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merlin grumpy jenkin cast heads

Has anybody done any porting work on merlins grumpy jenkins heads ( cast ) and to what affect on hp in the motor, did it help or not . Winter project maybe

They are stones stock, I used to run them on my blower motor, it was a stone too. I had them race ported, the numbers improved drastically especially the exhaust flow but the low flow numbers dropped which I hear is common. I never did run them and will use them some day so I can't report actual results BUT they respond quite well to a full out port job from everything I have ever seen and heard, Smitty

Quote:

Originally Posted by fastscarab22 (Post 3514079)

Has anybody done any porting work on merlins grumpy jenkins heads ( cast ) and to what affect on hp in the motor, did it help or not . Winter project maybe

PM JimV on here. He has done a ton with Merlin heads.
I have run his Merlins and so have many other on here.

Quote:

Originally Posted by fastscarab22 (Post 3514079)

Has anybody done any porting work on merlins grumpy jenkins heads ( cast ) and to what affect on hp in the motor, did it help or not . Winter project maybe

Both people above have answers i agree with.

But................what size Merlin heads and what exact engine build up do you have them on ?

Ron Potter ported and polished my 345's on my 540 he built...dyno video Monday or Tuesday!!! I cant wait...

I think they are 345 cc, i will check
731 crane cam
dart intake
holley 830
glm 4 inch exhaust with drew marine shotgun mufflers
crane ingition rev limiter set at 4350 ( hot wire )

Fukked up thing about merlins stock is the exhaust port is the same on them no matter how big the intake port is, never made sense to me, they ALL need to be ported , I had a pair of out of box 310's on my blown 540 and couldn't break 700 hp, went to afr 315 cnc's and a little bit bigger cam and made 945hp on next go around, Smitty

Quote:

Originally Posted by fastscarab22 (Post 3523235)

I think they are 345 cc, i will check
731 crane cam
dart intake
holley 830
glm 4 inch exhaust with drew marine shotgun mufflers
crane ingition rev limiter set at 4350 ( hot wire )

cid ?
compression ?
4350 rev limit - typo ? Or someone smoking crack ? LOL.
Please restate max rpms.

Quote:

Originally Posted by articfriends (Post 3523271)

You dummy. You just needed a Straub 24° split cam. :evilb:

Quote:

Straub at http://www.chevelles.com/forums/show...4&postcount=17
I ran into a similar situation about 6 or 7 years ago on 540 with a set of ported 990's. It was a nice dart block build in a '66-67 Chevelle. The owner was very disapointed when it made 540HP on the dyno. A mutual friend put him in contact with me and he pulled the heads and flowed them. They were around 48% or 50% I/E ratio. The Lunati that was in it was around a 6 degree split and it needed about 24 degrees of split or more. I lessoned the intake duration and increased the exhaust by a ton. The customer agreed to try it.

On a serious note, most stock (non ported) aftermarket heads from same manufacturer and same family style have same exhaust port on the different size cc heads.

The Merlins just happen to be not so good.

FastScarab,
My JimV Merlin heads are his Wedged and Ported. I think they are about 318cc intake runners when finished. 590HP one my 454's