Which heads are interchangeable?

[silverbullet02]

Never mind. You answered while I was typing!

 

[Bobalouie]

Bob... I don't know either but I would guess it's the larger volume/area in the chamber because of the plug hole. I do know that if you cc the heads you will know what the deal is in relation to comp. numbers.

Thats exactly it. By using a short reach adapter in a plug hole for a long reach plug, you effectively add volume to the cylinder and comp goes down.

 

[ally2dextreme]

If you want more MPH i would do 1.75 gears

 

[silverbullet02]

So I sit here wondering if anybody knows the answer to the original question.

 

[2003225X]

A stock 225x head is approximately 36.5cc. A 260/280/300 drag head cannot be interchanged with a 225x head.

 

[David Lanham]

Below is what Jay posed on S&F: I could not get the link to work:

"Just got through rebuild and moding a 225X motor today, shipping it this week, we machined heads to clean up damaged and replace OEM O rings ( looked as good as factory by the way , both water and compression side !!! ) Did compression tests and all with in 1-2 lbs, tally was a litle lower than I expected until I figured out the compression testor plug side adapter is short ( 1/2" thread ) the 225X motor is long reach ( like a Big Block Chevy ) SOOOO IF the compression fitting was to go to the correct depth as the normal long reach plug it would been right on my targets of 140 lbs at sea level..

Just food for thought..

Jay"

 

[catfish123]

I just wonder how much difference this really makes in the readings............when I find out, I'll let everyone know.

 

[SLOmofo]

1/4" by 14mm dia= how many cc's. give or take a smidge

 

[patches]

I came up with about 4 cc's

 

[SLOmofo]

Are you sure, looks like alot more to the naked eye! Smidges are fairly small, but not like a scouch or a RCH.

 

[patches]

I out 14 mm x 6.35 mm into a cylinder volume calculator and it spit out 3.91 cc

 

[LakeAnna]

I out 14 mm x 6.35 mm into a cylinder volume calculator and it spit out 3.91 cc

Eric I was trying to find something on the net to calculate the dang stuff... I used a syringe to figure my old ones... Not sure how close that was but they came up to 34cc (260 heads).
I pulled the plug, leveled the head and used thin tape to seal the plug hole in the chamber and filled it with water....hmmm I need to find something more productive to mess with.:big grin

 

[Bobalouie]

I think it is less than 1 cc. The formula is Pi * r^2 * H, where Pi is 3.14, the radius is 7mm or 0.275", and H is .25" Multiplying that all out you get 0.059 cubic inches, which converts to 0.966 CC.

Converting over to metric first yeilds 0.977cc.

 

[john4utvols]

I did not read every post but the first page I thought you said your rev limiter was 7300 or 7500. I'm not sure how close a 225x is to a 225 promax but we took a promax and raised the limiter to 7400 and changed the gear ratio to 1.75 and with a 28 we could hit 103-104 almost every day. We did try changing the compression to 145 but that didn't seem to matter on top end.

 

[john4utvols]

Thought I would throw this in on reading compression. I was reading compression on a motor and the battery was suppose to be full charged but it was reading 122 on all cylinders. So I put jumper cables on the battery and this made a big difference it jumped all the cylinders up to 128. This was a cold engine read too, i like to warm them up a little if i can. I always take all the plugs out when reading compression and try to put cables on to give the battery the maximize output.

 

[catfish123]

That 103-104 was on an XB2003???????????????????

 

[john4utvols]

Nope xb2002....... xb2003 would be around 98- 100. That was more of a example of what the gears did for our speed. It went from 94-96 to 103-104 by moving the rev limiter up to 7400 and changing the gears to 1.75

 

[msethsmile]

Castro, Chavez, Mao, Stalin, and ...

 

[suicidealli]

1.75 gears with a motor that has some torq, can really work well. The gear ratio changes the torq. The lower ratio means you will run a smaller pitch prop as well. The smaller the pitch the more efficient the is on average. When I go from 1.87 case to my 1.75 case my slip drops between 30-40 %. With 1.87 usually 7-9% slip with a good worked prop.
1.75 2-5%. so it is worth a couple mph on the big end, if you are running a 100. Not much but it is consistent.. Usually drop 2" of pitch for most props when you make the change... There are a lot more 26-28 pitchnprops out there then 30-32 props too. Usually cheaper as well in the used market.. The 3.0L guys buy up a lot of 30p props..

Roy