Hello all .. I have a 79 ironhead 1000cc sportster and am looking to put 900cc irohhead heads on it. I know that the bolt holes done line up as well as the fire ring recess in the head and probably the oil drainback holes as well. my question is ... don't the 900cc heads flow better than the 1000cc ones and can the 900 heads be reworked ( IE ... head bolt holes and fire ring on the head as well as the oil drainback holes be put in a position where they will work on 1000cc jugs ?

 

anyone even flippin read this section any more or am I just wasting my time ???

 

I don't know the answer but maybe in the engine section some one will post, or you could pm Scott from hillside or one of the other engine gurus on here they may be able to answer that question . By the way welcome from another seabee there are a few on here.

 

A few of us read this section often, myself every day. Your question is very unusual. I have never heard that 900 heads flow better than 1000, and am uncertain about the other comments you made about the fire ring and bolt holes - but them I am merely knowledgeable and definitely not expert. I left your question unanswered to see if someone more knowledgeable would chime in.

 

No, the old 900 (actually 883) heads don't flow better than the 1000 heads. Trying to fit them to 1000 barrels is a big waste of time and money.

 

hello all ... I must apologise about my impatience first thing. secondly ... I appreciate all the info ... it is very helpful. ill look up a set of 1000 cc heads and have the work done on those. btw .. anyone know the stock valve sizes?? second question. would it be a waste to go with larger intake and exhaust valves ?? I have a stock compression and stroke engine, but have an s&s intake and an ultima carb (currently installed on the bike) along with both a 1-3/4 inch and 2 inch pipes and I have but haven't installed the y cams I just bought. again ty for any and all advice. TY Iron, Low, and 83XLX

 

Larger intake and exhaust valves are a waste. The stock valves are plenty big enough, if perhaps a bit oversize to start with.

I have not heard of anyone using an Ultima carb on an IronHead. I see that they are a "performance" carb. What is the venturi size? The stock carb for 1979 is 34 mm Keihin; We have used up to 38 mm keihin and Mikuni, nothing bigger.

2" exhaust is too big. They look nice, and if they are drag pipes and you like LOUD they will sound good, but they are not better performance. 1-3/4" is better, probably best for size. A good 2-into-1 is best for power; 2-into-2 with crossover is pretty high up there also.

I am not knowledgeable about the various cam choices, except for PB+, which bring the engine to life at ~4000 RPM

 

Well, Iron ... the ultima carb is a knockoff S&S super e ... plan on going to an S&S brand once I have the cash. But the ultima has a slightly smaller venture than the S&S super E. I will say this .. the bike does have p cams in it ... and it would move out decent with the 1-3/4 inch pipes on it. again, ty Iron. BTW Iron .. nice sportster.

 

Here's a better look at it...

 

she purrs nicely, Iron. And she is great looking as well.