All Small Six No power after head swap

[Suns3tter]

Just wanted to say that this is my first post on here and i hope to get some answers.

Yesterday i swapped out my cracked and old small log head on my 1968 200 for a large log 1969 250 head. I am aware that this head is not the best swap but it is the only one i could find. I had it checked for cracks, I ported it, had it decked 0.060 to get the chambers down to 48cc and had the valves resurfaced. I felt confident doing this as it came directly from an engine that had never been apart (Original ford steel gasket) and my 200 that is in the car had previously been rebuilt and likely had the block decked.

Now to the issue. Ever since i bolted it into the car it has no power. It revs much faster, louder and quicker yet i feel like something isn't right. The carb is a weber 32/36, It has HEI ignition advanced to 14* (Yes i checked TDC when the head was off, the balancer hasn't slipped)

Adding to this is that whenever i take the PCV out of the valve cover and block it with my finger the engine always nearly dies.
Help me out please.

 

[mustang6]

Did you keep the same carb and distributor or did those get added in the swap? If you already had the carb did you keep the same adapter? I’m assuming you had one for the small intake originally and am wondering if it would seal OK on the large intake.

 

[bubba22349]

Did you happen to take any pictures of the parts that you used like the Carb adapter and the gasket fit to the head? How did you tune the Carb?

 

[Suns3tter]

Did you keep the same carb and distributor or did those get added in the swap? If you already had the carb did you keep the same adapter? I’m assuming you had one for the small intake originally and am wondering if it would seal OK on the large intake.

Same carb as before. It was the same adapter that i ported a bit to enlarge the hole just a slight more until i cast a custom one myself

 

[Suns3tter]

Did you happen to take any pictures of the parts that you used like the Carb adapter and the gasket fit to the head? How did you tune the Carb?

The gasket was self-made using a razor blade and holepuncher, i testfitted it before i bolted it on.
Idle mix 1 3/4 out idle set at 620rpm warm on the small log

 

[bubba22349]

Now to the issue. Ever since i bolted it into the car it has no power. It revs much faster, louder and quicker yet i feel like something isn't right. The carb is a weber 32/36, It has HEI ignition advanced to 14* (Yes i checked TDC when the head was off, the balancer hasn't slipped).

The gasket was self-made using a razor blade and holepuncher, i testfitted it before i bolted it on.

Idle mix 1 3/4 out idle set at 620rpm warm on the small log

First off that 1969 Larger Log Head is so much better several ways than the older 1963 1/2 To 1968 Log Heads and being Ported and Milled to 48 CC's, assumed that it probably also got a good 3 angle Valve Job with Back cutting that should make a big difference. Did you happen to measure how much the Pistons were down the hole from the Blocks Deck while the head was off? What kind of Cranking Compression do you have now and what were these Compression Test results?

As an example a typical rebuilt 200 Short Block having the common .030 over Replacement Pistons, these will have less Compression Height than the Original Ford 200 Pistons putting the Piston further down the hole. A stock 200 generally has the Piston Setting down from the deck .019 combined with the stock Steel Shim Head Gasket, and the 1968 Log Head, you will have a very good Quench distance of .041 and about a 8.7 to 1 Static Compression Ratio. With the replacement Piston this now goes to .030 down from the deck and with the newer FelPro Composition Head Gasket the Quench distance ends up at .077 and the compression Ratio is around 8.5 to 1 when the Ideal is more like 9.0 to 9.2 to 1 for use with 87 grade Fuel at Sea Level. In my area it can be considerably higher yet because of our Altitude here and I don't know about the local area your in and the fuel grades that are available to you. Rarely dose the Block Deck get Milled unless there were signs that it isn't flat anymore from being very Hot. Nor do they get Milled unless its asked for at rebuild and even than they usually only do a very light cut certainly not enough to compensate for the lose of the better Quench distance of .035 to .050 nor do these blocks get Zero Decked or even more so that the piston is Positive to the Block Deck (IE setting above the deck .010 or so) for the benefit of that improvement.

