300 Rebuild

THE FRENCHTOWN FLYER

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Another useful point is that the basic part number for a specific component will always be the same regardless of engine. For example a head casting is -6049-. A cam is -6250-. So much so that the base number is often left out on the part itself. So a forged crank will have C6TE-G forged into it where the complete part number is C6TE-6303-G.
 

Keystoner16

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THE FRENCHTOWN FLYER":32xig7hr said:
Look at the underside of the head by the thermostat hole. If the third digit is a "D" then it is a 300 truck head, used only in light trucks, and vans, not passenger cars. If it is an "A" it is a 240 head it could have been used in either a passenger car or a light truck / van.

 

Keystoner16

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Keystoner16":zo7m1h2a said:
THE FRENCHTOWN FLYER":zo7m1h2a said:
Look at the underside of the head by the thermostat hole. If the third digit is a "D" then it is a 300 truck head, used only in light trucks, and vans, not passenger cars. If it is an "A" it is a 240 head it could have been used in either a passenger car or a light truck / van.


After further filing...

 

pmuller9

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You have a 300 with the 76 cc chamber head.
How would you like to proceed?
Stock rebuild or some added performance?
 

Keystoner16

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pmuller9":2ndlvlne said:
You have a 300 with the 76 cc chamber head.
How would you like to proceed?
Stock rebuild or some added performance?

I'm thinking I would like to do a pretty mild build with some moderate performance gains if possible.
I would like to install a cam that would give me a little something more but nothing huge.
I was considering this one from Comp Cams
https://www.summitracing.com/parts/cca-66-248-4

As I may have mentioned, the engine had low compression (109 psi) across all cylinders. It developed misfires that would come and go during extended highway driving, and averaged about 8 mpg. It was still pretty peppy considering, and moved the van off the line OK. It fell flat on it's face whenever it encountered an incline though, and in a headwind you could just about watch the fuel gauge drop.
I had already been running a Clifford intake, and EFI exhaust manifolds for a while when I finally got around to pulling it for this rebuild. I was running an Edelbrack Thunder AVS 500cfm carb, and I think I am going to need to play with jetting a little.

So, back to a rebuild plan. I want to use the best components. I was planning on Comp pushrods, and lifters as well. Probably end up using Sealed Power bearings, and pistons. I am not sure at this point, but I am thinking the block will need to be bored. If not, then I would be happy to use 4 inch pistons.

The head is any area where I know I need some expert advice. I am wanting to replace the valves, valve guides, and springs, but have no idea what to buy or where to buy it. I would also like to replace the rocker studs with the screw in type, but again, a little lost as to process, or if I would even need to. I am someone who likes to overbuild things. I don't think I want to replace the rockers unless something else in my build plan dictates a need. I mean I would like to, but money is not endless so I'm trying to save some. Open to thoughts and ideas. I am also planning to port the head a small amount. Just enough to "gasket match" everything.

In conclusion, I would like a little more power, and reliability if possible. Also, if I can get the mpg up that would be really great. I think 12mpg would have me really happy. As always, I welcome insights and info. If my whole plan is stupid then I want to know that. Thanks.
 

pmuller9

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The Comp 268 cam has low enough valve lift where you can use the stock rocker arms but long enough duration to give you a wide working power band from an idle.
It is recommended to limit the compression ratio to 8.8 with the Comp 268 cam if you want to run 87 octane pump gas.

If you are measuring the bore at roughly 4.035", the cylinders may already be bored to 4.040" which may require a 4.060" bore to clean up the walls.
You will need to measure the cylinder walls first to see if this block will handle another overbore.
The Sealed Power pistons with a "D" dish can provide an 8.8 compression ratio if the block deck is cut for zero piston to block clearance.

If you are staying with the stock size valves then just do a valve job using the valves that are there if they are good.
If you want to replace the valves then go larger to a 1.94" intake and 1.60" exhaust.
SI valves have the stock size and oversize valves in the stock 4.810" length.

Screw in studs is a good insurance with the extra valve lift and additional spring pressure.
Your head may have the 5/16" thread, non adjustable rocker studs which you would want to replace.
Drilling and tapping the head for screw in studs is best done in a milling machine so the studs are in line and all at the same angle.

Porting a 300 six head DOES NOT include port matching or removing a lot of material off the port walls.
Most of the work is done in the bowl area and around the valve guides.
If you go with larger valves then it is matter of blending the larger throat into the bowl.
 

Max_Effort

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I'd go with a different cam than the comp. If your looking for economy with increased power, I'll suggest the Erson E270101. For a little more power and rpm, the Erson E270121.

Or I'd have Jones Cams grind a custom. Erson will also grind a custom.
 

bubba22349

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I am thinking about the pistion chooice that was used to rebuild your 300 short block in its past this may be why your compression was so low they seem to be setting pretty far down the hole. What's the piston compression height compared to a stock type 300 pistons? I think that a stock 351C Piston has a 1.651 compression height and that a stock 300 Piston measures 1.740 that's .089 difference down the hole. Now depending on if your block has had any decking done from its orginal 10.00 height this would account for quite a loss of compression from that of a stock 300 six'es 8.5 to 1 ratio. In any case in my opinion those 351C Pistions seem like they were a very odd choice to be considered for use with the stock length 300 connecting rods in a 300 short block rebuild. Good luck on your build your outlined plan should give you a much better engine combo for use in your truck. (y) :nod:
 

MechRick

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I wonder if those pistons are 351m-400? The pin size would work with late rods. Not sure on the comp height though.
 

xctasy

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All Canted Valve small blocks Fords:-

The 302 Cleveland ,
302 Boss, 351 Cleveland, 351 Boss
and 400 had a 1.647" piston compression height.

