bearings. If I pull the cam gear, I could loosen the retainer and tap the cam out from the back.
The Jalopy Journal