Has the HEI Ignition's total timing ever been checked? If your HEI distributor hasn't been recurved on a distributor machine for use in your 200 that could also be an issue as they usually come with the wrong advance curve to work good in a small Ford six, this can be done by trail & err with some time and testing. The Weber 32 / 36 also will probably need some more fine tuning too to get its jetting right. Do you have access to a Tail Pipe tester or a O2 gauge on your car, this can also be done the old school way with some time and testing. That sure is a great Picture of the sun set with the Mustang.

 

[Suns3tter]

First off that 1969 Larger Log Head is so much better several ways than the older 1963 1/2 To 1968 Log Heads and being Ported and Milled to 48 CC's, assumed that it probably also got a good 3 angle Valve Job with Back cutting that should make a big difference. Did you happen to measure how much the Pistons were down the hole from the Blocks Deck while the head was off? What kind of Cranking Compression do you have now and what were these Compression Test results?

As an example a typical rebuilt 200 Short Block having the common .030 over Replacement Pistons, these will have less Compression Height than the Original Ford 200 Pistons putting the Piston further down the hole. A stock 200 generally has the Piston Setting down from the deck .019 combined with the stock Steel Shim Head Gasket, and the 1968 Log Head, you will have a very good Quench distance of .041 and about a 8.7 to 1 Static Compression Ratio. With the replacement Piston this now goes to .030 down from the deck and with the newer FelPro Composition Head Gasket the Quench distance ends up at .077 and the compression Ratio is around 8.5 to 1 when the Ideal is more like 9.0 to 9.2 to 1 for use with 87 grade Fuel at Sea Level. In my area it can be considerably higher yet because of our Altitude here and I don't know about the local area your in and the fuel grades that are available to you. Rarely dose the Block Deck get Milled unless there were signs that it isn't flat anymore from being very Hot. Nor do they get Milled unless its asked for at rebuild and even than they usually only do a very light cut certainly not enough to compensate for the lose of the better Quench distance of .035 to .050 nor do these blocks get Zero Decked or even more so that the piston is Positive to the Block Deck (IE setting above the deck .010 or so) for the benefit of that improvement.

Has the HEI Ignition's total timing ever been checked? If your HEI distributor hasn't been recurved on a distributor machine for use in your 200 that could also be an issue as they usually come with the wrong advance curve to work good in a small Ford six, this can be done by trail & err with some time and testing. The Weber 32 / 36 also will probably need some more fine tuning too to get its jetting right. Do you have access to a Tail Pipe tester or a O2 gauge on your car, this can also be done the old school way with some time and testing. That sure is a great Picture of the sun set with the Mustang.

Thanks for all the detailed advice!
I did not measure it sadly but i assumed it was either milled or decked because the block had the same rounded sort of pattern etched into the metal as my head after it was milled as a result I did not wish to go further than 0.060 as i did not know how much they took off the block. The only thing i determined was that the pistons were stock replacement dished pistons and the car had previously had a remanufactured carb dating to 2018, so i assume that was when it was rebuilt.
I am not an engine builder, and it is my first car so this is a learning experience for me. What i can take away from this is that i need to check the compression ratio and then act accordingly. The head has to likely come off again due to the valve guides being bad and it burning oil so i might as well do it over right.
I do plan on replacing that HEI unit for a higher quality one as it is leaking oil internally everywhere and was a temporary permanent solution to the load o matic problem.

 

[bubba22349]

You are very welcome, even if you didn't measure the piston depth we can come up with a good estimate of your Compression Ratio by doing that Cranking compression test to see what PSI it has. I would guesstimate that you would need to get down to around a 44 CC Combustion chamber about another .020 Mill Cut to be at 9.0 to 1 that is if my calculations are right about what your short block specs are. Yes if you have worn out valve guides that's going to be a problem that needs to be addressed as it will foul out your spark plug quickly. Those HEI Clone distributors and even the Higher priced versions are known to have oiling problems but there is a Mod that can fix that too. Best of luck on your Mustang EDITED