From: "Erik Berg" [email protected]
Subject: Re: 4AGE/7AFE mod.

Scott Davis wrote:
 Here's my question.  Would it make any sense to take the crank out of a
 7A-FE motor, or the rods, or both, and put them into the 4A-GE as a sort
 of a "stroker kit?"  

It might have been a darned good idea, except that I think it would be 
physically impossible.  

First of all, I think it unlikely that you could fit a crank with that long of a 
stroke in a 4AGE block, without hitting things.  We're talking an 8.5mm stroke 
difference here, and the biggest stroker crank I've ever heard of for a 4AGE 
has only a 7mm increase.

According to Mike Dowe, the rod journal on the 7AFE crank is larger, by 
8mm.  Also, Justin Timbrell told us (thanks for all the great data, Justin!):
 To answer a previous question. The crank on the 7AFE has larger 
 diameters

By which I think he meant that *both* the rod and main journals are bigger.  
True, Justin?  OK, assuming the mains are different sizes, 'nuff said about 
a crank swap.  It ain't gonna happen, without spending more machining 
dollars than it would probably be worth.

Next issue: deck height, compared to the compression height.

Toyota made the deck taller on the 7AFE, for a good reason!

Here's some comparison data (all in mm):

                                 7AFE     4AGE
rod length             132.5     122
crank throw         42.75     38.5
stroke                     85.5        77

OK, now, what is the difference between the compression height of a stock 
4AGE and that of a stock 7AFE?  Assuming the same piston in the 4AGE and 
the 7AFE (which it isn't, but I suspect that is a minor deal...) it would be the 
difference in the rod length plus the difference in the crank throw.  In other 
words:

Difference in compression height = (132.5 - 122) + (42.75 - 38.5)  = 14.75mm

So, if you were actually able to stuff a 7AF crank and rods into a 4AG block, 
the piston would probably stand proud of the deck by about 13 to 14mm 
(half an inch-ish).  Not a happy deal!

I still think the hot ticket would be to do exactly what Justin did... plop a
4AGE head on the 7A block.

Just for grins, what is Justin's CR?  Can we calculate it, from the data I've 
dredged up here?

I'm not sure exactly what the deck heights of the blocks are, but I'm pretty 
sure they are *different* by 15.4mm.  Ass-u-me-ing that to be correct, and 
that Justin's original CR was 10:1 as he reported, I'm getting a result that the 
chamber volume difference, with the same piston, would be 3.35cc (larger 
volume for the 7AGE, compared to the 4AGE).  

The total chamber volume for the 4AGE with a 10:1 CR, would be 44cc.  The 
total chamber volume for the 7AGE would then be 44cc + 3.35cc = 47.35cc 
and therefore the CR would be..... about 10.3:1.  

Well, is this correct?  Can anyone find any errors in these calculations?

By the way, Justin you also wrote:
 You might be wondering what happened when I turned the key the first
 time ..... well unfortunately it started first time no problems and hasn't
 skipped a beat since .... how boring !!!

"Unfortunately"?!  Hey, that kind of bordom I could live with!

Regards,
Erik Berg