They were all 16 thou into the hole, but the block could be 8.206 Windsor based Boss 302, 9.206 (Cleveland 302/351), or 10.306 (Modified 351 or 400 Ford).

The 351 M was a 400 block engine with a logner con rods. No exception top the 1.647 rule.

Ford adjusted conrod length to suit the engine capacity, and the dome or dish as well.

If the pistons are 351M, That puts the pistons way, way down in 153 thou into the hole.

With a 10" tall block with a 6.21" rod and a 3.98" stroke, the stock piston should have been 1.800" compression to get a zero deck, but Ford created a short fall of 22 to 33 thou. 1.788 early engines, 1.767 for Hypre pistojs after 1994, and aftermarket, normally 1.776, a 24 thou shortfall.

Often, the 240/300/4.9 blocks come in at over 10.000".
 

Keystoner16

Well-known member
bubba22349":u9vz7jzw said:
I am thinking about the pistion chooice that was used to rebuild your 300 short block in its past this may be why your compression was so low they seem to be setting pretty far down the hole. What's the piston compression height compared to a stock type 300 pistons? I think that a stock 351C Piston has a 1.651 compression height and that a stock 300 Piston measures 1.740 that's .089 difference down the hole. Now depending on if your block has had any decking done from its orginal 10.00 height this would account for quite a loss of compression from that of a stock 300 six'es 8.5 to 1 ratio. In any case in my opinion those 351C Pistions seem like they were a very odd choice to be considered for use with the stock length 300 connecting rods in a 300 short block rebuild. Good luck on your build your outlined plan should give you a much better engine combo for use in your truck. (y) :nod:

I measured the compression height of the pistons in question to be 42mm (give or take), converted to inches comes to 1.65.
OD of piston measured 4 inches.
The deck measures at 10 inches exactly.

I have no idea what may have occurred, but nothing would surprise me as whoever owned this van before me did not one single thing correct as far as I can tell. It was cheapest, and easiest every single time.
 

Keystoner16

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Max_Effort":10ptoq4i said:
I'd go with a different cam than the comp. If your looking for economy with increased power, I'll suggest the Erson E270101. For a little more power and rpm, the Erson E270121.

Or I'd have Jones Cams grind a custom. Erson will also grind a custom.

The Erson seems like a good option. I am wondering how it fits with the rest of the components I plan to use. Would I have to change anything? Also, I notice it is is out of stock on their website, will definitely give them a call though.

Also, I am wondering about these pistons from Sealed Power
https://www.summitracing.com/parts/slp- ... /make/ford

Will these allow me to use 87 gas, as the D cup pistons are expected to do??

I am currently working on rebuilding the T170 transmission that was bolted to the 300 in the van, however, I am wanting to get the block into the machine shop soon, and they are going to want the cam with it for the purpose of fitting the cam bearings. So, I'll need to get that coming fairly soon.
 

pmuller9

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The Erson E270121 (TQ20H) cam will let you easily run 87 octane pump gas with an 8.8 compression ratio and the valve lift is still low enough so you can use the stock rocker arms

The round dish Sealed Power piston will drop the compression ratio into the lower 8s which is too low.
Stay with the "D" dish and machine the block deck to get the piston close to zero piston to deck clearance which will get you near an 8.8 compression ratio.
 

Keystoner16

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pmuller9":2jrgysq4 said:
The Erson E270121 (TQ20H) cam will let you easily run 87 octane pump gas with an 8.8 compression ratio and the valve lift is still low enough so you can use the stock rocker arms

The round dish Sealed Power piston will drop the compression ratio into the lower 8s which is too low.
Stay with the "D" dish and machine the block deck to get the piston close to zero piston to deck clearance which will get you near an 8.8 compression ratio.

Sounds great. Thank you for the quick feedback. (y)
 

Keystoner16

Well-known member
Hello All.
Just wanted to make a quick post in hopes of not being forgotten. It has been a while but I am making progress. I think. Maybe.
I have ordered and received my cam. Ended up getting the Erson E270101.
Spent a week in PA over Labor Day, but I am back in OR now and looking to get things going again. The block is going to the machine shop this Thursday AM.
Work list so far is:
-Removal of seized plug from block drain
-New cam bearings installed
-Deck resurfaced
-Checking cylinder bores for wear/out of round
-Boring cylinders if needed/possible
-Cleaning block/hot tank

I will obviously have them check the cylinders before proceeding with other work.
If I'm missing anything, please let me know.
Thanks very much.
 

Keystoner16

Well-known member
Ok, so the block, cam, and conn rods are all at the machine shop.
The shop will be doing a block prep package which includes extensive cleaning, magnafluxing the block for crack detection, flushing of oil/coolant passages, installing cam bearings, resurfacing the deck, and boring cylinders. Not sure what the cylinders will end up at yet. They will be measuring, and let me know what is required. I said I wanted as little material as possible removed.

One question regarding pistons.
At the shop they are attempting to sell me what they are calling "UPS" pistons. These are apparently pistons that were made specifically for UPS by Silv-o-lite. They told me they have a specific shape which improves the squish area. All that sounds good enough, but $216 for six pistons is a little bit more than I can comfortably afford. I am wondering if anyone is familiar with this piston.
Pretty sure these are the ones, found at Summit.
https://www.summitracing.com/parts/uem- ... /make/ford
The guy also said, "Sealed power is a shitty piston that's made in India." So there's that.

Really appreciate ant insights or info on those pistons. Thanks.
 
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