f5a head fits f8b

[hatch4play]

ha ha i have a few 500 and 800 heads at home and i have a f5a head that is identical to a f8b head only it has air injection so i have sen it off to get filled with some welds where the aire inject was. and i will have a extremely good condition head ha ha. i do have anothere 500 head that is miles different though. the head has y5a on the back and also s3

jimbo

[hatch4play]

sorry i was pretty vage in that msg i was at work sneaking it in but yeah i found one of the 500 heads is the same or could this be of an alto maybe? on my 800 heads they all have 784 and s3 on them and on this "500" head it has y5a and s3 i assume the y5a is for the 500cc? now i am really confused. i am thinking that in japan they were like yeah we got this basket of parts and this basket of parts and they went ieny minnie mony moe cause these frigen engines are all bitsas.

jimbo

[hatchman]

f5a and f8b arent interchangable on the f8b block

[Brayden]

This seems very odd to me as well, unless something changed with later model Altos. Every F5A head that I have seen has been different to the F8B, not only in gallery match but valve size as well. (F5A = smaller valves than F8B.)

Strange!

[hatch4play]

indeed very strange, but i dissasembled my f8b head and everything fits perfect in the 500 head, the valves are identical even, the cam is the same etc etc. i will post pics tonight for you all to make your own judgement, but if it is a 500 head it will certainly bolt to my f8b block

has anyone noticed a y5a marking on their head?

jimbo

[Brayden]

I had noticed that marking on a head, I'll have to check if I still have it and what it is.

[warregts]

Was that the head you got off me ??

[hatch4play]

nah its one i pulled of a 500 motor the one i got of you was a 500 head

[fleebag]

well guys the answer to all this is.#1. cams identical grinds from factory. #2 valve size idencal f8b,f5a. sohc. #3rockers,shafts,springs,retainers identical. #4port size (inlet only) smaller on f5a sohc. approx 22 mm f5a approx 28mm f8b. will vary a little due to casting. #5head bolts location ,thread pitch & length the same.#6 inlet ports shape changed with emission air inj. #7inlet gasket differences 'cauce of #6 & #4.....#8 cam belt no. teeth and section (eg sqare teeth round teeth.) #9 a F5A head will bolt to a F8b block but will not work because: suzuki shifted the bore ctrs F5a has a ctr to ctr of 72 mm & f8b ctr to ctr of 75.5mm. vicea versa,(f8b head on F5a block) valve clearance problems due to tighter ctr to ctr. cooling system holes /slots dont line up (head to block) a swap would cause cyl to fill with water. when suzuki grew f5a to f8b to get a +6.5mm bore increase and 12mm stroke increase (eg 543 to 796cc) castings patterns had to be'' tweeked abit'' far more cost effective than making new patterns& block............std cyl wall to wall approx 10mm f5a....F8B approx 7.5mm.# 10 headgaskets, ONLY F5A headgaskets can be used with f5a and F8B headgaskets on F8B any one who says different doesnt know these mtrs. there is only gasket for the mtr u have....the right one ....suzuki sells headgaskets to suit what u have. the bore hole (in the gasket) is the size of the max o.s. a/v from suzuki(plus a bit ) eg F8B this would be69.5mm-70mm...( eg.factory.h/g for F8B NO std bore h/g and NO o/s h/g).years ago factorys would go beyond the common o/s todayof 0.5mm or 1mm (20tho &40tho) these days blocks are cast thin as possible (to save on costs &weight) so o/s of plus1mm(40tho) is safe but beyond depends on casting/rust etc. sleaving can go bigger sizes safely,because sleaves arn't cast. How is a claimed 20tho o/s concided ''an overly large bore job''?

[Brayden]

A lot of the similarities must have to do with the model of F5A or F8B in question.

MightyBoy F5A and Alto F8B heads are very different. Valves size included. Colin has proven that much!

[fritz]

I never paid much attention to this thread a while ago, but tonight did a search because I noticed that my f5a valves are the same size as 2 f8b heads I have. Hmmm... Very strange... At least I'll have plenty of spares to do up the other heads with. - Although I'm still chasing another non-emissions f8b head.

Anyone know if there are quality issues with generic replacement new heads? A head shop told me a while ago that I could get a new head for around $300 -$400

[ike849]

Just reviving an old thread.....

I'm currently/finally in the process of rebuilding/exchanging parts on my f8b to then put in the MB. I noticed after rebuilding the head that the cam where the mechanical fuel pump rides/works off is rather badly gouged.

I was wondering did anyone know if the cam shaft on the f5a and f8b are the same in both bearing dimensions and cam grind/timing as i have a decent one in a f5a currently in the MB's.

[Brayden]

I don't know off the top of my head, but if you haven't got an answer from someone by tonight I'll check both workshop manuals to see if they shed any light.

[ike849]

have already checked the manuals, and they 'appear' to be the same, but wanted to know if someone has tried it and can confirm this???

[fritz]

I'm pretty sure I have used a f5a cam in my f8b.
When I had my head rebuilt, I let the head people pick the best one of about 3 I had.